Does COVID-19 cause heart problems? In late July 2020, the news from Germany wasn’t good. A study published online in the journal JAMA Cardiology in late-July 2020 found that, of 100 patients who had recently recovered from COVID-19, 78 of them showed abnormalities including heart-muscle inflammation, scarring, and inflammation of the membrane surrounding the heart (the pericardium).

Six months later, University of Colorado School of Medicine and UCHealth cardiologists studying the impact the coronavirus has on the heart have some good news to share. Their own experience with patients in Colorado, the findings of other scientists, and their ongoing clinical study all point to the same conclusion: COVID-19 does not appear to be causing widespread heart problems after all.

“I think what is out there is that myocarditis” – heart inflammation – “is pretty common in COVID-19. What we would say to that is that it’s not so common,” said Dr. Michael Bristow, a University of Colorado and UCHealth cardiologist whose lab specializes in studying the heart’s molecular details.

Heart problems and COVID-19

Bristow will be the first to tell you that the coronavirus affects the heart: after the lungs, it’s the second-most impacted organ, he said. But the coronavirus’s cardiac involvement seems to follow a pattern similar to that of the coronavirus’s impact across humanity. Many coronavirus patients, being asymptomatic, don’t even know they have it. Many others get just a little bit sick. Others feel awful for weeks or longer. About 14% of diagnosed cases end up hospitalized. About one in seven of those end up in intensive care.

Such cascading percentages also apply to the heart. Bristow said that perhaps roughly one-third of hospitalized coronavirus patients show elevated levels of enzymes such as troponin that indicate heart damage. Of that subset, maybe 2% to 5% end up with a detectible heart problem such as atrial fibrillation (irregular heartbeat) or a decrease in heart function. Multiply out the percentages and the chances of clinically significant cardiac problems from COVID-19 look to be less than 1% of diagnosed cases.

“But it’s up to physicians to detect these significant problems among the candidates who may have something seriously wrong,” Bristow said.

Consider also that most cases go uncounted. The Colorado COVID-19 modeling group’s most recent report estimated that only about one in five coronavirus cases in Colorado were diagnosed. That leaves us with roughly five to 10 notable heart problems for every 10,000 total COVID-19 cases.

Dr. Natasha Altman, a University of Colorado and UCHealth cardiologist who has consulted with many coronavirus patients, explained it this way.

“There’s still attention being paid to what’s going on in the cardiovascular system, but I think, with time, everything gets moderated, and our concerns are usually tempered,” she said.

CU study is a deep-dive into COVID-19 and the heart

Small numbers do get magnified when a disease infects as many as COVID-19 does: to perhaps 25,000 serious cardiac cases in the United States so far and nearly 400 in Colorado alone. Altman and Bristow are seeing such patients at UCHealth University of Colorado Hospital on the Anschutz Medical Campus, and they and colleague Dr. John Messenger are working on getting at the root of the coronavirus’s effects on the heart.

Their study focuses on critically ill patients admitted to the hospital and aims to more thoroughly explain how the SARS-CoV-2 virus itself and the immune system’s reaction to serious COVID-19 infection affects the heart. They’re starting with blood enzymes and other biomarkers, then doing echocardiograms, and finally taking tiny samples of heart muscle through a right-ventricular septal endomyocardial biopsy. Diverse specialists will look for and characterize heart-muscle genes and, should virus be found in the heart cells, viral genes; determine the degree of inflammation in cases of myocarditis; and assess heart-tissue damage.

The team is also paying close attention to genetic and biomarker-based evidence of ACE2-receptor expression – ACE2 receptors being the doors the SARS-CoV-2 viruses use to enter cells in the lungs and elsewhere. Recent research by a Bristow-led team showed that hospitalized heart-failure patients – whom one study found to die at five times the rate of comparable hospitalized patients – have greater ACE2 gene expression and, one assumes, more of those receptors for the coronavirus to latch onto as a result.

The big question that Bristow and colleagues seek to answer is whether these rare but very real heart problems are emerging from the body’s immune reaction to serious coronavirus infection in the lungs and beyond – or from the virus itself invading heart muscle.

It’s basic science research, but it’s far from merely academic. Different answers could dictate different treatments, Bristow and colleagues said.

“We’re looking at whatever ails the heart in a significant way,” Bristow said.