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Identification of akinetic but viable myocardium is important for the selection of patients for coronary revascularization. In order to assess predictive values of end-diastolic wall thickness and dobutamine induced wall thickening obtained by magnetic resonance imaging (MRI) and [18F]Fluorodeoxyglucose uptake assessed by positron emission tomography (F-18-FDG-PET), these parameters were compared to recovery of left ventricular function after successful revascularization. Forty patients with chronic myocardial infarction and regional a- or dyskinesia by ventriculography underwent rest- and dobutamine-MRI studies (10 microg dobutamine/kg body weight/min) and F-18-FDG-PET. Viability of the infarct region was considered to be present if; 1) end-diastolic wall thickness was > or =5.5 mm; 2) dobutamine induced wall thickening > or =2 mm could be measured; and 3) normalized F-18-FDG-uptake was > or =50% in > or =50% of akinetic segments. Preserved end-diastolic wall thickness was found in 32/40 patients, functional improvement during dobutamine infusion in 26/40 patients and preserved F-18-FDG-uptake in 29/40 patients. After revascularization regional left ventricular function improved in 25/40 patients. Positive and negative predictive values and diagnostic accuracy were 78%, 100%, and 83% for preserved end-diastolic wall thickness, 92%, 93%, and 93% for dobutamine inducible contraction reserve and 86%, 100%, and 90% for preserved F-18-FDG-uptake. Quantitative assessment of dobutamine induced systolic wall thickening by MRI and F-18-FDG-uptake by PET are highly accurate techniques for the identification of viable myocardium and prediction of functional recovery after successful revascularization. Preserved end-diastolic wall thickness results in an overestimation of viable myocardium compared to functional improvement, but wall thickness <5.5 mm excludes recovery of regional function.

Stress testing is the cornerstone in the diagnosis of patients with suspected coronary artery disease (CAD). Although exercise ECG remains the primary approach for the detection of ischemia in patients with chest pain syndromes, its sensitivity and specificity is limited and exercise ECG does not provide detailed information about the localisation and extent of CAD. Stress echocardiography has been used for the detection of ischemia for more than a decade and has become an increasingly popular noninvasive method for the detection of CAD. In experienced hands wall motion analysis based on stress echocardiography has proved to be as sensitive and specific for the detection of myocardial ischemia as scintigraphic techniques. Recent technical improvements, namely the availability of ultrafast imaging sequences with a significant reduction of imaging time have initiated several studies which examined the combination of pharmacological stress and magnetic resonance imaging (MRI) for the detection of suspected CAD. The most well developed stress-MRI technique is wall motion imaging during dobutamine stress. This technique is analogous to stress echocardiography, but MRI has the inherent advantages of better resolution, higher reproducibility and true long and short axis imaging with contiguous parallel slices. However, the clinical impact of MRI for the diagnosis of CAD is still low. Further technical developments including real time imaging and a reliable automated quantitative analysis of left ventricular function are required before stress-MRI becomes a serious challenge to stress-echocardiography in the clinical arena. Currently, only a few MRI facilities and physicians are dedicated to pharmacological stress testing with MRI and the future clinical impact of this promising technique will depend on its potential to provide information beyond myocardial function including perfusion, metabolism and coronary anatomy in form of a "one-stop"-shop for the cardiac patient.

Aims: A substantial number of patients with dysfunctional but potentially viable myocardium cannot be accurately evaluated by transthoracic echocardiography due to a poor acoustic window. This study compares the diagnostic value of alternative functional imaging techniques, such as dobutamine-transoesophageal echocardiography (dobutamine-TEE) and dobutamine magnetic resonance imaging (dobutamine-MRI) for the detection of viable myocardium and the prediction of left ventricular functional recovery in patients with chronic coronary artery disease following successful revascularization procedures., Methods and Results: Rest and low-dose (5, 10 microg dobutamine x min(-1) x kg(-1)) multiplane dobutamine-TEE and ultrafast cine-MRI studies were performed in 103 patients. Contractile recovery of an infarct region was predicted if a dobutamine contraction reserve could be assessed visually by TEE or MRI in > or =50% of infarct-related a- or dyskinetic segments. Revascularization of the infarct-related vessel was successful in 88 patients, and 4.9 +/- 0.7 months later 52 patients still had an angiographically controlled open target vessel. These patients underwent another rest MRI study to assess left ventricular functional recovery. A dobutamine contraction reserve was observed in 27/52 (52%) patients by TEE and in 26/52 (50%) patients by MRI. Functional improvement of the infarct region was diagnosed in 28/52 (54%) patients. The positive and negative predictive accuracy of dobutamine-TEE and dobutamine-MRI for the prediction of left ventricular functional recovery was not significantly different (85% vs 92%, ns and 80% vs 85%, ns). Diagnosis of a predominantly viable infarct region by TEE and MRI predicted a significant increase in left ventricular ejection fraction (TEE: 12 +/- 8% vs 2 +/- 7% P<0.001, MRI: 13 +/- 7% vs 2 +/- 7%, P<0.001) compared to infarct regions graded as scar., Conclusion: A qualitative visual analysis of TEE and MRI viability studies is highly accurate for the prediction of left ventricular functional recovery in patients with dysfunctional myocardium and proved to be a clinically valuable alternative if transthoracic dobutamine-echocardiography is unsuitable. To date, TEE is cardiologists' preferred choice for the assessment of myocardial viability but MRI may become significantly more attractive with increasing local availability and experience.

Diagnosis of congenitally corrected transposition of the great arteries (L-TGA) with situs inversus totalis in two adult patients was made by magnetic resonance imaging (MRI). Visualization of the complete anatomy and quantification of ventricular function was possible. Relevant concomitant disease such as perimembraneous ventricular septal defect, atrial secundum septal defect, tricuspid regurgitation, valvular pulmonic stenosis, and pulmonary artery dilatation were clearly depicted by MRI using standard spin-echo and gradient-echo techniques. Findings were confirmed by cardiac catheterization in both patients. In this rare and complex congenital cardiac anomaly, MRI is an excellent imaging modality as echocardiography may be difficult to interpret due to restricted imaging windows. MRI may help in the decision about the necessity to undergo further invasive evaluation and may help to make cardiac catheterization a straightforward procedure.

Background and Objective: The development of ultra-rapid gradient-echo sequence magnetic resonance imaging (MRI) makes it possible to visualize coronary arteries. But the clinical value of coronary artery MRI (MRCA) still needs to be established. It was the aim of this study to determine whether MRCA can demonstrate proximal parts of the coronary arteries and visualize haemodynamically relevant stenoses., Patients and Methods: MRCA was performed, using segmented 2D sequences and a navigator pulse, in 29 patients (22 men, seven women, mean age 60 +/- 10 years) in whom coronary heart disease (CHD) was suspected or who, with proven CHD (> or = 50% stenosis) further treatment was to be established. Exercise myocardial scintigraphy with single proton emission tomography (SPECT) was additionally performed in 20 of the patients., Results: Seven of 87 coronary arteries (8%) could not be demonstrated because the patients' claustrophobia necessitated premature termination of the investigation: these vessels were excluded from the final analysis. The mean length of the visualized coronary arteries was 12 +/- 4 mm for the main stem (LM), 36 +/- 14 mm for the left interventricular branch (LAD), 18 +/- 12 mm for the circumflex branch (CX) and 67 +/- 23 mm for the right coronary artery (RCA). Of 37 stenoses demonstrated by coronary angiography 29 were also visualized by MRCA: 13 of 18 LAD stenoses, two of three CX stenoses and 14 of 16 RCA stenoses. Mean sensitivity of MRCA was 78%, mean specificity 86%. In patients who had undergone exercise SPECT, coronary angiography demonstrated 26 stenoses, of which 16 (six LAD, two CX and eight RCA stenoses) were haemodynamically significant. Of these 16 stenoses MRCA demonstrated 13, but three stenoses (one RCA and two LAD stenoses) were not visualized, because the stenoses were distal to the demonstrated segments., Conclusion: MRCA can visualize moderately severe stenoses, especially of the proximal coronary arterial segments. This method represents an new approach to noninvasive diagnosis of CHD, but additional technical improvements will have to be made.

