Comparison of Kaplan–Meier survival curves and Cox regression analysis of mortality data
Figures 4 and 5 show the survival curves of patients with NSTEMI and STEMI. Considering confidence intervals, we found that the differences among the regions were borderline significant in the NSTEMI group, whereas the 1-year survival of the STEMI group (Figure 4 ) was significantly better in the WR. As several factors influence survival, multivariate analysis was also performed using Cox regression analysis. During multiple factor analysis, age, sex, prior ischaemic events (infarction or stroke), presence of comorbidities, revascularisation performed during treatment and region of settlement were considered.
In the STEMI group, age and history of stroke, comorbidities, diabetes mellitus and peripheral artery disease significantly worsened survival rates throughout the entire follow-up period, whereas the survival rates of patients who received PCI treatment were significantly better than of those who did not receive invasive treatment at all checkpoints. In the NSTEMI group, age and history of stroke, diabetes mellitus and peripheral artery disease significantly worsened patient outcomes throughout the entire follow-up period, whereas PCI treatment significantly lowered their mortality rates. When analysing both types of infarction together, age and history of stroke, diabetes mellitus and peripheral artery disease were confirmed to have a negative impact on survival rate, whereas PCI treatment showed a positive effect.
Logistical regression analysis confirmed several factors influencing survival (Figures 6 and 7); among them, the region with independent importance: 30-day mortality; in the case of STEMI, the risk of death in the WR was 12% lower than in the ER (Hazard ratio = 0.88, p = 0.01144). At the 1-year checkpoint the region did not influence survival. Analysis of the 1-year survival data of the NSTEMI group showed that the mortality risk of patients living in the CR was 13.9% lower than those in the ER (Hazard ratio = 0.861; p = 0.0218).