Presence of notched QRS on paced electrocardiographs as a predictor of poor response to cardiac resynchronization therapy

Background Cardiac resynchronization therapy （CRT） on patients with advanced and refractory heart failure has made remarkable progress.Clinically,notched QRS （nQRS） is commonly seen on electrocardiographs （ECGs） with bundle branch block morphology and on paced ECGs after implantation of a CRT device,which may reflect the heterogeneity of ventricular myocardial depolarization and electrical activity.The aim of this study was to determine whether patients with more nQRS myocardial segments on paced ECGs had a worse response to CRT than patients with fewer nQRS myocardial segments.Methods We prospectively enrolled 56 patients of CRT with chronic heart failure from People＇s Hospital affiliated to Peking University from January 2007 to October 2013.Based on nQRS segments on ECGs before CRT,we allocated them to two groups：fewer nQRS （〈2） myocardial segments （lateral,inferior,anterior segments） group （F-nQRS,G1,n=23） and more nQRS （≥2） myocardial segments group （M-nQRS,G2,n=33）.Then according to nQRS segments on ECGs after CRT,we divided them into two groups similarly：fewer nQRS （〈2） myocardial segments group （G3,n=24） and more nQRS （≥2） myocardial segments group （G4,n=32）.This study was approved by the ethics committee of People＇s Hospital.Results At 6 months in the baseline-ECG group,there was a greater absolute increase in left ventricular ejection fraction （LVEF） in G2 than in G1 （（11.5±8.9）% vs.（5.5±10.4）%,P=0.023）,with the incidence of nonresponse lower in G2than in G1 （9.1% vs.39.1%,P=0.018）.In the paced-ECG group,the absolute increase in LVEF was less in G4 than in G3 （（6.4±8.8）% vs.（12.5±10.4）%,P=0.024） and the incidence of nonresponse was higher in G4 than in G3 （31.3% vs.8.3%,P=0.039）.Multivariate analysis showed that fewer nQRS （〈2） myocardial segments on paced ECGs （odds ratio 13.920） was a predictor of positive response to CRT.Conclusion nQRS ≥2 myocardial segments （lateral,inferior,anterior） on paced ECGs may predict a poor response to CRT.