Device thrombosis in HeartMate II continuous-flow left ventricular assist devices: a multifactorial phenomenon

Continuous-flow left ventricular assist devices (CF-LVADs) are increasingly used to support patients with advanced heart failure (HF). Device thrombosis is a serious complication of CF-LVADs, but its precise prevalence and etiology remains uncertain.

Root-cause analysis was performed in all cases with device thrombosis confirmed upon explant among patients implanted with a HeartMate II (HM II) from January 1, 2009 to November 15, 2012. Cannula position and bend relief integrity were assessed and charts were reviewed with particular attention to anti-coagulation and infection profiles.

Nineteen of 177 patients (11%) were found to have device thrombosis of various etiologies after a mean of 351 ± 311 days, representing 0.12 event/patient-year. Of the 5 mechanically induced thromboses, proximate etiology was severely abnormal inflow cannula position in 3 patients and bend relief disconnect with deformed outflow graft in 2 patients. One patient had a hypercoagulable disorder with prior arterial embolism. In the remaining 13 patients (age 61 ± 14 years, 77% male, 69% Caucasian), "non-mechanical" device thrombosis occurred after 357 ± 383 days; INR at the time of diagnosis was 1.81 (1.62 to 2.07); and mean device speed was 8,855 ± 359 rpm. Five of 13 patients (38%) had an infection during the month leading up to device thrombosis. Of note, lactate dehydrogenase (LDH) was already elevated at the time of discharge in patients who would later develop non-mechanical device thrombosis (423 [354 to 766] vs 352 [272 to 373] U/liter, p < 0.01).

Device thrombosis is a multifactorial phenomenon, and differentiation of mechanical and non-mechanical causes is an essential step for individual diagnosis and treatment plans. Larger studies excluding patients with obvious mechanical etiology are needed to investigate biologic and/or management-related risk factors for device thrombosis. Our findings suggest that LDH may be an early risk marker. Due to the difficulty in treating late-stage device thrombosis, we suggest early use of simple tests to rule out both causes of thrombosis, such as X-rays and closer LDH monitoring (bi-weekly).