title: Current risks of HeartMate II pump thrombosis: Non-parametric analysis of Interagency Registry for Mechanically Assisted Circulatory Support data.
abstract: BACKGROUND
  Data from 3 institutions revealed an abrupt increase in HeartMate II (Thoratec) pump thrombosis starting in 2011, associated with 48% mortality at 6 months without transplantation or pump exchange. We sought to discover if the increase occurred nationwide in Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) data, and if so (1) determine if accelerated risk continued, (2) identify predictors, (3) investigate institutional variability, and (4) assess mortality after pump thrombosis.
  
  
  METHODS
  From April 2008 to June 2014, 11,123 HeartMate II devices were implanted at 146 institutions. Machine learning, non-parametric Random Forests for Survival was used to explore risk-adjusted thrombosis based on 87 pre-implant and implant variables, including implant date.
  
  
  RESULTS
  A total of 995 pumps thrombosed, with risk peaking within weeks of implant. The risk-adjusted increase in pump thrombosis began in 2010, reached a maximum in 2012, and then plateaued at a level that was 3.3-times higher than pre-2010. Pump exchange, younger age, and larger body mass index were important predictors, and institutional variability was largely explained by implant date, patient profile, and duration of support. The probability of death within 3 months after pump thrombosis was 24%.
  
  
  CONCLUSIONS
  Accelerated risk of HeartMate II thrombosis was confirmed by Interagency Registry for Mechanically Assisted Circulatory Support data, with risk subsequently leveling at a risk-adjusted rate higher than observed pre-2010. This elevated thrombosis risk emphasizes the need for improved mechanical circulatory support systems and post-market surveillance of adverse events. Clinicians cognizant of these new data should incorporate them into their and their patients' expectations and understanding of risks relative to those of transplantation and continued medical therapy.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute. Electronic address: smedirn@ccf.org.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Smedira
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute; Kaufman Center for Heart Failure; Department of Quantitative Health Sciences, Research Institute.
authors.forename: Eugene H
authors.initials: EH
authors.lastname: Blackstone
authors.affiliation: Department of Quantitative Health Sciences, Research Institute.
authors.forename: John
authors.initials: J
authors.lastname: Ehrlinger
authors.affiliation: Department of Quantitative Health Sciences, Research Institute.
authors.forename: Lucy
authors.initials: L
authors.lastname: Thuita
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Pierce
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute; Kaufman Center for Heart Failure.
authors.forename: Nader
authors.initials: N
authors.lastname: Moazami
authors.affiliation: Kaufman Center for Heart Failure; Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Randall C
authors.initials: RC
authors.lastname: Starling
mesh_terms: D005260:Female; D006353:Heart-Assist Devices / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology*; D012042:Registries; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D013927:Thrombosis / Q000453:epidemiology* / Q000209:etiology*
keywords: HeartMate II; INTERMACS; left ventricular assist device (LVAD); mortality; pump thrombosis; regulatory