New Indications for CRT
New Indications for CRT
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville.
Source: Stevenson WG, et al, and the Heart Failure Society of America Guideline Committee. Indications for cardiac resynchronization therapy: 2011 update from the Heart Failure Society of America Guideline Committee. J Card Fail 2012;18:94-106.
This paper reviews the recent data on the effectiveness of cardiac resynchronization therapy (CRT) in patients with milder forms of heart failure (NYHA classes 1 and 2) and revises the Heart Failure Society of America's (HFSA) 2010 Guidelines. The important trials reviewed were the Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction study (REVERSE), the Multicenter Automatic Implantable Defibrillator Trial with Cardiac Resynchronization Therapy (MADIT-CRT), and the Resynchronization-Defibrillation for Ambulatory Heart Failure Trial (RAFT).
The updated guidelines change recommendations in several areas. The new guidelines reflect the observation that the greatest benefit of CRT is seen in patients with left bundle branch block and a wide (≥ 150 ms) QRS duration. In such patients, CRT is now recommended in patients with a left ventricular ejection fraction below 36% and class II and class III heart failure symptoms. For ambulatory class IV patients, the QRS duration is increased from 120 msec to 150 msec. For patients with shorter QRS durations or a non-left bundle type IVCD, the evidence for benefit is less strong and the recommendation is that CRT may be considered. CRT is recognized as beneficial in Class II-III patients with a wide QRS and atrial fibrillation if ventricular pacing can be maintained. The evidence that CRT is of benefit in class I patients was not thought sufficient enough to warrant a positive recommendation.
The guidelines also comment on several other factors that are now recognized to affect the response to CRT. Most studies show more benefit in women than in men. The authors stress that the reasons for this are unknown and they do not support differences in practice or delivery of care based on gender. In MADIT-CRT, little improvement was seen with apical lead positions, and the guidelines now state that this should be avoided whenever possible. Finally, they state that the evidence for routine noninvasive assessment of dyssynchrony for patient selection and for post-procedure optimization of timing is uncertain and no single approach can be recommended.
Commentary
CRT has now been an accepted disease-modifying therapy in patients with class III heart failure symptoms, a widened QRS, and a severely depressed left ventricular ejection fraction for more than 10 years. Almost 50% of the ICDs implanted in the United States are now CRT-D devices. However, a significant proportion of patients fail to respond to CRT. CRT therapy is more frequently associated with complications and is more expensive. Recent studies have tried to expand the indications for CRT. These updated guidelines provide a very helpful overview of the recent CRT data, and recognize that patients with a wide left bundle branch block are the ones most likely to benefit. In contrast, patients with right bundle branch block are unlikely to benefit. The guidelines also argue that extending CRT to patients with very mild heart failure, NYHA class I, is probably not worth the increase in complications and cost.
This paper reviews the recent data on the effectiveness of cardiac resynchronization therapy (CRT) in patients with milder forms of heart failure (NYHA classes 1 and 2) and revises the Heart Failure Society of America's (HFSA) 2010 Guidelines.Subscribe Now for Access
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