Structural and left ventricular histologic changes after implantable LVAD insertion.

Long-term support on the implantable left ventricular assist device (LVAD) produces structural changes in the recipient's heart. To assess the possibility of heart "recovery" we reviewed the records of 19 HeartMate LVAD recipients to determine structural and left ventricular histologic changes during LVAD support. Intraoperative transesophageal echocardiographic studies were performed in the operating room before LVAD insertion, immediately after LVAD insertion, and at explantation and heart transplantation (mean duration of support, 76 +/- 34 days). The initiation of LVAD pumping led to an immediate decrease (p < 0.001) in left ventricular dimensions, which were not significantly different by the time of device explantation. Left ventricular fractional shortening did not significantly improve during LVAD support (0.07 +/- 0.03 before LVAD; 0.11 +/- 0.10 immediately after LVAD; 0.11 +/- 0.11 before explantation). Histologic specimens showed a significant reduction in the number of wavy fibers, and contraction band necrosis (p < 0.01), both markers of acute myocyte damage. However, myocardial fibrosis increased (p < 0.05). Myocyte diameter increased slightly (p = 0.07). We conclude that implantable LVAD support is associated with immediate changes in ventricular structure. Histologic markers of acute myocyte damage improve, but fibrosis increases. Because the structural changes occur immediately, they do not indicate "recovery" of left ventricular function, but merely changes in loading conditions.