Multi-institutional study finds increased thrombosis in HeartMate II LVADs

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1. Incidence of pump thrombosis associated with HeartMate II Left Ventricular Assist Device (LVAD) was found to have increased in recent years. 

2. Of note, this study was carried out at three institutions and may or may not represent a generalizable trend.

Evidence Rating Level: 1 (Excellent)

Study Rundown: This study demonstrated a rise in incidence of pump thrombosis associated with HeartMate II LVAD. In the study, rate of thrombosis was time-dependent and was approximately 4.7% by 6 months after implantation, and 12% by 24 months. These numbers were higher than the reference occurrence of thrombosis of 2 to 4% provided by previous trial and postmarketing studies. The study also found that the rate of thrombosis increased steeply since March 2011. The exact cause of the increase was unclear. As LVAD remains one of the life-sustaining treatments for patients with heart failure, clinicians should take into consideration this updated risk profile when evaluating borderline candidates. This study was well-powered with over 800 patients from three institutions.

Click to read the study, pulished today in NEJM

Relevant Reading: Advanced heart failure treated with continuous-flow left ventricular assist device

In-Depth [retrospective cohort study]: This study examined the incidence of pump thrombosis after implantation of HeartMate II Left Ventricular Assist Device (LVAD). The study included a total of 895 HeartMate II LVAD implants from 837 patients at three institutions: Cleveland Clinic, Washington University Barnes-Jewish Hospital, and Duke University Medical Center. Primary end point was confirmed pump thrombosis.

There were a total of 72 confirmed pump thromboses in 66 patients, and an additional 36 suspected thromboses in unique devices. The risk of confirmed pump thrombosis peaked at 1.4% within 1 month after implantation before decreasing to a constant risk of 0.4% per month. The estimated occurrences were 4.7% by 6 months, 7.5% by 12 months, and 12.3% by 24 months of support. The combined risk of confirmed plus suspected pump thrombosis was 2.0% within the first month before decreasing to a constant risk of 0.7% per month after 6-8 months. The estimated occurrences were 7.1%, 11.3%, and 18.3% for 6 months, 12 months and 24 months of support, respectively.

The incidence increased sharply after approximately March 2011, from 2.2% (95% confidence interval [CI], 1.5 to 3.4) to 8.4% (95% CI, 5.0 to 13.9) by January 2013 at 3 months after implantation, a trend consistent at all three institutions. The median time to confirmed pump thromboses also shortened from 18.6 months (95% CI, 0.5 to 52.7) before March 2011 to 2.7 months (95% CI, 0.0 to 18.6) during and after March 2011.

By Xiaozhou Liu and Xu Gao

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