Statistical analysis
Categorical variables are summarized as percentages. Normally distributed continuous data is expressed as mean ± SD and non-normally distributed data is expressed as median with interquartile range of 25th and 70th percentiles. For comparing variables, we used a χ2-test (categorical variables), a t-test (normally distributed continuous variables) and a Mann-Whitney U test (non-normal continuous variables). Kappa statistics were used to calculate the inter-observer variability in the extent and location of CAD detected in the coronary angiograms. Cumulative hazard and the survival curves following ICD intervention were analysed with the Kaplan-Meier survival analysis method and the statistical comparison using the log-rank test. Cox proportional hazards regression models were used to determine the predictors of survival. The co-efficients were expressed as hazard ratios with 95% confidence intervals. P value <0.05 was considered statistically significant.