Ductus arteriosus Botalli apertus is a congenital cardiovascular malformation usually diagnosed in childhood by echocardiography and/or cardiac catheterization. Reports about magnetic resonance imaging of ductus arteriosus Botalli apertus are rare. We report about three adult female patients and one adult male patient in whom magnetic resonance imaging was able to demonstrate the pathology. In all four patients quantitative data about right ventricular function were calculated. Pulmonary hypertension with Eisenmenger syndrome detected by cardiac catheterization had developed in three of the four patients excluding operative closure of the ductus. The patient in whom pulmonary hypertension had not developed underwent successful operative closure of the ductus. Magnetic resonance imaging is a non-invasive tool that can be used for diagnosis of ductus arteriosus Botalli apertus and it allows to quantify right ventricular function. Magnetic resonance imaging can be used repetitively in patients with Eisenmenger syndrome which may be helpful for better timing of combined heart-lung transplantation as ultimate therapeutic strategy because deterioration of right ventricular function can be monitored.

The identification of dysfunctional but viable myocardium in patients with coronary artery disease with or without a history of myocardial infarction is of paramount clinical importance since viable myocardial areas are most likely to benefit from revascularization, whereas revascularization of scar tissue will not lead to improvement of left ventricular function. In some patients cardiac catheterization itself already provides important clues to the presence of viable myocardium based on the degree of wall motion abnormalities, post-extrasystolic improvement of wall motion, the presence of collateral vessels or persisting angina in a patient with single vessel disease. However, due to the complexity of viability assessment especially in patients with severely depressed left ventricular function and multi-vessel disease, viability tests are usually requested after the results of coronary angiography are known. Among the diagnostic armamentarium to identify viable myocardium the most established techniques are single photon emission computed tomography (SPECT), positron emission tomography (PET) if available and dobutamine stress-echocardiography. With the application of magnetic resonance imaging (MRI) in clinical cardiology an important and exciting diagnostic tool has been added for the prospective identification of viable myocardium for purposes of guiding therapeutic interventions in individual patients. This article reviews comparative studies between MRI and established imaging techniques like PET, SPECT and dobutamine-echocardiography with respect to the assessment of viable myocardium in patients with acute myocardial infarction and chronic coronary artery disease.

With the application of magnetic resonance imaging (MRI) in clinical cardiology, important tools have been added to the currently available techniques for the evaluation of coronary artery disease (CAD). Technical advantages of MRI in comparison to established imaging techniques are the excellent spatial resolution, the characterization of myocardial tissue and the potential to acquire a three dimensional set of data. This allows the accurate assessment of left ventricular mass and volume and the determination of systolic wall thickening and wall motion abnormalities. Myocardial perfusion, metabolism and inducible myocardial ischemia with the use of pharmacological stress also can be assessed by MRI. Future technical improvements in real-time imaging and development of non-invasive visualization of the coronary arteries and coronary artery bypasses will constitute a considerable progress in clinical cardiology. A particular strength of MRI is the potential to encompass cardiac anatomy, function, perfusion, metabolism and coronary angiography in a single study. The replacement of multiple diagnostic tests with a single MR study allowing to assess different aspects of CAD may have a major impact on cardiovascular health care economics.

Objectives: This study sought to evaluate whether myocardial viability, as assessed by magnetic resonance imaging (MRI), reliably predicts postrevascularization left ventricular (LV) recovery., Background: Compared with positron emission tomographic findings, MRI has proved to be a reliable technique for the identification of residual myocardial viability. However, the predictive accuracy of MRI-assessed preserved end-diastolic wall thickness (DWT) and dobutamine-induced systolic wall thickening (SWT) for LV functional recovery has not yet been evaluated., Methods: Rest and low dose dobutamine MRI was performed in 43 patients with a chronic infarct (> or =4 months since ischemic event) and LV dysfunction who had undergone revascularization of the infarct-related vessel. On the basis of segmental evaluation of corresponding short-axis tomograms, infarct regions were graded viable by MRI if 1) DWT was > or =5.5 mm, and 2) dobutamine-induced SWT was > or =2 mm in > or =50% of dysfunctional segments related to the infarct region. Functional recovery was defined as SWT > or =2 mm in > or =50% of infarct-related segments at rest 4 to 6 months after successful revascularization., Results: Recovery of regional SWT could be observed in 27 (63%) of 43 patients. Comparison MRI grading before and after revascularization indicated that dobutamine-induced SWT was a better predictor of LV functional recovery (sensitivity 89%, specificity 94%) than was preserved DWT (sensitivity 92%, specificity 56%). Segments that remained akinetic after revascularization had significantly lower DWT (6.0+/-3.1 mm [n = 219] vs. 9.8+/-2.6 mm [n = 188], p < 0.001) than those with improved SWT. Left ventricular ejection fraction increased significantly in patients with dobutamine-induced SWT than in those with no contractile reserve (14+/-9% vs. 3+/-9%, p < 0.0002), and the magnitude of this increase was correlated with the number of dobutamine-responsive segments per infarct region (r = 0.68, p < 0.0001)., Conclusions: Quantitative assessment of dobutamine-induced SWT in chronic infarcts by MRI is a highly accurate predictor of LV functional recovery, and the presence of significantly reduced DWT reliably indicates irreversible myocardial damage. Therefore, dobutamine stress testing for the assessment of myocardial viability can be restricted to patients with preserved DWT.

Magnetic resonance techniques can be employed to depict valvular abnormalities but are especially helpful in quantifying regurgitant or stenotic lesions which cannot be quantitatively assessed by other noninvasive techniques. Gradient echo techniques and phase velocity mapping are the most important magnetic resonance pulse sequences employed for these purposes. Valvular regurgitation can be quantitated by measuring the area of signal void on conventional gradient-echo images, by calculating stroke volume differences from k-space segmented gradient echo images, by measuring the proximal convergence zone from velocity encoded images or by comparing stroke volumes of the ventricles from velocity measurements. In contrast to this variety of possibilities in regurgitant lesions, stenotic lesions can only be quantitated by using velocity mapping techniques. Magnetic resonance spectroscopy can be used to assess myocardial metabolism in chronic valvular lesions. However, this tool needs further development and more clinical data before its use can be recommended to assess the necessity and optimal timing of surgical intervention.

