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Nonuniformity of AH intervals during stimulation at different left atrial sites
F Suzuki1, T O Harada, T Kawara
1First Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Insights
Pacing the left atrium from different sites, specifically the anterior versus posterior coronary sinus (CS), significantly impacts atrium-His (AH) intervals. Understanding the precise pacing location is crucial for interpreting electrophysiological study findings on atrioventricular nodal conduction.
Area of Science:
- Electrophysiology
- Cardiology
- Cardiac Electrophysiology
Background:
- Left atrial stimulation via the coronary sinus (CS) typically yields shorter atrium-His (AH) intervals than right atrial stimulation.
- The impact of pacing at distinct anterior versus posterior left atrial sites (distal vs. proximal CS) on AH intervals remains uninvestigated.
Purpose of the Study:
- To compare the effects of stimulation from various atrial sites on stimulus-atrium (SA), AH, and stimulus-His intervals.
- To determine if pacing location within the left atrium (anterior vs. posterior CS) influences AH interval measurements.
Main Methods:
- Stimulation was performed from the anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS in 22 patients.
- Stimulus-atrium (SA), AH, and stimulus-His intervals were recorded on the His bundle electrogram.
- Paced cycle length was individualized but kept constant for comparing different atrial sites within each patient.
Main Results:
- Significant differences were observed in mean SA and AH intervals across the tested atrial stimulation sites (HRA, distal CS, mid-CS, proximal CS).
- Mean AH intervals decreased progressively from HRA (123 ms) to distal CS (104 ms), mid-CS (95 ms), and proximal CS (90 ms).
- A discrepancy of ≥15 ms in AH intervals between distal and proximal CS stimulation occurred in 13 patients, exceeding measurement error.
Conclusions:
- Pacing from anterior versus posterior left atrial sites (distal vs. proximal CS) results in significantly different AH intervals.
- A substantial proportion of patients exhibit notable discrepancies in AH intervals based on the specific CS pacing location.
- Accurate interpretation of electrophysiological studies on atrioventricular nodal conduction requires precise consideration of the left atrial stimulation site.
Abstract:
Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at different left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CS) affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atrial sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on: stimulus-atrium (SA), AH, and stimulus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900-350 msec, mean 532 +/- 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 +/- 10 msec, 57 +/- 10 msec, 44 +/- 11 msec, and 32 +/- 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for HRA vs proximal CS). The mean AH intervals were 123 +/- 23 msec, 104 +/- 28 msec, 95 +/- 15 msec, and 90 +/- 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CS). In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > or = 15 msec; in 9 patients this difference was only < or = 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.