The Ventriculophasic Response Revisited: Analysis of Clinical Correlations Using a New Proposed Definition Derived in Pacemaker Patients

Background: The ventriculophasic response (VR) refers to shortening of atrial cycle length during heart block when a QRS complex is interposed between P waves. No formal quantitative definition has heretofore been proposed, nor have its potential clinical correlations been studied. Hypothesis: We hypothesized that VR is present in selected patients who are distinguished by clinical features from those who lack VR. Methods: Pacing devices were temporarily programmed to VVI mode at 30 ppm as electrocardiogram and intracardiac electrograms were recorded at 50 mm/sec paper speed. We measured the percentage decrease in a P‐P interval (A‐A interval on the atrial electrogram) containing a QRS, compared to the preceding P‐P interval. Left ventricular ejection fraction (LVEF) was measured by echocardiogram. Results: Shortening of P‐P interval was observed chiefly when the interposed QRS occurred early in the anticipated P‐P interval (as judged by the preceding P‐P interval). P‐P shortening of 0% to 3% occurred randomly. Defining VR as being a >3% P‐P interval shortening when an interposed QRS occurred in the first 60% of the anticipated P‐P interval, we found that VR was present in 28 (55%) of our patients. It was quite reproducible, was more common in women (81% vs 37% of men; P = 0.004), and positively correlated with LVEF (r = 0.41, P = 0.004). It did not correlate with age, diabetes, or β‐blocker use. Conclusions: Using our newly derived definition of VR, we found the phenomenon was present in 55% of our patients. It was reproducible and more commonly seen in women and patients with LVEF ≥40%. © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.