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The determination of myocardial viability is crucial in patients with left ventricular dysfunction resulting from acute myocardial ischemia or chronic coronary artery disease. Viable myocardium will most likely benefit from revascularization procedures. However, the revascularization of scar tissue will not lead to improvement of ventricularfunction andfurthermore bears unnecessary riskfor the patient. Currently, echocardiographic and radionuclide techniques are the most established methods for the assessment of presence and extent of viable myocardium. Magnetic resonance imaging (MRI) also provides multiple approaches for determining viability of acute ischemically injured and hibernating myocardium. MRI can assess contractile reserve in a manner similar to echocardiography. Additionally, contrast-enhanced MRI can characterize myocardial ischemic injury, including the ability to discriminate viable from nonviable zones. Several new contrast media have been introduced for this purpose. This review addresses the progress toward the goal of defining myocardial viability based on MR techniques and focuses on the current and future role of MR in the assessment of viable myocardium.

Background Image-guided endovascular interventions have gained increasing popularity in clinical practice, and magnetic resonance imaging (MRI) is emerging as an attractive alternative to X-ray fluoroscopy for guiding such interventions. Steering catheters by remote control under MRI guidance offers unique challenges and opportunities. Methods In this review, the benefits and limitations of MRI-guided remote control intervention are addressed, and the tools for guiding such interventions in the magnetic environment are summarized. Designs for remote control catheter guidance include a catheter tip electromagnetic microcoil design, a ferromagnetic sphere-tipped catheter design, smart material-actuated catheters, and hydraulically actuated catheters. Remote control catheter guidance systems were compared and contrasted with respect to visualization, safety, and performance. Performance is characterized by bending angles achievable by the catheter, time to achieve bending, degree of rotation achievable, and miniaturization capacity of the design. Necessary improvements for furthering catheter design, especially for use in the MRI environment, are addressed, as are hurdles that must be overcome in order to make MRI guided endovascular procedures more accessible for regular use in clinical practice. Conclusions MR-guided endovascular interventions under remote control steering are in their infancy due to issues regarding safety and reliability. Additional experimental studies are needed prior to their use in humans.

Summary The purpose of this study was to 1) determine the threshold volume of coronary microemboli (

Methods In this study the HGF gene was injected intramyocardially in reperfused infarction (2 hr occlusion), for the purpose of evaluating this strategy as a therapeutic approach for protection from LV remodeling. MR imaging was performed at 3 days and 7–8 weeks on a 1.5-T MR clinical scanner (Philips Medical Systems). First pass perfusion, delayed contrast enhancement and cine MR imaging was used in the evaluation. Triphenyltetrazolium chloride (TTC) and histopathological (Masson's trichrome and Biotinylated Bandeiria simplicifolia isolectin B4) stains were utilized to quantify vascular density and myocardial viability. Results The peak signal intensity (SI), extents of hypoenhanced ischemic myocardium and max upslope data in the two groups were not significantly different at 3 days. At 7–8 weeks peak signal intensity was higher and maximum upslope data was steeper in treated animals compared to controls. The extent of hyperenhanced scar was significantly larger in control (13.2 ± 1.6% LV) compared with HGF treated (7.0 ± 0.5% LV) animals. TTC analysis also showed that the extent of scar tissue was significantly larger in control (12.0 ± 1.7%) compared with treated (6.6 ± 0.7% LV, P = 0.04) animals. There was no significant difference between the extent of hyperenhanced scar on MRI and TTC (P = 0.32). The infarction tended to be non-transmural with a residual thicker wall in treated compared with control animals both on MR images and TTC. Control animals showed evidence of LV remodeling, which was reflected by increased end systolic volumes and decline in ejection fraction. Treated animals showed a decrease from in end diastolic (2.15 ± 0.12 to 1.82 ± 0.12, P = 0.008) and end systolic (1.33 ± 0.07 to 1.00 ± 0.08, P = 0.001) volumes. They also showed increased ejection fraction (40.3 ± 1.3 to 45.7 ± 1.8, P = 0.001).

Background The NIH estimated that 7 million Americans suffer from coronary artery disease and ~500,000 patients die of heart attacks yearly. Jung et al found that the number of microemboli correlates with the size of myocardium at risk in patients with myocardial infarction [1]. Due to the population inhomogeneity it is difficult to grade and compare LV dysfunction in patients with acute microinfarct and large infarct caused by microemboli and LAD artery obstruction. The objectives of this study were to characterize and compare the effects of LAD occlusion/reperfusion and microvascular embolization on LV function using MRI.

Methods A hybrid X-ray and MRI system was used to catheterize the LAD in 6 pigs and deliver the embolic materials (40-120 μm, 250,000 count). The area at risk (AAR) was determined on first-pass perfusion (FPP) MRI before and after microembolization. Delayed enhancement (DE)-MRI and histochemical staining were used to visualize and measure microinfarcts. Analysis of longitudinal strain was performed on phase-contrast MRI and radial strain as well as global function on ssfp MRI using Segment http://seg ment.heiberg.se. Tagged MRI were analyzed to measure circumferential strain using HARP. The Student's t-test was used to determine if strain over the cardiac cycle differed between baseline, acute (1 h) and chronic phases (78 weeks).

Background Sheifer et al indicated that undetected infarction account for at least 20% of all infarctions and carry a prognosis as poor as detected ones [1]. Large myocardial infarction has been measured using both 3D and 2D delayed enhancement MRI, which was compared with histochemical staining [2]. The purpose of this MRI study was to 1) measure diffuse and large infarction size using delayed contrast enhanced 3D inversion recovery (IR) gradient echo (GRE) in beating and non-beating swine hearts and 2) compare the 3D measurements against 2D-IR GRE, histochemical staining and microscopic histopathology.