A study conducted in Italy found that three in ten patients hospitalised for pneumonia experienced some form of cardiovascular event such as heart failure, atrial fibrillation or myocardial infarction. The Sapienza University of Rome conducted a study with 1200 patients hospitalised due to pneumonia. Of these patients, 700 were men and 500 were women. They were all over 60 years of age. Follow-up was carried out thirty days after hospitalisation due to infection. 32% of patients experienced some type of cardiovascular complication, such as heart failure (24%), atrial fibrillation (9%) or myocardial infarction (8 %). The increase in risk of myocardial infarction in the short and long term was more evident when the pneumonia was more severe.
This shows that not only does pneumonia affect the lungs, but in severe cases it can be systemic, affecting other organs. A multicentre study conducted in Spain reported that cardiac complications are more common in pneumonia caused by pneumococcus (one type of bacteria that causes the disease). Additionally, age, smoking, chronic heart disease and initial severity of pneumonia are risk factors for early (30 days after admission) and late (one year after admission) cardiac complications.
Possible mechanisms have been described based on animal models to explain the cardiac complications stemming from pneumonia. On the one hand, pneumococcus causes lesions in the heart muscle by means of pneumolysin, a toxin produced by this bacterium. This toxin can also directly cause the death of cardiac myocytes.
On the other hand, cardiac damage (for example myocardial infarction) is mainly caused by decreased blood flow to the body's tissues, which is caused by coronary artery closure related to the formation of atherosclerotic plaque. This plaque contains inflammatory cells such as platelets, which accumulate after an infectious stimulus. Pneumococcus has been linked to the activation and hyperactivity of these platelets.
In the case of influenza virus, studies show that cardiac complications can occur due to direct effects of the virus on the myocardium (the cardiac muscle) or due to an exacerbation of existing heart disease.
This link between infection and heart disease makes vaccination all the more important, in the case of both pneumonia and influenza. Studies have shown 36% less risk of a cardiovascular event among adults who had received the influenza vaccine, compared to those who did not. This percentage was higher in people diagnosed with coronary heart disease.
Like influenza, pneumonia is an illness that affects a large part of the world's population and can be serious. The demonstrable link between infection and heart disease should be useful for the treatment of these infections, to encourage vaccination and design or test potential drugs to reduce the risk of developing heart disease.