Is the cardioprotective effect of pre-infarction angina blunted by age?

Abstract Funding Acknowledgements None. Background Pre-infarct angina (PIA) has been demonstrated to reduce infarct size and improve prognosis in ST-elevation myocardial infarction (STEMI). However, the effects of ischemic preconditioning with aging are still controversial. Purpose We aimed at comparing the effect of pre-infarction angina (PIA) on infarct size between two age groups. Methods We retrospectively studied consecutive STEMI patients treated by primary percutaneous coronary intervention (PCI) from January 2008 to December 2017. PIA was diagnosed if a patient had arm, jaw, or chest pain in the preceding eight days. Peak creatine kinase (CK) concentration was used as a surrogate of infarct size. Patients were divided into two groups, based on the median age: ≤62 years and >62 years. Multiple linear regression was used to identify independent predictors for infarct size that included total ischemic time and classic cardiovascular risk factors (hypertension, diabetes, dyslipidaemia, and smoking). Interaction between age and PIA was evaluated by 2-way factorial ANOVA. Results From the 1131 patients included in the study, 590 (52,2%) had ≤62 years and 541 (47,8%) had >62 years. Older patients were more often women (17.2% vs 8.6%, p<0.001) and had longer total ischemic time [4.6(3.0-9.0) vs 3.5(2.3-6.0) hours, p<0.001]. They also had higher prevalence of hypertension (32.8% vs 22.8%, p<0.001), diabetes (30.7% vs 18.7%, p<0.001) and were less likely to be smokers (26.9% vs 71.4%, p<0.001). The prevalence of PIA was similar across age groups (≤62Y 31.2% vs >62Y 32.0%, p=0.668). In older patients, PIA was associated with smaller infarct size [1.29(0.72-2.33) vs. 1.76(0.97-2.91) U/Lx103, p<0.001]. This difference was not observed for younger patients [1.72(0.95-3.40) vs. 1.81(0.94-3.37) U/Lx103, p=0.392]. There was no significant interaction between the existence of PIA and age on peak CK (p=0.280 for interaction) (Figure 1). In multivariate analysis, overall, PIA was associated with reduced peak CK (β=-0,320, p=0.011). On subgroup group analysis, PIA was a predictor of infarct size only in the older patients (β=-0,459, p=0.005), but not in the younger group (β=-0,182, p=0.394). Conclusion Older patients with PIA had significantly lower infarct size compared to patients in the same age group without PIA. After adjustment for risk factors and total ischemic time, PIA was a predictor of lower infarct size only for the older patients. These results suggest that the effect of pre-ischemic conditioning is not blunted by age, indicating that older patients should not be excluded from clinical trials investigation of cardioprotective strategies in STEMI patients.