Background: The benefits of de novo cardiac resynchronization therapy (CRT) in patients with QRS-prolongation and impaired left-ventricular function (LVEF) are well established. Current guidelines also recommend CRT-upgrade in patients requiring permanent or frequent right ventricular pacing (RVP) with symptomatic heart failure and reduced LVEF. Whereas several predictors of response to de novo CRT-implantation such as female gender, QRS-duration, non-ischemic cardiomyopathy (NICM) are known due to large prospective trials, similar factors regarding CRT-upgrade are currently lacking.
Methods and results: We examine 114 patients 3-6 months after CRT-upgrade due to frequent RVP (> 50%) and symptomatic heart failure. Response to CRT was evaluated by improvement in NYHA class referring to the Minnesota Living With Heart Failure Questionnaire. Only cardiomyopathy type and use of Angiotensin-converting-enzyme (ACE) inhibitor had an impact on response to CRT-upgrade in a linear regression model. Patients with NICM presented a greater responder rate than patients with ischemic cardiomyopathy (ICM) (80.4 vs. 60.3%, p < 0.05). Other traditional response predictors in de novo CRT recipients (e.g. QRS-width, female gender) showed no effect on CRT-response in this cohort.
Conclusion: Only underlying heart disease (NICM vs. ICM) and the use of ACE inhibitor were significant predictors of response to CRT-upgrade. In contrast to de novo CRT-recipients, where pre-implant QRS-duration is a key predictor, QRS-duration during RV-pacing has no significant impact on CRT-response in this cohort.
Keywords: CRT; Chronic right ventricular pacing; NICM.