To characterize energy metabolism in vivo after nontransmural anterior myocardial infarction, patients (group A, n = 19) with a stenosis of left anterior descending artery (LAD) and anterior wall hypokinesia by levocardiography were examined by phosphorus magnetic resonance spectroscopy (MRS). Spectra were compared to those of healthy volunteers (n = 15). The volume of interest was placed into the anterior myocardial wall by magnetic resonance imaging. Phosphorus spectra were recorded under optimal antiischemic medication. To separate the influence of coronary stenosis from that of the ischemic insult, additional patients (group B, n = 4) with LAD-stenosis but without left ventricular dysfunction were examined. The effect of antiischemic medication on the phosphorus spectra was evaluated in patient group C (n = 4), who had the same clinical features as group A. In these patients, MRS was first performed without antiischemic medication (washout period > one day) and then repeated during intravenous application of glyceroltrinitrate (GTN). Mean PCr/ATP-ratio was significantly lower in group A patients (1.24 +/- 0.18) than in healthy volunteers (1.74 +/- 0.23; p < 0.01 unpaired t-test). Patients with normal left ventricular function (group B) showed PCr/ATP-ratios (1.64 +/- 0.22) similar to those of normal controls (p = 0.23). After GTN infusion PCr/ATP-ratio of group C rose from 1.12 +/- 0.08 to 1.32 +/- 0.13 (p < 0.01 paired t-test). Thus, hypokinetic myocardium after nontransmural infarction is characterized by a larger decrease of the cellular energy buffer PCr compared to the myocardial ATP-content. These findings may reflect degenerative changes of myocytes due to disturbed microperfusion in viable areas of the infarct or remodeling processes of viable myocytes in the infarct region. Both mechanisms may lead to adaptive changes of cellular enzyme concentrations resulting in a reduced PCr content of the myocytes.

A dobutamine-induced contraction reserve in akinetic but viable myocardium, observed by echocardiography or magnetic resonance imaging (MRI), is a reliable indicator of myocardial viability. However, the comparative diagnostic accuracy of these 2 techniques is unknown. Therefore, 43 patients with myocardial infarction (infarct age > or = 4 months) and regional akinesia underwent dobutamine transesophageal echocardiography (TEE) and dobutamine MRI (10 microg dobutamine/ min/kg). Both imaging techniques were compared with the reference standard 18F-fluorodeoxyglucose positron emission tomography (FDG PET). An infarct region was considered viable if a dobutamine contraction reserve could be assessed visually by TEE or quantitatively by MRI in > or = 50% of segments graded "a" or dyskinetic at rest. Infarct regions were graded viable by PET if FDG uptake was > or = 50% of the maximal FDG uptake in a region with normal wall motion by left ventriculography. A dobutamine contraction reserve was found in 21 of 43 patients (49%) by TEE and MRI. A viable infarct region by FDG PET was diagnosed in 26 of 43 patients (60%). FDG uptake and dobutamine TEE were concordant in 36 of 43 patients (84%) and dobutamine MRI and FDG PET were concordant in 38 of 43 patients (88%). Sensitivity and specificity of dobutamine TEE and dobutamine MRI for FDG PET-defined myocardial viability were 77% versus 81% and 94% versus 100%, respectively. Both imaging techniques yielded similar results for the detection of myocardial viability as defined by FDG uptake, with a slightly higher sensitivity and specificity for the quantitatively evaluated dobutamine contraction reserve by MRI.

In four adult patients with congenitally corrected transposition (C-TGA) of the great arteries the typical anatomy and relevant additional lesions such as perimembranous ventricular septal defect (n = 3), secundum atrial septal defect (n = 2), sub-/valvular pulmonic stenosis (n = 3) and pulmonary artery dilatation (n = 4) and/or relevant tricuspid valve insufficiency (n = 3) were depicted by magnetic resonance imaging (MRI) using spin-echo and gradient-echo techniques. The severity of the additional lesions could be evaluated qualitatively. Therefore, in cases of C-TGA magnetic resonance imaging may provide additional information or in selected patients may serve as a useful alternative to conventional imaging techniques such as echocardiography and angiocardiography.

Background: There have been conflicting reports of whether substantial myocardial thinning alone as an indirect sign of myocardial scarring is sufficient evidence to exclude the presence of viable myocardium in patients with previous myocardial infarction and persisting regional left ventricular akinesia. Demonstration of a dobutamine-induced contraction reserve in postischemic viable but akinetic myocardium may serve as a direct indicator of myocardial viability. In the present study, end-diastolic wall thickness at rest and dobutamine-induced systolic wall thickening assessed by magnetic resonance imaging (MRI) were compared with corresponding [18F]fluorodeoxyglucose uptake as assessed by positron emission tomography (FDG-PET)., Methods and Results: Thirty-five patients with myocardial infarction (infarct age, > 4 months) and regional akinesia or dyskinesia assessed by left ventriculography underwent rest and dobutamine MRI studies (10 micrograms dobutamine.min-1.kg-1) and FDG-PET followed by segmental analyses of end-diastolic wall thickness, systolic wall thickening, and FDG uptake in corresponding short-axis tomograms. Two definitions of viability, as assessed by MRI, of a segment akinetic at baseline were used: (1) end-diastolic wall thickness of > or = 5.5 mm (the mean minus 2.5 SD of a healthy control group [n = 21]) and (2) evidence of dobutamine-induced systolic wall thickening > or = 1 mm. Segments were graded as viable by FDG-PET if FDG uptake was > or = 50% of the maximum uptake in a region with normal wall motion as assessed by left ventriculography. Preserved end-diastolic wall thickness in akinetic regions was found in 17 of 35 (48%) patients at rest, and functional recovery within the infarct region was found in 19 of 35 (54%) patients during dobutamine infusion. Viability of the infarct region was indicated by FDG-PET in 23 of 35 patients (66%), yielding a diagnostic agreement between FDG uptake and myocardial morphology in 29 of 35 (83%) and between dobutamine-induced contraction reserve and FDG-PET in 31 of 35 (89%). Of 2200 segments, 482 (22%) were akinetic at rest. Of these akinetic segments, 234 (48%) had preserved end-diastolic wall thickness, 251 (52%) had a dobutamine-induced contraction reserve, and 299 (62%) were graded as viable by FDG-PET. Correlations of FDG uptake with end-diastolic wall thickness at rest (r = .48) and with dobutamine-induced wall thickening (r = .42) were similar. Comparison of segmental MRI and FDG-PET gradings indicated that dobutamine-induced wall thickening was a better predictor of residual metabolic activity (sensitivity, 81%; specificity, 95%; positive predictive accuracy, 96% than was end-diastolic wall thickness (sensitivity, 72%; specificity, 89%; positive predictive accuracy, 91%). However, grading a segment as viable if at least one of both MRI parameters fulfilled viability criteria improved the sensitivity (88%) of MRI for FDG-PET-assessed metabolic activity without a major decrease in specificity (87%) or positive predictive accuracy (92%)., Conclusions: Viable myocardium is characterized by preserved end-diastolic wall thickness and a dobutamine-inducible contraction reserve. Both parameters should be taken into account to maximize the sensitivity of MRI in the detection of regions with signs of viability on FDG-PET images.

