Flow manipulation and the association with myocardial contractility during extracorporeal life support (FLAME)

Abstract

Background: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is an advanced technique in extracorporeal life support (ECLS) used to support extreme circulatory failure including patients with cardiac arrest and cardiogenic shock refractory to conventional support. It is a long-standing belief that peripheral V-A ECMO poses increased afterload to the inured heart, but conventional echocardiographic measurements are often insensitive in detecting subtle changes in loading conditions. Purpose: This study aimed to evaluate the effects of varying blood flow during peripheral V-A ECMO on intrinsic myocardial contractility, using detailed echocardiographic assessment including speckle tracking echocardiography (STE). Methods: Adult patients with acute cardiogenic shock who were supported by peripheral V-A ECMO from April 2019 to September 2020 were recruited. Serial hemodynamic and cardiac performance parameters were measured by transthoracic echocardiogram (TTE) within 48 hours after implementation of V-A ECMO, at different levels of extracorporeal blood flow – 100%, 120% and 50% of target blood flow (TBF). Results: A total of 30 patients were included. 22 (71%) were male, and the mean (SD) age was 54 (13) years. The major indications for V-A ECMO were myocardial infarction (19, 63% patients), and myocarditis (5, 17%). With a decrease in extracorporeal blood flow from 100% to 50% of TBF, mean arterial pressure (MAP) dropped from 76+/-3 to 64+/-3mmHg (p <0.001), and cardiac index (CI) increased from 0.89+/-0.13 to 1.27+/-0.18L/min/m2 (p < 0.001). All indices of left ventricular contractility improved at a lower extracorporeal blood flow: the myocardial contractility measured by global longitudinal peak systolic strain (GLPSS) improved from -3+/-0.7% to -5+/-0.8% (p < 0.001); left ventricular ejection fraction (LVEF) increased from 21.5+/-2.6% to 30.9+/-2.7% (p < 0.001) and 19.7+/-3.1% to 28.4+/-3.2% (p < 0.001) by biplane and linear methods, respectively; left ventricular index of myocardial performance (LIMP) improved from 1.51+/-0.12 to 1.03+/-0.09 (p < 0.001). Similar findings were reproduced when comparing left ventricular contractility at extracorporeal blood flows of 120% and 50% of TBF. Conclusions: The ECMO blood flow rate in peripheral V-A ECMO is inversely related to myocardial contractility, and is quantifiable by myocardial strain measured by STE.