 - Prolonged paced QRS duration will be defined as 150 ms, narrow paced QRS duration will be defined as 150 ms. All baseline characteristics of patient population will be expressed as percentages. Relative risk of SCD with prolonged paced QRS duration will be determined. Kaplan-Meier analysis will be done using the end-point of appropriate ICD therapy used as a surrogate marker of SCD, and clinical SCD to generate survival curves for each subgroup . 