Purpose: This study compared gradient-recalled echo (GRE) magnetic resonance (MR) imaging with technetium-99m-methoxyisobutyl isonitrile (MIBI) single photon emission computed tomography (SPECT) during the same dobutamine stress for the localization of coronary artery stenoses., Materials and Methods: In 35 consecutive patients (28 men and seven women, aged 41-79 years) with angiographically documented coronary artery disease, corresponding GRE MR images and SPECT tomograms were acquired at rest and during dobutamine infusion and were evaluated for regional wall motion or perfusion abnormalities., Results: Images in both examinations could be analyzed in 32 of 35 (91%) patients. Wall motion or perfusion abnormalities were observed in 27 of 32 (84%) GRE MR imaging and in 28 of 32 (87%) SPECT examinations. Sensitivity and specificity of dobutamine GRE MR imaging and dobutamine SPECT for the localization of left anterior descending coronary artery stenoses were 74% and 100% versus 70% and 100% for the combined left circumflex and right coronary artery perfusion territories., Conclusion: GRE MR imaging and SPECT have a high concordance with respect to the detection of a dobutamine-induced ischemic response.

Purpose: To compare the diagnostic value of magnetic resonance (MR) imaging and transesophageal echocardiography (TEE) in the follow-up of chronic dissection of the thoracic aorta., Materials and Methods: Follow-up MR imaging and TEE were performed in 25 consecutive patients with aortic dissection. Ten patients had a type I dissection and 15 had a type III dissection. All patients with type I dissection underwent surgical intervention. Ten of 15 type III dissections were managed medically, and five were managed with surgical intervention., Results: Identification of a persisting dissection and differentiation of the true and false lumina were equal with both methods. The arch vessels and all anastomoses in the surgically treated patients could be assessed only with MR imaging. An intimal flap in the aortic root and formation of an aortic thrombus were visualized in more detail with TEE. At least one entry site could be detected with both methods in 86% of the patients. TEE demonstrated small entry sites more frequently., Conclusion: MR imaging provides better visualization of anastomoses and easier comparison of serial studies; TEE should be employed if MR findings are equivocal.

To define the value of magnetic resonance imaging (MRI) in screening for bone metastases (BM) compared to bone scintigraphy (BSc) 102 patients with tumours with frequent BM were examined also by MRI of spine, pelvis, femora, and proximal tibiae. All patients had normal BSc and 96 (94%) normal MRI. Only 6% of the patients had focal abnormalities within the bone marrow. This indicates that there is a 94% probability of absence of BM if BSc is normal. Therefore, BSc should currently remain the method of choice for screening for BM. Despite MRI is sensitive and specific, with the common technique up to now it should not be used instead of BSc in screening because of costs, duration, and lack of whole body examination. MRI is a valuable adjunct in equivocal findings in BSc with negative results on radiographs.

Dobutamine pharmacological stress testing in conjunction with gradient-echo magnetic resonance imaging (MRI) may be a useful tool for the assessment of haemodynamically significant coronary artery stenoses. Therefore, 28 patients without previous myocardial infarction but significant proximal stenoses (> or = 70% diameter stenosis) of one or more coronary arteries were selected for dobutamine-MRI. Each patient underwent MRI at rest and during incremental dobutamine infusion (5, 10, 15 and 20 micrograms.kg-1.min-1). Additionally, all patients were submitted to exercise stress electrocardiography (EST). A total of 72 segments per patient obtained from identical short axis and transverse tomograms at rest and during dobutamine infusion were evaluated by two observers. Each segment was graded as normal, hypokinetic, akinetic or dyskinetic. Dobutamine-MRI was considered pathological if segmental wall motion deteriorated by at least one grade after dobutamine infusion. For comparison with coronary angiography, segmental wall motion gradings were related to the respective coronary artery territories. Peak rate-pressure product during steady-state dobutamine infusion (18.493 +/- 4.315 mmHg.min-1) was significantly lower (P < 0.01) than during EST (21.316 +/- 4.937 mmHg.min-1). Dobutamine-induced wall motion abnormalities were observed in 22/26 (85%) MR studies and 20/26 (77%) patients had a pathological EST. Regional asynergy induced by dobutamine-MRI occurred in 11/15 (73%) patients with single and 11/11 (100%) with multi-vessel disease. Sensitivity and specificity for the detection of a stenosed coronary artery were 87% and 100% for the left anterior descending, 62% and 93% for the left circumflex and 78% and 88% for the right coronary artery respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

In contrast to the established nuclear imaging techniques magnetic resonance imaging (MRI) is only in the early phase of its application to detect viable myocardium after myocardial infarction. Although MRI techniques have only recently been employed to assess residual myocardial viability three approaches have been described to achieve this purpose: First, the use of signal intensity changes on spin-echo images with and without the application of contrast media to define irreversible injury to the myocardium in acute and subacute infarcts; second, measurement of metabolite concentrations within the infarct area using magnetic resonance spectroscopy, and third quantitation of myocardial thickness and systolic wall thickening in chronic infarcts with and without positive inotropic stimulation. When applying magnetic resonance techniques to detect viable myocardium by imaging techniques, it is useful to distinguish between acute infarcts and chronic infarcts that are more than 16 weeks old. After the time, practically all infarcts have healed and the necrotic myocardium has been transformed into scar tissue. MRI seems ideally suited to detect and characterize chronic myocardial scar and distinguish it from viable but hibernating myocardium because it clearly depicts the regional wall thinning which is a typical feature of transmural infarcts (Figure 1). In contrast, more recent infarcts, even if they are transmural and fail to show any contraction during systole, may not yet exhibit myocardial thinning. Therefore, simply depicting the acutely injured myocardium by MRI is not sufficient to differentiate between necrotic and stunned, but viable myocardium. On the other hand, an increase in signal intensity of acutely infarcted myocardium, which appears on T2 weighted spin-echo MR images only a few hours after occlusion of a coronary artery, can be used to determine the extent of irreversible myocardial damage (Figure 2). It is not clear, however, whether this area of increased myocardial signal intensity that is seen within the first week after the event only represents necrotic myocardium or incorporates some edematous viable myocardium in the infarct border zone. After three weeks, true infarct size may be more closely approximated by the area of increased signal intensity because the edema surrounding the infarct has presumably regressed and signal abnormalities are restricted to the pathologically determined infarct area. More recently, new pulse sequences and high field magnets permit separate observation of the endocardial and epicardial portion of the left ventricular wall. This may further improve the detection of residual viable cells which are preferentially located near the epicardium.(ABSTRACT TRUNCATED AT 400 WORDS)

Safety and sensitivity of gradient-echo magnetic resonance imaging (MRI) for the identification of significant coronary artery stenoses using pharmacologic stress testing was assessed in 61 patients with > or = 70% stenosis of a major coronary artery and a normal left ventricle. After MRI at rest 28 patients underwent dobutamine-MRI during steady-state dobutamine infusion (5, 10, 15 and 20 micrograms/kg/min) and 33 patients had dipyridamole-MRI after high-dose dipyridamole infusion (0.75 mg/kg over 10 min). All patients additionally performed standard ECG exercise stress testing (EST). Segmental wall motion analysis was performed in basal and midventricular short axis tomograms by two observers. A segment was graded pathologic if transient dobutamine or dipyridamole induced wall motion abnormalities could be detected. For comparison to coronary angiography findings, each segment was assigned to one of the coronary artery perfusion territories. There were no serious side-effects during dobutamine and dipyridamole infusion leading to termination of the study protocol. Peak double product during dobutamine infusion was significantly higher (p < 0.001) than after dipyridamole infusion (18.493 +/- 4.311 versus 12.799 +/- 2.694 mm Hg/min). Overall sensitivity of dobutamine and dipyridamole-MRI for coronary artery disease (CAD) was 85% and 84%. Regional asynergy by dobutamine and dipyridamole-MRI was observed in 73% versus 79% patients with single- and 100% versus 92% with multi-vessel disease. Individual coronary artery stenoses were correctly identified by segmental wall motion abnormalities in 87% versus 81% for left anterior descending, 62% versus 86% for left circumflex and 78% versus 92% for right coronary artery stenoses. In conclusion, dobutamine and dipyridamole-MRI are well tolerated and safe non-exercise dependent tests for detection and localization of hemodynamically significant coronary artery stenoses with a similar diagnostic accuracy but with a better control of stress intensity and duration provided by dobutamine.

