Shaheed Rajaie Cardiovascular Medical Center, Mellat Park, Vali Asr Avenue, Tehran, Iran
Left or biventricular (BiV) pacing, or cardiac re synchronization therapy (CRT) is a new treatment for patients with advanced congestive heart failure (CHF) and left bundle branch block (LBBB). This therapy is based on the theory that synchronous BiV pacing is able to reduce atrioventricular (AV), inter- and intraventricular dyssynchrony (DYS). Although there is convincing evidence that CRT increases the left ventricular ejection fraction (LVEF), decreases mitral regurgitation (MR), and improves symptoms caused by heart failure, and reduces combined end points of all-cause mortality and hospitalization, the proportion of non responders (NR) to this therapy has been described and high as about one third to one half of patients with heart failure and LBBB. Here we review factors that may be responsible for this relatively high prevalence, and the ways for more accurate patient selection (Iranian Heart Journal 2003; 4 (4):49-.56).