Adapted from BMJ 2-9 May (Professor Kumar Raina) and 21-26 March (Katharine Lang, Journalist)
Many viral infections such as Covid and Influenza, Dengue Haemorrhagic Fever, and the onset of sepsis from any cause are associated with thrombotic complications.
Pathogen associated molecular patterns in the microbe activate pattern recognition receptors in the endothelial cells that line our blood vessels. This action triggers inflammatory cascades. Tight junctions between cells are weakened, coagulation is triggered and the glycocalyx is damaged. Whether viral proteins, bacterial lipopolysaccharides, or dengue NS1 protein, the blood vessels show the same type of damage.
Endothelial damage causes a diverse range of acute and chronic disease. Understanding this can help us understand the acute and long term effects of some infections.
Covid-19 infection started causing vascular complications such as myocardial infarction right from the onset at Wuhan. Later studies showed that 6% to 30% of patients admitted to hospital had myocardial injury. Although the virus enters the body from the respiratory system, it exerts its systemic effect via the vasculature affecting the lungs, heart, kidneys, and brain. There is damage to the small blood vessels, inflammation and clots, and perfusion of blood to the tissues is affected.
In the acute phase Covid-19 can cause myocarditis, myocardial infarction, and blood clots in the lungs. Those in the earliest wave were affected the most. The risk was equal to having prior coronary artery disease. In the first year after Covid you are more likely to experience stroke, heart rate irregularities, heart disease, peri-carditis, myocarditis and thromboembolism. Even having mild symptoms still increases the risk to some extent.
Hypertension, diabetes, obesity, old age, and pre-existing cardiovascular disease all magnify the risks of Covid infection. The severity of the initial infection matters too. Those admitted to hospital or intensive care units fare the worse.
Long covid is a complex multi-system disorder that can affect nearly every organ system and can be very disabling. In 2024 it affected 400 million people. Neurological, neuro-psychiatric and pulmonary symptoms are the most frequent problems. Then come the cardio-vascular problems.
One characteristic is dysautonomia (the autonomic nervous system doesn’t work correctly) and postural orthostatic tachycardia syndrome. Chest pain, palpitations, breathlessness and fainting are common problems. These are 1.6 times more likely in long covid sufferers compared to those without long covid. The initial severity of the infection, the higher the risk of cardiovascular complications.
Newer variants of Covid and infection in those already immunised don’t carry the same degree of risk compared to earlier waves of the infection. Some anti-viral drugs lessened the risk and others increased it. Vaccination is thought to be the best protection. Influenza vaccination also seems to protect against vascular complications. This is because the systemic inflammatory response is blunted when the person meets the infection.
Maintaining good blood pressure, good lipid control, and regular exercise are also protective.
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