Primary LV Unloading Improves Global and Regional Myocardial Blood Flow During Acute Coronary Occlusion: First In Vivo Study

Background: Left ventricular (LV) unloading reduces myocardial oxygen demand in acute myocardial infarction (AMI) and cardiogenic shock, yet its direct effects on myocardial blood flow during ischemia remain poorly defined. We evaluated the impact of primary LV unloading on global and regional myocardial blood flow and LV mechanics during coronary occlusion.

Methods: AMI was induced in Yorkshire pigs (n=3) via balloon occlusion of the left anterior descending artery in a hybrid PET/CT suite. Serial rubidium-82 PET imaging quantified global and regional myocardial blood flow at baseline, during occlusion, and during intervention. One animal received pharmacologic support with dobutamine and phenylephrine, while two animals underwent primary LV unloading with an Impella CP. LV volumes and function were assessed using intracardiac echocardiography with concurrent invasive hemodynamic measurements.

Outcome: Following LAD occlusion, PET-derived polar maps demonstrated a marked reduction in global and regional myocardial blood flow (MBF) across all coronary territories. Dobutamine modestly increased myocardial blood flow but was associated with increased LV volumes, whereas phenylephrine worsened myocardial perfusion. In contrast, primary LV unloading significantly increased both global and regional myocardial blood flow beyond ischemic baseline values while reducing LV volumes and filling pressures, despite persistent coronary occlusion. Rate–pressure product–corrected MBF analyses confirmed consistent perfusion improvement across LAD, LCX, and RCA territories with LV unloading. Notably, similar increases in MBF were observed at both P4 and P8 Impella flow settings, suggesting a robust unloading-mediated effect. Following coronary reflow, myocardial perfusion improved in both pharmacologic and unloading conditions; however, the magnitude and consistency of MBF recovery were greater with mechanical unloading. Collectively, these findings demonstrate a distinct and favorable myocardial perfusion profile with primary LV unloading compared with pharmacologic modulation during acute coronary occlusion (Figure1).

Conclusion: Primary LV unloading improves myocardial perfusion and ventricular loading conditions more effectively than inotropes or vasopressors during acute coronary occlusion. This study provides the first in vivo PET-derived demonstration of increased MBF during primary LV unloading, supporting LV unloading as a myocardial protective strategy in AMI and cardiogenic shock.