Myocardial Structural and Functional Response After Long-Term Mechanical Unloading With Continuous Flow Left Ventricular Assist Device: Axial Versus Centrifugal Flow

Abstract

Objectives: The aim of this study was to assess the impact of continuous-flow left ventricular assist device (LVAD) type-axial flow (AX) versus centrifugal flow (CR)-on myocardial structural and functional response following mechanical unloading.

Background: The use of continuous-flow LVADs is increasing steadily as a therapeutic option for patients with end-stage heart failure who are not responsive to medical therapy. Whether the type of mechanical unloading influences the myocardial response is yet to be determined.

Methods: A total of 133 consecutive patients with end-stage heart failure implanted with continuous-flow LVADs (AX, n = 107 [HeartMate II Thoratec Corporation, Pleasanton, California]; CR, n = 26 [HeartWare, HeartWare International, Framingham, Massachusetts]) were prospectively studied. Echocardiograms were obtained pre-LVAD implantation and then serially at 1, 2, 3, 4, 6, 9, and 12 months post-implantation.

Results: The 2 pump types led to similar degrees of mechanical unloading as assessed by invasive hemodynamic status and frequency of aortic valve opening. Myocardial structural and functional parameters showed significant improvement post-LVAD in both AX and CR groups. Left ventricular ejection fraction increased significantly from a mean of 18% to 28% and 26% post-LVAD in the AX and CR groups, respectively. Left ventricular end-systolic volume index and left ventricular end-diastolic volume index decreased significantly as early as 30 days post-implantation in the 2 groups. The degree of myocardial structural or functional response between patients in the AX or CR groups appeared to be comparable.

Conclusions: Long-term mechanical unloading induced by AX and CR LVADs, while operating within their routine clinical range, seems to exert comparable effects on myocardial structural and functional parameters.

Keywords: axial versus centrifugal; continuous flow; left ventricular assist device; mechanical unloading; myocardial function; myocardial structure.