DETERMINATION OF GLOBAL FUNCTION AND REGIONAL MECHANICS OF DYNAMIC CARDIOMYOPLASTY USING MAGNETIC-RESONANCE-IMAGING

This study used tissue tagged magnetic resonance (MR) to assess region al strain and generate pressure-volume (PV) loops in a canine model of cardiomyoplasty (CMP). Three dogs with rapid ventricular pacing induc ed heart failure underwent dynamic CMP chronic cardiac assistance for 1 year. At the end of the study period, we performed a MR study with t he myostimulator ''on'' and ''off'' and recording of left ventricular (LV) pressure. We determined the short axis displacement (D) and maxim al and minimal principal strains (lambda(1) and lambda(2)) by quantita tive two-dimensional regional spatial modulation of magnetization visu alization utility image analysis. LV PV loops were generated by combin ing the LV volume data from the MR images with the LV pressure recorde d during imaging. Muscle stimulation produced a leftward shift of the LV PV loops in two of the three dogs, and an increase in LV peak press ure and dp/dt max. In contrast, short axis lambda(1) and lambda(2) did not change significantly (p = NS). D increased significantly in the a nterolateral, posterolateral, and posteroseptal regions (p < 0.05) but did not change for the septal region (p = NS). Flap stimulation augme nts LV function in the absence of short axis strain change; this sugge sts that dynamic CMP exerts its main action along the long axis of the heart.