Enlargement of one of the heart's four chambers -- the right ventricle -- was the best predictor of which patients with severe Covid-19 infections were most likely to die, doctors reported to CNN.

These are the results of a new study, which has been accepted for publication in the Journal of the American College of Cardiology.

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A team of doctors from the Icahn School of Medicine at Mount Sinai looked at the health records of 105 Covid patients hospitalized at Mount Sinai Morningside in New York City between March 26th and April 22nd.

The reason is still unknown

Of the 105 patients in the study, 32 of them -- or 31% -- had dilation of the right ventricle based on an echocardiogram, or ultrasound of the heart. Of these, 41% died by the end of the study period, compared to 11% of those without right ventricular enlargement.

The reason behind the new findings remains unknown. Enlargement of the right ventricle may be caused by obstruction of blood flow in the lungs due to blood clots or lung tissue damage, according to the new study's authors. Direct damage to heart tissue by the coronavirus may also be a contributing factor, they added.

The only variable that was significantly associated with mortality

Enlargement of the right ventricle was the only variable that was significantly associated with mortality in this group of Covid-19 patients, the research team concludes.

This study provides important evidence associating right heart strain with adverse outcomes in hospitalized patients with COVID-19 infection," said Dr. Edgar Argulian, an assistant professor of medicine and a lead author on the study. "Clinicians can use bedside echocardiography as a readily available tool to identify patients with COVID-19 infection at the highest risk of adverse hospital outcomes," he added in a statement.

This is not the first time an association has been found between Covid-19 and right ventricular enlargement, CNN reports. Earlier this month, a case series in the New England Journal of Medicine described five critically ill Covid patients with enlargement of the right ventricle.

Coronavirus has previously been found to invade heart tissue because cardiac muscle cells are rich in ACE2 receptors - the molecular doorway used by the coronavirus, according to the American Heart Association.