You may have seen headlines claiming that coronavirus can leave many people with dangerous and lasting damage. But what’s the evidence? We look at recent research and news coverage comparing the effects of Covid-19 to heart attacks.
News stories have suggested that Covid-19 could cause damage to the heart, and that this damage could last beyond recovery from the disease. Some newspapers have even compared this to the damage caused by a heart attack. Much of this coverage has come from a study published at the end of July 2020, in which researchers looked at the hearts of people who had recovered from Covid-19 using cardiovascular MRI scans.
There was already research showing that Covid-19 could affect the heart during the illness itself. A recent BHF-funded study showed that around half of 1216 patients who received a heart scan while in hospital due to Covid-19 showed abnormalities in their heart function, with around one in seven showing severe abnormalities likely to have a major effect on their survival and recovery. This sounds very alarming, but is not specific to coronavirus – damage to the heart is also known to happen in severe flu.
Neither of these pieces of research mean that everyone who becomes infected with coronavirus will develop heart problems, or that if you’ve had the virus, you need to start worrying because of these findings.
There’s already lots of evidence that coronavirus affects your blood vessels, but damage to the heart is less proven, and when it comes to long-term damage, the picture is particularly unclear.
How was the study carried out?
The study involved 100 people from the Hesse region of Germany, who had been diagnosed with Covid-19 between three weeks and four months previously and no longer had respiratory symptoms. They ranged from people who had experienced no Covid-19 symptoms, those with mild symptoms and those who needed hospital treatment.
Participants had blood tests to measure levels of troponin and NT pro-Brain Natriuretic Peptide (BNP) – proteins which can indicate damage to the heart muscle and heart failure. They then had detailed MRI scans of their heart, looking at whether there were structural changes to the heart. They also used the scans to look for signs of changes in the make-up of the heart tissue, such as scarring or build-up of fluid within the heart muscle. These changes can be a sign of inflammation, and could affect the ability of the heart to function properly.
The team then compared their results with results seen in 50 healthy volunteers, and 57 people who had not had Covid-19 but had similar ‘risk factors’ to the 100 Covid-19 patients who took part (such as high blood pressure, diabetes, or coronary heart disease).
What were the results?
The researchers found that people who had been diagnosed with Covid-19, and particularly those who had needed hospital treatment, tended to have higher levels of troponin in their blood. However, while troponin testing is used to help identify serious heart damage (for example, that caused by a heart attack), lots of factors can cause troponin to be raised.
People in the recovered Covid-19 group also tended to have slightly worse measures of their heart’s ability to pump blood. Their lower ejection fraction (the percentage of blood which is pumped out of the heart each time it contracts) was an average of 56%, compared to 61% in healthy volunteers and 60% in people with the same risk factors. A normal ejection fraction is around 50-65%, so all three of these averages are in the normal range.
More than three quarters of the participants who had recovered from Covid-19 had an ‘abnormal finding’ on their cardiac MRI. This included any changes in measures of the size and function of the heart chambers, or changes that could indicate scarring and/or a build-up of fluid in the heart muscle or the pericardium (the protective layer that surrounds the heart).
However, it’s worth noting that some of these changes were also seen in the comparison groups – and could have been caused by something other than coronavirus. Some of the changes may not make any noticeable difference to the health of that person. Taken on their own, these results do not mean that everyone who has had coronavirus should be worried about developing heart problems.
The authors concluded that these findings are sufficient to justify further investigation of possible lasting cardiac effects of Covid-19.
How good was the research?
The study was carried out by an experienced team of researchers and did show evidence of statistically significant changes in blood test and scan results in people who had recovered from Covid-19. However, the study includes a relatively small number of participants (100), who were all at different stages in their recovery and who had experienced different levels of severity of the disease. So it’s difficult to know how these results might apply to others, or whether the changes seen in their hearts are part of a short-term response to stress of the infection, or something that will affect their health in the longer term.
The study was also not carried out in a randomised way (the gold standard way of carrying out research) so it’s harder to be certain that the results seen are not due to some hidden bias in the way that participants were selected.
We can’t tell from the study whether the signs of damage to heart function were caused by coronavirus, or had already happened before the virus.
Another important thing to consider is that a ‘statistically significant’ difference doesn’t always have a significant effect on patients. For example, the average ejection fraction of 56% in the recovered Covid-19 group was statistically significantly different from an average ejection fraction of 60% in the matched risk factor group – but a 4% difference in ejection fraction is unlikely to cause any noticeable difference to the patient, especially as both measures are still within the “normal” range.
Since this study was published, other scientists have been closely scrutinising the results. While the research community have generally agreed that this study indicates a need for further research in this area, experts have cautioned that the results need to be interpreted carefully. In particular, because this is a small, non-randomised study, and because the MRI measures used are not always an absolutely reliable indication of scarring or fluid in the heart. Others also believe they may have identified some errors in the way that the data was presented.
How good was the media coverage?
These results have received a lot of coverage, for example in the Daily Mail, and in The Sun with the headline ‘Coronavirus could cause SAME damage as a heart attack in 75% of patients’. This news coverage has worried a lot of people, and does not truly reflect the conclusions of the study.
For example, while it is true that raised troponin can be an indication that someone has experienced a heart attack, most participants in this study did not have troponin levels indicating that type of serious damage. Only 5 out of the 100 participants with recovered Covid-19 had severely elevated troponin. And a raised troponin level alone is not enough to make a heart attack diagnosis, and it doesn’t measure the long-term damage caused by the heart attack.
These articles do also not make it clear that people in this study were at different stages of their recovery, and that the heart changes seen were also seen in some people in the control groups. And while the study did show that 78% of the recovered Covid-19 group did have ‘abnormalities’ in their scans, it’s not the case that all of these abnormalities indicate severe damage to the heart.
The BHF view
Dr Sonya Babu-Narayan, BHF Associate Medical Director, said:
“This study shows some indications of changes in the structure and function of the hearts of people at different stages of their recovery from Covid-19. On its own, this study is not conclusive evidence that a high proportion of people who become infected with coronavirus will have short or long-term damage to their hearts.
However, this study has helped to continue an important dialogue in the scientific community and reinforces the need for ambitious, larger scale research into the potential for lasting cardiovascular consequences of coronavirus infection. This is a key focus of many of the flagship research projects prioritised through the BHF-NIHR Cardiovascular Partnership. This includes a project which will look at the prevalence and extent of heart muscle damage in people who have been hospitalised with Covid-19, and then assess their recovery after six months.”
People who develop new or worsening heart-related symptoms should still seek medical advice regardless of whether or not they have had Covid-19. If you are diagnosed with any heart or circulatory condition, such as heart attack, heart failure or stroke, during or after being ill from Covid-19, it’s important to attend the follow up care that you are offered.”
Published by the British Heart Foundation