title: Relation of QRS duration to response to cardiac resynchronization therapy.
abstract: Left bundle branch block (LBBB) is the most reliable electrocardiographic predictor of responsiveness to cardiac resynchronization therapy (CRT). However, not all patients with LBBB will respond to CRT. Our aim was to investigate the interaction between QRS duration, LBBB-type morphology, and the responsiveness to CRT. We retrospectively analyzed electrocardiograms of 243 patients who underwent CRT implantation according to current clinical indications. A 6-month reduction of left ventricular end-systolic volume >15% was used to identify CRT responders. The clinical end point consisted of death, hospitalization for heart failure and sustained rapid ventricular tachyarrhythmias. An LBBB morphology was present in 169 patients (70%) and 101 of these (60%) were responders to CRT. Analyzing the interaction between QRS duration and CRT responsiveness in patients with LBBB, a "U shaped" distribution resulted, with nonresponders clustered between 120 and 130 ms and above 180 ms. The receiver operating characteristic curve analysis identified 178 ms as the optimal cut-off value of QRS to predict a nonresponsiveness to CRT (area under the curve = 0.67 [95% confidence interval 0.57 to 0.76]). At multivariate analysis, only an ischemic cause and a QRS ≥178 ms were independent predictors of nonresponsiveness to CRT (area under the curve = 0.75). Patients with LBBB with QRS ≥178 ms had greater likelihood of adverse clinical events during a mean follow-up of 32 months (p = 0.049). In conclusion, in patients with LBBB undergoing CRT, a marked QRS widening (i.e., ≥178 ms) is related to worse echocardiographic responsiveness and lower event free survival rate compared with patients with an intermediate QRS widening.
authors.affiliation: Department of Cardiology, SS. ma Annunziata Hospital, Azienda Unità Sanitaria Locale Ferrara, Cento, Italy. Electronic address: biagio.sassone@gmail.com.
authors.forename: Biagio
authors.initials: B
authors.lastname: Sassone
authors.affiliation: Department of Cardiology, SS. ma Annunziata Hospital, Azienda Unità Sanitaria Locale Ferrara, Cento, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Gambetti
authors.affiliation: Department of Cardiology, S. Anna Hospital, University of Ferrara, Ferrara, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bertini
authors.affiliation: Institute of Internal Medicine and Cardiology, Careggi Hospital, University of Florence, Florence, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Beltrami
authors.affiliation: Department of Arrhythmology, Cliniche Humanitas Gavazzeni, Bergamo, Italy.
authors.forename: Giosuè
authors.initials: G
authors.lastname: Mascioli
authors.affiliation: Department of Cardiology, SS. ma Annunziata Hospital, Azienda Unità Sanitaria Locale Ferrara, Cento, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Bressan
authors.affiliation: Department of Cardiology, SS. ma Annunziata Hospital, Azienda Unità Sanitaria Locale Ferrara, Cento, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Fucà
authors.affiliation: Department of Cardiology, SS. ma Annunziata Hospital, Azienda Unità Sanitaria Locale Ferrara, Cento, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Pacchioni
authors.affiliation: Department of Cardiology, SS. ma Annunziata Hospital, Azienda Unità Sanitaria Locale Ferrara, Cento, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Pedaci
authors.affiliation: Department of Arrhythmology, Cliniche Humanitas Gavazzeni, Bergamo, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Michelotti
authors.affiliation: Institute of Cardiology, Policlinico S. Orsola-Malpighi, University of Bologna, Bologna, Italy.
authors.forename: Maria Letizia
authors.initials: ML
authors.lastname: Bacchi Reggiani
authors.affiliation: Institute of Internal Medicine and Cardiology, Careggi Hospital, University of Florence, Florence, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000502:physiology*; D020257:Ventricular Remodeling / Q000502:physiology*