Prevalence and outcomes of acute coronary syndrome patients with and without standard modifiable risk factors undergoing percutaneous coronary intervention
Authors: Ball J , Dinh D , Brennan A , Ajani A , Clark D , Freeman M , Oqueli E , Hiew C , Nanayakkara S , Walton T , Shaw J , Chan W , Reid C , Stub D 
Published: November 2023

Background

Prevention strategies in acute coronary syndrome (ACS) have focused on patients with standard modifiable risk factors (SMuRFs; diabetes, hypercholesterolaemia, hypertension, and current smoking). There is increasing awareness that SMuRF-less patients may represent a unique subset of patients experiencing ACS.

Purpose

To investigate the prevalence, characteristics, and outcomes of SMuRF-less ACS patients compared to those with SMuRFs undergoing percutaneous coronary intervention (PCI) in a major city in Australia.

Methods

We analysed data from adult (≥18 years) ACS patients receiving PCI between 2005 and 2020 using a PCI Registry which contains data for all patients undergoing coronary intervention at one of six major hospitals. Patients with a known history of coronary artery disease were excluded. Overall clinical characteristics and outcomes for those with and without SMuRFs were examined. The primary outcome was 30-day all-cause mortality. Secondary outcomes included in-hospital outcomes, myocardial infarction (MI), revascularisation, and major adverse cardiovascular and cerebrovascular (MACCE) events at 30 days. Long-term mortality was investigated using Cox-proportional hazards regression.

Results

From 1 January 2005 to 31 December 2020, 2,727 (14.4%) of 18,988 patients were SMuRF-less. Mean (± standard deviation [SD]) age was similar between patients with and without SMuRFs (63±13 vs 63±12 years) and there were more females with SMuRFs (25% vs 20%, p&lt;0.001). SMuRF-less patients were less likely to have a history of cerebrovascular disease (1.2% vs 4.2%, p&lt;0.001), peripheral vascular disease (0.6% vs 3.0%, p&lt;0.001), and chronic lung disease (8.6% vs 10.1%, p=0.014). They were more likely to present with out-of-hospital cardiac arrest (6.6% vs 3.9%, p&lt;0.001) and ST-elevation MI (59% vs 51%, p&lt;0.001). The left anterior descending artery was the target lesion in 46% of SMuRF-less patients compared to 39% of those with SMuRFs. During hospital stay, SMuRF-less patients were more likely to experience post-procedural cardiogenic shock (4.5% vs 3.6%, p=0.019) and arrhythmia (11.2% vs 9.9%, p=0.029). At 30 days, all-cause mortality did not differ between those with and without SMuRFs (3.2% vs 3.6%, p=0.290). Similarly, there were no differences in 30-day MI, revascularisation, and MACCE. During mean follow-up of approximately 7 years, being SMuRF-less was associated with a 12% decreased rate of mortality (adjusted Hazard Ratio 0.88 [95% confidence interval 0.78, 0.99], p=0.035).

Conclusions

Despite differences in characteristics (rates of cardiac arrest and ST-elevation MI), no difference in 30-day outcomes was observed among those with and without SMuRFs. However, SMuRF-less patients had lower hazard for long-term mortality. These findings suggest SMuRF-less patients may have novel risk factors and improved long-term outcome warranting further research.