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The introduction of coronary CT angiography (cCTA) has reinvigorated the debate whether management of patients with suspected coronary artery disease (CAD) should be primarily based on physiological versus anatomical testing. Anatomical testing (i.e., cCTA or invasive catheterization) enables direct visualization and grading of coronary artery stenoses but has shortcomings for gauging the hemodynamic significance of lesions for myocardial perfusion. Conversely, rest/stress myocardial perfusion imaging (MPI) has been extensively validated for assessing the clinical significance of CAD by demonstrating fixed or reversible perfusion defects but has only limited anatomical information. There is early evidence that contrast medium enhanced dual-energy cCTA (DECT) has potential for the comprehensive analysis of coronary artery morphology as well as changes in myocardial perfusion. DECT exploits the fact that tissues in the human body and iodine-based contrast media have unique absorption characteristics when penetrated with different X-ray energy levels, which enables mapping the iodine (and thus blood) distribution within the myocardium. The purpose of this communication is to describe the practical application of this emerging technology for the comprehensive diagnosis of coronary artery disease in the context of the currently used tomographic imaging modalities (cCTA, nuclear MPI, MR MPI). [ABSTRACT FROM AUTHOR]

This study investigated the discriminatory value of quantitative atherosclerotic plaque markers derived from coronary computed tomography angiography (cCTA) in patients with first acute coronary syndrome (ACS) compared with patients with stable coronary artery disease (CAD). Forty patients (56.9 ± 9.3 years, 55% men) admitted with their first ACS and Framingham risk score-matched controls with stable CAD were retrospectively analyzed. All patients had undergone cCTA followed by invasive coronary angiography. Total plaque volume, calcified and noncalcified plaque volumes, plaque burden (in %), remodeling index, lesion length, presence of napkin-ring sign, segment involvement score, and segment stenosis score were derived from cCTA and compared between both groups on a per-lesion and per-patient level. Patients with ACS showed a significant higher number of obstructive CAD and higher values for segment stenosis score, segment involvement score, noncalcified plaque volume, lesion length, and remodeling index than the stable angina group (all p <0.05). On a per-lesion level, culprit lesions had significantly higher values for plaque burden, total plaque volume, noncalcified plaque volume, remodeling index, lesion length, and prevalence of napkin-ring sign in comparison to nonculprit lesions (all p <0.05). On receiver-operating characteristics (ROC) analysis, a stepwise model demonstrated incremental discriminatory power for identifying ACS both per-patient (area under the curve 0.92, p <0.0001) as well as per-lesion (area under the curve 0.88, p <0.0001). cCTA-derived culprit plaque markers show discriminatory value both on a per-patient and per-lesion level. A combination of markers added to the Framingham risk score yields the greatest discriminatory ability., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: To evaluate quantitative markers derived from coronary CT angiography (coronary CTA) for the prediction of major adverse cardiac events (MACE)., Materials and Methods: Pooled data from two centers in the US and Europe were retrospectively analyzed. Forty-six patients (65.5 ± 8.1 years, 62% male) with suspected coronary artery disease (CAD) who had undergone dual-source CCTA and had experienced MACE within 12 months were included and compared to a Framingham risk score matched cohort (n = 46) without MACE. Various quantitative markers derived from coronary CTA were compared between both groups: Total plaque volume (TPV), calcified and non-calcified plaque volumes (CPV and NCPV), plaque burden (%), remodeling index, lesion length, presence of Napkin-ring sign, segment involvement score (SIS), and segment stenosis score (SSS). Discriminatory power of these markers for predicting MACE was assessed., Results: Patients with MACE had significantly more obstructive CAD with higher plaque burden, SSS, and SIS (all p < 0.05) compared to controls. MACE-related lesions showed higher median TPV (122.6 mm 3 vs. 76.3 mm 3 ), NCPV (67.3 mm 3 vs. 56.1 mm 3 ), plaque burden (66.3% vs. 44.9%), greater lesion length (23.1 mm vs. 19.2 mm), and higher prevalence of Napkin-ring sign (63% vs. 32%) (all p < 0.05). On multivariable analysis, odds ratios (OR) for MACE on a per-patient level were 1.07 for plaque burden (p = 0.0002) and 1.13 for SSS (p = 0.049). On a per-lesion basis OR for lesion length was 1.05 (p = 0.042), 1.03 for plaque burden (p = 0.018), 1.28 for remodeling index (p = 0.026), and 1.68 for the Napkin-ring sign (p = 0.031). At receiver operating characteristics analysis a combination of markers (Framingham risk score + Napkin-ring sign + lesion length + remodeling index) showed the highest predictive value for MACE (AUC 0.92, p = 0.013)., Conclusion: Coronary CTA-derived markers portend predictive value for MACE on a per-patient (plaque burden and SSS) and per-lesion level (lesion length, plaque burden, remodeling index, and Napkin-ring sign). A combination of markers added to the Framingham risk score has the highest predictive power., (Copyright © 2016 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.)

