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%.