Ventriculophasic Modulation of Atrioventricular Nodal Conduction in Humans

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 149Ϯ33 to 177Ϯ22 mm Hg (PϽ0.001) and sinus cycle length from 844Ϯ169 to 1010Ϯ190 ms (PϽ0.001) 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. (Circulation. 1998;97:2245-2251.)

Heart rate turbulence: A 5-year review

“…The pooled RR and AV delay vs beat number profiles showed a 6% difference between maximum and minimum RR, and a difference < 2% for AV delay. It is probable that just as ventriculophasic modulation of AV nodal conduction is masked by opposing effects of ventriculophasic modulation of the sinus rate [ 38 ], increases in PP interval prevent AV nodal conduction delay from becoming manifest in the case of HRT.…”

Paroxysmal Tachycardia with Pauses to Ponder

“…The mechanism appears to involve arterial pressure induced phasic changes in baroreceptor‐mediated vagal input to the sinus node 4 . Since baroreceptor firing could also affect AV nodal conduction, ventriculophasic modulation of AV nodal conduction is possible as demonstrated by Skanes and Tang 5 in patients with infra‐Hisian second degree AV block. The arterial pulse wave resulting from conducted beats was followed by lengthening of the AH interval by 20 ms, which is similar to the 15 ms change in HH interval noted in our patient.…”

Variation in P wave rate during AV block

“…5 A recent study of 35 subjects showed that VR increases during deep breathing and thus may be indicative of intact parasympathetic tone. 6,7 In addition, the observed positive correlation between the likelihood of VR and a higher LVEF has led to the hypothesis that brisk ventricular contraction or emptying may play a key role in the development of VR. 4 In a study of elderly, pacer-dependent patients with complete AV block, the magnitude of VR decreased with markers of LV systolic function (lower LVEF, larger LV diameter and wider QRS complex) leading the authors to hypothesize that the absence of VR may herald worsening cardiomyopathy.…”