Impact of atrial fibrillation on mortality and non-fatal clinical outcomes in 28 492 patients who had undergone open-heart aortic versus mitral valve surgery: a statewide population-linkage study
Authors: Ne J Y A , Chow C , Chow V , Hyun K , Kritharides L , Brieger D , Ng A 
Published: October 2024

Abstract

Background
Postoperative atrial fibrillation (AF) is common after cardiac surgery and has been associated with increased mortality and morbidity. Few studies have defined the impact of AF status (New-AF versus Prior-AF) on clinical outcomes during long-term follow-up and compared AF-related clinical outcomes between patients who had undergone isolated aortic valve surgery (AVSx) or mitral valve surgery (MVSx).

Purpose
This study aims to examine the impact of AF status on clinical outcomes in patients who had undergone AVSx versus MVSx using a statewide-population administrative database.

Methods
Patients who had open-heart cardiac valve surgery (1 January 2003 to 31 March 2021) identified from the Admitted-Patient-Data-Collection database in an Australian state, were stratified by AF status (No-AF vs New-AF vs Prior-AF during index admission for valve surgery) and followed up to 31 March 2022. A linkage look-back to year-2001 was performed to identify prior-AF history. Kaplan-Meier and multivariable Cox regression were performed to assess the impact of AF status on all-cause mortality. Fine-Gray competing risk analysis to account for the competing death events was used to assess non-fatal clinical outcomes.

Results
The overall cohort comprised 28 492 patients (median age 71.6yrs [interquartile range (IQR) 62.7–78.3yrs; 65.6% males): AVSx, n=18949; MVSx, n=9543 (Table 1). During a median follow-up of 6.6yrs (3.42–10.5yrs), Prior-AF and New-AF patients had significantly higher all-cause mortality (AVSx – Prior-AF: 1771 (57.9%) vs New-AF: 2854 (41.5%) vs No-AF: 2961 (32.8%); MVSx – Prior-AF: 1126 (41.0%) vs New-AF: 1034 (29.8%) vs No-AF: 747 (22.4%) (both Kaplan-Meier logrank P&lt;0.001). After adjusting for differences in baseline characteristics and admission year-groups, in the AVSx subgroup, both new-AF and prior-AF were independently associated with all-cause mortality (aHR=1.16, 95%CI=1.10–1.22; aHR=1.69, 95%CI=1.59–1.79 respectively, both P&lt;0.001) compared to no-AF patients. In the MVSx subgroup, only prior-AF was associated with increased risk of all-cause mortality (aHR=1.47, 95% CI=1.33–1.61, P&lt;0.001). Competing risk analyses showed higher rehospitalisation rates for AF and congestive cardiac failure for new-AF and prior-AF groups compared to No-AF patients after both AVSx and MVSx, whereas the rehospitalisation rate for ischemic stroke was only significantly higher in the AVSx new-AF and prior-AF subgroups (all p &lt; 0.05) (Table 2).

Conclusions
Patients undergoing open-heart aortic or mitral valve surgery are at risk of significant adverse clinical outcomes including death, heart failure and ischaemic stroke, with the target valve and baseline AF status having a differential impact on clinical outcomes. Drivers behind these high rates of adverse outcomes should be explored further and strategies should be developed and tailored accordingly to different surgical patient groups to improve their prognosis.