Original Investigation | Cardiology
Recurrence of Atrial Fibrillation in Patients With New-Onset Postoperative
Atrial Fibrillation After Coronary Artery Bypass Grafting
Florian E. M. Herrmann, MD; Amar Taha, MD; Susanne J. Nielsen, RN, PhD; Andreas Martinsson, MD, PhD; Emma C. Hansson, MD, PhD;
Gerd Juchem, MD; Anders Jeppsson, MD, PhD
Abstract
Key Points
IMPORTANCE New-onset postoperative atrial fibrillation (POAF) occurs in approximately 30% of
patients undergoing coronary artery bypass grafting (CABG). It is unknown whether early recurrence
is associated with worse outcomes.
Question Is early atrial fibrillation (AF)
recurrence in patients with new-onset
postoperative atrial fibrillation (POAF)
after coronary artery bypass grafting
OBJECTIVE To test the hypothesis that early AF recurrence in patients with POAF after CABG is
associated with worse outcomes.
(CABG) associated with worse
outcomes?
Findings In this cohort study of 10 609
DESIGN, SETTING, AND PARTICIPANTS This Swedish nationwide cohort study used prospectively
patients with POAF after CABG, early
collected data from the SWEDEHEART (Swedish Web System for Enhancement and Development
AF recurrence was not associated with
of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) registry
an increased risk of all-cause mortality
and 3 other mandatory national registries. The study included patients who underwent isolated first-
(primary endpoint), stroke, or
time CABG between January 1, 2007, and December 31, 2020, and developed POAF. Data analysis
thromboembolism within 2 years after
was performed between March 6 and September 16, 2023.
discharge. Early recurrence was
associated with an increased risk of
EXPOSURE Early AF recurrence defined as an episode of AF leading to hospital care within 3 months
heart failure hospitalization and major
after discharge.
bleeding.
Meaning These findings suggest that
MAIN OUTCOMES AND MEASURES The primary outcome was all-cause mortality. Secondary
outcomes included ischemic stroke, any thromboembolism, heart failure hospitalization, and major
bleeding within 2 years after discharge. The groups were compared with multivariable Cox regression
patients with early AF recurrence after
CABG with POAF constitute a risk group
for which follow-up is advisable.
models, with early AF recurrence as a time-dependent covariate. The hypothesis tested was
formulated after data collection.
+ Supplemental content
RESULTS Of the 35 329 patients identified, 10 609 (30.0%) developed POAF after CABG and were
included in this study. Their median age was 71 (IQR, 66-76) years. The median follow-up was 7.1 (IQR,
Author affiliations and article information are
listed at the end of this article.
2.9-9.0) years, and most patients (81.6%) were men. Early AF recurrence occurred in 6.7% of
patients. Event rates (95% CIs) per 100 patient-years with vs without early AF recurrence were 2.21
(1.49-3.24) vs 2.03 (1.83-2.25) for all-cause mortality, 3.94 (2.92-5.28) vs 2.79 (2.56-3.05) for heart
failure hospitalization, and 3.97 (2.95-5.30) vs 2.74 (2.51-2.99) for major bleeding. No association
between early AF recurrence and all-cause mortality was observed (adjusted hazard ratio [AHR], 1.17
[95% CI, 0.80-1.74]; P = .41). In exploratory analyses, there was an association with heart failure
hospitalization (AHR, 1.80 [95% CI, 1.32-2.45]; P = .001) and major bleeding (AHR, 1.92 [1.42-2.61];
P < .001).
CONCLUSIONS AND RELEVANCE In this cohort study of early AF recurrence after POAF in patients
who underwent CABG, no association was found between early AF recurrence and all-cause
(continued)
Open Access. This is an open access article distributed under the terms of the CC-BY License.
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Recurrence of AF in Patients With New-Onset Postoperative AF After CABG
Abstract (continued)
mortality. Exploratory analyses showed associations between AF recurrence and heart failure
hospitalization, oral anticoagulation, and major bleeding.
