Electrocardiographic criteria of true left bundle branch block: a simple sign to predict a better clinical and instrumental response to CRT.
BACKGROUND
Cardiac resynchronization therapy (CRT) has proved to be very effective in improving morbidity and mortality in patients affected with severe congestive heart failure. Its efficacy has been shown to be greater in patients with left bundle branch block (LBBB). The aim of our study was to verify if newly proposed criteria for true LBBB identify patients with a better clinical and instrumental response to CRT.


METHODS
Between May 2007 and April 2011, 111 patients with left ventricular ejection fraction (LVEF) ≤ 35% and LBBB morphology received a CRT device and were divided into two groups according to QRS morphology. Group 1 (61 patients) consisted of patients with "true" LBBB morphology; group 2 (50 patients) consisted of patients with "false" LBBB. The primary endpoint was the utility of criteria for true LBBB to predict a composite endpoint of all-cause mortality and hospital admission with heart failure. The secondary endpoint was the utility of the same criteria to predict an absolute increase in LVEF ≥ 10%.


RESULTS
"False" LBBB morphology and a dose of bisoprolol <5 mg at last follow-up were the only parameters related to clinical outcome in multivariate analysis (respectively: hazard ratio [HR] 3.98, confidence interval [CI] 95% 1.51-10.48; HR 0.15, CI 95% 0.05-0.43). "True" LBBB morphology was the only variable significantly related to a greater increase in LVEF (HR 4.57, CI 95% 1.36-8.28).


CONCLUSIONS
True LBBB morphology is related to a higher event-free survival rate in CRT patients and better echocardiographic response.
Department of Arrhythmology, Cliniche Humanitas Gavazzeni, Bergamo, Italy.
Giosuè
G
Mascioli
Luigi
L
Padeletti
Biagio
B
Sassone
Massimo
M
Zecchin
Elena
E
Lucca
Stefania
S
Sacchi
Giulio
G
Boggian
Anna Ludovica
AL
Tondo
Chiara
C
Belvito
Nikoloz
N
Bakhtadze
Alessio
A
Borrelli
Gianfranco
G
Sinagra
D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use; D017298:Bisoprolol / Q000627:therapeutic use; D002037:Bundle-Branch Block / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D018572:Disease-Free Survival; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000188:drug therapy / Q000401:mortality / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D013318:Stroke Volume / Q000502:physiology; D016896:Treatment Outcome
D000959:Antihypertensive Agents; D017298:Bisoprolol