Treadmill Exercise Stress Echocardiography Exposes Impaired Left Ventricular Function in Patients Recovering from Hospitalization with COVID-19 Without Overt Myocarditis Versus Historical Controls

Abstract

Background: Usual clinical testing rarely reveals cardiac abnormalities persisting after hospitalization for COVID-19. Such testing may overlook residual changes responsible for increased adverse cardiac events post-discharge. Methods: To further elucidate long-term status, we performed exercise stress echocardiography (ESE) in 15 patients age 30-63 without myocarditis 3 to 31 months after hospital discharge. We compared patient outcomes to published data in healthy comparisons (HC) exercising according to the same protocol. Results: Patients' treadmill exercise (Bruce protocol), averaging 8.2 min, was halted by dyspnea or fatigue. Pre-stress baselines in recovering patients (RP) matched HC except for higher heart rate: mean 81 bpm for RP and 63 for HC (p<0.0001). At peak stress, RP had significantly lower mean left ventricular (LV) ejection fraction (67% vs 73%, p<0.0017) and higher peak early mitral inflow velocity/early mitral annular velocity (E/e', 9.1 vs 6.6, p<0.006) compared with HC performing equal exercise (8.5 min). Thus, when stressed, patients without known cardiac impairment showed modest but consistently diminished systolic contractile function and diastolic LV compliance during recovery vs HC. Peak HR during stress was significantly elevated in RP vs HC; peak SBP also trended higher. Average pulmonary artery systolic pressures among RP remained normal. Conclusions: Our measurements during ESE uniquely identified residual abnormality in cardiac contractile function not evident in the unstressed condition. This finding exposes a previously-unrecognized residual influence of COVID-19, possibly related to underlying autonomic dysfunction, microvascular disease, or diffuse interstitial changes after subclinical myocarditis; it may have long-term implications for clinical management and later prognosis.