title: Selecting patients for cardiac resynchronization therapy: electrical or mechanical dyssynchrony?
abstract: Cardiac resynchronization therapy (CRT) markedly reduces morbidity and mortality in patients with heart failure and prolonged QRS duration. Landmark trials have included over 4000 patients based on their electrocardiogram. A few small, observational, non-randomized, single centre studies of short duration have suggested that echocardiographic measurement of mechanical dyssynchrony may better identify patients likely to benefit from CRT. We objectively review the meaning and measurement of electrical and mechanical dyssynchrony, the strengths and weaknesses of echocardiographic indices of dyssynchrony, and the controversial issue of predicting response to treatment. We conclude that proposals to alter current guidelines for patient selection, and include echocardiography, are misguided. Echocardiographic assessment will only become credible and applicable to clinical practice once used to select patients for large prospective randomized trials which show an improvement in clinical outcome.
authors.affiliation: Department of Cardiology, Stobhill Hospital, Balornock Road, Springburn, Glasgow G21 3UW, UK. nathawkins@hotmail.com
authors.forename: Nathaniel M
authors.initials: NM
authors.lastname: Hawkins
authors.forename: Mark C
authors.initials: MC
authors.lastname: Petrie
authors.forename: Michael R
authors.initials: MR
authors.lastname: MacDonald
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Hogg
authors.forename: John J V
authors.initials: JJ
authors.lastname: McMurray
mesh_terms: D001145:Arrhythmias, Cardiac / Q000150:complications / Q000000981:diagnostic imaging / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D018618:Echocardiography, Doppler, Color / Q000379:methods; D006333:Heart Failure / Q000150:complications / Q000628:therapy*; D006801:Humans; D018579:Patient Selection; D011379:Prognosis; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000628:therapy