Standard modifiable risk factors (SMuRF) paradox for the prognosis in the patients with acute myocardial infarction
Authors: Takasaki A , Kurita T , Takeuchi T , Omura T , Masuda J , Seko T , Tanigawa T , Kitamura T , Kakimoto H , Dohi K 
Published: October 2024

Abstract

Background
Hypertension, diabetes, dyslipidemia and smoking are recognized as standard modifiable risk factors (SMuRFs) for adverse cardiovascular events such as acute myocardial infarction (AMI).
Recent studies have shown that AMI patients without SMuRFs are associated with increased mortality compared to those with SMuRFs.
However, the relationship between the number of SMuRFs in patients with AMI and mortality has not been well evaluated.

Purpose
The purpose of this study was to evaluate the clinical characteristics and prognosis of AMI patients stratified by the number of SMuRFs.

Methods
We studied 6,706 AMI patients between 2013 and 2021 using data from the Mie ACS registry, a retrospective and multicenter registry. For the purpose of this study, only AMI patients as their first cardiovascular events were included in this analysis. Therefore, after excluding patients with a known history of coronary artery disease (n=982), 5724 AMI patients were included in the current analysis.
All-cause mortality was compared with 30-day and after 30-day mortality in AMI patients stratified by the number of SMuRFs as the primary outcome. In addition, all-cause mortality rate was compared in AMI patients without and with SMuRFs after propensity score matching on age, sex, body mass index, Killip classification, cardiac arrest before presentation, multivessel disease, left main truck disease, hemoglobin and emergent percutaneous coronary intervention.

Results
Among 5,724 AMI patients, 672 patients (11.7%) did not have SMuRFs. The median age of patients without SMuRFs was higher than that of patients with any SMuRFs (73 y.o. vs. 70 y.o, P&lt;0.001), and higher prevalence of female and severe Killip class was observed in patients without SMuRFs compared with those with any SMuRFs (P&lt;0.001, respectively).
According to the KM survival curves stratified by number of SMURFs, an increased number of SMURFs was associated with higher 30-day survival rates (P=0.035), and the 30-day landmark analysis showed a trend toward higher survival in patients with the highest number of SMURFs, although not statistically significant (Figure1).
Multivariate Cox regression analysis showed that 0 SMuRF was an independent prognostic factor for 30-day mortality with hazard ratio of 1.55 (95%CI; 1.13-2.13, P&lt;0.001). In addition, KM survival curves after propensity score matched analysis showed the poor 30-day mortality in 0 SMuRF group (P=0.036), there was no significant difference in after 30-day mortality between the two groups (Figure 2).

Conclusions
Patients without SMuRFs had a high 30-day mortality rate, but once they survived the acute phase, their prognosis was comparable to patients with SMuRFs. Moreover, the SMuRF paradox was recognized in the acute phase. This finding highlights the need for early identification of the individuals at risk of developing MI despite the absence of SMuRFs and strict acute management regardless of the number of SMuRFs.