STRUCTURAL AND LEFT-VENTRICULAR HISTOLOGIC-CHANGES AFTER IMPLANTABLE LVAD INSERTION

Long-term support on the implantable left ventricular assist device (L VAD) produces structural changes in the recipient's heart. To assess t he possibility of heart ''recovery'' we reviewed the records of 19 Hea rtMate LVAD recipients to determine structural and left ventricular hi stologic changes during LVAD support. Intraoperative transesophageal e chocardiographic studies were performed in the operating room before L VAD insertion, immediately after LVAD insertion, and at explantation a nd heart transplantation (mean duration of support, 76 +/- 34 days). T he initiation of LVAD pumping led to an immediate decrease (p < 0.001) in left ventricular dimensions, which were not significantly differen t by the time of device explantation. Left ventricular fractional shor tening did not significantly improve during LVAD support (0.07 +/- 0.0 3 before LVAD; 0.11 +/- 0.10 immediately after LVAD; 0.11 +/- 0.11 bef ore 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 change s occur immediately, they do not indicate ''recovery'' of left ventric ular function, but merely changes in loading conditions.