Study Design Patients with LBBB and LV dysfunction Patients with Narrow / Normal QRS 100 Patients qualifying for CRT Responders

Study Design Overall Objective Determine CRT safety and efficacy in patients who are indicated for an ICD with NYHA Class III, narrow QRS duration (<130 ms) and evidence of mechanical dyssynchrony as measured by echocardiography/Tissue Doppler Imaging Primary Endpoint Improvement in Peak VO2 during CPET of at least 1.0ml/kg/min at 6 months. Secondary Endpoints Improvement in QoL score at 6-months Improvement in NYHA classification at 6-months

Efficacy Analysis/Study Flow Mark, I’ve tried to make this slide less busy Delete extraneous information A total of 156 (80 Control + 76 CRT) were available for efficacy analysis

Six-minute Hall Walk Distance (m) Efficacy Data 30 40 50 60 70 Baseline 6-months Quality of Life Median & 95% Conf Int p = 0.91 20 40 60 80 100 41% 46% % Improved in Peak VO2 p = 0.63 Control CRT 250 300 350 400 Baseline 6-months Six-minute Hall Walk Distance (m) Median & 95% Conf Int p = 0.23 Improved No Change Worsened 20 40 60 80 100 29% 54% 64% 41% 8% 5% NYHA Class p = 0.006 Control (n = 80) CRT (n = 76) Control (n = 80) CRT (n = 76)

(% improved from baseline) Peak VO2 by sub-group 80 Peak VO2 (% improved from baseline) 20 40 60 100 QRS ≥ 120 ms p = 0.02 QRS < 120 ms p = 0.45 QRS Duration (% improved from baseline) 20 40 60 80 100 Ischemic p = 0.82 Non-ischemic p = 0.25 Cardiomyopathy Type Control (n = 80) CRT (n = 76)

Conclusion In this randomized controlled trial, CRT did not improve Peak VO2 during exercise in patients with NYHA Class III heart failure, QRS duration <130ms, and an EF ≤ 35%. However, the subgroup of patients with QRS duration between 120 ms and 130 ms benefited from CRT. Additional research will be critical to further our understanding of the role of CRT in this patient population.