Background: In a pig model of subacute MI, left ventricular (LV) unloading using Impella increased myocardial perfusion in the infarcted tissue, but not in the border and non-ischaemic remote myocardium.
Hypothesis: Impella-mediated LV unloading results in reduced coronary flow in the normal myocardium due to coronary auto-regulation.
Methods: Naïve pigs (n=5) underwent LV unloading with Impella during simultaneous monitoring of the LV pressure–volume relationship and coronary flow and pressure.
Results: Impella full support increased mean arterial pressure (median: 92.94 mmHg versus 105.6 mmHg, p=0.0024) together with minimum coronary pressure (median: 77.25 mmHg versus 97.65 mmHg, p<0.001). End-systolic volume (median 50.00 ml versus 17.00 ml, p=0.0042), end-diastolic pressure (median 17.00 mmHg versus 8.00 mmHg, p<0.001) and heart rate (72 BPM versus 68 BPM, p<0.001) were decreased, suggesting efficient unloading of the LV in normal heart. Interestingly, both peak and minimum coronary flow were decreased by Impella. Calculated microvascular resistance was increased as a result of increased coronary pressure and reduced flow, but with no large change in right atrial pressure. Detailed analysis of coronary flow and pressure waves by wave intensity analysis revealed no significant change in coronary suction wave.
Conclusion: LV unloading using Impella reduced coronary flow in normal myocardium. Increased coronary pressure, reduced LV wall stress, and lack of significant changes in right atrial pressure and coronary suction wave strongly suggest the role of auto-regulation as a mechanism.