Non-invasive assessment of left ventricular contractility by myocardial work index in veno-arterial membrane oxygenation patients: rationale and design of the MIX-ECMO multicentre observational study

Abstract

Introduction and aims: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is an increasingly utilized therapeutic choice in patients with cardiogenic shock, however, high complication rate often counteracts with its beneficial cardiopulmonary effects. The assessment of left ventricular (LV) function in key in the management of this population, however, the most commonly used measures of LV performance are substantially load-dependent. Non-invasive myocardial work is a novel LV functional measure which may overcome this limitation and estimate LV function independent of the significantly altered loading conditions of VA-ECMO therapy. The Usefulness of Myocardial Work IndeX in ExtraCorporeal Membrane Oxygenation Patients (MIX-ECMO) study aims to examine the prognostic role of non-invasive myocardial work in VA-ECMO-supported patients.

Methods: The MIX-ECMO is a multicentric, prospective, observational study. We aim to enroll 110 patients 48-72 h after the initiation of VA-ECMO support. The patients will undergo a detailed echocardiographic examination and a central echocardiography core laboratory will quantify conventional LV functional measures and non-invasive myocardial work parameters. The primary endpoint will be failure to wean at 30 days as a composite of cardiovascular mortality, need for long-term mechanical circulatory support or heart transplantation at 30 days, and besides that other secondary objectives will also be investigated. Detailed clinical data will also be collected to compare LV functional measures to parameters with established prognostic role and also to the Survival After Veno-arterial-ECMO (SAVE) score.

Conclusions: The MIX-ECMO study will be the first to determine if non-invasive myocardial work has added prognostic value in patients receiving VA-ECMO support.

Keywords: critical care; echocardiography; extracorporeal membrane oxygenation; myocardial work index; speckle-tracking echocardiography.

Figure 1

The overview of the study population and the main objectives.

Figure 2

Clinical examples. The patient on the left is a typical subject of poor prognosis based on the SAVE score system: an elderly obese male (76 years old) with non-ST elevation myocardial infarction presented at admission with severe heart failure. The patient was admitted with manifest markers of CS. Prior to the catheterization, the patient had cardiac arrest with shockable rhythm, leading to multiple DC shocks and endotracheal intubation. VA-ECMO was initiated, and the patient underwent percutaneous revascularization. On echocardiography, his GWI value was relatively good even on high minute volume support (Supplementary Video S1). Despite the poor expected outcome, the patient was successfully weaned from the mechanical circulatory support, was discharged from the ICU at day 14, and discharged to rehabilitation at day 22. The patient on the right is a young male (35 years old) with decompensated non-ischemic cardiomyopathy. Inotropic support and intravenous diuretic therapy was initiated, however, a slow decline in his circulatory state was observed (INTERMACS profile 2–3). The multidisciplinary team decision was initiation of VA-ECMO, as the patient was eligible for bridging to long-term mechanical circulatory support or heart transplantation. His echocardiography examination is remarkable for practically similar EF and GLS values to the other patient (Supplementary Video S2). Notably, GWI was significantly lower compared to the patient on the left. Despite the complex therapy, the patient had an unfavourable outcome and died in progressive circulatory failure on the 5th day of the VA-ECMO treatment.