Cardiac functional remodeling indices in acute experimental infarction under the influence of inotropic agents

Abstract

To study the time course changes of cardiac left ventricular (LV) geometry in acute experimental infarction by coronary artery ligation under the influence of inotropic agents. Methods: Cardiac remodelling indices depicted in the LV functional geometry such as lengths of LV long axis (LongAxL) and short axis (ShortAxL), their fractional shortening (LongAxFS and ShortAxFS) and a new recommended “function index” (FI=LongAxFS/ShortAxFS) were monitored echocardiografically in 20 anesthetized swines. Measurements were obtained before (control) and during a 75 min period following left anterior descending coronary artery (LAD) ligation. Results: In the initial 11 animals studied ejection fraction (EF), LongAxFS and FI decreased significantly below control values all over the 75 min period after LAD ligation and ShortAxFS increased progressively above control values and maximized at the 45th min. In order to investigate the underlying mechanism of these changes, LAD ligation was performed under dobutamine infusion in the remaining 9 animals: EF, LongAxFS and FI failed initially into a decline and EF returned to control values at the 45th min and LongAxFS, FI at the 75th min. ShortAxFS remained unchanged vs control under dobutamine throughout the 75 min period. The changes in FI obtained under dobutamine infusion after ligation were best bivariately correlated (r=0.72, p<0.001) and independently associated in a multiple regression model (b=0.45, p<0.001) with the changes in EF. Conclusion: The echocardiography remodelling adaptation of LV functional geometry observed in acute experimental infarction consists in deterioration contractility across the LV Long Axis and in compensatory increase contractility of the Short Axis. Dobutamine infusion at a rate of 5 μg/kg/min was correcting both EF and LongAxFS and eliminating compensatory ShortAxFS changes to prevent the acute, unfavourable  remodelling of the LV. Furthermore as manifested by all indices in this study, the new “function index” FI in early post myocardial infarction period predicts the complex LV functional geometry, cardiac remodelling and EF changes