Left Ventricular Unloading Increases the Coronary Collateral Flow Index Before Reperfusion and Reduces Infarct Size in a Swine Model of Acute Myocardial Infarction

Abstract

BackgroundUnloading the left ventricle and delaying reperfusion reduces infarct size in preclinical models of acute myocardial infarction. We hypothesized that a potential explanation for this effect is that left ventricular (LV) unloading before reperfusion increases collateral blood flow to ischemic myocardium.Methods and ResultsAcute myocardial infarction was induced by balloon occlusion of the left anterior descending artery for 120 minutes in adult swine, followed by reperfusion for 180 minutes. After 90 minutes of occlusion, animals were assigned to 30 minutes of continued occlusion (n=6) or to 30 minutes of support with either an Impella CP (n=4) or venoarterial extracorporeal membrane oxygenation (n=5) with persistent occlusion. The primary end point was measures of microcirculatory blood flow including the collateral flow index (CFI) during left anterior descending artery occlusion as (Pw−RA)/(Pa−RA), where Pa, Pw, and RA are aortic, coronary wedge, and right atrial pressure, respectively. Infarct size was quantified using triphenyltetrazolium chloride. Compared with continued occlusion, Impella, not venoarterial extracorporeal membrane oxygenation, reduced infarct size relative to the area at risk. Before reperfusion, Impella reduced LV stroke work by 25% and increased the CFI by 75%, but venoarterial extracorporeal membrane oxygenation did not. Among all groups, the change in CFI between 90 and 120 minutes correlated inversely with the change in LV stroke work (r 2=0.44, P=0.01) and infarct size (r 2=0.41, P=0.02).ConclusionsWe report for the first time that 30 minutes of LV unloading during coronary occlusion increases the CFI, which correlates inversely with LV stroke work and infarct size. Venoarterial extracorporeal membrane oxygenation failed to increase the CFI and did not reduce infarct size.

Unloading using Impella CP during profound cardiogenic shock caused by left ventricular failure in a large animal model: impact on the right ventricle

“…Previous animal studies have demonstrated a correlation between SW and infarct size in the failing heart. Therefore, although speculative, the increase in SW of the failing LV could have a negative impact and may affect infarct healing and ultimately outcome [22].…”

Door-to-unload: Left Ventricular Unloading Before Reperfusion in ST-elevation Myocardial Infarction

“…Preclinical studies evaluating LV unloading during coronary occlusion with Impella technology have focused on the timing and duration of LV unloading, as well as the level of support needed. Table 1 summarizes important preclinical studies in large animal models [23,[37][38][39][40][41][42][43]. Meyns et al showed that support before reperfusion is crucial to achieve substantial reduction in infarct size [37].…”

Left Ventricular Assist Devices for Acute Myocardial Infarct Size Reduction: Meta-analysis

“…These 26 studies evaluated a total of 488 animals, including 265 subjects assisted with either surgical or percutaneous LVAD. Types of LVAD included trans-valvular pumps in 13 studies (Impella in nine studies [10,[16][17][18][19][20][21][22][23]; Hemopump in four studies [24][25][26][27]); LV-distal arterial bypass in four studies (2 LV-femoral artery [28,29]; 1 LV-carotid artery [30]; and 1 LV-descending aorta [31]), left atrial-femoral artery bypass in five studies [29,[32][33][34] (including one TandemHeart study [35]), left atrial-ascending aorta bypass in one study [36], and right atrial-femoral/subclavian artery bypass in six studies [17,32,37] (3 studies with LV vent [38][39][40]) (Fig. 2).…”