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Current risks of HeartMate II pump thrombosis: Non-parametric analysis of Interagency Registry for Mechanically
Nicholas G Smedira1, Eugene H Blackstone2, John Ehrlinger3
1Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute.
Insights
HeartMate II pump thrombosis risk significantly increased nationwide after 2010, plateauing at a higher rate. This highlights the need for better mechanical circulatory support systems and vigilance regarding device safety.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Device Safety
Background:
- An observed increase in HeartMate II pump thrombosis at three institutions prompted investigation into nationwide trends.
- This rise in thrombosis was associated with high mortality rates, necessitating further study.
- The study aimed to validate the increase in the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) database and analyze associated factors.
Purpose of the Study:
- To determine if the accelerated risk of HeartMate II pump thrombosis occurred nationwide.
- To identify predictors of pump thrombosis and assess institutional variability.
- To evaluate the mortality associated with HeartMate II pump thrombosis.
Main Methods:
- Analysis of 11,123 HeartMate II implantations from April 2008 to June 2014 across 146 institutions using INTERMACS data.
- Application of machine learning, specifically non-parametric Random Forests for Survival, to analyze risk-adjusted thrombosis.
- Inclusion of 87 pre-implant and implant variables, including implant date, to identify thrombosis predictors.
Main Results:
- A nationwide increase in HeartMate II pump thrombosis was confirmed, with risk peaking in 2012 and plateauing at 3.3 times the pre-2010 rate.
- Key predictors identified included pump exchange, younger age, and larger body mass index.
- The probability of death within three months following pump thrombosis was 24%.
Conclusions:
- The study confirms an accelerated and sustained risk of HeartMate II thrombosis, emphasizing the need for improved mechanical circulatory support devices.
- Post-market surveillance of adverse events is crucial for mechanical circulatory support systems.
- Clinicians and patients should be aware of the elevated thrombosis risks and consider them in treatment decisions relative to transplantation and medical therapy.
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.
