Pre-implant left ventricular apex position predicts risk of HeartMate II pump thrombosis

Background: Thrombosis within a left ventricular assist device (LVAD) is a devastating complication that often necessitates device exchange. Few studies have evaluated the relationship between patient anatomy and pump thrombosis. We hypothesize that lateral displacement of the left ventricular (LV) apex increases risk for pump thrombosis. Methods: All patients who underwent primary implantation of a HeartMate II (HM2) device (Thoratec, Pleasanton, CA) at a single center (2009-2015) were evaluated. Operative mortalities and patients without imaging were excluded. The angle of the LV apex relative to the midline was measured on preoperative computed tomography scans by two independent surgeons. Pump thrombosis was defined as lactic dehydrogenase >700 with clinical symptoms of hemolysis or LVAD malfunction. Univariate and Cox Proportional Hazards analysis was performed to evaluate the impact of LV apex angle on long-term freedom from pump exchange for thrombosis. Results: Of 122 patients who met inclusion criteria for this study, 16 (13.1%) underwent exchange for presumed pump thrombosis. Of these patients, six (37.5%) required more than one exchange. Patients undergoing exchange for thrombosis had greater LV angle (43.8 ± 9.7 vs 49.5 ± 11.2, p = 0.037) with LV apex angle being a significant predictor of LVAD exchange for thrombosis (hazard ratio = 1.047, P = 0.046). Additionally, when surgeon measurements were compared there was good inter-observer reliability (Pearson Correlation = 0.89). Conclusion: A laterally displaced left ventricular apex correlates with a higher risk of pump thrombosis in patients undergoing HM2 implantation. LV apex angle is an easily obtained, reproducible measurement that should be considered when selecting a ventricular assist device.