An increasing number of ST‐segment–elevation myocardial infarction (STEMI) patients have no standard modifiable cardiovascular risk factors (SMuRFs) such as hypertension, diabetes, hypercholesterolemia and smoking, Australian figures show.

One in five STEMI patients (19%) with no prior history of cardiovascular disease also had no SMuRFs, according to data from the Australian GRACE (Global Registry of Acute Coronary Events) and CONCORDANCE (Cooperative National Registry of Acute Coronary Syndrome Care) registries.

And the proportion of STEMI patients without modifiable risk factors increased from 14% to 23% during the study period of 1999 to 2017, while these patients also had poor outcomes.

Published in the Journal of the American Heart Association, the study led by Dr Stephen Vernon of the Kolling Institute and Department of Cardiology, Royal North Shore Hospital, Sydney, analysed data from 3081 STEMI patients from 42 Australian hospitals identified from the registries as having no prior history of cardiovascular disease.

For the primary outcome of the study, individuals with MACE but no history of modifiable risk factors  had a significantly higher in‐hospital mortality rate (6% versus 4%) than individuals with one or more SMuRFs. This occurred despite there being no difference in presenting characteristics and only modest differences for In‐hospital management.

However, the rates of recurrent ischaemic symptoms (12% versus 16%) and clinical heart failure (7% verse 11%) were lower in SMuRF‐less patients compared with patients with 1 or more SMuRFs.

There were no differences in the rates of recurrent in‐hospital MI, cardiogenic shock, or major bleeding between the groups. There were also no clinically significant differences in the unadjusted rates of recurrent myocardial infarction, heart failure, or MACE in the first 6 months postdischarge.

The data showed a significant increase in the proportion of STEMI patients with no SMuRFs (P=0.0067)  during the study period. In contrast, there was no such change in a 3773‐subject subgroup of patients with non–ST‐segment–elevation acute coronary syndrome.

Interestingly, the proportion of SMuRF‐less STEMI patients was a third higher in men than women.

The study authors said the finding of a “not insubstantial” and increasing proportion of STEMI patients having no modifiable risk factors showed that more attention was needed for this  underappreciated group, particularly in light of their higher in‐hospital mortality.

“Although it is essential that we continue at a community and primary healthcare level to identify and address the burden of known risk factors for atherosclerosis, parallel efforts should continue toward unravelling the biological mechanisms underlying disease in SMuRF‐less individuals,” they wrote.

“New technologies and data science advances in omics and multiomics approaches will allow novel discovery approaches to be adopted in accurately phenotyped cohorts with the potential to identify as yet unknown biological networks and processes.”

With the current lack of circulating blood markers of atherosclerosis “activity,” there may be a wider role for other methods – such as coronary calcium scoring – to identify atherosclerosis in people with no risk factors, they suggested.

“Currently, international guidelines do not recommend screening with coronary artery calcium or computed tomographic coronary angiography in patients deemed at low risk based on traditional risk factor scores.

“Data highlighting the burden of disease in the SMuRF‐less population and the dramatic difference earlier detection and targeted prevention would make suggest the need for more widely accessible markers of subclinical disease particularly relevant for these individuals.”