Affiliation:
1. From the Department of Medicine, University of Ottawa, Ontario, Canada.
Abstract
Background
—Baroreceptor-mediated phasic changes in vagal tone have been hypothesized to cause ventriculophasic sinus arrhythmia (VPSA). The objectives of this study were to demonstrate ventriculophasic modulation of AV nodal conduction and to substantiate the role of the baroreflex on ventriculophasic AV nodal conduction (VPAVN) by pharmacological perturbation of parasympathetic tone.
Methods and Results
—Twelve patients with infra-Hisian second-degree heart block and VPSA were studied. Incremental atrial pacing was performed until AV nodal Wenckebach block at baseline, after phenylephrine infusion, and after atropine. AV nodal conduction curves were constructed for each phase and compared. At baseline, VPAVN was present in 9 of 12 patients on the steep portion of the AV nodal conduction curves. Phenylephrine increased systolic blood pressure from 149±33 to 177±22 mm Hg (
P
<0.001) and sinus cycle length from 844±169 to 1010±190 ms (
P
<0.001) and shifted the AV nodal conduction curves up and to the right. Phenylephrine induced VPAVN in 2 of 3 patients in whom it was not present at baseline and in 11 of 12 total. Atropine abolished both VPSA and VPAVN in all patients.
Conclusions
—VPAVN was demonstrated in patients with infra-Hisian second-degree AV block. It was accentuated by phenylephrine and abolished by atropine, suggesting a baroreflex mechanism for VPSA and VPAVN.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine
Reference30 articles.
1. Heart block
2. Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretation . 2nd ed. Philadelphia Pa: Lea & Febiger; 1993:26.
3. Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretation . 2nd ed. Philadelphia Pa: Lea & Febiger; 1993:22.
Cited by
25 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献