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

Area of Science:

• Cardiovascular Engineering
• Biomedical Device Design
• Medical Device Safety

Background:

• Implantable continuous-flow left ventricular assist devices (LVADs) like HeartMate II (HM II) and HeartWare HVAD (HW) are critical for heart failure management.
• Design modifications were implemented in HM II and HW devices to address life-threatening pump malfunctions.
• Evaluating the impact of these design changes on pump thrombosis and cable damage is essential for patient safety.

Purpose of the Study:

• To assess the effect of design modifications on pump malfunctions in HeartMate II (HM II) and HeartWare HVAD (HW) left ventricular assist devices (LVADs).
• To compare the incidence of pump thrombosis and cable damage between old and new designs of HM II and HW LVADs.
• To determine if recent design improvements have altered the overall safety profile of these widely used LVADs.

Main Methods:

• Retrospective analysis of pump malfunctions (thrombosis, cable damage) in HM II (n=191) and HW (n=347) patients.
• Stratification of patients based on pre- and post-modification device designs (HM II cable relief, HW inflow cannula sintering, sealed grafts).
• Comparison of event rates per patient-year (EPPY) and Kaplan-Meier analysis to evaluate the impact of design changes.

Main Results:

• Improved HM II cable strain relief reduced cable damage incidence from 0.06 to 0 EPPY (P=0.03).
• Introduction of sealed grafts in HM II was associated with increased pump thrombosis (0.02 to 0.14 EPPY, P<0.001).
• Titanium sintering in HW pumps showed a trend towards reduced thrombosis (0.10 to 0.07 EPPY, P=0.45), with 4% thrombosis in sintered vs 15% in non-sintered pumps.

Conclusions:

• Modified HM II cable relief and HW inflow cannula sintering significantly reduced specific life-threatening complications.
• Sealed grafts in HM II appear linked to a higher pump thrombosis incidence.
• Despite varied impacts of specific modifications, overall LVAD complication rates remained similar between HM II and HW over 2.5 years post-design changes.