JAMA Network Open. 2024;7(3):e241537. doi:10.1001/jamanetworkopen.2024.1537
Introduction
New-onset postoperative atrial fibrillation (POAF) is common after coronary artery bypass grafting
(CABG), with a reported incidence of 21% to 34%.1-3 In most studies on this condition, POAF after
CABG is associated with an increased short-term and long-term risk of stroke,4 thromboembolism,
and heart failure hospitalization.5 Although POAF is thought to be a transient event, its negative
association with long-term morbidity and mortality6,7 suggests a possible sentinel role, making POAF
after cardiac surgery akin to a marker of generally enhanced cardiovascular risk.
Only a few previous studies have reported on atrial fibrillation (AF) recurrence in patients with
POAF after CABG.5,8,9 These studies showed that patients with POAF after CABG have a substantial
risk of AF recurrence during the first postoperative years. Taha et al5 reported a 4-fold increased
adjusted risk of AF in patients with POAF after CABG during 8 years of follow-up compared with
those without POAF, and Ahlsson et al8 reported an 8-fold increased risk. To our knowledge, no
previous investigations of AF recurrence in the POAF population have evaluated the potential
association between recurrence and outcomes.
In this large registry study of patients with POAF after CABG, we tested the hypothesis that
early AF recurrence is associated with outcomes. We investigated the association of AF recurrence
within the first 3 months after discharge with all-cause mortality, ischemic stroke, any
thromboembolism, heart failure hospitalization, and major bleeding within the first 2 years after
discharge.
Methods
This cohort study was approved by the Swedish Ethical Review Authority, which waived the need for
individual patient consent because registry data were used. The study was performed in accordance
with the Declaration of Helsinki10 and followed the Strengthening the Reporting of Observational
Studies in Epidemiology (STROBE) reporting guideline.
Study Design and Patient Cohort
This study drew its population from the Swedish Cardiac Surgery Registry,11 which is part of the
SWEDEHEART (Swedish Web System for Enhancement and Development of Evidence-Based Care in
Heart Disease Evaluated According to Recommended Therapies) registry.12 Eligible patients were
identified and were included if they were aged 18 years or older and underwent first-time isolated
CABG between January 1, 2007, and December 31, 2020. Patients who did not survive to discharge
and those with AF prior to surgery were excluded (Figure 1). Patients were considered to have POAF
if they (1) were reported in the SWEDEHEART registry or the National Patient Register13 to have
developed new-onset AF during the index hospitalization or (2) underwent postoperative electrical
cardioversion during the index hospitalization, as reported in the National Patient Register. Patients
were considered to have experienced AF recurrence if they had experienced POAF during the index
CABG hospitalization and presented to a hospital or hospital-affiliated outpatient clinic after the
CABG index hospitalization, with AF recorded as the main diagnosis in the National Patient Register.
Early AF recurrence was defined as AF recurrence within the first 3 months after discharge from
the CABG index hospitalization, similar to early AF recurrence after AF ablation.14 All included
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patients were followed until death, emigration, or the end of the study period (December 31, 2020).
No patients were lost to follow-up. Patients who emigrated were censored at the time of emigration.
Data Sources
Baseline characteristics, including preoperative AF, were collected from the SWEDEHEART registry11
and the National Patient Register.13,15 Postoperative outcome data were collected from the National
Patient Register. Information about postoperatively dispensed medications was collected from the
Swedish National Prescribed Drug Register. Mortality data were collected from the National Cause of
Death Register. Information from each of the aforementioned registries was linked using the unique
personal identification number allocated to each Swedish citizen at birth or after immigration.
The Swedish Cardiac Surgery Registry has documented all cardiac surgical procedures in
Sweden since 1992. The National Patient Register has documented all diagnoses associated with
hospital admissions since 1987 and hospital outpatient visits since 2001. This registry has full
coverage and a validity of 85% to 95%, depending on the diagnosis.15 Codes from the International
Classification of Diseases, Tenth Revision (ICD-10), were used to identify diagnoses and outcome
events (eTable 1 in Supplement 1). The National Prescribed Drug Register has documented
information regarding all dispensed prescription drugs since July 2005 using Anatomical Therapeutic
Chemical classification codes (eTable 2 in Supplement 1). The Swedish Cause of Death Register has
collected all data regarding deaths in Sweden since 1961.16
Outcome Variables
The primary outcome variable in this study was all-cause mortality within 2 years of discharge after
CABG. Secondary outcome variables were ischemic stroke, any thromboembolic event (including
ischemic stroke, transient ischemic attack [TIA], or systemic embolism), heart failure hospitalization,
and major bleeding. Outcome events were considered as having occurred if they led to a hospital
admission or death.