Magnetic resonance imaging (MRI) has been used in conjunction with dipyridamole induced wall motion abnormalities for the noninvasive detection of coronary artery disease (CAD). To assess the clinical usefulness of dipyridamole-MRI for the localization of CAD and to evaluate the relation between dipyridamole induced wall motion abnormalities and myocardial perfusion 33 patients with severe CAD (> 70% diameter reduction) underwent MRI at rest and after dipyridamole infusion (0.75 mg dipyridamole/kg over a period of 10 minutes). All patients performed exercise stress testing and 20 patients of the study group additionally had rest and exercise stress 99mTc-methoxyisobutyl-isonitrile-SPECT (MIBI-SPECT). Two patients (6%) could not be evaluated due to severe motion artifacts during dipyridamole MRI. Segmental wall motion and perfusion of corresponding short axis planes were related to the major coronary arteries using a standardized segmental coronary artery perfusion pattern. Detection of wall motion abnormalities or perfusion defects by 2 blinded observers in consensus was the criterion for grading a segment normal or pathologic. For localization of CAD, segmental gradings were related to the presumed coronary artery territories. Stress-ECG was pathologic in 19/31 patients yielding a sensitivity of 61% and dipyridamole induced angina was present in 68% (21/31) of patients. Dipyridamole-MRI detected coronary artery disease with a sensitivity of 84% (26/31 patients) and all patients with new wall motion abnormalities also had dipyridamole induced angina. For the subgroup of 20 patients with MIBI-SPECT images, CAD was detected by both MIBI-SPECT and Dipyridamole-MRI in 90% (18/20) of patients. Dipyridamole-MRI and MIBI-SPECT gradings agreed in 55/60 (92%) coronary artery perfusion territories. There were no significant differences with respect to the sensitivities of Dipyridamole-MRI/MIBI-SPECT for the localization of individual coronary artery stenoses yielding 81%/78% for left anterior descending, 80%/80% for left circumflex and 92%/89% for right coronary artery stenoses. However, specificity of Dipyridamole-MRI (89%) for the detection of RCA stenoses was slightly better than for MIBI-SPECT (80%).

Magnetic resonance techniques have only recently been employed to assess residual myocardial viability after myocardial infarction. Three approaches have been described to achieve this purpose: First, the use of signal intensity changes on spin-echo images with and without the application of contrast media to define irreversible injury to the myocardium in acute and subacute infarcts; second, measurement of metabolite concentrations within the infarct area using magnetic resonance spectroscopy, and third, quantitation of myocardial thickness and systolic wall thickening in chronic infarcts. This paper reviews the pertinent literature and compares MR techniques with other imaging techniques used in the diagnosis of myocardial viability.

In 20 patients with an angiographically documented coronary artery stenosis of > or = 70% and normal LV function at rest MRI was performed before and after dipyridamole infusion (0.75 mg/kg BW). In all patients MIBI-SPECT was obtained at rest and after dynamic symptom-limited exercise. In 18 patients MIBI-SPECT showed ischemia and in 18 patients dipyridamole MRI showed a wall motion impairment. In the segments representing the 29 stenosed vessels ischemia in MIBI-SPECT was diagnosed correctly in 24 instances (sensitivity 83%, specificity 90%) and a wall motion abnormality was present in MRI in 23 instances (sensitivity 79%, specificity 90%). Dipyridamole GE-MRI is not superior to MIBI-SPECT in the diagnosis of ischemia.

To assess the ability of magnetic resonance imaging (MRI) to identify morphologic and functional abnormalities associated with transmural anterior and inferior myocardial infarction, 18 patients with anterior myocardial infarcts and 11 patients with inferior myocardial infarcts confirmed by ECG and cine-ventriculography underwent gradient-echo MRI of transverse and short-axis imaging planes. Myocardial perfusion of corresponding imaging planes was measured by 99mTc-methoxyisobutyl-isonitrile single-photon emission computed tomography (MIBI-SPECT). Transmural scar by MRI was defined as diastolic wall thickness 2.5 SD below corresponding normal values of a healthy control group (n = 21). MIBI-SPECT scar was defined as a MIBI uptake less than 2.5 SD below mean values of a healthy control group (n = 11). By MIBI-SPECT, 231 segments contained normal tissue and 161 contained scarred myocardium. In 352/392 (90%) segments gradings based on diastolic wall thickness and MIBI-SPECT gradings were identical. Diastolic wall thickness was significantly higher in normal than in scarred MIBI-SPECT segments (10.3 +/- 1.5 vs 5.2 +/- 2 mm, p less than 0.0001). Additionally, normal segments by MIBI-SPECT showed significantly higher systolic wall thickening than scar segments (5.5 +/- 1.5 vs 0.6 +/- 1.6 mm, p less than 0.0001). The correlation between MRI and MIBI-SPECT assessed infarct size was r = 0.91 for anterior and r = 0.77 for inferior myocardial infarcts. The agreement between MIBI-SPECT perfusion defect size and regions with reduced diastolic wall thickness on MRI tomograms was significantly better for anterior myocardial infarcts than for inferior myocardial infarcts.(ABSTRACT TRUNCATED AT 250 WORDS)

Gradient echo nuclear magnetic resonance (NMR) imaging and transesophageal two-dimensional color Doppler echocardiography are flow-sensitive techniques that have been used in the diagnosis and grading of valvular regurgitation. To define the diagnostic value of gradient echo NMR imaging in the detection of regurgitant flow in cardiac valve prostheses and the differentiation of physiologic leakage flow from pathologic transvalvular or paravalvular leakage flow, 47 patients with 55 valve prostheses were examined. Color Doppler transesophageal echocardiography was used for comparison. Surgical confirmation of findings was obtained in 11 patients with 13 valve prostheses. Gradient echo NMR imaging showed regurgitant flow in 37 of 43 valves with a jet seen on transesophageal echocardiography and it detected physiologic leakage flow in 4 additional valves. There was 96% agreement between the two methods in distinguishing between physiologic and pathologic leakage flow. The methods differed on jet origin of pathologic leakage flow in six prostheses. The degree of regurgitation was graded by both NMR imaging and transesophageal echocardiography, according to the area of the regurgitant jet visualized; gradings were identical for 75% of valve prostheses. Quantification of jet length and area showed a good correlation between the two methods (r = 0.85 and r = 0.91, respectively). Gradient echo NMR imaging is a useful noninvasive technique for the detection, localization and estimation of regurgitant flow in cardiac valve prostheses. However, because transesophageal echocardiography is less time-consuming and less expensive, gradient echo NMR imaging is unlikely to displace transesophageal echocardiography and should be used only in the occasional patient who cannot be adequately imaged by echocardiography.

