Factors affecting ventriculophasic response: An investigation in patients with permanent pacemaker.

BACKGROUND: Ventriculophasic response (VR) refers to the shortening of the atrial cycle length (P-P-interval) that occurs during the heart block when a QRS complex is interposed between two P-waves. The aim of this study was to determine the factors affecting this phenomenon.

METHODS: Thirty patients with high grade heart block treated with dual chamber pacemaker were studied. The pacer function of the patients' device was temporarily programmed to the ventricular-inhibited mode at 30 pulses per minute. A total of 330 recordings containing two P-waves with an interposed QRS and its previous P-P interval without any QRS were collected. The VR was defined as being present when the P-P interval with an interposed QRS shortened more than 3% compared to the preceding P-P interval.

RESULTS: The VR was present in 45% of the recordings. In the multivariate logistic regression analysis, only a mid position of the interposed QRS was a positive predictor for presence of VR. However, there were no differences between recordings with or without VR groups according to QRS duration, paced or intrinsic interposed QRS. Hypertension and age had a negative correlation with the presence of VR when the QRS was interposed in the mid part.

CONCLUSION: We found that the VR was present in approximately half of our cases. This phenomenon was mostly affected by position of the interposed QRS according to the previous P-P interval.