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CARDIAC RESYNCHRONIZATION THERAPY: STATE-OF-THE-ART PAPER

Selecting Patients for Cardiac Resynchronization Therapy

The Fallacy of Echocardiographic Dyssynchrony

Nathaniel M. Hawkins, MBChB^_*,_*, Mark C. Petrie, MBChB, BSc, MD, Malcolm I. Burgess, MBChB, BSc, MD^_* and John J.V. McMurray, MD

^_* University Hospital Aintree, Liverpool, United Kingdom
Golden Jubilee National Hospital, Glasgow, United Kingdom
Western Infirmary, Glasgow, United Kingdom

Manuscript received August 1, 2008; revised manuscript received October 14, 2008, accepted November 2, 2008.

^_* Reprint requests and correspondence: Dr. Nathaniel M. Hawkins, Aintree Cardiac Centre, University Hospital Aintree, Longmoor Lane, Liverpool L9 7AL, United Kingdom (Email: nathawkins{at}hotmail.com).

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with heart failure. International guidelines unanimously endorse QRS prolongation to identify candidates for implantation, based on over 4,000 patients randomized in landmark trials. Small, observational, nonrandomized studies with surrogate end points have promoted echocardiography as a superior method of patient selection. Over 30 dyssynchrony parameters have been proposed. Most lack validation in appropriate clinical settings, including demonstration of short- and long-term reproducibility and intra- and interobserver variability. Prospective multicenter trials have proved informative in unexpected ways. In core laboratories, parameters exhibit striking variability, poor reproducibility, and limited predictive power. We are concerned that many centers today are using these techniques to select patients for CRT. Publication density and bias have misinformed clinical decision making. Echocardiographic parameters have no place in denying potentially life-saving treatment or in exposing patients to unnecessary risks and draining health care resources. Such measures should not stray beyond the research environment unless validated in randomized trials with robust clinical end points. The electrocardiogram remains a simple, inexpensive, and reproducible tool that identifies patients likely to benefit from CRT. Patient selection must use the parameter prospectively validated in landmark clinical trials: the QRS duration.

Key Words: cardiac resynchronization therapy • heart failure • dyssynchrony • tissue Doppler imaging

Abbreviations and Acronyms   CI = confidence interval   CRT = cardiac resynchronization therapy   HF = heart failure   IVMD = interventricular mechanical delay   LV = left ventricle/ventricular   LVEF = left ventricular ejection fraction   LVESV = left ventricular end-systolic volume   LVPEP = left ventricular pre-ejection period   NYHA = New York Heart Association   ROC = receiver-operator characteristic   ROI = region of interest   RT3DE = real-time 3-dimensional echocardiography   SPWMD = septal-to-posterior wall motion delay   SRI = strain rate imaging   TDI = tissue Doppler imaging   T = time to peak strain   To = time to onset peak velocity   Ts = time to peak systolic velocity   TSI = tissue synchronization imaging

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