Download Cardiac Resynchronization Therapy (CRT): Expanding the role of

Cardiac Resynchronization Therapy
Martin Green, MD, FRCPC
Professor of Medicine
University of Ottawa Heart Institute
Ottawa, Ontario Canada
Cardiac resynchronization therapy (CRT) or biventricular pacing is now demonstrated to
be effective therapy for both improvement in cardiac function as well as mortality in
certain groups of patients with LV dysfunction.
First studies in surgical patients were performed by Cazeau et al in 1994.
Since then the techniques, technologies and indications have evolved considerably.
Studies have shown benefit in ventricular remodeling and performance and more recently
in heart failure events and mortality.
Patients likely to benefit include those with Class 2-3 NYHA heart failure and wide
LBBB. These generally are patients with QRS > 130 msec and LVEF < 0.35.
There are still many patients (20-30%) who do not respond to CRT. Some factors
predicting nonresponse are amount of scar, LV lead position, RBBB, and narrower QRS.
Detailed results of large clinical trials of CRT will be presented.
The COMPANION study compared patients with CRT and CRT-D with patients
randomized to Optimal Pharmacologic Therapy. Results are shown below:
The CARE-HF study was the first to show mortality benefit in patients with more severe
CHF (mostly NYHA class 3):
MADIT-CRT randomized patients with less severe CHF (mostly NYHA class 2-3) but
included heart failure therapy change in the primary endpoint. There was no significant
mortality reduction.
RAFT included patients with NYHA 2-3 CHF and showed a reduction in mortality as
well as heart failure hospitalizations:
Death
at
Any
Time
During
the
Study
Ev
en
t‐
fre
e
Su
rvi
va
l
ICD‐CRT
(5‐yr
survival
rate
0.714)
HR
(95%
CI)
0.75
(0.62,
0.91)
P=0.003
ICD
(5‐yr
survival
rate
0.654)
In conclusion CRT benefit is now well-documented for patients with NYHA class 2-3
CHF, LBBB QRS > 130 msec, and LVEF < 0.35.
Issues related to nonresponse will require continued evaluation.
References:
1. Cleland JGF et al; The Effect of cardiac Resynchronization Therapy on Morbidity
and Mortality in Heart Failure (CARE-HF). N Engl J Med 2005; 352.
2. Linde C et al; Randomized Trial of Cardiac Resynchronization in Mildly
Symptomatic Heart Failure Patients and in Asymptomatic Patients with Left
Ventricular Dysfunction and Previous Heart Failure Symptoms (REVERSE).
JACC vol 52, No. 23, 2008.
3. Moss AJ et al; Cardiac-Resynchronization Therapy for the Prevention of HeartFailure Events. N Engl J Med 2009; 361.
4. Bristow MR et al; Cardiac-Resynchronization Therapy with or without an
Implantable Defibrillator in Advanced Chronic Heart Failure.
N Engl J Med 2004;350:2140-2150.
5. Bilchick KC et al; Bundle Branch Morphology and Other Predictors of Outcome
after Cardiac Resynchronization Therapy in Medicare Patients.
Circulation 2010;122;2022-2030.
6. Tang ASL et al; Cardiac-Resynchronization Therapy for Mild-to-Moderate Heart
Failure (RAFT). N Engl J Med; November 14, 2010.
7. van der Wall EE et al; Cardiac Resynchronization Therapy; Evaluation by
Advanced Imaging techniques. Int J Cardiovasc Imaging (2010) 26:199-202.