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

2. 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

3. Efficacy Analysis/Study Flow
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A total of 156 (80 Control + 76 CRT) were available for efficacy analysis

4. 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)

5. (% 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)

6. 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.