The effect of cardiac surgery type on incidence of post-operative atrial fibrillation amongst patients with post-procedural conduction disease
Authors: Pezard-Snell M , Swinn T , Dimitropoulos G , Sammut E , Barman P 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Approximately 1% of cardiac operations result in post-operative heart block (PoHB). Post -operative atrial fibrillation (PoAF) has been quoted as occurring in 40-50% of combined coronary artery bypass graft (CABG) and valvular procedures, 25% of CABG only and 30% of valve only procedures. The co-existence of PoAF in patients with PoHB, and the link to operation type is less well documented.

Purpose
To investigate characteristics predisposing patients post cardiac surgery for PoHB and PoAF.

Methods
We screened patients who had undergone CABG, aortic or mitral valve replacements (AVR and MVR respectively) or mitral valve repairs at Bristol Royal Infirmary between 1/1/2010 and 1/4/2020. We created a merged surgical and electrophysiological database identifying patients with permanent pacemakers inserted within 30 days of cardiac surgery for PoHB to create our final database. By reviewing electronic notes we identified patients in this cohort who developed PoAF prior to discharge. We excluded patients with congenital heart defects or known prior atrial fibrillation. We then analysed the incidence of both PoHB and PoAF for different operation subtypes.

Results
Of the 10779 operations, 6625 (61%) were CABG-Only, 4124 (38%) were Valve-Only and 1219 (11%) were combined CABG&Valve. In total 85 (0.8%) patients developed PoHB. There was a higher proportion of female patients in the PoHB group but no other demographic differences (See Table 1). In terms of operation type, the PoHB group contained a significantly higher proportion of patients who had undergone AVR (78% vs. 28%, p&lt;0.001). There was also a significant association with operations performed on cardiopulmonary bypass and with longer cross clamp time however this did not remain statistically significant on multivariate analysis. Valve surgery was associated with a higher proportion of patients developing PoHB than CABG, with AVR relating to the highest PoHB rates (AVR 2.0%, MVR 0.9%, CABG 0.2%, p&lt;0.0001). Both mechanical and bioprosthetic AVR were associated with a higher proportion of patients developing PoHB than MVR.
In our cohort 34/85 (41%) patients with POHB developed post-operative AF. After univariate analysis of the patient and operation factors listed in Table 1, only age and body mass index were predictors of development of PoAF after multivariate analysis (age: odds ratio 1.81 (1.02-1.36), p=0.024, BMI: odds ratio 1.09 (1.02-1.17), p=0.01), with no association to surgical parameters.

Conclusion
PoHB occurs commonly following both CABG and valve procedures, with higher incidence in the setting of valve surgery, with our data showing a 2 fold higher chance of PoHB in patients undergoing aortic versus mitral valve replacements. In contrast, there is no clear relationship between type of surgery and development of postoperative atrial fibrillation in this cohort but larger studies are warranted.