Enhanced atrioventricular conduction in patients without preexcitation syndrome: relation to heart rate in paroxysmal reciprocating tachycardia.

Abstract

We studied the electrophysiologic characteristics of atrioventricular (AV) nodal conduction in patients with reciprocating tachycardia (RT) without ventricular preexcitation, and the relation of these characteristics to RT cycle length (CL). Thirty-five symptomatic patients who had a normal PR interval (0.13-0.20 second) during sinus rhythm underwent detailed intracardiac electrophysiologic study during which ventricular preexcitation was excluded, and the RT mechanism was determined. RT was due to reentry using an accessory AV pathway capable of conduction only in the retrograde direction (concealed AP) in 13 patients (37%) and to reentry within the AV node in 22 (63%). Dynamic properties of AV conduction (assessed by degree of AH prolongation during progressive increase in atrial pacing rate) were normally distributed (p less then 0.005); 12 patients (34%) fulfilled the criteria for enhanced AV conduction (EAVC). The patients with EAVC had a shorter RT CL than did patients without EAVC (294 +/- 43.3 msec vs 360 +/- 68.1 msec, p less than 0.01). However, CL differences were primarily due to the influence of EAVC in the subgroup of patients with RT using a concealed AP (EAVC CL, 274 +/- 35.1 msec; without EAVC, 326 +/- 15.7 msec, p less than 0.005). The RT CL in patients with reentry within AV node was not measureable influenced by concomitant EAVC (EAVC, 314 +/- 43.8 msec; without EAVC, 376 +/- 76.8 msec) (NS). This study suggests that despite the presence of a normal PR interval during sinus rhythm, dynamic AV conduction responses can vary widely in patients with RT. In patients with RT using a concealed AP, but not in those with reentry within the AV node, coexisting diminished physiologic AV conduction slowing may be associated with more rapid tachycardia rates.

Control of supraventricular tachycardia by VVI pacing in a patient with drug‐induced enhanced atrioventricular conduction

“…A 56-year-old doctor developed severe chest pain and had received emergency AC bypass surgery for acute myocardial infarction because of rapidly progressive cardiogenic shock (7). Recovery had been uneventful for 24 hours postoperatively until transient ventricular tachycardia developed.…”

Enhanced AV Nodal Conduction and Brenchenmacher Tracts

“…These studies [6][7][8][9] clearly show that the LGL syndrome eponym should be abandoned since the presence of a short PR is not a necessary feature for the tachycardia substrate. Specifically, patients with AV nodal reentry, atrial tachycardia, atrial fibrillation, etc., may suffer from these arrhythmias whether the PR is short or normal.…”

“…Further studies [6][7][8] emphasized that the AV nodal refractory period was short in these patients and that a small minority of patients would show an essentially flat A-H response with respect to atrial overdrive pacing with an unchanged A-H during programmed atrial extrastimuli. A seminal study was reported by Jackman et al 9 in an invasive electrophysiologic study of 180 patients.…”