Myocyte Power Output in Humans with End-Stage Heart Failure: Effects of LVAD Treatment

Abstract

Patients in heart failure are sometimes implanted with a left ventricular assist device (LVAD) to bridge them to transplant. Clinical data shows that ∼15% of these patients recover pump function and can subsequently have their LVAD removed. The goal of our study was to determine whether cellular level maximal power output of the left ventricle improves after patients are fitted with LVADs. Myocardial samples were obtained (1) from the left ventricle apex of patients when they were implanted with a LVAD and (2) from the left ventricle free wall when they subsequently received a heart transplant. Non failing cardiac samples were also obtained from organ donors for comparison. All samples were snap frozen in liquid nitrogen and stored in the vapor phase of liquid nitrogen. Multicellular preparations were then obtained by chemically permeabilizing the samples in 1% Triton solution after mechanical homogenization. These preparations were connected between a force transducer and a motor and maximally activated in a saturating Ca2+ solution. Once force had reached steady state, the preparations were allowed to shorten against pre-set loads imposed using SLControl software. Maximum power output was determined from the force-velocity curves. Preliminary results suggest that LVAD treatment improved cellular level maximum power output and isometric force. There was also a trend towards a lower maximum shortening velocity post-LVAD. Further studies, will determine whether intrinsic ventricular function is improved by LVAD implantation as well as the molecular mechanisms that may mediate any observed responses.