Limited Response to CRT in Patients with RVD. Introduction: Patients with left ventricular dysfunction (LVD) and LV dyssynchrony may respond to cardiac resynchronization therapy (CRT). However, right ventricular dysfunction (RVD) is a predictor of decreased survival in patients with LVD, and its influence on clinical response to CRT is unknown. The purpose of this study was to examine the effect of RVD on the clinical response to CRT. Methods and Results: A retrospective cohort of consecutive patients who underwent implantation of a CRT implantable cardioverter-defibrillator (ICD) were included and deemed to have RVD based on a RV ejection fraction <0.40. A lack of response to CRT was defined as: death, heart transplantation, implantation of an LV assist device, absent improvement in NYHA functional class at 6 months or hospice care. Among 130 patients included (mean age 58 ± 11 years, 68.5% male, 87.7% Caucasian, 51.5% nonischemic cardiomyopathy), 77 (59.2%) had no response to CRT as defined above. Of the nonresponders, 43 (56%) had RVD and 34 (44%) did not have RVD (P = 0.02). After adjustment for age, race, gender, cardiomyopathy type, atrial fibrillation, serum sodium, and severe mitral regurgitation, RVD (adjusted OR = 0.34, 95%CI 0.14-0.82), female gender (adjusted OR = 0.36, 95%CI 0.14-0.95), and serum creatinine (adjusted OR = 0.25, 95%CI 0.09-0.71) were independently associated with decreased odds of response to CRT. There was a significant difference in survival of patients with and without RVD after CRT (log rank P = 0.01). Conclusion: RVD represents a strong predictor of lack of clinical response to CRT in patients with CHF due to LVD and should be considered when prescribing CRT. (J Cardiovasc Electrophysiol, Vol. 21, pp. 431-435, April 2010) © 2009 Wiley Periodicals, Inc.