FEASIBILITY AND SAFETY OF HM II TO HVAD VS. HM II TO HM II EXCHANGE STRATEGY FOR PUMP THROMBOSIS

Abstract

The reported incidence of pump thrombosis (PT) with the Heartmate II (HMII) LVAD has increased, yet neither recent HMII design changes nor specific mechanical risk factors appear to fully explain this rise in PT. Our institutional approach is to consider pump exchange (PE) to the Heartware (HVAD) in HMII patients with PT. We compared our experience with HMII-HMII vs. HMII-HVAD exchanges to determine if the latter strategy is feasible, well-tolerated, and associated with similar clinical outcomes compared with the prevailing standard of HMII-HMII exchange. This was a retrospective case series of all HMII patients who underwent PE (n=9) from 2009-2013 for suspected PT (Group A: HMII-HMII, n=4; Group B: HMII-HVAD, n=5). We assessed the following post-PE outcomes: INTERMACS-defined right ventricular failure (RVF) and major bleeding; renal failure requiring dialysis; recurrent suspected PT; NYHA FC; and mortality at 90 days and at 1 year. The majority of patients underwent initial HMII implantation from 2012-2013 (n= 8; 89%). Of the group A patients, 75% were BTT at time of exchange. The median time to PE was 207 days (range 42 to 1311). Manufacturer analysis confirmed HMII PT in 8 patients, with 1 patient’s pump deemed inconclusive. Overall survival following PE was 89% at 90-days and 67% at 1 year. Survival by groups at 90 days and at 1 year was: 75% and 50% (Group A) vs. 100% and 80% (Group B). Patients in both groups were either NYHA FC 2 or 3 at 90 days. Post-PE morbidity included: RVF (Group A 50% vs. Group B 20%), renal failure (Group A 25% vs. Group B 20%), major bleeding (Group A 50% vs. Group B 40%) and recurrent suspected PT (Group A 50% vs. Group B 20%). Two patients had recurrent suspected PT following HMII to HMII (1 urgently transplanted; 1 died suddenly by 1 year). One patient with recurrent PT following HMII to HVAD exchange had a known hypercoagulable state, and also died within 1 year post-exchange (at 285 days). HMII to HVAD PE is an acceptable and surgically feasible strategy for those with HMII PT. Our experience indicates that HMII to HVAD PE is not associated with increased morbidity or mortality compared with HMII to HMII exchange. While the rates of recurrent PT may appear to favour exchange to HVAD, this warrants larger clinical study, and a firmer understanding of the pump-specific risks related to the HMII.