title: Cardiac resynchronization therapy: Part 1--issues before device implantation.
abstract: Cardiac resynchronization therapy (CRT) has been used extensively over the last years in the therapeutic management of patients with end-stage heart failure. Data from 4,017 patients have been published in eight large, randomized trials on CRT. Improvement in clinical end points (symptoms, exercise capacity, quality of life) and echocardiographic end points (systolic function, left ventricular size, mitral regurgitation) have been reported after CRT, with a reduction in hospitalizations for decompensated heart failure and an improvement in survival. However, individual results vary, and 20% to 30% of patients do not respond to CRT. At present, the selection criteria include severe heart failure (New York Heart Association functional class III or IV), left ventricular ejection fraction <35%, and wide QRS complex (>120 ms). Assessment of inter- and particularly intraventricular dyssynchrony as provided by echocardiography (predominantly tissue Doppler imaging techniques) may allow improved identification of potential responders to CRT. In this review a summary of the clinical and echocardiographic results of the large, randomized trials is provided, followed by an extensive overview on the currently available echocardiographic techniques for assessment of LV dyssynchrony. In addition, the value of LV scar tissue and venous anatomy for the selection of potential candidates for CRT are discussed.
authors.affiliation: Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands. jbax@knoware.nl
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Bax
authors.forename: Theodore
authors.initials: T
authors.lastname: Abraham
authors.forename: S Serge
authors.initials: SS
authors.lastname: Barold
authors.forename: Ole A
authors.initials: OA
authors.lastname: Breithardt
authors.forename: Jeffrey W H
authors.initials: JW
authors.lastname: Fung
authors.forename: Stephane
authors.initials: S
authors.lastname: Garrigue
authors.forename: John
authors.initials: J
authors.lastname: Gorcsan
authors.forename: David L
authors.initials: DL
authors.lastname: Hayes
authors.forename: David A
authors.initials: DA
authors.lastname: Kass
authors.forename: Juhani
authors.initials: J
authors.lastname: Knuuti
authors.forename: Christophe
authors.initials: C
authors.lastname: Leclercq
authors.forename: Cecilia
authors.initials: C
authors.lastname: Linde
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Mark
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Monaghan
authors.forename: Petros
authors.initials: P
authors.lastname: Nihoyannopoulos
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Schalij
authors.forename: Christophe
authors.initials: C
authors.lastname: Stellbrink
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
mesh_terms: D002303:Cardiac Output, Low / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D004452:Echocardiography; D006801:Humans; D010138:Pacemaker, Artificial; D018579:Patient Selection; D016032:Randomized Controlled Trials as Topic