Around 50 per cent of patients who have been hospitalised with severe COVID-19 and who show raised levels of a protein called troponin cause damage to their hearts. The injury was detected by magnetic resonance imaging (MRI) scans at least a month after discharge, according to new findings published today (Thursday) in the European Heart Journal Damage includes inflammation of the heart muscle (myocarditis), scarring or death of heart tissue (infarction), the restricted blood supply to the heart (ischaemia) and combinations of all three. The study of 148 patients from six acute hospitals in London is the largest study to date to investigate convalescing COVID-19 patients who had raised troponin levels indicating a possible problem with the heart. Troponin is released into the blood when the heart muscle is injured. Raised levels can occur when an artery becomes blocked or there is inflammation of the heart. Many patients who are hospitalised with COVID-19 have raised troponin levels during the critical illness phase when the body mounts an exaggerated immune response to the infection. Troponin levels were elevated in all the patients in this study who were then followed up with MRI scans of the heart after discharge in order to understand the causes and extent of the damage.