Demonstration of a Left Atrial Input to the Atrioventricular Node in Humans

Abstract

Background-During right atrial stimulation, the anterior and posterior approaches provide inputs to the atrioventricular (AV) node. The purpose of the present study was to determine how activation proceeding from the left atrium reaches the AV node. Methods and Results-We studied AV nodal conduction during right and left atrial (coronary sinus) stimulation in 46 patients (27 women and 19 men; mean age, 46Ϯ4 years) who had structurally normal hearts. At an identical cycle length (600 ms), left atrial stimulation resulted in shorter A-H intervals than right atrial stimulation (73Ϯ3 ms versus 99Ϯ3 ms; PϽ0.05). In addition, atrial electrograms recorded close to the His bundle changed from near to far field potentials when stimulation was shifted to the left atrium. The A-H interval prolonged as the site of pacing was progressively moved from the distal to the proximal coronary sinus. During constant pacing from the distal coronary sinus, atrial activation close to the His bundle could be advanced by late extrastimuli delivered at the anterior and posterior approaches (up to 11Ϯ2 ms and 9Ϯ1 ms, respectively), without altering His bundle activation time. In contrast, late extrastimuli delivered at the inferoparaseptal mitral annulus advanced both the A and H electrograms in 19 of 20 patients, which is consistent with a left-sided input to the AV node. Right and left atrial stimulation resulted in similar AV nodal function. Conclusion-The mitral annulus provides a left atrial input to the human AV node.

The effect of atrial pacing site on electrophysiological properties of the atrioventricular junction and induction of atrioventricular nodal reentry in patients with typical atrioventricular nodal reentrant tachycardia

“…In all mentioned studies LA stimulation resulted in shorter AH intervals than did RA stimulation. Moreover, Suzuki et al [8] and Gonzalez et al [3] documented (although not consistently) that AVN conduction depends on CS pacing site. Suzuki et al [8] reported that the AH interval was the longest with stimulation from the HRA, followed by the distal, mid, and proximal CS; however, in some patients the AH interval was identical or longer when measured during proximal vs. distal CS pacing.…”

“…Gonzalez et al [3] found that the AH interval prolonged as the site of pacing was moved from the distal to the proximal CS, but it was always shorter compared with RA stimulation. They explained this finding by a gradual shift between two atrial inputs: from the mitral annulus (MA) that could represent the functional counterpart of the leftward posterior extension to the rightward posterior approach [3].…”

“…However, the obtained outcomes cannot be reliably referred to AVNRT patients because of their marginal participation in those studies. Moreover, different right (high, mid, or low) and left atrial pacing sites (via different CS sites, a persistent foramen ovale or a transseptal puncture) and EPS protocols seem to be the possible reason for conflicting results [1][2][3][4][5][6][7][8]. In all mentioned studies LA stimulation resulted in shorter AH intervals than did RA stimulation.…”

“…They indicated that a wavefront from the distal CS propagates toward the AV node mainly via the anterior LA approach, from the mid and proximal CS via the posterior LA approach, and from the HRA via the anterior RA approach [8]. Gonzalez et al [3] found that the AH interval prolonged as the site of pacing was moved from the distal to the proximal CS, but it was always shorter compared with RA stimulation. They explained this finding by a gradual shift between two atrial inputs: from the mitral annulus (MA) that could represent the functional counterpart of the leftward posterior extension to the rightward posterior approach [3].…”

“…Clinical studies in humans have shown the site of atrial stimulation to influence atrioventricular (AV) conduction times and refractory periods, the demonstration of dual atrioventricular nodal (AVN) pathways, and induction of AVN reentry [1][2][3][4][5][6][7][8]. These studies often found conflicting results that could be explained by different atrial pacing sites and the electrophysiological study (EPS) protocol applied.…”