Why COVID-recovered patients have cardiac events when exercising

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The primary symptoms of COVID-19 are respiratory, but concerns about the involvement of other organs such as the heart have been repeatedly raised.

In addition to heart-related complications occurring during the course of COVID-19, an increase in the frequency of cardiovascular events has been noted for several months following the infection. Countries such as Japan, Norway, and Australia have observed excess mortality even during the relatively benign Omicron variant, a significant portion of which is attributed to such events. Alongside traditional risk factors like tobacco use and high cholesterol, COVID-19 has now been recognized as an additional risk factor for cardiovascular disease. The mechanism underlying this association has intrigued scientists.

An organ that works continuously without a break in a person’s lifetime, the heart could suffer from problems occurring in its muscle, blood vessels or nervous system.

Myocarditis or inflammation of the heart muscle has been described among COVID patients and to a lesser degree, among people who had mRNA-based vaccination. The incidence following vaccination was highest among young men, while that following SARS-CoV-2 infection was greater among people over 40 years. While uneventful clinical recovery is the norm, persistent MRI abnormalities in the heart muscle have been documented even months afterwards. The long-term effects are unknown at this time.

A recent study from a leading heart centre in the U.S. showed that some people who recovered from COVID-19 developed a unique type of heart disease. While evaluating people who had persistent symptoms, the authors looked at the microvascular blood supply to heart muscle using a special PET technique called MFR or Myocardial Flow Rate. They found compromised microcirculation among COVID-recovered patients, which worsened over the subsequent six-nine months. These individuals also suffered more cardiac events during the follow-up period, when compared with people who did not have COVID-19.

Unlike conventional coronary angiograms that primarily focus on the larger coronary arteries surrounding the heart, MFR studies assess the tiny branches that penetrate deep into the heart muscle. When the heart works harder, the muscle needs more oxygen. This is supplied by an increased amount of blood flowing through these tiny branches. Although normal at baseline, if blood flow fails to increase during exercise, the heart muscle suffers ischemia or lack of oxygen supply. This could result in chest pain, shortness of breath or excessive tiredness.

Authors believe that this defect in the microcirculation is from ongoing inflammation within the delicate inner lining of these blood vessels. This is distinct from typical coronary artery disease, where visible blockages occur within the large calibre coronary arteries.

The severity of the defect in microcirculation was proportional to the initial severity of COVID. As the study did not include people who had uneventful recovery from COVID, it is unknown at this time whether people without lingering symptoms have this problem lurking within their heart.

Although most healthy people in the post-vaccine era recover easily from COVID-19, one out of 10 to 20 individuals go on to develop assorted lingering symptoms that last for several months. The above study suggests that at least a subset of these individuals could be suffering from such microvascular problems. At this time, there is no approved drug available for the treatment of such an ongoing inflammation of the endothelium, reiterating the need to avoid reversible risk factors like smoking. The study indicates that such patients could benefit from closer monitoring and appropriate intervention.

The current COVID-19 caseload in India is low. However, being a cyclical viral illness, further waves are expected. Japan, for instance, has just entered its 9th wave. The multi-system nature of this disease and uncertainty over long-term impact of repeated infections makes a case for avoiding reinfections to the extent possible.

(Rajeev Jayadevan is co-Chairman, National IMA COVID Task Force)

• The primary symptoms of COVID-19 are respiratory, but concerns about the involvement of other organs such as the heart have been repeatedly raised.
• Alongside traditional risk factors like tobacco use and high cholesterol, COVID-19 has now been recognized as an additional risk factor for cardiovascular disease.
• The multi-system nature of this disease and uncertainty over long-term impact of repeated infections makes a case for avoiding reinfections to the extent possible.