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(Circulation. 2007;116:1434-1436.)
© 2007 American Heart Association, Inc.

Editorial

Highlighting the R in CRT

David A. Kass, MD

From the Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Md.

Correspondence to Dr David A. Kass, Division of Cardiology, Ross 835, Johns Hopkins Medical Institutions, 720 Rutland Ave, Baltimore, MD 21205. E-mail dkass@jhmi.edu

Key Words: Editorials • heart failure • pacing • remodeling • Doppler imaging • electrical stimulation

An extract of the first 250 words of the full text is provided, because this article has no abstract.

Treatment of congestive heart failure by artificial pacing first attracted attention in the early 1990s when reports showed that standard right ventricular apical pacing with a shortened atrioventricular delay improved heart function in a subgroup of patients.¹ However, few seemed to benefit from this approach,² whereas by altering the pacing site to the left ventricle and using biventricular stimulation in patients with intramyocardial conduction delay, one achieved more consistent functional improvement.^3,4 The short-term response was greater in patients with a wider QRS complex, typically a left bundle branch pattern,⁵ and subsequent clinical trials that showed biventricular pacing improved morbidity^6,7 and mortality⁸ principally selected only those patients with a prolonged QRS duration.

Article p 1440

However, the story was never that straightforward, as investigators found that the correlation between basal QRS duration and immediate mechanical responses to biventricular pacing was poor⁵ and not predictive of long-term outcome.⁹ QRS narrowing after cardiac resynchronization therapy (CRT) was not useful either.^10,11 Furthermore, patients with a narrow QRS but mechanical dyssynchrony also benefited from CRT. This situation posed a problem because it was clear from the outset that identification of the right patients was important given the invasive nature and expense of CRT. In an early attempt to predict short-term response, we found mechanical dyssynchrony (assessed with magnetic resonance imaging) or the combination of QRS duration with functional data (basal dP/dt_max) better predicted short-term responders.⁵ Shortly after, echo-Doppler imaging methods were developed to assess dyssynchrony, and multiple groups found that these methods better predicted . . . [Full Text of this Article]

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