[Survival analysis of the patients with acute myocardial infarction by use of penalized splines]

ABSTRACT

Cardiovascular diseases are one of the most common causes of death and also major health problems in the world. The classical methods such as Cox regression are used in most medical studies on survival distribution, while this model assumes a linear relationship between log hazard ratio and risk factors which is not useful in many cases. The present study was performed to use the method of penalized splines to analyze the survival rate of the patients who had acute myocardial infraction. This research was a prospective descriptive-analytical study of longitudinal type which included 650 patients with acute myocardial infarction. Patients were followed for one year from the moment of diagnosis of MI, for survival analysis. The collected data were recorded in a check-list for every patient. Two different multivariate methods, proportional hazard regression and Cox model with penalized splines were used. Data analysis was carried out using R version 2.12 software and significant levels were considered 0.05. The mortality rate of the patients in a period of one year was 10.3% [67patients]. History of smoking, hypertension, diabetes, hyperlipidemia, arrhythmia and heart block were detected in 48%, 33.4%, 17.7%, 15.3%, 30% and 10.3% of the patient respectively. Based on Cox model with penalized splines the factors affecting survival rate were age, ejection fraction and use of streptokinase. Knowledge of the survival rate and factors affecting survival in the patients with acute MI can be used to provide the patients with valuable services, and to take measures to control and reduce mortality rate which can lead to increased life expectancy of these patients