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).