18-01: Is Conduction Block during Sinus Rhythm Associated with Development of Post-Operative Atrial Fibrillation?

Purpose: Conduction block (CB) is associated with initiation and persistence of atrial fibrillation (AF). It is unknown if and in what extent CB is present in electrically non-remodeled atria during sinus rhythm (SR). Aims of the study are to quantify the amount and spatial distribution of CB measured at a high-resolution scale at the entire epicardial surface of the atria and to test the correlation between CB and development of early post-operative AF (PoAF).

Methods: High-resolution (128/192 electrodes; inter-electrode distances 2.0mm) intra-operative epicardial mapping of the right atrium (RA), Bachmann's Bundle, pulmonary vein area and left atrium during SR was performed in 209 patients (175 male, age 66 ± 9.6years) with coronary artery disease. The area underneath the mapping array was divided into 1cm2 quadrants. Differences in activation times between neighboring electrodes were calculated in areas of 2x2 electrodes. The maximum activation time difference between two adjacent electrodes was calculated to identify conduction delay (CD, ≥7 ms ) and CB (≥11 ms). Prevalence and amount of CD and CB were quantified per quadrant. PoAF was documented by ECG or continuous rhythm recording.

Results: Recordings were derived from a total of 390,379 sites, resulting in 1,868 ± 285 electrodes per patient. Areas of CD/CB were present in all patients and at respectively 2,273 (34%) and 1,470 (22%) quadrants. Median prevalence of CD was 1.4 (0.2–3.7)%, intra-atrial variation was 8.3(1.2–33.4)%/cm2. Median prevalence of CB was 1.3(0.1–3.5)% and intra-atrial variation was 11.3(0.1–31.5)%/cm2. CD and CB mainly occurred at quadrants confined to the superior intercaval area of the RA. Sixty-three patients (30%) developed PoAF. There was no correlation between CD/CB and PoAF (P > 0.5).

Conclusion: Quantification of the amount and spatial distribution of CD and CB per 1cm2 during SR demonstrated a wide intra- and inter-individual variety. The prevalences of CD/CB were very low, however a predilection site at the superior RA could be identified. CD/CB was not associated with development of PoAF. Our dataset generates a detailed reference dataset for future research on the arrhythmogenic substrate of AF.