Changes in Total Cardiac Output and Oxygen Extraction During Exercise in Patients Supported With an HVAD Left...

Following implantation of a left ventricular assist device (LVAD), acceptable functional performance is now being achieved; however, peak VO₂ and peak work load (watts) remain considerably limited. Maximum physical capacity is essentially dependent on generated cardiac output (CO) and arteriovenous oxygen difference (avDO₂ ). We investigated the changes in CO and avDO₂ during exercise in LVAD patients with an HVAD pump (HeartWare Inc., Framingham, MA, USA). Approximately 6 weeks after implantation, 20 patients (100% male, 60.8 ± 7.3 years old, BMI 25.7 ± 3.3) underwent a six-minute walk test (6MWT), a cardiopulmonary exercise test (CPET), and noninvasive hemodynamic measurement. The mean six-minute walking distance (6MWD) was 403 m (68% of predicted), and mean peak VO₂ was 10.9 mL/kg/min (39% of predicted). Mean total CO improved from 3.8 L at rest to 7.0 L at maximum exercise. The mean avDO₂ increased from 7.4 mL/dL (44% of oxygen content) at rest to 13.2 mL/dL (75% of oxygen content) at maximum exercise. There was a significant increase in both total CO (P < 0.01) and avDO₂ (P < 0.05) between rest and sub-maximum exercise. As exercise levels increased, however, no further significant changes were achieved. Long-term studies, especially in combination with exercise programs, would be desirable in order to observe the development of these parameters.