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Patients who have a myocardial infarction (MI) without standard modifiable risk factors (SMuRFs) such as hypertension, hypercholesterolemia, or smoking have a worse outcome than patients with 鈮�1 of these risk factors, according to an evaluation of a registry that has enrolled more than 60,000 patients with an ST-elevated MI (STEMI).¹ The increased risk of poor outcomes in these individuals was particularly pronounced in women.¹

STEMI in the absence of SMuRFs is not uncommon, and it might be increasing. In one study, the prevalence climbed from 10.9% in 2006 to 27.4% in 2014.² In a national registry in Australia, the proportion of STEMI patients without SMuRF rose from 14% in 1999 to 23% in 2017.³ In this latter study, SMuRF-less STEMI patients had higher rates of in-hospital major adverse cardiac events (MACE) and mortality than those with 鈮�1 SMuRFs.³

In a new STEMI study comparing SMuRF-less patients to those with 鈮�1 SMuRF, clinical outcomes were evaluated from 62,048 STEMI patients in the Swedish MI registry, SWEDEHEART. The comparison evaluated those patients without prior history of coronary artery disease who entered the registry between January 1, 2005, and May 25, 2018. Of these, 9228 (14.9%) met the criteria for absence of SMuRF (defined as hypertension, diabetes, hypercholesterolemia, or smoking). Outcomes were examined overall and by gender.¹

The median ages of those with or without SMuRF (68 vs 69 years, respectively) were similar although significantly different due to the large sample size of patients with SMuRF(P<0.0001). The proportion of females was lower in the SMuRF-less population relative to those with 鈮�1 SMuRF (23.5% vs 34.5%; P<0.0001).¹

Relative to patients with 鈮�1 SMuRF, SMuRF-less patients had a higher rate of in-hospital mortality (9.6% vs 6.9%; P<0.0001). At 30 days, the risk of all-cause mortality was almost 50% greater (OR 1.47; P<0.0001) for SMuRF-less STEMI patients relative to those with 鈮�1 SMuRF. The difference in the absolute rate of all-cause 30-day mortality for SMuRF-less patients compared with patients with 鈮�1 SMURF was greater in women (17.6% vs 11.1%) than in men (9.3% vs 6.1%).¹

The registry data revealed different management of SMuRF-less patients relative to those with 鈮�1 SMuRF. Although percutaneous coronary interventions (PCI) were offered at a similar rate, those without SMuRF were significantly less likely to be discharged on statins (85% vs 88.5%; P<0.0001), angiotensin system inhibitors (75.2% vs 82%; P<0.0001) or beta blockers (88.7% vs 91%; P<0.0001). When adjustments were made for the anticipated benefit of these medications, the rate of 30-day mortality in the SMuRF-less patients was reduced but not eliminated.¹

Although the proportion of patients without SMuRF did not increase over time in the Swedish registry as it has in previously published observational studies, the authors noted that the nearly 15% of STEMI patients without SMuRF in this national registry still represents a substantial subgroup.¹

This study challenges a common misperception that cardiovascular disease can be eliminated simply by effective control of SMuRF, according to Gemma A. Figtree, MD, a cardiologist and professor of medicine at the University of Sydney, Australia. She believes that the SMuRF-less population is often overlooked and in need of new treatment strategies. According to Dr. Figtree, the first author of this study, one immediate need is more data about the risks of failing to discharge SMuRF-less patients on guideline-based therapies, such as statins, ACE inhibitors, and beta blockers.

鈥淎 meta-analysis of the specific effectiveness of these [guideline-directed] therapies in the SMuRF-less group would be a good start,鈥� Dr. Figtree said. Although she believes that the increased mortality among SMuRF-less STEMI patients relative to those with 鈮�1 conventional risk factors is likely due to increased rates of arrhythmia, she called for proactive research to determine how management of this group could be improved.

Published: May 25, 2021