Background. Left ventricular (LV) electrical dyssynchrony reflected by prolonged paced QRS duration is a predictor of development of heart failure during right ventricular apical (RVA) pacing.
Methods. Electrophysiological study was performed in 50 patients. Multipolar catheters were placed in the His bundle region and in the right ventricular apex (RVA). The His bundle-ventricular activation (HV) interval during sinus rhythm, and QRS duration during both sinus rhythm (native QRS) and RVA pacing were measured. Left ventricular dimensions were obtained.
Results. Patients had normal to poor LV function (ejection fraction range: 20-75 %) and a variable degree of His-Purkinje system disease (HV interval range: 40-153 ms). Left ventricular ejection fraction (EF), end-systolic diameter and HV interval correlated with both native and paced QRS duration (R= -0.64, 0.62, 0.36 and -0.52, 0.48, 0.28 respectively, p<0.05). With multiple stepwise regression analysis only native QRS duration was identified as an independent predictor of paced QRS width (R=0.73, p<0.001). In patients with normal systolic LV function (EF>50%, n=34) only HV interval correlated with native QRS duration (R=0.38, p=0.013), which in turn predicted paced QRS width (R=0.37, p=0.016). In patients with reduced EF (n=16) LV dimensions and HV interval both correlated with native QRS duration (R=0.57, 0.47 and 0.48, respectively, p<0.05). With stepwise regression HV interval and native QRS width were identified as independent predictors of paced QRS duration (R=0.72 and 0.74, respectively, p<0.01).
Conclusion. The single best predictor of a prolonged paced QRS complex, reflecting electrical dyssynchrony, is baseline native QRS duration. This in turn is determined by His-Purkinje system function in patients with normal or reduced LV EF and LV dimensions in patients with reduced systolic LV function.
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