Statistical Analysis
The cumulative incidence of AF recurrence after CABG was calculated using regression modeling,
taking into account the competing risk of death.17 Cumulative incidences are presented with 95%
CIs. We compared patients with vs without early AF recurrence after surgery. Descriptive statistics
are presented as medians and IQRs for continuous variables and as counts and percentages for
categorical variables. For the comparison of baseline characteristics, the Wilcoxon test was used for
continuous data and the Pearson χ2 test was used for categorical data. The median follow-up time
was calculated using the reverse Kaplan-Meier method.18 Associations between early AF recurrence
Figure 1. Flowchart of Population Selection
39 550 Patients underwent first-time isolated
CABG in Sweden, 2007-2020
4221 Excluded
633 Did not survive to hospital discharge
3588 Had preoperative AF
35 329 Survived past hospital discharge and
had no preoperative AF
24 720 Did not develop POAF
10 609 Developed POAF
698 Had early AF recurrence
9911 Had no early AF recurrence
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AF indicates atrial fibrillation; CABG, coronary artery
bypass grafting; POAF, new-onset postoperative atrial
fibrillation.
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Recurrence of AF in Patients With New-Onset Postoperative AF After CABG
and outcome events were assessed by observing AF recurrence as a time-dependent covariate
updated continuously during follow-up. Applying this methodology, outcome events were only
interpreted as having occurred in a patient with early AF recurrence if a patient experienced the AF
recurrence event prior to or on the day of the outcome events. Any outcome events occurring prior
to AF recurrence events were interpreted as having occurred in a patient without early AF
recurrence.
The association between early AF recurrence and outcomes was investigated using Cox
proportional hazards models. Further outcome-associated variables were included in models used
for the calculation of adjusted hazard ratios (AHRs; eTable 3 in Supplement 1 lists the variables
included in each model). The proportional hazards assumption was evaluated by visual inspection of
residual graphs and investigation of the Schoenfeld individual test. The assumption was not violated
in any model. Event rates were calculated based on the time-to-event data as prepared for the Cox
models respecting the time dependence of AF recurrence and subsequently only attributing time
and events to early AF recurrence after AF recurrence events.
A sensitivity analysis was performed to assess the robustness of the results depending on an
adapted interpretation of event-specific time at risk as related to the time-dependent covariate early
AF recurrence (eMethods in Supplement 1). E values were calculated to evaluate the influence of
confounding due to unknown or unmeasured variables.19,20 The calculations provide a value that
describes what the magnitude of the association of the unmeasured confounder would have to be
with each of the 2 investigated variables to explain away the observed association between the 2
variables. Hypothesis testing was performed with a significance level of P < .05. All statistical analyses
were performed using R, version 4.2.2 (R Project for Statistical Computing),21 and the R packages
survival, survminer, tableone, tidycmprsk, and ggplot2. Data analysis was performed between March
6 and September 16, 2023.
Results
Study Cohort
During the study period, 39 550 patients underwent first-time isolated CABG. A total of 633 (1.6%)
did not survive to be discharged from the hospital and 3588 (9.1%) had a history of AF prior to
surgery (Figure 1). Of the remaining 35 329 patients, 10 609 (30.0%) developed POAF after surgery
and were therefore included in the study cohort. Forty-two patients (0.4%) emigrated during
follow-up and were censored at the time of emigration. The median age of the POAF study cohort
was 71 (IQR, 66-76) years; 81.6% of patients were men and 18.4% were women. A total of 6.5% of
patients had an ischemic stroke, 6.3% had a TIA, and 56.2% had acute coronary syndrome before
surgery. Also, 30.3% of the patients had diabetes and 13.6% had heart failure. Baseline patient
characteristics are presented in Table 1. The median follow-up was 7.1 (IQR, 2.9-9.0) years.