Objective: To evaluate quantitative markers derived from coronary CT angiography (coronary CTA) performed prior to percutaneous coronary intervention (PCI) with stent placement for predicting in-stent restenosis (ISR) as defined by quantitative coronary angiography (QCA)., Materials and Methods: We retrospectively analyzed the data of 74 patients (60 ± 12 years, 72% male) who had undergone dual-source coronary CTA within 3 months prior to a PCI procedure that included stent placement. Quantitative markers of the target vessel were derived from coronary CTA: Total plaque volume (TPV), calcified and non-calcified plaque volumes (CPV and NCPV), plaque burden (PB in %), remodeling index (RI), and lesion length (LL). Marker performance for predicting ISR, as defined by QCA at follow-up, was assessed., Results: Twenty-one of 74 stented lesions showed ISR on follow-up (mean 616 ± 447 days). When comparing stent length and LL in patients with ISR, a trend towards less complete stent coverage of the target lesion was observed in cases with ISR (17/21 vs. 4/53 cases, p = 0.07). In multivariate analysis (corrected for dyslipidemia), the following markers showed predictive value for ISR (odds ratio [OR]): NCPV (OR 1.08, p = 0.045), LL (OR 1.38, p = 0.0024), and RI (OR 1.13, p = 0.0019). Sensitivity and specificity for ISR were: NCPV 65% and 80%, LL 74% and 74%, and RI 71% and 78%. At receiver-operating characteristics analysis, NCPV (0.72, p = 0.001), LL (0.77, p < 0.0001), and RI (0.79, p < 0.0001) showed discriminatory power for predicting ISR. A combination of these markers showed incremental predictive value (AUC 0.89, p < 0.0001) with sensitivity and specificity of 90% and 84%, respectively., Conclusion: Coronary CTA-derived NCPV, LL, and RI portend predictive value for ISR with incremental predictive value when combining these parameters., (Copyright © 2016 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.)

On a subcellular level, atherogenesis is characterized by the translocation of proatherogenic lipoproteins into the arterial wall. An inflammatory response involving complex repair mechanisms subsequently causes maladaptive vascular changes resulting in coronary stenosis or occlusion. The chronology of the underlying processes occurring from atherosclerosis to myocardial ischemia affect the selection and interpretation of diagnostic testing. An understanding of the ischemic cascade, atherosclerosis, coronary remodeling, plaque morphology, and their relationship to clinical syndromes is essential in determining which diagnostic modalities are useful in clinical practice., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Unlabelled: Transient ischemic dilation (TID) in the setting of abnormal stress-rest cardiac SPECT myocardial perfusion imaging (MPI) has been linked with increased cardiovascular risk. However, the significance of TID in the setting of an otherwise normal SPECT MPI study has not been clearly established. In this study, cardiac CT was used to evaluate the prevalence of atherosclerotic lesions and the severity of coronary artery stenosis in patients with TID of the left ventricle with or without associated myocardial perfusion defects on SPECT MPI., Methods: The study population consisted of 1,553 consecutive patients who had undergone both cardiac CT and SPECT MPI within 1 mo between January 1, 2006, and September 1, 2011. Patients included in the study group had a pathologic TID value defined as ≥1.18 for men and ≥1.22 for women. Coronary CT angiography was used to evaluate each coronary segment for the presence and composition of atherosclerotic plaque and the degree of coronary stenosis. TID-positive patients were compared with a 2:1 risk-factor-matched-pair control cohort without TID., Results: TID was identified in 30 patients who were compared with TID-negative risk-factor-matched controls (n = 60). When compared with the TID-negative control cohort, TID-positive patients had no significant differences in the presence and extent of atherosclerosis, the degree of coronary artery stenosis, or the calcium score at cardiac CT. Similarly, there were no significant differences in these CT measures in TID-positive patients with a normal perfusion study (n = 20) when compared with TID-negative patients with a normal perfusion study (n = 48). In addition, there was no significant difference in the incidence of major adverse cardiac events when comparing both the TID-positive patients and the TID-negative control cohort and when comparing patients who were TID-positive with normal perfusion with patients who were TID-negative with normal perfusion., Conclusion: The presence of TID with an otherwise normal SPECT MPI study does not translate into a greater extent of coronary artery disease as assessed by cardiac CT or increased risk for future major adverse cardiac events., (© 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)

