Explaining trends in heart attack: prevention has improved, mortality rates are down, hospitalisation remains the same
A report in Circulation from the Framingham Heart Study, which compared acute myocardial infarction (AMI) incidence in 9824 men and women over four decades, has proposed an explanation for the apparent paradox of improved prevention, falling mortality rates but stable rates of hospitalisation. The study found that over the past 40 years rates of AMI diagnosed by ECG decreased by 50%, whereas rates of AMI diagnosed exclusively by infarction biomarkers doubled. This "evolving" diagnosis of AMI, say the investigators, "offers an explanation for the apparently steady national AMI rates in the face of improvements in primary prevention".
However, the investigators emphasise that this study – like others before it – highlights a "40-50%" reduction in heart disease mortality in the USA from 1968 to 2000 and a 50% decline in the incidence of AMI when diagnosed by ECG. This, they propose, "implies that primary prevention efforts have influenced the incidence of AMI". That the incidence of hospitalised AMI has not similarly declined is explained by the greater sensitivity of diagnostic AMI biomarkers; they note, for example, that the detection rate of AMI by troponin was higher than in earlier decades.