Right Ventricular Response to Exercise in LVAD-Supported Patients vs. Heart Failure and Normal Subjects

Abstract

<h3>Purpose</h3> Knowledge of right ventricular (RV) responses to exercise in LVAD-supported patients is limited. RV reserve might be impaired in LVAD patients. We sought to determine RV reserve during exercise in LVAD patients vs. HF and control subjects. <h3>Methods</h3> In 2016-20, 25 LVAD patients underwent upright ergometer CPET with first-pass radionuclide imaging (n=20), with (n=13) or without (n=12) invasive hemodynamic monitoring. LVAD patients were compared to HFrEF (EF < 40%, n=31), HFpEF (EF ≥ 50%, rest mean PAP ≥ 25, PAWP ≥ 15 mmHg, n=54) and 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 RVEF was 41% (LVAD), 40% (HFrEF), 47% (HFpEF), 51% (normal) (p<0.01). On exercise, normal subjects augmented RVEF but LVAD and HF groups did not. Peak VO₂ was 11 (LVAD), 11.9 (HFrEF), 14.2 (HFpEF), 22.7 mL/kg/min (normal) (p<0.01). Peak filling pressures were similar in LVAD and normal subjects. Peak cardiac output (CO) was 9.9 (LVAD), 7.1 (HFrEF), 9.9 (HFpEF), 13.9 L/min (normal) (p<0.01). MeanPAP/CO slope was highest in HFrEF (5.8 mmHg/L/min [3.2-7]), intermediate in LVAD (2.6 [2-4.9]) and HFpEF (3.7 [2.7-4.8]), and lowest in normal (1.8 [1.4-2.1]) (p<0.01). Peak PVR was highest in HFrEF (2.1 Wood units [1.7-3.2], intermediate in LVAD (1.4 [1-1.8]) and HFpEF (1.5 [1.1-2]), and lowest in normal (1 [0.7-1.3]) (p<0.01). Peak RV stroke work index (RVSWI) was lowest in LVAD (0.7 mmHg.L/m² [0.5-0.9]) vs. normal (1.1 [1-1.3]), HFrEF (1.2 [1.1-1.4]) and HFpEF (1.2 [1-1.6]) (p<0.01). Peak RAP/PAWP ratio was highest in LVAD (0.6 [0.5-0.9]) vs. normal (0.5 [0.4-0.6]), HFrEF (0.4 [0.3-0.5]) and HFpEF (0.4 [0.3-0.6]) (p=0.02) (Fig. 1). <h3>Conclusion</h3> At peak upright exercise, LVAD patients had poorer RV reserve than HF and normal subjects (lower RVSWI, higher RAP/PAWP ratio). Research aimed at RV optimization is needed to improve exercise tolerance in LVAD patients.