The hemodynamic effects of femoro-femoral venoarterial (VA) extracorporeal membrane oxygenation (ECMO) on pulmonary capillary wedge pressure (PCWP) remain poorly defined. High ECMO flow is believed to increase PCWP and the risk of pulmonary edema; yet, supporting in vivo physiological data are lacking.

The purpose of this study was to evaluate the impact of incremental femoro-femoral VA-ECMO flow variations on PCWP, hemodynamic, and echocardiographic parameters in patients with cardiogenic shock during the early phase of VA-ECMO support, after stabilization.

This prospective, single-center interventional study was conducted at Pitié-Salpêtrière Hospital, Paris, France. The ECMO-Flow trial consisted of stepwise VA-ECMO flow variations from 2 to 4 L/min in 0.5-L/min increments. Hemodynamic assessment included pulmonary artery catheter measurements, transthoracic echocardiography, and blood gas analyses.

A total of 80 patients were included. At baseline, 27 patients (34%) had PCWP ≥18 mm Hg. Left ventricular (LV) dilation, mitral regurgitation, elevated central venous pressure (CVP), and preserved right ventricular (RV) function were associated with higher baseline PCWP. During the ECMO-Flow trial, PCWP decreased in 29 patients (36%), remained stable in 46 (58%), and increased in only 5 (6%), despite a concomitant rise in LV afterload. CVP significantly decreased, while RV afterload remained unchanged. Indexed stroke volume decreased and myocardial work remained stable despite an increase in LV afterload. Throughout the ECMO-flow trial, a significant PCWP decrease was observed in patients with better baseline LV and RV function and lower CVP.

As VA-ECMO flow increases, the expected rise in PCWP caused by afterload elevation appears to be counterbalanced by a reduction in RV preload, resulting in a neutral effect in most patients, a significant PCWP decrease in approximately one-third, and an only infrequent increase.