Heart disease has been listed among the comorbidities for Covid-19 – that is, pre-existing conditions that can worsen the outcome of the disease. Emerging evidence indicates that around 10 percent of hospitalized Covid-19 patients have heart disease, diabetes, and high blood pressure compared to patients with lung disease, such as asthma and chronic obstructive pulmonary disease (COPD), who make up just 6 percent.
This trend towards patients with heart disease having worse outcomes compared to those with lung disease is seen across hospital reports from China, Italy, the US, and the UK. The disease has also been found to cause damage to the heart, both in patients with and without heart disease, as myocarditis – an infection of the heart – causes damage and scarring. It can be detected via a blood test to search for a protein called troponin. Studies from Italy and China both found that severely ill patients had raised troponin in their bloodstream.
Exactly why the heart plays such a significant role in the progression of the disease isn’t yet clear, though some mechanisms have been suggested. One centers around the ACE2 receptor on the cell surface, which there are a greater number of in patients with underlying heart disease. The SARS-CoV-2 coronavirus that causes Covid-19 has a spike protein that enables it to attack human cells, and this spike protein attaches to the ACE2 receptor. An increased number in ACE2 receptors therefore makes it easier for the pathogen to attack the body.
The second mechanism relates to our body’s capacity to mount an immune response when under attack from an invading pathogen such as coronavirus. Doing so requires the body to use up more energy than usual, which is why we get a temperature when we’re sick, as our metabolism is forced to speed up to meet the energetic demands to fight off the illness.
The bodies of most healthy people won’t have to struggle too hard to do this, but those with underlying health issues might not be able to mount the necessary response to fight the viral infection on their own. This reduced immune response results in more severe disease and worse outcomes as the virus is able to surge through the body, attacking important organs such as the heart and lungs. Research is currently underway to see if donations of plasma from recovered patients can help to support those less able to mount an immune response in slowing the spread of the virus within the body.
This isn’t the first time a respiratory disease outbreak has been associated with damage to the heart and worse outcomes for those with heart disease. The 2009 H1N1 flu outbreak, also called swine flu, saw a significantly increased number of heart complications in patients infected with H1N1 compared to previous flu outbreaks. Hospital reports found around 62 percent of H1N1 patients had myocarditis.
[H/T: The Conversation]