Wellbeing-of-The Right Heart Forecasts-The Fate-of-The Left Heart During Heart Attack

Abstract

Acute myocardial ischemia (aka heart attack) is one of the major causes of death or subsequent heart failure in surviving patients. Current triage and treatment strategies for heart attack mainly focused on the wellbeing of the left ventricle (LV) due to its obvious importance to survival, and completely ignored the other half of the heart: right ventricle (RV). Given the close proximity to the carnage, we wondered, what RV goes through during a heart attack. In this study, we observed the RV function and LV function simultaneously using pressure-volume loop method in a mouse model of acute myocardial ischemia and reperfusion. In young male mice (n=80), the left coronary artery was temporarily occluded for 30 min and released for 30 min before sacrifice. We observed a substantial RV functional deterioration during ischemia/reperfusion in some of the subjects with or without RV ischemia. Therefore, we formed two groups retrospectively among the subjects who had no myocardial ischemia in RV (including intraventricular septum) based on the changes in RV contractile function: group A (reduced by less than 10% from pre-ischemic baseline; n=9) and group B (reduced by more than 10%; n=10). In RV, systolic and diastolic functional parameters were significantly different between two groups at the end of the ischemia and also at the end of reperfusion (Figure, left panel; PRSW=Preload Recruitable Stroke Work, a load-independent ventricular systolic functional index). Arterial Elastance (Ea), an indicator of arterial resistance of pulmonary circulation, was significantly different between two groups. Arterio-ventricular coupling (AV coupling), an indicator of energy transfer efficiency between heart and vessel, did not differ between two groups. In LV, size of myocardial ischemic area did not differ between the two groups. LV systolic and diastolic functional parameters were not significantly different at the end of ischemia between two groups. However, a significantly better recovery of LV systolic and diastolic functional parameters and AV coupling were observed in group A compared to group B at the end of reperfusion (Figure, right panel). Ea, an indicator of arterial resistance of general circulation, did not differ between two groups. Our results indicated that: (1) RV can sustain damages from LV ischemia; and (2) a better preserved RV function indicates a better recovery of LV functions after a heart attack.