Effect of atrial pacing on ventricular rate during atrial fibrillation. A human study.

OBJECTIVE

This research study tests the hypothesis that atrial pacing near the atrioventricular node during atrial fibrillation can affect ventricular rate.

METHODS

In 13 patients, two monophasic action potential catheters were advanced into the low anterior septum (ANT) and the low posterior septum (POST) near the atrioventricular node. After induction of atrial fibrillation, measurement of the excitable gap was attempted at the ANT and POST regions. During atrial pacing, ventricular cycle length (CL) at the longest excitable gap was compared to ventricular CL at the shortest excitable gap by pairwise analysis.

RESULTS

Transient capture of ANT tissue during ANT pacing was observed in six patients, whereas transient capture of POST tissue during POST pacing was observed in four patients. The ventricular response to ANT and POST pacing at multiple rates was recorded in six and seven patients, respectively. An increase in POST pacing CL by 40 +/- 24 ms prolonged (P < 0.05) ventricular CL by 45 +/- 56 ms. Conversely, an increase in ANT pacing CL by 48 +/- 42 ms shortened (P < 0.05) ventricular CL by 45 +/- 40 ms.

CONCLUSIONS

ANT and POST pacing CL affected ventricular CL during atrial fibrillation, even though capture was transient. The opposite direction of the effects of ANT and POST pacing CL on ventricular CL may indicate that the atrial impulses from the POST region are more likely to conduct to the ventricle than impulses from the ANT region as the CL of activation is decreased.