(178) Prospective Comparison of the Effect of Venovenous ECMO Flow Rates on Right Ventricular Function

Introduction: Venovenous extracorporeal membrane oxygenation (VV ECMO) for patients with respiratory failure results in improved gas exchange, decreased pulmonary arterial pressure, and in turn, improved right ventricular (RV) function. However, RV dysfunction in patients on VV ECMO remains common and is associated with higher mortality. It is unknown whether VV ECMO flow rate is a factor affecting the RV function. This prospective study aims to evaluate RV function at varying levels of ECMO flow.

Methods: Patients with respiratory failure supported on VV ECMO had echocardiography performed by a board-certified critical care echocardiographer at moderate flow rate, after 20 minutes of support at high- (50% above moderate, up to 2L/min higher), then after 20 minutes of support at low- (50% below, up to to 2L/min lower) flow rate. RV size and function were assessed by measuring tricuspid annular plane systolic excursion (TAPSE), tissue doppler index (TDI) S’ and fractional area change (FAC), RV end diastolic area (EDA), RV:LV ratio, and tricuspid annulus diameter. Normal RV function was defined as ≥2 of the following: FAC ≥35%, TDI S’ ≥10cm/s, TAPSE ≥17mm.

Results: Ten patients were enrolled between February 2023 and July 2024. All patients had normal RV function at moderate- [median 3.80L/min (IQR 3.36, 4.01)], high- [5.45L/min (5.03, 5.95)], and low-flow [2.00L/min (2, 2.09)] rates. From low- to high-flow, the mean change in TAPSE was -0.04cm (SD=2.12), in TDI S’ was -1.11 (SD=4.52), and in FAC was -2.73cm2 (SD=7.48). From low- to high flow, the mean change in RVEDA was -0.67cm2 (SD=4.62), in RV:LV ratio was 0.01 (SD=0.11), and in tricuspid annulus diameter was 0.04mm (SD=0.23).

Conclusions: This prospective study found that changes in RV size and function in relation to the alteration of ECMO flow were small and without consistency. RV function remained normal at all flow rates. Despite limitations including small sample size and short duration of flow alterations, this study suggests no direct effect of VV ECMO flow rate on RV size and function.