Separate to atherosclerosis, heart disease risk factors also include age, genetics, and exposure to chemical or environmental influences. Cardiomyopathies (affecting heart muscle growth or performance) can be inherited or can be acquired following other heart and circulatory conditions, such as hypertension or a heart attack.^12,13

Other sources of heart damage include:^13,14,15

• excess circulating iron
• ‘stress’ hormones such as adrenaline
• infection, such as in endocarditis (affecting the inner lining of the heart) with bacteria entering the blood stream, for example via diseased gums, skin infections, injections or surgery
• a build-up of amyloid protein deposits due to genetic mutations or ageing.

Heart valve diseases – such as stenosis (where a heart valve stiffens) or regurgitation (the heart valve does not close properly) – are often due to the heart ageing but can be an abnormality present from birth. Infection, such as rheumatic fever, an autoimmune condition following a streptococcal throat or skin infection, can also damage heart valves.^16,17,18

Gut microbiota may also influence heart conditions. A recent study has found that an increased level of phenylacetylglutamine (PAG), a metabolite produced in the gut by bacteria digesting dietary proteins, is associated with a proportionately increased risk and severity of heart failure.^19,20

Myocarditis, inflammation of the heart muscle, is often caused by a viral infection such as flu or Covid-19. Other causes include bacterial (eg following a chest infection) or fungal (eg after athlete’s foot) infections. Auto-immune diseases such as lupus, exposure to toxins such as carbon monoxide or cocaine, and adverse reactions to medication and vaccines have also been associated with myocarditis.²¹

Pericarditis, inflammation of the pericardium, the protective sac around the heart, is also often caused by viral infections, as well as inflammatory conditions such as rheumatoid arthritis. Less common causes include injury (such as a road accident or heart attack), health conditions such as cancer, kidney failure, or underactive thyroid, and medicines or vaccines.²²