COVID 19 damages the heart?
The COVID 19 virus has unleashed a pandemonium across the world due to its high infectivity and consequent mortality especially in the elderly and other vulnerable groups of people. This write up aims to summarize the relevant information about the virus infection particularly related to whether COVID 19 damages the heart, reiterate some of the “facts” and bust some of the “myths” associated with it.
The COVID 19 virus:
COVID 19 is an acronym coined by the W.H.O on February 11th 2020 for the term Corona Virus Disease of 2019. The COVID 19 is an RNA virus which has ribonucleic acid as its genetic material. Other viruses which have deoxy ribonucleic acid as their genetic material are called DNA viruses.
The COVID 19 virus is spherical, invisible to the naked eye, and ranges in diameter between 0.06 to 0.14 microns. The surface of the sphere is dotted with spikes all around which causes it to resemble the sun and hence the name “corona virus”. COVID 19 primarily causes disease in animals (zoonotic virus), but it has at some point in time “jumped species” to cause disease in humans as well.
Invasion into the body:
It invades the human body via the respiratory tract or the conjunctiva of the eyes when droplets from infected persons travel in the air during breathing, coughing etc, or when one touches the surface of an object on which the virus is present and then inadvertently touches ones nose, mouth or eyes.
It then travels down into the respiratory tract and ultimately reaches the alveoli of the lungs. Here the virus triggers a severe inflammatory response first in the lungs and then in all parts of the body. This inflammatory response in the lungs causes thrombosis (clot formation) in the small blood vessels of the lung resulting in inadequate gas exchange and varying degrees of hypoxia which if severe can be fatal. Hypoxia may confound cardiac evaluation by Treadmill testing as you may be unable to achieve the target heart rate.
Systemic Inflammatory Response – the killer:
When the inflammatory response spreads to other organs of the body it is termed as a “systemic inflammatory response” and the ensuing disease it causes is termed systemic “inflammatory response syndrome” (SIRS). This systemic inflammatory response syndrome along with systemic hypoxia are the mechanisms by which COVID 19 damages the heart and various organs in the body. Direct invasion of the myocardial cell is not one of the known mechanisms by which COVID 19 damages the heart.
The COVID 19 illness:
COVID 19 damages the heart in approximately 30% of people requiring hospitalization but contributes to approximately 40% of all deaths in hospital.
SIRS and hypoxia can are common mechanisms by which COVID 19 damages the heart. Hypoxia can predispose to angina and myocardial infarction by adversely tilting the balance of blood flow to the heart muscles when pre-existing blocks are already present. They can also predispose to worsening of pre-existing blocks by endothelial inflammation and rupture of vulnerable plaques on the intima of the blood vessels. Formation of blood clots in the small coronary arteries and arterioles can cause sudden reductions in blood supply with catastrophic consequences.
SIRS and hypoxia can decrease the contractility of the heart muscle and thus worsen a pre-existing cardiac failure. They are the most coomon ways by which COVID 19 damages the heart. In most reports the virus has not been shown to directly invade the heart muscle (myocardium). People who have had a myocarditis form other causes are not more prone to COVID 19 induced direct myocardial damage.
Autopsy studies have not demonstrated presence of viruses inside myocardial cells. The cells only exhibit evidence of damage caused by hypoxia and SIRS. SIRS and hypoxia can trigger arrhythmias including atrial fibrillation.
Some reports have suggested that patients on ACEI and ARB medications (drugs commonly used for treatment of hypertension) may have a severe form of the disease but this theory is not backed by hard evidence and most authorities now do not recommend stoppage of these drugs if one has been diagnosed with the COVID 19 illness. All other cardiac medications can also be continued safely under medical supervision.
Most studies reveal that coexisting Diabetes and Hypertension predispose to mortality but their exact mechanisms are unclear. It may just be that they are just more prevalent in the older population. If you smoke as well, then, its a a double whammy! Not looking after one self will ensure that COVID 19 damages the heart.
In conclusion …
If your infection is asymptomatic, mild or moderate then cardiac involvement is very unlikely. COVID 19 damages the heart only in severe infections. If you have a severe COVID 19 infection you may have (not necessarily have!) a cardiac involvement as well. The treatment of severe COVID 19 infection aims to minimize clot formation in the blood vessels of the lung (microthrombosis) and prevent a severe SIRS along with the use of drugs that directly kill the virus (virucidal drugs). Virucidal drugs alone are never enough.