Comparative Long-Term Outcomes after Cardiac Resynchronization Therapy in Right Ventricular Paced Patients versus Native Wide Left Bundle Branch Block Patients

BACKGROUND: The current guidelines is unclear when we should upgrade a patient with right ventricular pacing (RVP) to cardiac resynchronization therapy (CRT), although the deleterious effect of chronic RVP is established with recent trials.OBJECTIVES: We compared the long-term survival after CRT in patients upgraded from RVP to those with native left bundle branch block (LBBB) having QRS > 150ms and compared the mechanical properties associated with CRT response in these groups.METHODS: Overall 135 patients from a single center, 85 with native wide LBBB and 50 with RVP, implanted CRT were studied prospectively. Baseline LV typical contraction pattern was determined by speckle tracking echocardiography in the apical 4-chamber view. The pre-defined end-point was death, heart transplantation or LV assists device implantation over 4 years.RESULTS: The RVP patients had a significantly favorable long-term outcomes with adjusted hazard ratio (HR) of 0.36, 95% confidence interval (CI) 0.14 to 0.96 (p=0.04). Both groups had nearly 70% patients with typical contraction pattern. The absence of a typical pattern was associated with higher risk of an end-point with adjusted HR 5.43, 95% CI 2.31 to 12.72, p<0.001. Among the patients with typical pattern, activation of the apical septal segment occurred more frequently in the RVP group and base or mid septal segments in the LBBB group.CONCLUSION: Patients with HF upgraded from RVP have more favorable long-term outcomes after CRT than native LBBB patient with QRS ≥ 150ms. Contraction pattern assessment can be used to identify potential responders in the RVP group.