The Covid-19 can damage the heart both directly and indirectly, and lead to complications ranging from inflammation of the heart (myocarditis), injury to heart cells (necrosis), heart rhythm disorders (arrhythmias), heart attack, and muscle dysfunction that can lead to acute or protracted heart failure, experts said.
“Covid-19 is a vascular disease that injures heart cells and muscle. It also leads to the formation of blood clots, both in the microvasculature and large vessels, which can block blood supply to the heart, brain and lungs and lead to stroke, heart attack and respiratory failure,” said Dr Ravi R Kasliwal, chairman of clinical and preventive cardiology department at Medanta -The Medicity Hospital.
A US study using MRI found cardiac abnormalities in 78 of 100 patients who had recently recovered from Covid-19, including 12 of 18 asymptomatic patients. Sixty patients had ongoing myocardial inflammation consistent with myocarditis, found the study, which was published in the Journal of American Medical Association Cardiology in July.
“Even people with mild disease or no symptoms can develop life-threatening cardiovascular complications. What’s worrying is that this holds true for healthy adults with no pre-existing risk factors, which raise their risk of complications,” said Dr Kasliwal, who recommends that everyone who has recovered from Covid-19 be screened for heart damage
Extensive cardiac involvement is what differentiates Sars-CoV-2, the virus that causes Covid-19, from the six other coronaviruses that cause infection in humans, writes cardiologist Dr Eric J Topol, founder, director and professor of molecular medicine at the Scripps Research Translational Institute in La Jolla, California, in the journal Science.
The four human coronaviruses that cause cold-like symptoms have not been associated with heart abnormalities, though there have been isolated reports linking the Middle East Respiratory Syndrome (MERS) caused by MERS-CoV) with myocarditis, and cardiac disease with the Severe Acute Respiratory Syndrome (SARS) caused by Sars-CoV.
Sars-CoV-2 is structurally different from Sars-CoV. “The virus targets the angiotensin-converting enzyme 2 (Ace2) receptor throughout the body, facilitating cell entry by way of its spike protein, along with the cooperation of proteases. The heart is one of the many organs with high expression of Ace2. The affinity of Sars-CoV-2 to Ace2 is significantly greater than that of SARS,” according to Dr Topol.
Topol notes the ease with which Sars-CoV-2 infects heart cells derived from induced pluripotent stem cells (iPSCs) in vitro, leading to a distinctive pattern of heart muscle cell fragmentation evident in autopsy reports. Besides directly infecting heart muscle cells, Sars-CoV-2 also enters and infects the endothelial cells that line the blood vessels to the heart and multiple vascular beds, leading to a secondary immune response. This causes blood pressure dysregulation, and activation of a proinflammatory response leading to a cytokine storm, which is a potentially fatal systemic inflammatory syndrome associated with Covid-19.
Studies have found that injury to heart cells reflected in blood concentrations of a cardiac muscle-specific enzyme called troponin affects at least one in five hospitalised patients and more than half of those with pre-existing heart conditions, which raises the risk of death. Patients with higher troponin amounts also have high markers of inflammation (including C-reactive protein, interleukin-6, ferritin, lactate dehydrogenase), high neutrophil count, and heart dysfunction, all of which heighten immune response.
“The heightened systemic inflammatory responses and diminished blood supply because of clotting, endotheliitis (blood vessel inflammation), sepsis, or hypoxemia (oxygen deprivation) because of acute lung infection leads to indirect cardiac damage,” said Dr Kasliwal.
The cardiovascular damage associated with Sars-CoV-2 infection can persist beyond recovery. Since the virus affects the heart as much as the respiratory tract, further research is needed to understand why some people are more vulnerable to heart damage than others.