Purpose: We compared cost-effectiveness and potential lifetime benefits of using dual-energy computed tomography (DECT) for myocardial perfusion assessment instead of single photon emission computed tomography (SPECT) for the workup of coronary artery disease (CAD)., Materials and Methods: A decision and simulation model was developed to estimate cost and health effects of using DECT myocardial perfusion imaging instead of SPECT for identifying patients in need of invasive imaging and possible revascularization. The model was based on the performance indices of stress/rest DECT compared with stress/rest SPECT for detecting myocardial perfusion deficits in 50 patients (mean age 61±10 years) with CAD. Stress/rest perfusion and delayed enhancement cardiac MRI served as reference standard. For DECT a reimbursement of US$1700 was assumed but costs of cardiac MRI were not included in the model. All other actual healthcare costs in these patients were derived from MUSC's hospital billing system., Results: Compared with cardiac MRI, DECT (versus SPECT) had 90% (85%) sensitivity and 71% (58%) specificity for identifying patients with obstructive CAD. Compared with the no imaging and no treatment strategy, routine SPECT gained 13.49 quality-adjusted life-years (QALYs) with an incremental cost-effectiveness ratio (ICER) of US$3557 (in 2010) per QALY. In comparison, DECT ICER was lower (US$3.191 per QALY, p=0.0002) and an additional 0.64 QALYs was obtained (total of 14.13 QALYs) if compared with the SPECT strategy as well as the no imaging and no treatment strategy., Conclusion: Using DECT as the first-line imaging test for myocardial perfusion for the workup of patients with CAD has the potential to provide gains in QALYs, while lowering costs if compared to routine myocardial perfusion SPECT., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

Background: The performance of dual-energy CT (DECT) for the detection of myocardial blood volume deficits has not systematically been compared with single-energy CT (SCT) spectra., Objective: We evaluated the accuracy for detection of myocardial blood volume deficits in DECT and SCT compared with 99m-Tc-Sestamibi-SPECT (single-photon emission CT) during rest and stress., Methods: 47 patients underwent rest/stress SPECT myocardial perfusion imaging and cardiac DECT on a dual-source CT scanner. The A- and B-tubes were operated with 140 kV and 80 kV/100 kV, respectively. DECT raw data were reconstructed by (1) only using high-energy (140 kV) CT spectra, (2) only using low-energy (80 kV/100 kV) CT spectra, (3) merging data (30% low- and 70% high-energy CT spectra), and (4) DECT-based iodine maps. Two independent, blinded observers analyzed all CT data according to each of the 4 reconstruction strategies for myocardial blood volume deficits., Results: Specificity and positive predictive values were relatively similar between the 4 reconstruction strategies, with highest specificity (98%) of SCT datasets based on 140 kV for mixed perfusion deficits seen on SPECT. DECT iodine maps showed highest sensitivity, negative predictive value, and accuracy of 91%, 97%, and 93%, respectively, for mixed perfusion deficits. Analysis with receiver operating characteristics showed highest area under the curve values (0.84-0.93) with the use of DECT iodine maps in the detection of purely fixed and mixed perfusion deficits., Conclusion: DECT iodine maps show superior performance for the detection of fixed and mixed perfusion deficits compared with SCT spectra., (Copyright © 2011 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.)

