Unexpected Abrupt Increase in Left Ventricular Assist Device Thrombosis

Study Questions:

Is there an increase in pump thrombosis in patients receiving the HeartMate II (HMII) left ventricular assist device?


Data were collected from three institutions (Cleveland Clinic, Washington University Barnes-Jewish Hospital, and Duke University) on 837 patients where 895 devices were implanted between 2004 and mid 2013. The primary endpoint was confirmed pump thrombosis. The secondary endpoints were confirmed and suspected thrombosis, longitudinal lactate dehydrogenase (LDH) levels, and outcomes after pump thrombosis (pump replacement or explantation, urgent heart transplantation, medical treatment, or death).


The mean age of the patients was 55 ± 14 years old, and 21% were women. Seventy-two confirmed pump thromboses were observed in 66 patients, and 36 thromboses were suspected. The risk of pump thrombosis peaked at 1.4% per month within 1 month after implantation with estimated occurrences of pump thrombosis of 4.7% during HMII support for 6 months, 7.5% during 12 months, and 12.3% during 24 months of support. At all three institutions, there was an increase in confirmed pump thrombosis after March 1, 2011; from 2.2% (95% confidence interval [CI], 1.5-3.4) at 3 months after implantation to 8.4% (95% CI, 5.0-13.9) by January 1, 2013. On average, the LDH level increased from 540 IU/L (95% CI, 388-695) to 1490 IU/L (95% CI, 1350-1600) in 6 weeks, leading to confirmed pump thrombosis. Thrombosis was managed by heart transplantation in 11 patients and pump replacement in 21. Of the 40 patients who did not undergo heart transplantation or pump replacement, mortality was 48.2% (95% CI, 31.6-65.2) 6 months after the diagnosis of pump thrombosis.


The rate of pump thrombosis in HMII devices has been increasing. Patients with pump thrombosis have increased mortality unless the patient undergoes cardiac transplantation or pump replacement.


With the rate of pump thrombosis in the HMII increasing, elevated LDH levels continue to be the most useful biomarker of hemolysis associated with pump thrombosis. Predisposing patient and device factors continue to be investigated to determine successful therapeutic strategies.

Clinical Topics: Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Cardiac Surgery and Heart Failure, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Heart Transplant, Mechanical Circulatory Support

Keywords: Washington, Risk, Hemolysis, Biological Markers, Thrombosis, Heart-Assist Devices, Heart Failure, L-Lactate Dehydrogenase, Confidence Intervals, Heart Transplantation

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