Pump thrombosis in the Thoratec HeartMate II device: An update analysis of the INTERMACS Registry

Abstract

Background: Pump thrombosis in durable continuous-flow pumps is a barrier to long-term mechanical circulatory support. Earlier Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) data identified an increasing risk of pump thrombosis in recent years with the HeartMate II (HMII) left ventricular assist device. The current analysis examines pump thrombosis in the patient cohort extended through June 2014.

Methods: The INTERMACS identified 9,808 adult patients from 144 institutions receiving a primary HMII implant between April 2008 and June 30, 2014. Pump thrombosis was identified at time of explant, transplant or death. Risk factors for pump thrombosis were examined by multivariable analysis in the hazard function domain. The association between pump thrombosis and implant year was modeled in the hazard domain.

Results: Parametric hazard modeling of thrombosis by year of implant identified an increasing risk of pump thrombosis from 2009 through 2013, followed by a decrease in the risk during the first half of 2014, which was most apparent during the first 3 months post-implant. Risk factors for pump thrombosis included younger age (p < 0.001), higher body mass index (p = 0.02), history of non-compliance (p = 0.004), severe right heart failure (p = 0.02), later date of implant (p < 0.0001), and elevated lactate dehydrogenase during the first month post-implant (p < 0.0001). Subsequent pump thrombosis was more likely if the initial pump exchange indication was pump thrombosis (p < 0.0001).

Conclusions: The small, but progressive increase in the incidence of pump thrombosis observed between 2010 and 2013 with the HMII pump had reversed somewhat in the first half of 2014. Identification of marked elevation of lactate dehydrogenase during the first month offers an opportunity for early intervention strategies.

Keywords: HeartMate II; INTERMACS; LVAD; heart failure; pump thrombosis.