Why Some People Suffer from Cardiovascular Events and Symptoms following COVID-19       

We know that SARS-CoV-2 not only attacks the lungs in COVID-19, but is essentially a vascular virus resulting in (1) dysfunction of the cells that line blood vessels and (2) a propensity for the development of blood clots, strokes and heart attacks, even in the year following the apparent recovery from seemingly mild COVID-19.

A few points that will help you understand what I mean by “dysfunction of the cells that line blood vessels:”

• Blood vessels are lined with cells – we call these endothelial cells
• Blood vessels are dynamic, that is to say that they change size. With veins, the change in size is more of a passive phenomenon, dependent upon the volume of blood and gravity, because veins don’t incorporate muscles in their structure. For example, if you are sitting down reading this, place one of your hands in your lap with the palm down and your fingers outstretched. As you look at the top of your hand between the wrist and where your fingers begin, you likely see a couple of veins sticking up. If you slowly elevate your hand, keeping your palm down so that you can observe those veins, it is likely that by the time your hand gets to your shoulder level, the vein appears flat or at least much less prominent. With you hand in your lap and below your heart level, gravity causes blood to accumulate in the veins and distends them. As you raise your hand above your heart level, gravity is emptying the blood from the veins and returning that blood to the heart. The reason that blood doesn’t accumulate and remain in the veins that are in the most gravity-dependent portion of your body is that although veins don’t have their own muscles incorporated around the outside of them as arteries do, veins simply allow neighboring muscles to contract, squeeze the veins, and move the blood up against gravity. For example, if you are standing still, you will be upright, so blood will tend to pool in the veins of your feet and legs. (If you stand perfectly still and for a long time, then you may experience what we saw of the poor Royal Guard member who was standing watch over the Queen’s coffin earlier this year – fainting. The reason people who faint generally regain consciousness quickly is that now lying prone and without the effect of gravity to keep blood in the legs, all that pooled blood returns to the heart and restores circulation to the brain.
• Unlike veins, arteries are covered with muscle cells that help propel blood against gravity to deliver oxygen to all the organs of your body. But, lining the inside of these arteries are endothelial cells, and these cells allow arteries, especially the smaller arteries in our body, dilate or constrict, as necessary, to adjust blood flow in response to constant changes in temperature, altitude (e.g., climbing or diving), heart rate, blood pressure, etc. In cases of endothelial dysfunction, which can occur for a number of reasons, these endothelial cells become stiff and less able to adjust blood flow in the arteries by either dilating or constricting. For example, doctors often speak of atherosclerosis which refers to the accumulation of plaques of cholesterol and other material inside arteries, often from the effects of smoking, diabetes, high blood pressure and/or a variety of lipid disorders, but the lay public often refers to this as “hardening of the arteries,” which is a great phrase because these arteries do become stiffened and are less able to constrict or dilate as necessary. When atherosclerotic plaques are deposited in coronary arteries (the arteries on the surface of the heart that carry oxygenated blood to the heart muscle, those arteries can become too narrow or even plugged up and then cause chest pain (angina) and eventually a heart attack (myocardial infarction).
• But, what we have discovered with the SARS-CoV-2 virus that causes COVID-19 is that the virus can infect endothelial cells (these cells have the ACE-2 receptor on their cell surface), and as a consequence, endothelial dysfunction can occur.

Okay, now we are ready to discuss some of the cardiovascular consequences of COVID-19.

A recent study: Coronary microvascular health in symptomatic patients with prior COVID-19 infection: an updated analysis | European Heart Journal – Cardiovascular Imaging | Oxford Academic (oup.com) sheds much new light on the pathogenesis that potentially contributes to cardiac symptoms and events following COVID-19.

The investigators compared positron emission tomography (PET) scanning results from patients who had appeared to have recovered from acute COVID-19 (271 subjects) with a control group (815 participants) with similar cardiovascular risk factors, but without a history of prior infection.

During exercise, blood flow to heart muscle via the coronary arteries should increase. PET scanning allowed for the determination of myocardial blood flow during exercise compared to that at rest and that ratio was used to estimate the myocardial flow reserve (MFR) (in other words, how much could study participants’ blood flow increase in the coronary arteries with exercise to allow the heart muscle to get the additional oxygen it needs due to the increased needs associated with exercise. A healthy subject will increase the blood flow through their coronary arteries by 2 – 2.5-fold, i.e., will have a MFR > 2).

The study group who had recovered from COVID was significantly more likely than the control group to have a MFR < 2, at a median of 174 days following their infection.

The decrease in MFR occurred at similar rates despite the particular variant the patient was infected with, however, the decrease in MFR was more prevalent in association with severe infection.  

What this all means is that at 6 months after some people who had COVID had seemed to have recovered from the infection, we could see evidence of endothelial dysfunction in the coronary arteries, meaning that the blood flow through the coronary arteries with exercise did not increase as it should, which in turn means that those patients’ hearts might not be adequately perfused with blood during strenuous exercise. This would in turn result in the heart muscle potentially not getting enough increased blood flow to satisfy the needs of the heart muscle for more oxygen and nutrients during exercise or stress, which in turn can lead to abnormal heart beats, arrhythmias or even heart attacks.

Take home message: If you get COVID, be sure to rest and allow your body the chance to recover. Keep in mind that it appears that your risk for a cardiovascular event remains increased for at least a year following your infection. When you feel that you have recovered, realize that your body still may be dealing with the consequences of infection. So don’t rush to return to your normal level of exercise. Slowly and progressively resume your exercise program. Be aware of what your body is telling you. If you experience palpitations (racing of the heart beat or irregularity in your heart beat), excessive shortness of breath, or any chest pains, especially chest pains that occur with your exercise, but then resolve with rest, call your doctor and get evaluated promptly and defer resuming your exercise until you get evaluated and get instructions from your doctor. If you experience shortness of breath at rest or develop chest pain that doesn’t resolve promptly with rest, don’t wait, call an ambulance and get to the hospital for evaluation. Never drive yourself if you are experiencing these symptoms.