Hemodynamic Effects of Reducing LV Afterload With Impella or Intra-Aortic Balloon Counterpulsation During Veno-Arterial Extracorporeal Membrane Oxygenation in Cardiogenic Shock: HERACLES Trial

Background: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) provides organ support in cardiogenic shock but increases left ventricular (LV) afterload, potentially impairing cardiac recovery. LV unloading with an intra-aortic balloon pump (IABP) or micro-axial flow pump (mAFP) may mitigate this effect. HERACLES compared their effects on myocardial oxygen supply and demand. Methods: Patients receiving VA-ECMO for cardiogenic shock were randomized to LV unloading with IABP or mAFP, stratified by ischemic/non-ischemic etiology. Distal coronary, aortic and LV pressures and coronary flow (inverse mean transit time, Tmn) were measured with and without unloading. Myocardial oxygen demand was estimated as the area under the LV pressure curve in systole (TTI) x heart rate (HR). The primary endpoint was the change in myocardial oxygen supply-demand ratio calculated as [(Tmn * TTI*HR)off / (Tmn * TTI *HR)unload]. Secondary endpoints included changes in coronary flow [device flow ratio (DFR) =(Tmn)off/ (Tmn)unload], oxygen demand per beat (DTTI), contractility (DdP/dtmax) and filling pressure (DLVEDP). Results: Twenty-four patients were enrolled (age 51 [46-57]; 46% male; 96% SCAI D/E; 38% ischemic). At randomization, lactate was 4.3 mmol/L [IQR 2.5 to 8.4], LV ejection fraction 10% [10 to 17], LVEDP 18 mmHg [14 to 24]. The myocardial oxygen supply-demand ratio improved with IABP but not mAFP (1.48 [1.23 to 2.10] vs 0.97 [0.92 to 1.39]; P=0.036), driven predominantly by differential reduction of TTI. Coronary pressure increased but flow was unchanged with mAFP (DFR 1.00 [0.86 to 1.13]). Coronary flow increased marginally with IABP (DFR 1.16 [1.00 to 1.51]). LV pressures decreased with both devices and contractility with IABP only, with no between-group differences. Thirty-day mortality was similar (38% vs 45%, p=0.84). Conclusions: In VA-ECMO supported SCAI D/E cardiogenic shock, IABP improved myocardial oxygen supply-demand balance, whereas mAFP did not. Further research is needed to determine whether these mechanistic differences translate to clinical outcomes.