In April, a team of cardiologists led by Professors Eike Nagel and Valentina Puntmann at Goethe University in Frankfurt started studying the hearts of people recently recovered from Covid-19. Within days, they discovered something alarming: months after recuperating from the most obvious Covid symptoms, patients were still presenting with cardiac problems including elevated levels of troponin (a protein related to heart damage) and inflammation.
“At the end of the first week of the study, when we had seen about five patients Dr Puntmann and I looked at each other and said: ‘This is shocking’,” Nagel wrote in an email. “We see much more involvement than we expected’.”
Their study, published in July, found that close to 80 per cent of recovered Covid patients still had cardiac abnormalities two to three months after diagnosis with the virus. For 60 per cent of them, the issue was continued inflammation of the heart muscle. That alone was a frightening finding, but more worrying was their discovery that even patients who had only mild or moderate symptoms of Covid – or no symptoms at all – still showed signs of heart damage.
Their findings caused a stir and have been subject to challenge by other researchers, but Nagel and Putmann say their conclusion – that Covid could be causing widespread heart damage even in less severe cases – still stands.
Right now, that means there could be thousands of people suffering from the symptoms of Covid-related heart injuries: chest pain, palpitations and grinding exhaustion. In decades to come, it could mean more cases of heart failure.
How many are affected?
In the early days of the pandemic, data from China showed that around 20 per cent of patients hospitalised with Covid-19 developed a cardiac injury. Months on researchers are still trying to understand exactly what happens to the heart after a bout of infection and what impact that might have in the long-term.
Much remains unknown, but several studies have shown that for a subset of Covid patients heart damage is persisting long after the infection has subsided.
Austrian research based on patients who fell ill in the Alps last winter showed nearly 59 per cent of them had heart dysfunction six weeks after discharge from hospital. A non-peer reviewed study of 139 health workers in Spain who had recovered from Covid found that 40 per cent of them either fulfilled the diagnostic criteria for myocarditis (inflammation of the heart muscle) or for pericarditis (swelling in the fluid-filled membrane that surrounds the heart) ten weeks after recovery.
What causes the damage?
There are three main theories:
- Heart strain. There’s a link between ordinary flu and increased risk of heart attack so it stands to reason that Covid, as a respiratory virus, could put a similar strain on the heart. The hypothesis is that the virus’s impact on the lungs – breathing difficulties, reduced lung capacity, pneumonia – may be putting extreme pressure on the heart to circulate oxygen around the body.
- Cytokine storm. Severe inflammation set off by an increased cytokine response could be another culprit. When released by immune cells cytokine proteins trigger the body’s responses to infection. These responses include inflammation, so when too many proteins are released, the inflammatory response may be exaggerated. This is most likely for people who were extremely sick with the virus.
- Infection. Another probable cause of heart injury in long Covid patients is that the virus itself could be infecting heart tissue by binding to an enzyme – Angiotensin-converting enzyme 2 (or ACE2 for short) – which is found on its cell membranes. The virus attaches itself to the ACE2 enzyme as an entry point to these cells. Once it’s in it spreads the viral infection and triggers an inflammatory response in the heart muscle causing viral myocarditis. Myocarditis is pretty rare, but it’s associated with other serious viruses including mumps, measles, Coxsackievirus and the 2009 H1N1 swine flu virus.
There’s another way that Professor Nagel thinks Covid could damage the heart: by triggering autoimmune disease – a low-intensity variant of the cytokine storm that can affect even people who’ve only had a mild bout of the virus. “Most people believe that the main damage of myocarditis occurs due to the virus itself,” he says. “This is actually only the case in severe acute cases. In many patients, the acute damage is limited but they develop autoimmune responses which can last for months or years.”
What it means
We know a good deal about myocarditis, which could give clues about what is to come. Myocarditis often goes away on its own but for a small number of people it can reoccur years later. In severe cases it can leave the heart’s tissue scarred and the muscle weakened, leading to heart failure. According to the Myocarditis Foundation, the condition is a factor in 45 per cent of all heart transplants in the US.
This doesn’t mean everyone with Covid-related heart damage has it for life. Doctors don’t know yet how long on average it will last, for the simple reason that they are dealing with it in real time and it hasn’t gone away. The concern is that even if only a small proportion of Covid sufferers end up with long-term heart damage, the spread of the virus is such that even a small percentage will amount to a lot of people.
How many? Yesterday the Johns Hopkins Coronavirus Resource Center counted 31,103,347 confirmed cases since the start of the pandemic. More than 30 million of those patients are still alive. If the sample studied by Nagel and Puntmann were representative of the big picture, that would imply nearly 15 million people with inflammation of the heart muscle two to three months after infection. Even if this overstates the long-term problem by an order of magnitude, it still points to a whole new category of heart disease.