Incidence of AF Recurrence
The cumulative incidence (95% CI) of AF recurrence requiring hospital care was 3.8% (3.5%-4.2%)
at 1 month, 6.7% (6.2%-7.1%) at 3 months, 10.0% (9.5%-10.6%) at 1 year, and 12.1% (11.4%-12.7%) at
2 years after discharge (Figure 2). Five years after discharge, 18.1% of patients (95% CI, 17.3%-18.8%)
had experienced at least 1 AF recurrence event compared with 26.8% (25.8%-27.9%) at 10 years and
33.1% (31.1%-35.2%) at 14 years after discharge (Figure 3 and eTable 4 in Supplement 1). Cumulative
incidences did not differ when comparing different time frames in which patients underwent CABG
(eFigure in Supplement 1). The median time to AF recurrence was 15.8 (IQR, 1.9-58.2) months in the
whole study cohort and 21 (IQR, 6-49) days in patients with early recurrence.
Drug Dispensing Data
The proportion of patients with early AF recurrence who had been dispensed an oral anticoagulant
increased from 33.3% directly after discharge to 83.2% at 1 month and 90.0% at 3 months; the
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corresponding values for patients without early AF recurrence were 20.7%, 29.0%, and 31.9%,
respectively. The prevalence of antiplatelet therapy at 6 months after discharge was 81.5% in
patients with early AF recurrence and 92.1% in patients without early AF recurrence.
The proportion of patients dispensed β-blockers during the first 6 postoperative months was
93.8% in patients with early AF recurrence and 93.6% in patients without early AF recurrence. The
prevalence of amiodaron was 22.1% in patients with early AF recurrence and 14.0% in patients
without early AF recurrence. The prevalence of digoxin was 13.5% in patients with early AF
Table 1. Baseline Clinical Characteristics of Patients With New-Onset POAF After CABG With and Without Early
AF Recurrencea
Early AF recurrence
(n = 698)b
No early AF recurrence
(n = 9911)
P value
Female
114 (16.3)
1837 (18.5)
.16
Male
584 (83.7)
8074 (81.5)
.16
Age, median (IQR), y
70 (66-76)
70 (66-76)
.42
Acute coronary syndrome
385 (55.2)
5578 (56.3)
.59
Previous percutaneous coronary intervention
110 (15.8)
1736 (17.5)
.26
Hypertension
519 (74.4)
7434 (75.0)
.73
Diabetes
164 (23.5)
3049 (30.8)
<.001
Heart failure
89 (12.8)
1359 (13.7)
.51
Characteristic
Sex
Left ventricular ejection fraction <50%
189 (27.2)
3137 (31.8)
.01
Previous ischemic stroke
37 (5.3)
654 (6.6)
.21
Previous hemorrhagic stroke
4 (0.6)
75 (0.8)
.75
Previous transient ischemic attack
43 (6.2)
625 (6.3)
.94
Previous systemic embolism
3 (0.4)
53 (0.5)
.92
Peripheral vascular disease
64 (9.2)
1079 (10.9)
.18
≥2
665 (95.3)
9449 (95.3)
>.99
≥4
CHA2DS2-VASc score
350 (50.1)
5343 (53.9)
.06
Kidney failure
23 (3.3)
396 (4.0)
.41
Kidney replacement therapy
4 (0.6)
52 (0.5)
>.99
Chronic respiratory disease
60 (8.6)
1091 (11.0)
.06
Liver disease
3 (0.4)
94 (0.9)
.24
History of cancer
116 (16.6)
1711 (17.3)
.70
Abbreviations: AF, atrial fibrillation; CABG, coronary
artery bypass grafting; CHA2DS2-VASc, congestive
heart failure, hypertension, age, diabetes, prior stroke
or transient ischemic attack or thromboembolism,
vascular disease, age, and sex category; POAF,
postoperative atrial fibrillation.
a
Unless indicated otherwise, values are presented as
No. (%) of patients.
b
Recurrence within 3 months of discharge.
