972-105 Afterload Reduction Selectively Improves Myocardial Deformation After Infarction in Adjacent Noninfarcted Regions

Abstract

left ventricular remodeling post-infarction (post-MI) is accompanied by persistent dysfunction in the non-infarcted adjacent region. Chronic afterload reduction (ALR) therapy has a salutary effect on post-MI remodeling. The relative contribution of mechanical unloading to this effect remains unclear. We hypothesized that improved adjacent (ADJ) region dysfunction contributes to the beneficial effect of ALR. We therefore studied myocardial deformation in ADJ and remote (REM) non-infarcted regions in 5 sheep two months after anteroapical infarction during control (C) and after nitroprusside infusion (NP). Using magnetic resonance tissue tagging and finite element analysis techniques, we measured deformation using the orthogonal principal strains, λl (1 + greatest systolic elongation), λ2 (1 - greatest systolic shortening), and β or angular deviation of λl from the radial direction. With NP. LV systolic pressure fell from 94 ± 9 to 69 ± 7 mmHg (p < 0.05) while end-diastolic pressure was unchanged, as measured by a high-fidelity catheter. Results (mean ± S.E.): REM deformation and its orientation were similar in C and NP In contrast: ADJλI ADJ λ2 ADJβ(°) C 1.06 ± 0.02 † 0.88 ± 0.01 † 45.6 ± 7.6 † NP 1.09 ± 0.03 † 0.83 ± 0.01 * † 25.8 ± 2.4 * † ANOVA P NS < 0.05 < 0.05 * p < 0.05 vs. Control † p < 0.05 REM vs. ADJ Thus in the ADJ regions, λl and λ2 were reduced compared to REM, and λ2 decreased after NP. denoting greater systolic shortening. The most important change with NP was the normalization of ADJ β, resulting in a greater contribution to pump function. In conclusion, improved mechanical function in the ADJ non-infarcted regions, particularly the orientation of principal strains, is an important determinant of the beneficial effect of ALR on post-MILV function.