Native QRS complex duration predicts paced QRS width in patients with normal left ventricular function and right ventricular pacing for atrioventricular block.

INTRODUCTION: Prolonged paced QRS duration is a predictor of development of heart failure during chronic right ventricular pacing. One determinant of paced QRS width might be His-Purkinje system dysfunction, manifested in wide native (escape or conducted beat) QRS complexes in patients with atrioventricular (AV) block.

METHODS: Fifty patients with normal left ventricular function who are undergoing implantation of a pacemaker for AV block were enrolled. The duration of the QRS complex was measured on the surface electrocardiogram during escape rhythm in 28 patients with total AV block and during conducted beats in 22 patients with second-degree, fixed ratio (2:1 or 3:1) AV block, as well as during ventricular paced rhythm after pacemaker implantation in all patients.

RESULTS: A close, positive correlation was found between native and paced QRS duration in the second-degree AV block group (R = 0.74, P < .001). This association was also significant but less pronounced in the total AV block group (R = 0.46, P = .014).

CONCLUSION: Native QRS width, especially in case of fixed ratio (2:1 or 3:1) second-degree AV block, is a predictor of paced QRS duration in patients with AV block and normal left ventricular function. Wide QRS complex before implantation may carry a higher risk of developing heart failure with right ventricular pacing.