Interregional differences in the systolic and diastolic response of nonischemic myocardium to remote coronary occlusion

Background: Previous work showed a twofold increase in stiffness of nonisch emic myocardium at the base during ischemia of the left anterior wall. Whet her the diastolic response of nonischemic myocardium to remote ischemia dep ends on the localization of the ischemic or the nonischemic area is unknown . Methods: In dogs with open chests, regional function in ischemic and nonisc hemic myocardium was assessed (sonomicrometry) before and 5 min after occlu sion of the left anterior descending coronary artery (LAD; n = 7) or the le ft circumflex coronary artery (LCX; n = 7). Results: In nonischemic myocardium at the base, left anterior descending an d left circumflex coronary artery occlusion both resulted in a twofold incr ease in chamber stiffness, whereas contractility and peak lengthening rate remained unchanged. In nonischemic myocardium of the posterior wall, left a nterior descending coronary artery occlusion resulted in a significant (P < 0.05 us, control, P < 0.05 vs. base) increase (mean +/- SD) in chamber sti ffness (25 +/- 6%), contractility (17 +/- 5%), and peak lengthening rate (2 8 +/- 6%). In nonischemic myocardium at the apex, left circumflex coronary artery occlusion resulted in a significant (P < 0.05 us. control, P < 0.05 vs. base) increase in chamber stiffness (15 +/- 5%), contractility (16 +/- 4%), and peak lengthening rate (19 +/- 6%). Conclusions: Stiffening of remote nonischemic myocardium occurs regardless of the localization of the ischemic and nonischemic area. The systolic and diastolic responses of nonischemic myocardium are not necessarily homogenou s but may vary among different regions.