In order to evaluate postoperative sequelae and ventricular function after Mustard-operation in patients with transposition of the great arteries (TGA), 30 patients were assessed by magnetic resonance imaging in EKG-triggered spin-echo (SE) and gradient-echo (GE) technique. Twenty-three patients, aged 4.7 to 15.8 years, had transposition of the great arteries with intact ventricular septum with or without left-ventricular outflow tract obstruction (TGA+IVS +/- SPS). Seven patients aged 9.5 to 21.7 years had transposition of the great arteries with ventricular septal defect (TGA+VSD). Five patients showed a residual baffle leak, one had a pulmonary venous obstruction, five an obstruction at the caval veins, 13 a left-ventricular outflow tract obstruction, and 14 a tricuspid regurgitation. Right-ventricular enddiastolic volume in patients with TGA+VSD (77.0 +/- 25.5 ml/m2) was significantly higher than in patients with TGA+IVS +/- SPS (61.2 +/- 12.0 ml/m2). In TGA+VSD right-ventricular ejection fraction (47.6 +/- 13.0%) was significantly lower than in patients with TGA+IVS +/- SPS (56.7 +/- 10.7%). The ratio of muscle masses of right to left ventricle was 1.8:1 in patients with TGA+IVS +/- SPS and 2.5:1 in patients with TGA+VSD. In conclusion, after Mustard-operation in patients with transposition of the great arteries (TGA) magnetic resonance imaging provides a comprehensive and noninvasive assessment of postoperative sequelae, residuae, and ventricular function and will, therefore, become the method of choice for postoperative evaluation.

To assess the ability of magnetic resonance imaging (MRI) to identify the anatomic and functional abnormalities associated with completely scarred myocardium, 20 patients with chronic transmural myocardial infarction confirmed by electrocardiography and cineventriculography were examined by gradient echo MRI. Myocardial perfusion at rest was assessed in corresponding transverse sections using 99mTc-methoxyisobutyl-isonitrile single-photon emission computed tomography (MIBI-SPECT). MRI scar was defined as diastolic wall thickness (DWT) 2.5 SD below corresponding normal values or systolic wall thickening (delta WT) less than or equal to 1 mm. For MIBI-SPECT images, scar was defined as a MIBI uptake less than 2.5 SD below normal values. By MIBI-SPECT, 152 segments contained normal tissue and 88 contained scarred myocardium. In 226 of 240 (94%) segments, MRI gradings by DWT and MIBI-SPECT gradings were identical. DWT by MRI was higher in normal than in scarred MIBI-SPECT segments (10 +/- 1 versus 4 +/- 2 mm, p less than 0.001). In 230 of 240 (96%) segments, MRI gradings by delta WT and MIBI-SPECT gradings were identical. Segments graded normal by MIBI-SPECT showed higher delta WT by MRI than scar segments (5 +/- 1 versus 0.3 +/- 1 mm, p less than 0.001). MIBI-SPECT perfusion defect size and regions with reduced DWT on MRI tomograms correlated well (r = 0.85). This study indicates that myocardial regions fulfilling electrocardiographic and ventriculographic criteria for transmural myocardial scar are clearly depicted by regional diastolic wall thinning and delta WT less than or equal to 1 mm on gradient echo MR images.(ABSTRACT TRUNCATED AT 250 WORDS)

In 20 patients with multiple myeloma, the results of MR, x-ray, bone scintigraphy, bone marrow scintigraphy and bone marrow biopsy were compared. MR proved the most sensitive imaging method for the detection of bone marrow infiltration followed by x-ray examinations. Bone marrow scintigraphy and especially bone scintigraphy revealed false-negative results more often. These findings were more impressive by the direct comparison of several investigated regions showing different findings of each imaging method. False-positive results were not found. In 4 patients false-negative results of bone marrow biopsy had to be assumed because of definitely pathological findings by x-ray and MRI.

Gradient-echo (GRE) and spin-echo (SE) magnetic resonance (MR) imaging was performed in 31 patients with chronic left ventricular (LV) thrombi. Thrombi were confirmed or excluded at surgery or by means of other corroborative diagnostic techniques. MR images were evaluated by three reviewers without knowledge of results of corroborative studies. Diagnoses were graded unequivocal if agreed on by three observers and probable if agreed on by two observers. With SE imaging, 12 of 18 confirmed thrombi were detected unequivocally, five were considered probable, and one was not detected. With GRE imaging, 16 of the 18 thrombi were visualized unequivocally; two were considered probable. With SE technique, thrombus was unequivocally excluded in nine of 13 cases and exclusion was considered probable in four. One finding was false-negative. Exclusion of thrombus with GRE imaging was unequivocal in 10 of 13 cases and probable in two, and one finding of thrombus was false-positive. GRE imaging resulted in improved differentiation of thrombi from the surrounding blood pool and myocardium and thus was diagnostically superior to SE imaging in detection of LV thrombi.

Although magnetic resonance imaging is currently only employed to solve diagnostic problems in a few selected patients, the special features of the technique such as its inherent three-dimensional capabilities and the prospect of angiographic noninvasive imaging suggest that this technique will become more important with future technical improvements. This overview summarizes the present status of magnetic resonance imaging in the depiction of coronary arteries and bypass grafts, the diagnosis of myocardial ischemia, the depiction of chronic myocardial infarcts including the detection of residual viable myocardium, and the diagnosis of complications associated with myocardial infarction.

To assess the feasibility, safety and usefulness of gradient-echo magnetic resonance imaging (MRI) combined with pharmacologic stress testing for the detection of coronary artery disease, 23 patients without previous myocardial infarction but with significant stenosis (greater than 70% diameter stenosis) of greater than or equal to 1 major coronary artery were selected for dipyridamole-MRI stress testing. Each patient underwent MRI at rest, and high-dose dipyridamole-MRI (0.75 mg/kg over 10 minutes) of corresponding basal and midventricular short-axis tomograms. Additionally, these patients performed symptom-limited exercise stress tests. All short-axis tomograms were evaluated on a standardized segmental basis by grading each segment as normal, hypokinetic, akinetic or dyskinetic. Dipyridamole-MRI was considered pathologic if segmental wall motion deteriorated by greater than or equal to 1 grade after dipyridamole. For comparison with coronary angiography, segmental wall motion gradings were related to the respective coronary artery territories in the short-axis plane. Pathologic dipyridamole-MRI was obtained in 18 of 23 (78%) patients. For 1- and 2-vessel diseases, sensitivity was 69 and 90%, respectively. Exercise stress tests were pathologic in 14 of 23 (66%) patients. For 1- and 2-vessel diseases, sensitivity of exercise stress test was 58% (7 of 12 patients) and 77% (7 of 9), respectively. Sensitivity/specificity of dipyridamole-MRI for the localization of the stenosed coronary artery was 78/100% for left anterior descending, 73/100% for left circumflex, and 88/87% for right coronary artery stenoses. It is concluded that dipyridamole-MRI is a feasible nonexercise-dependent test for detection and localization of functionally significant coronary artery disease.

