Revisiting the Achilles Heel of Exercise Capacity in Continuous Flow LVAD Patients Using Invasive Exercise Hemodynamics

Background Continuous flow left ventricular assist devices (cfLVADs) have greatly improved survival and quality of life for patients with end-stage heart failure. However, exercise capacity remains poor and little is known about hemodynamics during exercise. We describe observations from invasive cardiopulmonary exercise (iCPEX) tests in 3 patients with continuous flow LVADs. Methods Three patients with cfLVADs (HeartMate II, HeartMate 3 and HeartWare HVAD) underwent iCPEX with a pulmonary artery catheter placed via the right internal jugular vein and using an exercise bicycle protocol with a 10 Watt ramp. Ventilatory measurements were made with a Sensormedics CPX testing unit (Sensormedics, VMAX Encore 29C). One subject also had a radial arterial line for blood pressure monitoring. Results The peak oxygen consumption averaged 1.03 ± 0.32 L/min (36.8% mean max. predicated) or 9.5± 1.7 mL/kg/min. Respiratory quotient averaged 1.2 ±0.1. With exercise, cardiac output increased modestly from 7.8 ± 2.8 to 10.8 ± 2.6 L/min. There was a progressive increase in pulmonary capillary wedge pressure (PCW) in all patients, from 25 ± 12 to 34 ± 13 mmHg. Right atrial pressure changed minimally in 2 subjects (20 to 24 mmHg and 6 to 10 mmHg), while there was a rise in RA pressure towards the end of exercise in one subject with known poor right ventricular function (14 to 28 mmHg). In the subject monitored with an arterial line, there was a rise in blood pressure from 94 to 106 mmHg mean and an increase in pulse pressure from 18 to 54 mmHg. Conclusion Hemodynamics during exercise in patients with cfLVADs demonstrates a modest increase in cardiac output that is associated with a non-physiologic increase PCW. Peak oxygen consumption was well below predicted. The rise in PCW with only a modest increase in exercise cardiac output raise the question of whether automated circulatory control to increase pump performance with exercise could lead to improved exercise capacity in cfLVAD patients. Figure 1