Low Peak VO2 and Pulse Pressure Augmentation on Exercise in LVAD Patients with Recovery and Pump Explant

Abstract

<h3>Purpose</h3> Recovered LVAD patients have normal EF and hemodynamics, but knowledge of their exercise response is scarce. We compared exercise responses in LVAD vs. HF and normal subjects. <h3>Methods</h3> In 2016-20, 25 LVAD patients had upright ergometer CPET with first-pass radionuclide imaging (n=20), with (n=13) or without (n=12) invasive hemodynamic monitoring. Five had pump explant for recovery after exercising at low pump speeds. LVAD patients were compared to HFrEF (EF < 40%, n=31) vs. normal subjects (EF ≥ 50%, rest mean PAP ≤ 20, PAWP < 15 mmHg, n=41). Values are expressed as median (25^th-75^th interquartile range). P < 0.05 was considered significant comparison across all groups. <h3>Results</h3> Median EF was 55% (explant), 19% (no-explant), 23% (HFrEF), and 63% (normal) (p<0.01). On exercise, LVAD patients did not augment EF as other groups. Peak VO₂ was 14 (explant), 10.1 (no-explant), 11.9 (HFrEF), and 22.7 mL/kg/min (normal) (p<0.01). Max-predicted heart rate (HR) was 90% (explant), 69% (no-explant), 68% (HFrEF), and 89% (normal) (p<0.01). Explant patients did not widen radial artery pulse pressure as normal subjects (Δ pulse pressure 18 vs. 32 mmHg, p<0.01) (Fig 1A). At rest, from supine to upright position, filling pressures dropped in HF and normal subjects but were unchanged in LVAD patients. Peak CO was similar between explant and normal (13.9 L/min [9.9-14.6] vs. 13.9 [11.9-17.1]), but low in no-explant and HF groups (6.9 [6.3-10.5] vs. 7.1 [5.8-9.1]). PAWP/CO slope was lowest in explant and normal (1.4 mmHg/L/min [0.8-2.2] vs. 1.1 [0.9-1.6]), but high in no-explant and HFrEF groups (3.2 [2.2-4.5] vs. 4.2 [2.3-5.4]) (Fig 1B). <h3>Conclusion</h3> Explant patients had higher peak CO, peak HR and lower PAWP/CO slope than no-explant group. Despite normal EF and hemodynamics, explant patients did not completely normalize peak VO₂ or pulse pressure augmentation on exercise. Efforts aimed at improving CO (e.g. pump speed modulation) and reducing chronotropic incompetence may help improve exercise tolerance for LVAD patients.