The Use of Myocardial Deformation Imaging

Overview

Myocardial deformation imaging allows analysis of myocardial viability in ischemic left ventricular dysfunction. This study will evaluate the predictive value of myocardial deformation imaging for improvement in cardiac function after revascularization therapy in comparison to contrast-enhanced cardiac magnetic resonance imaging (ceMRI). In 55 patients with ischemic left ventricular dysfunction, myocardial viability was assessed using pixel-tracking-derived myocardial deformation imaging and ceMRI to predict recovery of function at 9±2 months follow-up. For each left ventricular segment in a 16-segment model peak systolic radial strain will be determined from parasternal 2D echocardiographic views and the amount of late hyperenhancement (LE) and maximal thickness of myocardial tissue without LE using ceMRI. The hypothesis is that compared with segments showing functional improvement, those that failed to recover had lower radial strain and lower thickness without LE and higher LE.

Between August 2004 and June 2006 195 patients with ischemic left ventricular dysfunction underwent MRI for the definition of myocardial viability. Onehundred-ten patients with non-ischemic cardiomyopathy or acute coronary syndromes were excluded from the study to avoid possible acute ischemia or stunning. Within the 85 patients with chronic ischemic heart disease, six patients refused participation in this study and five patients had echocardiographic windows insufficient for participation. Within the remaining 74 patients 55 patients underwent revascularization and 19 had no revascularization. These 55 patients form our study group! Functional recovery will be assessed using echocardiographic images before and 9±2 months after revascularization with a Vivid Seven System (GE Vingmed, Horton, Norway). Parasternal long-axis and short-axis views at basal, midventricular and apical levels, as well as 3 standard apical views (4 chamber, 2 chamber, and long axis) have been acquired (frame rate 56 to 92 frames/s). Segmental wall motion will be determined using the following score: 1=normokinetic, 1.5= mildly hypokinetic, 2= moderately or severely hypokinetic, 3= akinetic, or 4= dyskinetic. A segment is considered to demonstrate functional improvement during follow-up if it improved by at least 1 grade. Global functional recovery was considered in case of an increase in ejection fraction\>5% at follow-up. The three acquired parasternal short axis views will be analysed with the aid of a dedicated software package (EchoPAC BT 05.2, GE Vingmed, Horton, Norway). This system allows analysis of peak systolic circumferential and radial strain from short axis views based on detection of natural acoustic markers. The system calculates mean strain values for whole predefined LV segments, including all myocardial layers from the endocardium to epicardium. All patients underwent cMRI within a few hours of the baseline echocardiographic study on a 1.5-T whole-body MR scanner (Intera, Best, Philips, the Netherlands). The assignment to a hyperenhancement category reflects the extent of hyperenhancement within each segment by visual assessment considering a 5-group scale: 0% hyperenhancement (group 1), 1 to 25% hyperenhancement (group 2), 26 to 50% hyperenhancement (group 3), 51 to 75% hyperenhancement (group 4) and 76 to 100% hyperenhancement (group 5). In addition, the maximal thickness of myocardial tissue without late hyperenhancement will be determined for each LV segment. This is considered to be a parameter of the remaining viable myocardium.