Abstract 6991: Impaired Systemic Oxygen Extraction Relates to Reduced Exercise Capacity in Post-COVID-19 Long Hauler Syndrome

Abstract

Introduction: Following acute coronavirus 2019 (COVID-19) disease, at least 10% of patients report some form of residual limitation, most commonly dyspnea and fatigue. These COVID-19 “long haulers” experience symptoms that are largely unexplained by pulmonary function testing (PFT), echocardiogram and chest computed tomography (CT). Using invasive cardiopulmonary exercise testing, this pilot study characterized exercise limitation in 5 patients with persistent symptoms 1 year following mild COVID-19 illness. Methods: Following written informed consent, data were obtained in accordance with an IRB-approved protocol entailing placement of radial and pulmonary arterial catheters for pressure monitoring and blood sampling prior to and during maximum upright incremental exercise. Rest and exercise pulmonary hemodynamics, ventilation and gas exchange were recorded. Aerobic exercise capacity was estimated by peak O 2 consumption (VO 2 ). Results: All patients had normal biventricular and valvular function on resting echocardiogram, no evident parenchymal lung disease on CT, and normal PFTs. Resting mean pulmonary arterial pressure was ≤20 mmHg for all patients with pulmonary vascular resistance <3 Woods units. At maximum exercise, all patients exhibited normal respiratory, cardiac output (% predicted), and total pulmonary vascular resistance responses, but demonstrated clearly depressed aerobic capacity (peak VO 2 <80% predicted). Reduced peak VO 2 was associated with impaired systemic O 2 extraction as indicated by an arterial-venous O 2 content difference (adjusted for hemoglobin) of <80% ( Figure 1 ). Conclusion: This case series provides preliminary evidence that reduced peak aerobic capacity among long haulers is primarily attributable to a peripheral (i.e., impaired systemic O 2 extraction), rather than central cardiopulmonary, limitation. These results suggest that systemic microcirculatory dysfunction contributes to exercise limitation.