Artificial valve prostheses are often regarded as a contraindication for magnetic resonance imaging (MRI), although preliminary in vitro studies suggested, that patients with these metallic implants might safely undergo MR examination. This study reports on the experience with a group of 89 patients with 100 heart valve prostheses who were examined by spin-echo MR and gradient-echo MR. MR examination was performed in all patients without complications. The spin-echo sequence showed advantages in the depiction of anatomical structures like paravalvular abscesses. Anatomical structures adjacent to the artificial valve were clearly visible and the metal components of the valves showed no or only small artifacts. Artifacts were accentuated when using gradient-echo sequences. Gradient-echo sequences provided valuable information regarding the presence of valvular insufficiency. Physiological valvular regurgitation was easy to differentiate from pathological paravalvular or transvalvular regurgitation. These results demonstrate that patients with artificial valve prostheses can be imaged by MR without risk and that prosthesis-induced artifacts do no interfere with image interpretation.

In order to assess the diagnostic possibilities of magnetic resonance imaging (MRI), 30 children (mean age 11.5 years) with d-transposition of the great arteries (TGA) corrected by the Mustard procedure were studied. Patient values were compared to those of 10 healthy volunteers. The most important postoperative abnormalities such as baffle leaks, systemic or pulmonary venous obstructions, left ventricular outflow tract (LVOT) stenosis and tricuspid regurgitation were assessed. Cardiac volumes and muscle mass were measured. Baffle leaks were found in 5 and obstruction of the baffle limbs in 6 patients. On gradient echo images 13 patients showed signs of LVOT stenosis and 12 tricuspid incompetence. Right ventricular end diastolic volumes in patients were significantly higher than the left ventricular volumes, but slightly lower than right ventricular volumes in the normals. In patients with TGA and ventricular septal defect (VSD) (n = 7) right ventricular (RV) volumes were found to be higher than in patients with intact ventricular septum (n = 23) and in normals. In contrast to the normal RV function of patients after Mustard surgery only patients with previous VSD showed a diminished RV ejection fraction. The muscular mass in TGA patients showed a ratio of 1.9:1 between right and left ventricles. In normals the ratio was 1:1.5. Magnetic resonance imaging allows a quantitative insight into the ventricular function and the morphology of the heart after inflow correction. Thus, it supplements the noninvasive evaluation of TGA patients.

To evaluate the diagnostic potential of magnetic resonance imaging (MRI) to diagnose and evaluate tricuspid incompetence (TI), right ventricular angiography (RVA) and MRI were compared in 51 patients. For angiographic semi-quantification a 4-grade modified Sellers classification was used. Several MRI-parameters (jet volume, jet area, number of slices with visible jet, duration of the regurgitation and volume of the right atrium) were examined concerning their validity to evaluate TI and compared to the angiographic data. Limits for MRI jet areas and volumes for each angiographic group were defined to obtain the best agreement with angiographic results. Thirty of 34 patients with angiographically visible TI (sensitivity = 88%) were diagnosed correctly with MRI. The 4 remaining patients also showed a small regurgitant jet which was, however, interpreted as physiologic. One of the 17 patients without angiographic TI was diagnosed as mild TI by MRI (specificity = 94%). MRI classification using jet volume (46/51 = 90% correct classifications) was not significantly better than the easier and faster MRI classification using jet area (43/51 = 84%). The other parameters (number of slices, duration of regurgitation and volume of the right atrium) showed considerable overlap between angiographic groups and did therefore not allow a classification into 4 grades. However, simple classification into hemodynamic relevant and irrelevant TI was possible. Thus MRI is able to diagnose TI with good sensitivity and specificity. Classifications based on jet volume and jet area showed good agreement with angiographic results. However, both parameters depend on the magnet and the pulse sequence used and must therefore be specifically determined for each imaging routine.

Solitary abnormalities in bone scintigrams of cancer patients are a finding causing special diagnostic problems. In a prospective study the value of MRI imaging of the bone marrow was to be ascertained when compared to recognized X-ray studies, as a method of clarifying suspect bone scintigraphy findings. 25 cancer patients presenting with a solitary suspect abnormality in bone scintigrams were examined by X-rays and MRI. In 15 patients, MRI showed that metastases were the probable cause of the hot spot. In 7 patients, radiography, the routinely used method to confirm or exclude the presence of metastases, failed to detect these metastases. In the remaining 10 patients other causes of increased activity in the bone scintigrams could be demonstrated, e.g. fracture, degenerative disease, benign tumour. The results were confirmed by biopsy, operation, autopsy or follow-up. Considering the clinical consequences of the diagnosis of bone metastases, we suggest that a bone marrow MRI of the affected region should be performed to clarify the cause of a solitary hot spot in bone scintigrams of cancer patients, especially if X-ray studies are inconclusive.

Cardiac function can be assessed using conventional spin-echo magnetic resonance imaging. However, long imaging times and poor temporal resolution have limited the clinical applicability of this technique. A new dynamic magnetic resonance pulse sequence avoids these shortcomings using lower flip angles, shorter repetition and echo times and gradient refocused echoes. The entire heart can thus be imaged with a temporal resolution of 60 ms within 20 min. Display of 15 images of the cardiac cycle in a movie loop allows excellent visual assessment of cardiac motion and intracardiac blood flow. Applications of this new technique include blood flow measurements, visualization of regurgitant or shunt blood flow in patients with valvular regurgitation or ventricular septal defect, assessment of regional wall thickening in patients with myocardial disease, and three-dimensional determination of ventricular and atrial volumes.

Magnetic resonance imaging (MR) is a relatively new non-invasive imaging method that has not been used as a routine procedure in pediatric cardiology. To evaluate MR in pediatric cardiology we performed 110 examinations in 91 children during the period from December, 1984, to November, 1987. The children were divided into the following groups: 1) Diseases of the great vessels (54 examinations in 39 children); 2) Cardiac diseases (42 examinations in 39 children); 3) Diseases of the pericardium (four examinations in three children); 4) Ten children without cardiovascular diseases (imaging of the heart in conjunction with examination of other organs). The ages of the children ranged from five weeks to 19 years in the following distribution: 13% infants, 20% children 2-5 years, 30% children 6-14 years, 37% adolescents from 15 to 19 years. On the basis of our experiences we conclude that MR can be used as an additional diagnostic tool in pediatric cardiology, especially for imaging of areas that are not well visualized by echocardiography, i.e., the great vessels and their branches and in addition, the right ventricle, in older children.

Dynamic magnetic resonance imaging (MRI) was performed in patients with aortic regurgitation (N = 14) and/or mitral regurgitation (N = 13), documented and graded for severity by angiography. Eight healthy persons were studied for comparison. Turbulent retrograde blood flow through incompetent valves causes signal loss of blood, thus permitting detection of the valvular defect. To determine the severity of regurgitation by dynamic MRI, several parameters were analyzed, including the number of slices with visible signal loss, the time course of the signal loss, and its maximal area and maximal volume. All regurgitant lesions were visualized in dynamic images. The area of signal loss correlated well with the angiographic severity of aortic and mitral regurgitation. A slightly better correlation was found for the volume of signal loss. Significant differences were also found for the other parameters. Analysis of the regurgitant jet, characterized by signal loss on dynamic MR images permits a semiquantitative assessment of the severity of regurgitant lesions of left-sided valves. Three-dimensional determination of the jet volume is a possible advantage of MRI compared to other noninvasive methods.

Para-aortic pseudoaneurysms after prosthetic replacement of an aortic valve was diagnosed by magnetic resonance imaging (MRI) in two patients and confirmed at surgery. The abscesses had not been visualized in either case by computed tomography and echocardiography, but in one it had been demonstrated by angiography. MRI can thus precisely define site and extent of a para-aortic pseudoaneurysm after aortic valve replacement without any interference by artefact, noninvasively and without use of contrast media.

