Like every coronavirus, the novel coronavirus (SARS-CoV-2) is called so for the spiky projections arising from its outer surface. As a result the virus looks as if it’s wearing a crown, the Latin for which is ‘corona’. This is the same reason the arteries of the heart are called the coronary arteries.
While we’re scrambling to keep as many people from being infected by the novel coronavirus as possible, and treating the symptoms of those who have been severely affected, we still have a lot to learn about how the virus affects different organs of the human body.
For example, there are many controversies about what we know of how the virus affects the heart, and the cardiovascular system in general, and which medicines can be used to treat the consequences.
Though the virus’s primary target is the respiratory system, the cardiovascular system is also affected. The virus uses its crown-like projections – called the spike proteins – to bind to a receptor molecule called angiotensin converting enzyme 2 (ACE-2), produced by cells of the heart as well as of the lungs. After binding, the virus enters the cells and hijacks the cellular machinery to make more copies of itself. The ACE-2 plays a key role in the functioning of the heart, including in the development of blood pressure.
Once the virus has entered the lungs, the body tries to fight the virus off by producing chemical compounds called cytokines. In a small fraction of patients, this process can quickly turn aggressive, and the body produces too many cytokines in a cytokine storm. This could cause the patient’s lungs to fail, rendering them unable to infuse the blood with oxygen.
Oxygen is the principal source of energy for all cells and organs in the body. So when there’s reduced supply of oxygen to the heart muscles, the heart also begins to fail.
The cytokines also enter the blood and precipitate a drop in blood pressure, which further dampens the heart’s ability to pump blood.
To compensate for the reduced oxygen supply and the lower blood pressure, the heart begins to beat faster. This is helpful but only at first, as the heart will eventually grow tired and fail.
People with heart conditions are not at higher risk of contracting COVID-19 relative to the general population. However, doctors have observed that once people with heart conditions do get COVID-19, they tend to go on to develop a severe form of the infection plus other complications. Doctors have also noted that COVID-19 has a fatality rate of around 0.9% in patients with associated illnesses but 6-10% in patients with high blood pressure and other related ailments.
The reason for this association is not yet clear – but it could simply be because many older people (70+ years old) also have high blood pressure, and older people are at higher risk of dying due to COVID-19.
Pregnant women who have heart ailments may be at higher risk, too.
Currently there is no evidence that the virus can directly infect the heart valves, muscles or their covering or implanted cardiac devices like pacemakers and defibrillators. However, a cytokine storm could stress the heart enough to rupture fatty plaques or blocks inside the heart’s arteries, resulting in heart attacks.
Another point of debate among cardiologists has to do with two key medicines currently used to treat high blood pressure: angiotensin-converting enzyme-inhibitors and ACE-2 receptor blockers. Researchers have speculated that people taking these drugs could theoretically develop more lung complications following a COVID-19 infection.
However, we don’t yet have evidence to confirm this hypothesis. The major-guideline forming cardiology societies and associations, such as the European Society of Cardiology, the American Heart Association and the British Cardiac Society, have recommended that heart patients continue taking these drugs since they have proven benefits. Stopping cardiac medications without advice from a cardiologist can easily complicate one’s condition.
Notably, the Indian Council of Medical Research has also issued guidelines for frontline healthcare workers, who are at higher risk of contracting COVID-19, to consume hydroxychloroquine as a prophylactic. However, there is scant evidence that hydroxychloroquine works as intended and that it’s safe. That being said, indiscriminate use without advice from a physician or without an advance ECG test can become life-threatening due to a condition called long QT syndrome – in which electrical changes in the heart, and corresponding changes in the heart’s rhythm called torsades de pointes (French for ‘twisting of peaks’), could result in sudden cardiac death.
Altogether, like so many other diseases, COVID-19 also affects the heart, and its causative virus has in this and other ways taken the world by storm. There is no known cure for the virus’s effects as yet and only supportive care can be provided. And while many researchers are looking for vaccines to protect against the virus’s effects, we can acquire an effective treatment or cure only through detailed studies of the disease’s pathology through postmortem studies and deep understanding of the virus’s microbiology.
In all, prevention will need physical distancing but a cure will need the coming together of the best in science.
Dr Binoy John is a senior consultant interventional cardiologist and specialist in heart failure and advanced cardiac diseases, Chennai.