Cardiac resynchronization therapy (CRT) provides benefits for heart failure patients including improved quality of life, exercise capacity, and cardiac structure and function. While guidelines recommend CRT primarily for patients with left bundle branch block (LBBB) and QRS duration over 150 ms, randomized controlled trials included patients without LBBB who still demonstrated benefits. Additional factors like late ventricular activation may help identify non-LBBB patients likely to respond. Atrial fibrillation is also not an absolute contraindication as AV node ablation to ensure biventricular pacing can produce similar benefits to CRT as seen in sinus rhythm patients.

1. Cardiac Resynchronization Therapy:
Should Non-LBBB or Patients With
Atrial Fibrillation Receive CRT?
Michael R Gold, MD, PhD
Medical University of South Carolina
Charleston, SC
Disclosures: Consultant, Speaker Fees and Clinical Trials –
Boston Scientific, Medtronic, St Jude

2. Cardiac Resynchronization
Therapy: Weight of Evidence
 9,000 patients evaluated in randomized
controlled trials of heart failure
 Consistent improvement in quality of life,
functional status, and exercise capacity
 Strong evidence of changes in LV structure
– ↓ LV volumes and dimensions
–  LVEF
– ↓ Mitral regurgitation
 Reduction in HF and all-cause morbidity and
mortality

3. Pivotal RCTs of CRT
• NYHA II-IV
• LVEF < 35%
• QRS > 120-130 msec
• NRS (except RAFT)
• No study was restricted to LBBB or
even stratified randomization by BBB
or QRS duration

4. Subgroups Discouraged or
Prohibited from CRT by Updated
Guidelines
1. Non-LBBB
2. QRS < 150 msec
3. AF

5. RBBB in CRT Trials
 Advanced HF
– MIRACLE
– CONTAK CD
– COMPANION
– CARE HF
 Mild HF
– REVERSE
– MADIT-CRT
– RAFT
(28)
(33)
(162)
(35)
(82)
(228)
(161)

6. RBBB is not LBBB
Byrne MJ, Helm RH, et al. J Am Coll Cardiol 2007; 50: 1484-90.

7. Fantoni C, Kawabata M, Massaro R et al. J Cardiovasc Electrophysiol. 2005 Feb;16(2):112-9
Electrical Activation in RBBB and LBBB

8. Egoavil CA, Ho RT, Greenspon AJ, Pavri BB. Heart Rhythm. 2005 Jun;2(6):611-5.

9. COMPANION
Bristow, N Engl J Med. 2004;350:2140-50.

10. Heart Failure (HF) Event or Death by QRS Pattern in MADIT-
CRT Patients
LBBB Non-LBBB

11. RAFT
Tang. N Engl J Med. 2010 363:2385-2395.

12. 12
REVERSE: Clinical Composite Subgroup
Analysis
0.01 0.1 1 10
All Patients
Ischemic
Non-ischemic
CRT-P
CRT-D
NYHA Class I
NYHA Class II
Male
Female
0.26
0.90
0.46
0.52
Interaction
P-value
0.01 0.1 1 10
LBBB
RBBB
IVCD
Non-white
White
> 65 yrs
< 65 yrs
0.75
0.60
0.01
Odds Ratio with 95% CI Odds Ratio with 95% CI
CRT ON
Better
CRT OFF
Better
CRT ON
Better
CRT OFF
Better

13. What is the QRS Morphology
Hiding?
Can we identify patients or pacing
sites with late mechanical or
electrical LV activation?

14. Hara H, et al. Eur Heart Journal. 2012.

15. Must be More Than Just RBBB
Hara H, et al. Eur Heart Journal. 2012.

16. Physiologic Guided Lead Positioning:
QLV Interval Measurement

17. Q-LV Interval to Predict Acute Response
R = 0.74
-5
0
5
10
15
20
25
30
35
40
0 50 100 150 200
Q-LV (ms)
%LV+dP/dTmax
R
NR

18. Results: CRT Response By QLV Quartiles

19. Impact of QRS Duration
Cleland et al
Eur Heart J
2013

20. LVESV Response by Subgroup
Univariate Logistic Regression Results

21. RAFT: Primary Outcome

22. Mean F.U. :
25.2 + 18 months
673 pts 162 Permanent AF
114 pts
AF-abl
48 pts
Drugs + VRR
BVP % at 2 months
> 85% 85%
1. AVJ ablation and reverse remodelling
J Am Coll Cardiol 2006; 48 (4): 734-743

23. 1) Significant EF
increase both in SR and
AF-abl
No change for AF
drugs
3) Similar LVESV
reductions in SR and AF-
abl
2) Functional capacity score
increase both in SR and AF-
abl

24. Meta Analysis of AVJ ablation for CRT.

25. 1812 pts
Inadequate % BIV
pacing
AF pts
AF pts
 50% mortality if BIV pacing< 92%
25% pts BIV <
92%

26. Summary
 CRT response rates are best in the presence
of sinus rhythm, LBBB and QRS > 150 msec
 However, RCT included or studied other
groups of patients who show benefit, albeit
more variable
 Late electrical mechanical activation helps
identify subjects with non-LBBB who respond
 AV node ablation improves CRT response in
AFib