Graft Resistance Difference after HVAD to HeartMate 3 Left Ventricular Assist Device Exchange

Area of Science:

• Cardiovascular Engineering
• Medical Device Technology

Background:

• The discontinuation of the HeartWare Ventricular Assist Device (HVAD) necessitates increased use of the HeartMate 3 for left ventricular assist device replacements.
• Retaining parts of the HVAD's 10-mm outflow graft during HeartMate 3 implantation may require higher device operating speeds compared to using the standard 14-mm HeartMate 3 graft.

Purpose of the Study:

• To evaluate the hemodynamic impact of using a remnant HVAD outflow graft with the HeartMate 3 left ventricular assist device.
• To determine the effects of partial HVAD graft retention on HeartMate 3 performance parameters, including rotor speed and power consumption.

Main Methods:

• An in vitro study was conducted using steady-state flow conditions.
• Samples included HeartWare Ventricular Assist Device (HVAD), HeartMate 3, and hybrid HVAD/HeartMate 3 grafts of varying lengths (125-375 mm).
• Flow rates from 3.0 to 6.0 L/min were applied to simulate clinical scenarios.

Main Results:

• At clinically relevant flow rates (4.3 and 6.0 L/min), HeartMate 3 rotor speeds increased from 5350 to 5700 rpm and 6350 to 6900 rpm, respectively, when using the full HVAD graft compared to the HeartMate 3 graft.
• Corresponding power consumption increased by 16% (3.7 to 4.3 W) and 24% (5.5 to 6.8 W) at these flow rates.

Conclusions:

• While no severe immediate consequences were identified, using a remnant HVAD graft necessitates higher HeartMate 3 rotor speeds.
• This can lead to reduced patient battery runtime and increased power consumption.
• Complete replacement with the HeartMate 3 graft is the preferred approach from an engineering perspective for optimal device function and patient benefit.