Background: In cardiovascular disease, prevention strategies targeting standard modifiable cardiovascular risk factors (SMuRFs; hypertension, diabetes, hypercholesterolaemia, and smoking) are crucial; however, myocardial infarction in the absence of SMuRFs is not infrequent. The outcomes of individuals without SMuRFs are not well known.
Methods: We retrospectively analysed adult patients with first-presentation ST-elevation myocardial infarction (STEMI) using data from the Swedish myocardial infarction registry SWEDEHEART. Clinical characteristics and outcomes of adult patients (age ≥18 years) with and without SMuRFs were examined overall and by sex. Patients with a known history of coronary artery disease were excluded. The primary outcome was all-cause mortality at 30 days after STEMI presentation. Secondary outcomes included cardiovascular mortality, heart failure, and myocardial infarction at30 days. Endpoints were also examined up to discharge, and to the end of a 12-year follow-up. Multivariable logistic regression models were used to compare in-hospital mortality, and Cox-proportional hazard models and Kaplan-Meier analysis for long-term outcomes.
Findings: Between Jan 1, 2005, and May 25, 2018, 9228 (14·9%) of 62 048 patients with STEMI had no SMuRFs reaching diagnostic thresholds. Median age was similar between patients with SMuRFs and patients without SMuRFs (68 years [IQR 59-78]) vs 69 years [60-78], p<0·0001). SMuRF-less patients had a similar rate of percutaneous coronary intervention to those with at least one modifiable risk factor, but were significantly less likely to receive statins, angiotensin converting enzyme inhibitors (ACEIs) or angiotensin receptor blockade (ARB), or β-blockers at discharge. By 30 days after presentation, all-cause mortality was significantly higher in SMuRF-less patients (hazard ratio 1·47 [95% CI 1·37-1·57], p<0·0001). SMuRF-less women had the highest 30-day mortality (381 [17·6%] of 2164), followed by women with SMuRFs (2032 [11·1%] of 18 220), SMuRF-less men (660 [9·3%] of 7064), and men with SMuRFs (2117 [6·1%] of 34 600). The increased risk of 30-day all-cause mortality in SMuRF-less patients remained significant after adjusting for age, sex, left ventricular ejection fraction, creatinine, and blood pressure, but was attenuated on inclusion of pharmacotherapy prescription (ACEI or ARB, β-blocker, or statin) at discharge. Additionally, SMuRF-less patients had a significantly higher rate of in-hospital all-cause mortality than patients with one or more SMuRF (883 [9·6%] vs 3411 [6·5%], p<0·0001). Myocardial infarction and heart failure at 30 days were lower in SMuRF-less patients. All-cause mortality remained increased in the SMuRF-less group for more than 8 years in men and up to the 12-year endpoint in women.
Interpretation: Individuals who present with STEMI in the absence of SMuRFs have a significantly increased risk of all-cause mortality, compared with those with at least one SMuRF, which was particularly evident in women. The increased early mortality rates are attenuated after adjustment for use of guideline-indicated treatments, highlighting the need for evidence-based pharmacotherapy during the immediate post-infarct period irrespective of perceived low risk.
Funding: Swedish Heart and Lung Foundation, National Health and Medical Research Council (Australia).
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