Ongoing Exercise Intolerance Following COVID-19: A Magnetic Resonance-Augmented Cardiopulmonary Exercise Test Study.

Background Ongoing exercise intolerance of unclear cause following COVID-19 infection is well recognized but poorly understood. We investigated exercise capacity in patients previously hospitalized with COVID-19 with and without self-reported exercise intolerance using magnetic resonance-augmented cardiopulmonary exercise testing. Methods and Results Sixty subjects were enrolled in this single-center prospective observational case-control study, split into 3 equally sized groups: 2 groups of age-, sex-, and comorbidity-matched previously hospitalized patients following COVID-19 without clearly identifiable postviral complications and with either self-reported reduced (COVID) or fully recovered (COVID) exercise capacity; a group of age- and sex-matched healthy controls. The COVIDgroup had the lowest peak workload (79W [Interquartile range (IQR), 65-100] versus controls 104W [IQR, 86-148]; =0.01) and shortest exercise duration (13.3±2.8 minutes versus controls 16.6±3.5 minutes; =0.008), with no differences in these parameters between COVID patients and controls. The COVID group had: (1) the lowest peak indexed oxygen uptake (14.9 mL/minper kg [IQR, 13.1-16.2]) versus controls (22.3 mL/min per kg [IQR, 16.9-27.6]; =0.003) and COVID patients (19.1 mL/min per kg [IQR, 15.4-23.7]; =0.04); (2) the lowest peak indexed cardiac output (4.7±1.2 L/min per m) versus controls (6.0±1.2 L/min per m; =0.004) and COVID patients (5.7±1.5 L/min per m; =0.02), associated with lower indexed stroke volume (SVi:COVID 39±10 mL/min per m versus COVID 43±7 mL/min per m versus controls 48±10 mL/min per m; =0.02). There were no differences in peak tissue oxygen extraction or biventricular ejection fractions between groups. There were no associations between COVID-19 illness severity and peak magnetic resonance-augmented cardiopulmonary exercise testing metrics. Peak indexed oxygen uptake, indexed cardiac output, and indexed stroke volume all correlated with duration from discharge to magnetic resonance-augmented cardiopulmonary exercise testing (<0.05). Conclusions Magnetic resonance-augmented cardiopulmonary exercise testing suggests failure to augment stroke volume as a potential mechanism of exercise intolerance in previously hospitalized patients with COVID-19. This is unrelated to disease severity and, reassuringly, improves with time from acute illness.