Time course of hemodynamic changes in rats with healed severe myocardial infarction

Abstract

Male rats were monitored for 8 mo after severe myocardial infarction (MI) to chronicle hemodynamic and left ventricular (LV) functional changes. Blood pressure (BP), heart rate (HR), cardiac output index (CO), regional blood flow, and systemic vascular resistance (SVR) were measured with catheters and radiolabeled microsphreres at 4, 7, 10, 20, and 35 wk after coronary artery ligation (n = 10-16/group) or sham operation (control; n = 9-14/group). At 4 wk, 43 .+-. 1% of the LV circumference was scarred, peak LV BP, LV dP/dtmax, mean BP, SVR, and HR were 11-38% less than control (P < 0.05), and LV end-diastolic pressure (LVEDP) was increased by 313% (P < 0.05). Mean BP, LVEDP, LVBP, and LV dP/dtmax did not further deviate after 4 wk. However, CO and SVR changed progressivley and were 67 and 33%, respectively, of control by 35 wk (P < 0.05) when blood flow to stomach, small intestine, and kidney was 55, 38, and 27% of control. Lung and heart weights were significantly increased by 148 and 22% at 4 wk, and remained elevated, and lung dry weight-to-wet weight ratio was reduced at 7 and 10 wk. Thus the trajectory of rats with healed severe MI reflects progressive cardiac decompensation, cardiac output redistribution, and terminal heart failure.