Nuclear-cardiological diagnostic methods require close cooperation between cardiology and nuclear medicine groups. This review article summarizes the advantages (non-invasive, quantitative, effect of exercise) and the disadvantages (limited resolution, limited specificity, radiation exposure) of the methods. Methods used routinely in the clinic are radionuclide ventriculography and myocardial scintigraphy with Tl-201. The indications for and limitations of these methods are discussed. The important advantages of nuclear magnetic resonance imaging (MRI) are the large field of view which includes extra cardiac structures, choice of slice width and orientation, good resolution and the simultaneous evaluation of morphology, functional parameters, flow phenomena and some differentiation between tissues. Presently, MRI is indicated in problem cases, e.g., aortic aneurysm, dissecting aneurysm, constrictive pericarditis, cardiac and paracardiac tumors. MRI also provides useful complementary information in valvular regurgitation, congenital malformations, cardiomyopathies and intracavitary thrombi. However, magnetic resonance imaging is still under development so that its overall value in the diagnosis of cardiac diseases cannot yet be definitely assessed.

NMR imaging is a noninvasive technique that has been shown to provide high-quality images of the heart. Due to the signal characteristics of flowing blood, inherent contrast between blood pool and myocardium is achieved without the use of contrast media. This paper briefly describes technical aspects of NMR imaging of the heart, normal cardiovascular anatomy, applications of the technique in patients with ischemic heart disease, and the potential of NMR imaging for functional studies in various forms of heart disease.

Forty-four patients with recent cardiac catheterization because of recurrent chest pain after coronary artery bypass surgery were studied by magnetic resonance imaging to evaluate graft patency. To assess the efficacy of this non-invasive method 92 coronary artery bypass grafts were examined by the spin-echo technique. ECG-gated transversal sections were acquired between the diaphragm and the aortic arch. The specificity of magnetic resonance imaging was 83% (48/58) for patent grafts. However, the sensitivity in the detection of occluded bypasses was only 56% (19/34). Despite the good specificity, clinical applications of this method are limited because of its low sensitivity.

Gated magnetic resonance imaging of the heart displays cardiac structures with excellent resolution. This ability should be useful for assessment of cardiac physiology where acquisition of systolic and diastolic images is required. In this study, left ventricular ejection fraction was determined in 50 patients from oblique long axis views of the left ventricle using the area length formula. Angulated views were obtained by electronic gradient angulation. For comparison, all patients had monoplane angiocardiography in the RAO position. Forty-five patients were also studied by radionuclide ventriculography. Ejection fractions determined by MRI and angiocardiography were closely correlated (r = 0.90). Correlation between MRI and radionuclide ventriculography was also acceptable (r = 0.79). In addition to global left ventricular function, MR images provide information about regional wall motion. In order to acquire a three-dimensional set of images at various phases of the cardiac cycle, shorter imaging times are mandatory. A new imaging technique with potential for functional studies uses low flip angles, short repetition times and gradient refocused echoes. Up to 40 images can be obtained within one cardiac cycle. When displayed in a looped fashion, visual assessment of cardiac motion, intracardiac blood flow, and systolic wall thickening is possible. Potential advantages of functional studies by MRI are the concomitant acquisition of anatomical information and the three dimensional frame of reference.

One hundred and seven patients with malignant Hodgkin and non-Hodgkin lymphoma were examined by bone marrow scintigraphy, MRI of bone marrow and bone marrow biopsy to detect bone marrow infiltration. The study included 2 patients where autopsy findings were subsequently available, 3 patients with blind rebiopsy and one patient with guided rebiopsy. The findings of bone marrow imaging and biopsy were classified as normal (grade 0), suggesting reactive changes of bone marrow (grade 1) or suspicious for infiltration (grade 2). About half of all results of biopsy and imaging methods agreed completely. There was a difference of two steps in the classification in only 2 cases (MRI) and 5 cases (scintigraphy). In patients with chronic lymphocytic leukemia false negative findings by both bone marrow imaging techniques were frequent. Unilateral blind bone marrow biopsy is usually accepted as the golden standard for the presence or absence of tumor infiltration. Although a positive biopsy result must be accepted as proof of bone marrow infiltration, our results indicate that a negative biopsy does not exclude tumor involvement. In all 4 patients with infiltration suspected on MRI or scintigraphy results but with normal findings or reactive changes in the first blind biopsy, blind rebiopsy or guided rebiopsy confirmed the results of the imaging methods. In both patients evaluated at autopsy the preceding MRI and scintigraphy results were confirmed completely, although in both of these patients antemortem biopsy had indicated different findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance imaging provides three-dimensional images of the heart with good spatial and temporal resolution. Therefore, right and left ventricular function can be assessed without assumptions regarding ventricular morphology. Depiction of intracardiac blood flow with gradient echo sequences permits estimation of the severity of valvular regurgitation. Using improved paramagnetic contrast media magnetic resonance imaging may be able to directly visualize regions of ischemic myocardium. Real-time imaging of the heart will be possible using echo planar techniques. Although quantification of cardiac parameters by MRI is still mainly a research tool, clinical applications will emerge in the near future.

Non-invasive detection of stenotic lesions of the renal arteries remains an important clinical problem. Recent advances in magnetic resonance angiography represent a significant progress towards achieving non-invasive diagnosis of vascular diseases. The purpose of this study was to evaluate the possibilities of assessment of renal artery stenosis with commonly available hard- and software equipment. Imaging of renal arteries was performed with a ECG-gated fast multiphase gradient echo sequence which allows production of a series of images in different heart phases. Examinations were performed in 15 healthy volunteers and in 12 patients with angiographically verified renal artery stenosis. In 10 patients additional dynamic studies with fast imaging during short breath-holding periods after administration of gadolinium-DTPA served for the assessment of renal perfusion. A superconducting system operating at 1.5 T was used to produce gradient echo sequences with small flip angles and dephasing gradients of constant amplitude. To find the optimal imaging method for depiction of the renal arteries the following parameters were systematically varied: respiratory gating, resolution, number of excitations, slice thickness, phase encoding direction, rephasing gradients, flip angle and echo time. A good visualization of the vessels was always possible and using the best parameter combination even the narrowed lumen could be assessed in some cases. With this technique or with gadolinium-enhanced dynamic studies the perfusion of the kidneys can be demonstrated. However, quantitation of the stenosis or quantitation of renal perfusion was not possible; even the depiction of the stenotic lesion was successful only in half of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study was to evaluate the diagnostic information that may be obtained in patients with atrial septal defect (ASD) and/or with anomalous pulmonary venous return using spin echo and gradient echo magnetic resonance imaging (MRI). The interatrial septum and pulmonary veins were studied in 31 patients and in 16 healthy volunteers. In all patients cardiac anatomy and dilatation due to right-sided volume overload was well depicted. In 87% of the patients examined by spin echo technique and in 100% of the patients examined by gradient echo technique the defect was reliably documented. All cases of anomalous pulmonary venous return were shown. MRI diagnosis of ASD was improved by combined use of spin echo and gradient echo techniques. The new MRI sequence was particularly helpful in patients with small ASDs and anomalous pulmonary venous return.