Recent research suggests that multidetector-row CT may have potential as a standalone modality for integrative imaging of coronary heart disease, including the assessment of the myocardial blood supply. However, the technical prerequisites for volumetric, time-resolved imaging of the passage of a contrast medium bolus through the myocardium have only been met with latest generation wide-detector CT scanners. Second-generation dual-source CT enables performing electrocardiographic (ECG)-synchronized dynamic myocardial perfusion imaging by a dedicated "shuttle" mode. With this acquisition mode, image data can be acquired during contrast medium infusion at 2 alternating table positions with the table shuttling back and forth between the 2 positions covering a 73-mm anatomic volume. We applied this acquisition technique for detecting differences in perfusion patterns between healthy and diseased myocardium and for quantifying myocardial blood flow under adenosine stress in 3 patients with coronary heart disease. According to our initial experience, the addition of adenosine stress volumetric dynamic CT perfusion to a cardiac CT protocol comprising coronary artery calcium quantification, prospectively ECG-triggered coronary CT angiography, and delayed acquisition appears promising for the comprehensive assessment of coronary artery luminal integrity, cardiac function, perfusion, and viability with a single modality., (Copyright 2010 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.)

To evaluate the performance of dual-energy computed tomography (CT) for integrative imaging of the coronary artery morphology and the myocardial blood supply, 36 patients (15 women, mean age 57 +/- 11 years) with equivocal or incongruous single photon emission CT (SPECT) results were investigated by a single-contrast medium-enhanced, retrospectively electrocardiographic-gated dual-energy CT (DECT) scan with simultaneous acquisition of high and low x-ray spectra. Thirteen patients subsequently underwent invasive coronary angiography (ICA). The DECT data were used to reconstruct anatomic coronary CT angiographic images and to map the myocardial iodine distribution within the left ventricular myocardium. Two independent observers analyzed all DECT studies for stenosis and myocardial iodine defects. A segmental comparison was performed between the stress/rest SPECT perfusion defects and DECT iodine defects and between the ICA and coronary CT angiographic findings for stenosis. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were estimated, along with the kappa statistics. Overall, DECT had 92% sensitivity and 93% specificity, with 93% accuracy for detecting any type of myocardial perfusion defect seen on SPECT. Contrast defects at DECT correctly identified 85 (96%) of 89 fixed and 60 (88%) of 68 reversible myocardial perfusion defects. The interobserver agreement was very good (weighted kappa = 0.87). Compared with ICA, coronary CT angiography had 90% sensitivity, 94% specificity, and 93% accuracy for the detection of >50% stenosis. In conclusion, our initial experience suggests that DECT, as a single examination, might be promising for the integrative analysis of the coronary artery morphology and the myocardial blood supply and is in good agreement with ICA and SPECT.

Objective: The purpose of this study was to examine the relation between the coronary CT angiographic findings of calcified and noncalcified plaque burden and stenosis severity and the myocardial perfusion imaging finding of ischemia., Materials and Methods: Seventy-two patients (41 men, 31 women; mean age, 56 years) underwent coronary CT angiography and stress-rest SPECT myocardial perfusion imaging. Calcium scoring was performed. Coronary CT angiograms were analyzed for stenosis and noncalcified or mixed plaque. A plaque analysis tool was used to calculate the volume of noncalcified plaque components. SPECT images were analyzed for perfusion defects. Data were analyzed per patient and per vessel., Results: A total of 53 purely noncalcified, 50 mixed, and 201 purely calcified plaques were detected. Forty-five stenoses were rated > or = 50%, 19 of those being > or = 70%. Myocardial perfusion imaging depicted perfusion defects in 37 vessels (13%) in 24 patients (18 reversible, 19 fixed defects). Vessels with > or = 50% stenosis had significantly (p = 0.0009) more perfusion defects in their supplied territories (11 with, 22 without perfusion defects) than did vessels without significant lesions (26 with, 229 without perfusion defects). In vessel-based analysis, the sensitivity of coronary CT angiography in prediction of any perfusion defect on myocardial perfusion images was 30% with 91% specificity, 33% positive predictive value, and 90% negative predictive value. Between vessels with and those without perfusion defects, there was no significant difference in Agatston or calcium volume score (p = 0.25), but there was a significant difference in noncalcified plaque volume (44 +/- 77 vs 19 +/- 58 mm(3); p = 0.03). Multiple stepwise regression analysis showed noncalcified plaque volume was the only significant predictor of ischemia (p = 0.01)., Conclusion: At coronary CT angiography, noncalcified plaque burden is a better predictor of the finding of myocardial ischemia at stress myocardial perfusion imaging than are calcium score and degree of stenosis.

