Almost one in 12 middle-aged and elderly people have a myocardial scar, new research suggests, but the events that caused 80 per cent of the scars – which usually indicate a previous heart attack – went undetected.

Volunteers were aged between 45 and 84 years and free from clinical cardiovascular disease when they enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA) investigation in the US. Ten years later, 1,840 participants underwent cardiac magnetic resonance imaging.

Several conditions other than heart attacks can cause myocardial scars, including hypertrophic cardiomyopathy, sarcoidosis and amyloidosis, but no participants had characteristics suggesting that they had one of these relatively rare conditions.

Overall, 7.9 per cent showed myocardial scars but only 1.7 per cent had experienced a clinically recognised myocardial infarction, so 78 per cent of the scars were undetected clinically or by electrocardiogram.

Each 8.9 year increase in age and each 4.8kg/m² increase in BMI was associated with a 61 and 32 per cent greater risk of a myocardial scar respectively. Hypertension increased the risk by 61 per cent. Men were almost six times (odds ratio 5.76) more likely to show a myocardial scar than women and smokers were twice as likely as those who had never smoked.

Further studies need to assess the clinical relevance of undetected myocardial scars, say the authors. “The broad result should apply in the UK since the cardiovascular risk profile is similar,” lead author David Bluemke, director of radiology and imaging sciences at the NIH clinical center in Bethesda, Maryland, told Pharmacy Magazine.

“Individuals who are at highest risk have hypertension, obesity and smoke – these individuals tend to be frequently observed by pharmacists. Many of the most commonly prescribed medications for cardiac disease, such as statins, and treatments for diabetes, seemed to decrease or moderate the frequency of scars in the heart.” 

^{(JAMA 2015; 314:1945-1954)}