Elevated Pulmonary Artery Pressure (Part 6)
Patients who were not contacted and confirmed to be alive and who were not matched to a death certificate were considered alive as of the last date included in the National Death Index file, namely, December 31,1986. Copies of death certificates were obtained for decedents and served as the sole source of information for assigning primary cause of death. The mean follow-up interval for all patients was 117 weeks. A total of 103 deaths were recorded, 89 percent of which were coded as due to a primary cardiac cause. buy ventolin inhalers
Data were coded and entered into a computerized database and analyses were performed with programs available on SPSS — PC + (SPSS, Inc, Chicago, Illinois) and BMDP (University of California Press, Berkeley, California). For analyses comparing two groups, xa tests were used for dichotomous variables and two-tailed t tests were applied to continuous variables. Multivariate survival analyses were carried out with the Cox regression model using the maximum partial likelihood ratio method available through programs included in BMDP Covariates included in this model that had no predictive value were excluded from the analyses presented herein, including sex, age, and smoking status. Survival curves for the comparison of two groups were constructed using the Kaplan-Meier product limit function and differences in the probability of survival tested with the generalized Wilcoxon statistic. In these analyses, “improvement X2” refers to the improved prediction of the model when the associated term was added.