The clinical applicability of a method for quantifying pericardial effusion (PE) was studied. The pericardial and cardiac volumes were determined from border tracings of 2-dimensional echocardiograms fitted with 3-dimensional disk models. The PE volume was the difference between pericardial and cardiac volumes. A phantom study included 54 cases with different volumes and viewing geometry showed a correlation coefficient r = 0.98 and an accuracy of +/- 6%. A clinical study included 20 cases showing that the estimated PE volume correlated well with that drained surgically (between 100 mL and 1200 mL): y = 0.81 x + 120 mL; r = 0.91, P <.0001. The percent error, determined by the standard error of the estimate (114 mL) over mean (548 mL), was 20%. Intraobserver variability was 4% and interobserver variability 6%. The 3-dimensional disk method provides a quick and convenient way to quantify PE from 2-dimensional echocardiograms with acceptable accuracy and reproducibility.

Left ventricular ejection fractions (LVEF) are routinely measured and result in critical decision-making algorithms in cardiology. This study was conducted to compare the accepted standard two-dimensional (2-D) echocardiogram ejection fraction (EF(ECHO)) with single photon emission computed tomography rest ejection fraction (EF(SPECT)). Data were acquired and analyzed from 51 inpatients. EF(ECHO) was obtained using modified Simpson's rule in the four-chamber apical view, and gated EF(SPECT) was computed by an automated method (Siemens ICON software). Comparison between EF(ECHO) and EF(SPECT) was done by linear regression, Bland-Altman, and receiver operator characteristic (ROC) analyses. Linear regression analysis revealed EF(SPECT) = 1.12 x EF(ECHO) - 3.6%, r = 0.93, n = 51, P < 0.0001. Bland-Altman analysis showed that the limits of 95% confidence for the difference between EF(SPECT) and EF(ECHO) were - 12% to 18%. Ninety-eight percent of the datapoints were within the limits of confidence. The ROC analysis showed that the sensitivity and specificity for detecting abnormal EF (< or = 50%) were 85% and 86% with EF(SPECT), and 91% and 90% with EF(ECHO). This study showed good correlation as well as agreement between SPECT and two-dimensional echocardiograms in measuring EF.

Background: Echocardiographic automated border detection (ABD) provides on-line, beat-to-beat estimation of left ventricular (LV) ejection fraction (EF). Sensitivity and specificity of using ABD-EF for diagnosing LV dysfunction in routine clinical situations have not been previously studied., Hypothesis: Analysis of ABD-EF data based on receiver operating characteristic (ROC) should provide useful information about sensitivity and specificity for clinical diagnosis of LV function based on ABD-EF., Methods: The study group included 50 consecutive patients with EF measured by both ABD and radionuclide ventriculography (RVG). ABD-EF was recorded for 25 consecutive heart beats in the apical four-chamber view. Data were analyzed statistically by linear regression, Bland-Altman plot, and ROC. In ROC analysis, abnormal LV function was defined RVG-EF < or = 40%., Results: ABD and RVG showed a moderate correlation in the EF measurements: slope = 0.93, intercept = 17%, r = 0.79 (n = 50). Interbeat variability in ABD was diminished by averaging consecutive beats; standard error of estimate (SEE) decreased from 15.6% without averaging to 12.5% with 25-beat averaging. Bland-Altman analysis indicated that ABD-EF compared unfavorably with RVG-EF, with limits of agreement from -11% to 39%. ABD-EF showed a systematic overestimation (p < 0.005), which was compensated by increasing the threshold for abnormal ABD-EF to 56%. With the optimized threshold, ABD-EF provided 89% sensitivity and 89% specificity (85% overall diagnostic accuracy) for diagnosing abnormal LV function., Conclusion: This study explored the limitations of on-line echocardiographic measurement of EF in a clinical setting and provided useful data for assessing interbeat variability, sensitivity, and specificity.

