While some people are able to recover from the effects of SARS-CoV-2 infection, others continue to suffer the after-effects of COVID-19 for much longer. Inability to exercise much is one of these persistent COVID symptoms. But there are still unanswered issues as to why some COVID patients continue to have reduced exercise capacity while others recover without this issue.
In a study recently published in the Journal of Infectious Diseases, a group of researchers at UC San Francisco found that people with chronic Covid often had lower-than-expected exercise capacities, with chronotropic incapacity (insufficient heart rate increase during exercise) being the key. the reason Additionally, they found an association between reductions in exercise capacity and early post-Covid elevations of inflammatory biomarkers. Additionally, they found that decreased heart rate during exercise may be linked to Epstein-Barr virus (EBV).
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First author Matthew Durstenfeld, MD, MAS, designed the cardiovascular substudy as part of the Long-Term Effects of Infection with Novel Coronaviruses (LIINC) led by Michael Peluso, MD, MHS, UCSF assistant professor of medicine. The LIINC was designed to assess physical and mental health after COVID-19 infection by including individuals representing the full spectrum of acute illness and post-acute recovery. The study began in November 2020 using echocardiograms to assess cardiac conditions underlying post-COVID symptoms.
When the initial echocardiogram-based study did not reveal the cardiac mechanisms of the symptoms, the team modified the study protocol to conduct a second visit with study participants a year later for advanced tests including cardiopulmonary exercise testing (CPET), cardiac magnetic resonance imaging (CMR). ), and ambulatory heart rhythm monitoring. Participants in the substudy also had blood samples collected and processed for serum and plasma at their echocardiogram visit.
Sixty participants with an average age of 53 years were studied about a year and a half after their Covid infection. On CPET, 49% of those with symptoms had reduced exercise capacity compared to 16% of those without symptoms. Adjusted peak VO2 (the amount of oxygen the body consumes during exercise) was 16.9% percent lower than predicted in those with symptoms. Chronotropic dysfunction was a common finding, and inflammatory biomarkers and antibody levels in the first few months after COVID-19 were negatively correlated with peak VO2 more than a year later.
“The findings suggest that chronotropic incompetence — failure to achieve 80% of the expected maximum heart rate during exercise — contributes to exercise limitation in prolonged COVID,” said Durstenfeld, a cardiologist and assistant professor of medicine at UCSF. “We also found evidence of EBV reactivation in all individuals with chronotropic dysfunction, however, we found no evidence of myocarditis, cardiac dysfunction, or clinically significant arrhythmias.”
The authors note the clinical diagnostic challenge that symptomatic patients present when there are no objective findings of cardiac dysfunction on multimodality cardiopulmonary testing. They suggest translational and proof-of-concept clinical research to characterize the distinct phenotypes and mechanisms of post-acute COVID symptoms is urgently needed to identify potential therapies.
Until more treatments are available, the authors believe that people with low exercise capacity may benefit from exercise training to improve their symptoms. Patient advocates have raised significant concerns about the safety of exercise in those with overlapping myalgic encephalitis/chronic fatigue syndrome.
“Although exercise is unlikely to cure long-term covid, preliminary data suggest that exercise training is the only intervention that has been demonstrated to improve exercise capacity, symptoms and quality of life,” Durstenfeld said. “Given patient concerns that exercise may worsen symptoms for some people, we need to rigorously study the role of exercise in prolonged COVID.”
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