Design changes in continuous-flow left ventricular assist devices and life-threatening pump malfunctions

Abstract

Objectives: The implantable continuous-flow left ventricular assist devices (LVADs) HeartMate II (HM II) and HeartWare HVAD (HW) underwent design modifications. The impact of these changes on life-threatening pump malfunctions was evaluated.

Methods: We retrospectively analysed pump malfunctions due to thrombosis or cable damage in patients supported with primarily implanted HM II (n = 191) and HW (n = 347), separated into patients supported with the old and new pump designs. In 2010, the cable strain relief of the HM II device was improved (132 patients with old and 79 with new) and sealed grafts were introduced (68 patients with sealed inflow connector and outflow graft and 125 without). In 2011, titanium sintering of the inflow cannula of HW pumps was introduced (137 patients with a non-sintered and 210 with a sintered inflow cannula).

Results: The median support time was 1.12 (0-6.1) years for all HM II and 0.59 (0-4.2) years for all HW patients. The cumulative rate of events per patient-year (EPPY) was 0.11 in HM II patients, compared with 0.09 EPPY in HW patients (P = 0.32). After introduction of the new cable design, incidence of cable damage in HM II patients dropped from 0.06 to 0 EPPY (P = 0.03), whereas pump thrombosis increased from 0.02 to 0.14 EPPY (P < 0.001) after the sealed graft was introduced. Pump thrombosis occurred in 4% of patients supported with HW with a sintered inflow cannula vs 15% with a non-sintered pump; the incidence changed from 0.10 to 0.07 EPPY in sintered pumps (P = 0.45). Kaplan-Meier analysis showed no differences over a period of 2.5 years for events when the HM II cohort with sealed graft and new cable design (n = 68) was compared with the HW group with a sintered cannula (P = 0.14).

Conclusions: The modified cable strain relief of the HM II pump and the sintering of the inflow cannula of the HW pump demonstrated a significant reduction in the incidence of life-threatening pump-related complications, whereas the sealed inflow connector and outflow graft seem to be associated with a higher incidence of pump thrombosis. However, the overall incidence of pump-related complications after the latest design changes was similar for both pumps over a 2.5-year period.

Keywords: Cable damage; HeartMate II; HeartWare HVAD; LVAD; Pump exchange; Pump thrombosis.