QRS morphology and ventricular dyssynchrony in patients with chronic right ventricular pacing

Abstract

Background: Mechanical dyssynchrony (MD) is associated with poor outcomes in many different populations. However, the predictors for the development of MD after chronic right ventricular (RV) pacing are not well known.

Methods: Pacing QRS morphology and MD using echocardiography was analyzed in 175 consecutive patients that have pacemaker implantation during a 7.6 year median follow-up. Predictive score for MD was constructed using QRS morphology variables and calculated by summing the points of the 4 variables: duration (≥150 ms, 1 point), transition (1 point), notching (2 points), and left-axis deviation (1 point), based on a multivariate-adjusted risk relationship with MD.

Results: Sixty-eight (38.9%) patients developed MD. Patients with MD had worsened left ventricular systolic function (ejection fraction from 64.6±10.6% to 59.1±10.4%, p<0.001) and heart failure symptoms (New York Heart Association functional class increase from 1.1±0.3 to 1.9±0.8, p<0.001). In an electrocardiographic analysis, QRS duration≥150 ms, the presence of precordial axis transition, notching, and left-axis deviation were strongly associated with MD. Predictive score for MD using QRS morphology parameters displayed an excellent graded relationship with MD (score 0: 3.4% vs. 1: 12.5% vs. 2: 22.6% vs. 3: 45.0% vs. 4: 57.9% vs. 5: 72.7%, linear p<0.001) (model performance c-static 0.78, 95% confidence interval 0.72-0.85, p<0.001).

Conclusion: Patients with MD experienced a decline in left ventricular systolic function and an increase in heart failure symptoms after chronic RV pacing. A new scoring system using QRS morphology is considered a simple and efficient tool for predicting the development of MD after chronic RV pacing.

Keywords: Cardiac pacing; Electrocardiography; Heart failure; Mechanical dyssynchrony; Pacemaker.