At the start of the pandemic, epidemiologists made a striking observation. Compared to the general population, people with cardiovascular disease (CVD) were more than twice as likely to contract severe forms of COVID-19. Over the past six months, death rates from COVID-19 have dropped significantly, but cardiovascular disease remains a major predictor of poor outcomes. What have we learned about heart disease and COVID-19 during this time?
Pre-existing heart problems and poor metabolic health increase risk of severe COVID-19
As I described in a blog post in April, certain health conditions, such as diabetes, increase the risk of severe COVID-19 by suppressing the immune system; others, like asthma, increase the risk by weakening the lungs. However, in the early months of the pandemic, it was not entirely clear how CVD increased the risk of severe COVID-19. We now have two explanations.
The first is that pre-existing heart disease, such as damaged heart muscle or blocked heart arteries, weakens the body’s ability to survive the stress of the disease. A person with a vulnerable heart is more likely to succumb to the effects of fever, low oxygen levels, unstable blood pressure, and blood clotting disorders – all possible consequences of COVID-19 – than they are. a previously healthy person.
A second explanation relates to the underlying poor metabolic health, which is more common in people with heart disease. Poor metabolic health refers to conditions such as type 2 diabetes or prediabetes and obesity, which in turn cause inflammation and a risk of blood clots, worsening the effects of COVID-19 and increasing the likelihood of devastating complications of COVID-19.
How does COVID-19 cause heart damage?
The SARS-CoV-2 virus can damage the heart in several ways. For example, the virus can directly invade or inflame heart muscle, and it can indirectly harm the heart by upsetting the balance between oxygen supply and demand. Heart damage, which can be measured by elevated levels of the troponin enzyme in the bloodstream, has been detected in about a quarter of patients hospitalized with severe COVID-19 illness. Of these patients, about a third have pre-existing CVD.
Inflammation of the heart muscle
The majority of people with COVID-19 will have mild symptoms and make a full recovery. However, about 20% will develop pneumonia and about 5% will develop serious illness. In the severe form of COVID-19, the body’s immune system overreacts to the infection, releasing inflammatory molecules called cytokines into the bloodstream. This so-called “cytokine storm” can damage several organs, including the heart.
Inflammation of the heart muscle, called myocarditis, usually only occurs in patients with advanced COVID-19 disease. Myocarditis can result from direct cardiac invasion by the virus itself, or more generally from inflammation caused by a cytokine storm. When this happens, the heart can become enlarged and weakened, resulting in low blood pressure and fluid in the lungs. Although this severe form of myocarditis is rare, recent studies suggest that a milder form of inflammation of the heart muscle may be much more common than previously recognized. A recent study showed that asymptomatic heart inflammation was seen on magnetic resonance imaging in up to three-quarters of patients who had recovered from severe COVID-19.
Increased demand for oxygen and decreased oxygen supply lead to heart damage
Fever and infection speed up the heart rate, increasing the work of the heart in patients with COVID-19 who develop pneumonia. Blood pressure can drop or soar, putting additional stress on the heart, and the resulting increase in oxygen demand can lead to heart damage, especially if the arteries or heart muscles were unhealthy to begin with.
Heart damage is most often caused by heart attacks, which result from a blood clot forming in a vulnerable heart artery, blocking the flow of oxygen to the heart muscle. Inflammation linked to COVID-19 increases the risk of this type of heart attack by activating the body’s coagulation system and disrupting the lining of blood vessels. When inflamed, this liner loses its ability to resist the formation of clots. These blood clots in the heart’s large and small arteries cut off its oxygen supply. The increased tendency to clot can also lead to blood clots in the lungs, which can lead to low levels of oxygen in the blood. Severe pneumonia further decreases the oxygen in the blood. When the demand for oxygen exceeds the supply, the heart muscle is damaged.
Finding a ray of hope and reducing risks through a healthy lifestyle
People with cardiovascular disease who engage in healthy behaviors can strengthen their defenses against COVID-19 while reducing the long-term risk of cardiovascular disease itself. This means a lot of physical activity and a healthy diet such as mediterranean diet. Cook at home when you can, and walk outside with friends if your gym is temporarily closed. Purchase an inexpensive, easy-to-use monitor to measure your blood pressure at home. And continue to follow CDC safety guidelines for wearing masks, physically distancing, and avoiding large gatherings.