Mechanical left ventricular unloading prior to reperfusion reduces infarct size in a canine infarction model

Abstract

We tested the hypothesis that unloading the left ventricle just prior to reperfusion provides infarct size reduction compared with left ventricular (LV) unloading postreperfusion and reperfusion alone. Twenty-four mongrel dogs were subjected to 2 hr of left anterior descending artery occlusion and 4 hr of reperfusion. A transvalvular (TV) left ventricular assist device (LVAD) was inserted just prior to reperfusion and maintained during the rest of the experiment (LV Assist Pre group). In the LV Assist Post group, the TV LVAD was inserted and activated just after reperfusion. A control group was subjected to reperfusion alone with a sham-TV LVAD. At baseline, the hemodynamic data were similar in the three groups. Myocardial infarct size expressed as percentage of area at risk was significantly reduced in the LV Assist Pre group compared to the control group (P = 0.011) and to the LV Assist Post group (P < 0.05). At 4 hr of reperfusion, transmural myocardial blood flow in the ischemic zone was slightly higher in the animals unloaded prior to reperfusion compared to controls and significantly higher than in the LV Assist Post group (P = 0.04). Postreperfusion end-diastolic wall thickness returned to baseline level in the TV LV Assist Pre group compared to both controls and TV LV Assist Post group. In these latter two groups, a significant increase in postreperfusion end-diastolic wall thickness and contraction band necrosis in the central ischemic zone correlated well with the degree of reperfusion injury. LV unloading prior to, but not after, reperfusion reduces the extent of myocardial necrosis in canine hearts subjected to 2 hr of left anterior descending artery occlusion and 4 hr of reperfusion compared to either reperfusion alone or LV unloading after reperfusion.

Mechanically Unloading the Left Ventricle Before Coronary Reperfusion Reduces Left Ventricular Wall Stress and Myocardial Infarct Size

“…Several preclinical studies have shown that activation of either an intra-aortic balloon pump or a catheter-mounted axial flow pump before coronary occlusion can reduce MI size in surgical models of AMI. [32][33][34] These studies suggest that the timing of mechanical circulatory support activation is a critical determinant of myocardial salvage in AMI. However, the clinical relevance of device activation before the onset of myocardial ischemia is limited.…”

Intra-aortic balloon pump in intensive cardiac care: A registry in Florence

“…So far, this indication is supported mainly by experimental data [15,16]. In a randomized experimental study, Azevedo et al [16] demonstrated that IABP counterpulsation improves the time course of recovery of LV systolic function after reperfused AMI.…”

2015 SCAI/ACC/HFSA/STS clinical expert consensus statement on the use of percutaneous mechanical circulatory support devices in cardiovascular care (Endorsed by the American heart assocation, the cardiological society of India, and sociedad latino Americana de cardiologia intervencion; Affirmation of value by the canadian association of interventional cardiology–association canadienne de cardiologie d'intervention)

“…However, as described above, the CRISP-AMI study [101] found no difference in mean final infarct size between STEMI patients (not complicated by cardiogenic shock) who received routine IABP compared with those who did not. Animal studies of LV unloading with Impella appeared more favorable [56,[119][120][121] and a preliminary clinical report of Impella for infarct size reduction in the STEMI setting was encouraging [122]. The Minimizing Infarct Size with Impella 2.5 Following PCI for Acute Myocardial Infarction (MINI-AMI) trial sought to measure this benefit, but this study was terminated before completion [123].…”