This study presents a novel approach to modeling the electrocardiogram (ECG): the Gaussian pulse decomposition. Constituent waves of the ECG are decomposed into and represented by Gaussian pulses using an iterative algorithm: the chip away decomposition (ChAD) algorithm. At each iteration, a nonlinear minimization method is used to fit a portion of the ECG waveform with a single Gaussian pulse, which is then subtracted from the ECG waveform. The process iterates on the resulting residual waveform until the normalized mean square error is below an acceptable level. Three different minimization methods were compared for their applicability to the ChAD algorithm; the Nelder-Mead simplex method was found to be more noise-tolerant than the Newton-Raphson method or the steepest descent method. Using morphologically different ECG waveforms from the MIT-BIH arrhythmia database, it was demonstrated that the ChAD algorithm is capable of modeling not only normal beats, but also abnormal beats, including those exhibiting a depressed ST segment, bundle branch block, and premature ventricular contraction. An analytical expression for the spectral contributions of the constituent waves was also derived to characterize the ECG waveform in the frequency domain. The Gaussian pulse model, providing an intuitive representation of the ECG constituent waves by use of a small set of meaningful parameters, should be useful for various purposes of ECG signal processing, including signal representation and pattern recognition.

A phenomenological model of the cardiopulmonary circulation is developed with a focus on the interaction between the right heart and the left heart. The model predicts the hemodynamic consequences of changing circulatory parameters in terms of a broad spectrum of pressure and flow waveforms. Hemodynamics are characterized by use of an electrical analog incorporating mechanisms for transseptal pressure coupling, pericardial volume coupling, intrathoracic pressure, and baroreflex control of heart rate. Computer simulations are accomplished by numerically integrating 28 differential equations that contain nonlinear and time-varying coefficients. Validity of the model is supported by its accurate fit to clinical pressure and Doppler echocardiographic recordings. The model characterizes the hemodynamic waveforms for mitral stenosis, mitral regurgitation, left heart failure, right heart failure, cardiac tamponade, pulsus paradoxus, and the Valsalva maneuver. The wave shapes of pulmonary capillary wedge pressure under the above conditions are also accurately represented. Sensitivity analysis reveals that simulated hemodynamics are insensitive to most individual model parameters with the exception of afterload resistance, preload capacitances, intrathoracic pressure, contractility, and pericardial fluid volume. Baseline hemodynamics are minimally affected by transseptal coupling (up to 2%) and significantly affected by pericardial coupling (up to 20%). The model should be useful for quantitative studies of cardiopulmonary dynamics related to the right-left heart interaction under normal and disease conditions.

Considers the quantification of percent diameter stenosis in digital coronary arteriograms of low spatial resolution. To improve accuracy and reproducibility an edge-preserving smoothing method, called the directional low-pass filter (DLF), was developed to suppress quantum noise by averaging image intensity in a direction parallel to the vessel border. Accuracy of stenosis quantification was assessed by using stenosis phantoms. The standard error of the estimate (SEE) was 0.76 pixel-length (p) without spatial filtering and further reduced to 0.50 p by DLF; the average deviation as a measure of the regularity of border definition was also reduced by DLF from 1.00 to 0.68 p (n=50, P<0.001). It was shown that the DLF outperformed the conventional moving average filter and median filter. Reproducibility in terms of intraframe variability was assessed by using coronary arteriograms obtained from 10 patients. Intraframe variability of the percent stenosis measurements was reduced from 3.5% to 2.9% by DLF (n=10, P<0.005). An analysis of variance showed, however, that the interframe variability cannot be reduced by any of the spatial filters under investigation. The result of this study has provided a guideline for angiographically based quantification of percent stenosis under limited imaging resolution and suggests a new method for improving accuracy and reproducibility by directional low-pass filtering.

The resting and exercise hemodynamics in seven patients with pericardial constriction and in one patient with cardiac amyloidosis are described. Equalization of left and right heart diastolic filling pressures was observed in all cases, both at rest and during exercise. This hemodynamic response, although typical, should not be considered pathognomonic of pericardial constriction.

In three cases of acute pericarditis with pericardial effusion, the presence of fibrous strands within the fluid-filled pericardial cavity was demonstrated by M-mode and cross-sectional echocardiography. Pericardiocentesis proved difficult in all three. No patient progressed to constrictive pericarditis.