Abstract 2938: Progressive Borderzone Myocardial Dyssynchrony in an Experimental Model of Apical Myocardial Infarction: A Real-Time Three-Dimensional Echocardiographic Study
Background: Expansion of the hypocontractile borderzone myocardium (BZM) has been repeatedly implicated in the pathogenesis of congestive heart failure following myocardial infarction (MI). We hypothesize that longitudinal quantification of BZM dyssynchrony following myocardial infarction is possible using real-time three-dimensional echocardiography (rt-3DE).
Methods: Rt-3DE was perfomed in 9 male sheep before, immediately after and 10 weeks after anterior MI. Manual endocardial tracing was perfored in 8 long-axis planes for each image set. Global and regional volume curves were calculated with Tomtec CardioView software. End systolic delay (ESD) for each of the 16 left ventricular segments was defined with reference to the first segment to reach end systole. The BZM was defined as the six segments adjacent to the apical infarct zone. The average ESD of the 6 BZM segments, as well as the systolic dyssynchrony index (SDI) where the SDI was defined as the STDEV of the ESD for the BZM segments, was calculated for each subject before MI, immediately after MI and 10 weeks after MI.
Results: EF decreased significantly (p < 0.05) between each time point. ESD increased significantly (p < 0.001) immediately after MI and during the 10 week follow-up interval. SDI increased significantly (p < 0.05) during the 10 week follow-up interval. QRS widening did not occur in any subject.
Conclusion: Rt-3DE is useful for quantifying regional dyssynchrony. The BZM became increasingly hypokinetic with respect to normal myocardium following anterior MI. Additionally, the BZM itself developed dyssynchrony over the follow-up interval. Both phenomena occured in the absence of QRS widening. Rt-3DE may help identify candidates for BZM resynchronization and may facilitate image guided BZM resynchronization therapy.