Figure 2. Atrial Fibrillation (AF) Recurrence Within 24 Months of Discharge in Patients
With Postoperative Atrial Fibrillation (POAF) After Coronary Artery Bypass Grafting (CABG)
Cumulative incidence of AF recurrence, %
14
12
10
8
6
4
2
0
0
3
6
9
12
15
18
21
Time after discharge, mo
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24
Cumulative incidence of AF recurrence, adjusted for
the competing risk of death, within 24 months of
discharge in patients with new-onset POAF after
CABG. Shaded area indicates 95% CIs.
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recurrence and 2.7% in patients without early AF recurrence. Finally, the prevalence of sotalol was
8.5% in patients with early AF recurrence and 7.9% in patients without early AF recurrence.
Outcomes With and Without Early AF Recurrence
All-Cause Mortality
A total of 397 patients died during the first 2 years after discharge. The mortality rate (95% CI) was
2.21 (1.49-3.24) per 100 patient-years with early AF recurrence and 2.03 (1.83-2.25) without early AF
recurrence. After multivariable adjustment, early AF recurrence was not associated with increased
mortality risk (AHR, 1.17 [95% CI, 0.80-1.74]; P = .41) (Table 2).
Figure 3. Atrial Fibrillation (AF) Recurrence Within 14 Years of Discharge in Patients
With Postoperative Atrial Fibrillation (POAF) After Coronary Artery Bypass Grafting (CABG)
Cumulative incidence of AF recurrence, %
50
40
30
20
10
0
0
2
4
6
8
10
12
14
Time after discharge, y
Cumulative incidence of AF recurrence, adjusted for
the competing risk of death, within 14 years of
discharge in patients with new-onset POAF after
CABG. Shaded area indicates 95% CIs.
Table 2. Event Rates and HRs Within 2 Years of Discharge in Patients With New-Onset POAF After Coronary Artery Bypass Grafting
With and Without Early AF Recurrence
Outcome
No. of events
Person-years
at risk
Early AF recurrence vs no early AF recurrence, HR (95% CI)b
a
Event rate (95% CI)
Unadjusted
Adjustedc
P value
1.12 (0.75-1.65)
1.17 (0.80-1.74)
.41
0.91 (0.57-1.45)
0.98 (0.62-1.56)
.93
0.77 (0.50-1.19)
0.86 (0.56-1.32)
.49
1.72 (1.27-2.34)
1.80 (1.32-2.45)
.001
1.80 (1.33-2.44)
1.92 (1.42-2.61)
<.001
All-cause mortality
AF recurrence
27
1222
2.21 (1.49-3.24)
No AF recurrence
370
18 221
2.03 (1.83-2.25)
Ischemic stroke
AF recurrence
19
1192
1.59 (0.99-2.53)
No AF recurrence
366
17 837
2.05 (1.85-2.27)
Any thromboembolism
AF recurrence
22
1185
1.86 (1.20-2.85)
No AF recurrence
494
17 688
2.79 (2.56-3.05)
Heart failure hospitalization
AF recurrence
45
1143
3.94 (2.92-5.28)
No AF recurrence
492
17 611
2.79 (2.56-3.05)
Major bleeding
AF recurrence
46
1159
3.97 (2.95-5.30)
No AF recurrence
484
17 660
2.74 (2.51-2.99)
Abbreviations: AF, atrial fibrillation; HR, hazard ratio; POAF, postoperative atrial fibrillation.
a
Calculated for a maximum of 2 postoperative years and calculated as events per 100 patient-years. Both event rate and HR calculations observed the time dependence
of the variable AF recurrence.
b
Recurrence within 3 months of discharge.
c
Adjusted for patient characteristics and comorbidities.
