Conduction and voltage characteristics associated with new-onset postoperative atrial fibrillation
Authors: Van Schie MS , Veen D , Kharbanda RK , Starreveld R , Taverne YJHJ , Bogers AJJC , De Groot NMS 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): CVON-AFFIP [grant number 914728], NWO-Vidi [grant number 91717339]

Background
Postoperative atrial fibrillation (PoAF) is the most common complication encountered after cardiac surgery, with incidences ranging from 20-80% depending on the type of procedure. Still, pathophysiological mechanisms underlying development of PoAF remain partially unclear. It is generally accepted that PoAF requires both a trigger and a susceptible atrial substrate for genesis and maintenance of the arrhythmia. The transition from early PoAF (E-PoAF) to late PoAF (L-PoAF) is considered to progress from a trigger-driven to a more substrate-driven disease. Therefore, development of L-PoAF is more likely to occur in patients with more extensive pre-existing substrate at time of surgery. Particularly in patients with new-onset PoAF, whom lack AF induced remodeling, characterization of the atrial substrate could aid in our understanding of PoAF development.

Purpose
To examine 1) severity of conduction disorders as well as voltage characteristics, such as low-voltage areas (LVAs), 2) to compare these characteristics between patients without and with new-onset PoAF, and 3) to establish whether it predicts progression to L-PoAF within five years after cardiac surgery.

Methods
Intra-operative epicardial mapping (interelectrode distance 2mm) of the right and left atrium (RA, LA), Bachmann’s Bundle (BB) and pulmonary vein area (PVA) was performed during SR in 263 patients (27 male, 67 ± 11 years) with new-onset PoAF. Unipolar electrograms were used to define potential amplitudes, LVAs, conduction velocity (CV) and the amount of conduction disorders. A p-value &lt;0.05 was considered statistically significant.

Results
37% of the patients developed new-onset PoAF within the first days after surgery. These patients had significantly slower CV at BB (90.9[82.5–99.4] vs. 87.0[75.5–95.1] cm/s) and more conduction disorders at BB and PVA (6.10[3.83–9.09] vs. 7.26[4.53–11.19] % and 4.26[2.55–6.24] vs. 4.78[3.12–7.50] %) compared to those who remained in SR. In addition, compared to the SR group, voltages in PoAF patients were particularly lower at BB, PVA and LA (5.70[3.82–7.80] vs. 4.53[2.52–6.85] mV, 4.21[2.41–6.55] vs. 3.62[1.94–5.65] mV and 5.79[3.85–7.62] vs. 4.89[3.23–7.10] mV), while more LVAs were found at all defined atrial regions. These differences were even more dominantly present in patients with AF recurrence after a period of new-onset E-PoAF. This transition to L-PoAF could even occur 5 years after surgery and was only found in patients who also developed E-PoAF.

Conclusions
Patients who develop new-onset PoAF already have substantial signs of atrial remodeling prior to cardiac surgery compared to those who remained in SR. Additionally, patients who had AF recurrence after new-onset PoAF have even more extensive signs of atrial substrate, and AF recurrence can even occur up to 5 years after surgery. Therefore, in patients with new-onset PoAF, rhythm monitoring should carefully be performed in the years after cardiac surgery. Abstract Figure.