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Stroke or Any Thromboembolism
A total of 385 ischemic strokes and 516 thromboembolic events (composite of ischemic stroke, TIA,
and systemic embolism) occurred within the first 2 years after discharge. The ischemic stroke rate
(95% CI) was 1.59 (0.99-2.53) events per 100 patient-years in patients with early AF recurrence and
2.05 (1.85-2.27) without early AF recurrence. After multivariable adjustment, early AF recurrence
was not associated with ischemic stroke risk (AHR, 0.98 [95% CI, 0.62-1.56]; P = .93). The rate (95%
CI) of any thromboembolism was 1.86 (1.2-2.85) events per 100 patient-years with early AF
recurrence and 2.79 (2.56-3.05) without early AF recurrence. No association was observed between
early AF recurrence and thromboembolic risk (AHR, 0.86 [95% CI, 0.56-1.32]; P = .49).
Heart Failure Hospitalization
A total of 537 heart failure hospitalizations occurred within the first 2 years after discharge. The rate
(95% CI) for heart failure hospitalization was 3.94 (2.92-5.28) events per 100 patient-years with early
AF recurrence and 2.79 (2.56-3.05) without early AF recurrence. After multivariable adjustment,
early AF recurrence was associated with an increased risk of heart failure hospitalization (AHR, 1.80
[95% CI, 1.32-2.45]; P = .001).
Major Bleeding
A total of 530 bleeding events occurred within the first 2 years after discharge. The event rate (95%
CI) for major bleeding was 3.97 (2.95-5.30) events per 100 patient-years with early AF recurrence
and 2.74 (2.51-2.99) without early AF recurrence. After multivariable adjustment, early AF recurrence
was associated with an increased risk of major bleeding (AHR, 1.92 [95% CI, 1.42-2.61]; P < .001).
Sensitivity Analysis
Results of the sensitivity analyses are presented in eTable 5 in Supplement 1. The results supported
the main analysis. E values for the association of heart failure hospitalization and major bleeding with
AF recurrence were 3.0 and 3.2, respectively, for the estimates and 2.0 and 2.2, respectively, for the
lower confidence limits.
Discussion
In this nationwide observational study of Swedish patients with new-onset POAF after CABG, early
AF recurrence leading to hospital care was common, occurring within 3 months in 6.7% of patients.
Early AF recurrence was not associated with an increased risk of all-cause mortality (the primary
endpoint). The exploratory analyses suggested that early AF recurrence was associated with heart
failure hospitalization, increased dispensation of oral anticoagulants, and an increased risk of major
bleeding events during the first 2 years after discharge.
The observation that “atrial fibrillation begets atrial fibrillation” describes that electrical
remodeling caused by AF results in a condition favoring continued AF.22 Previous studies have
suggested that POAF may favor later development of AF. Depending on the study, variable incidence
of AF recurrence after CABG has been observed. Butt et al23 reported that 8.7% of all hospitalizations
in the first year after CABG in Denmark are due to AF. Their study did not differentiate between
patients who had experienced POAF and those who had not. In a community-based study
investigating patients who had undergone CABG, valvular surgery, or both, a 1-year incidence of AF
recurrence of 18% was reported in patients with POAF.9
The SWEDEHEART registry documents all patients undergoing cardiac surgery in Sweden.
When combined with other mandatory national registries, it has the capacity to deliver complete
follow-up data, with registration of any hospitalization and hospital-affiliated outpatient contact
enabling the calculation of a cumulative incidence of AF recurrence in postsurgical populations. The
cumulative incidence of 10.0% at 1 year observed in this study is near the 8.7% rate reported by Butt
et al.23 After 14 years, the cumulative incidence of AF recurrence in our population was 33.1%. It is
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noteworthy that the episodes reported in our study are clinically relevant episodes leading to
hospitalization or treatment at a hospital outpatient clinic. In a study comparing 30-day continuous
electrocardiogram monitoring with standard of care, the underreporting of subclinical POAF in
cardiac surgery patients was highlighted by a 17.9% absolute difference in AF detection rate.24 Using
continuous cardiac rhythm monitoring, 2 studies demonstrated that both the incidence of POAF and
the AF recurrence rate after CABG are most likely underestimated.25,26
Several studies have documented associations between POAF after CABG and increased risk of
complications. Postoperative AF has been associated with an increased risk of all-cause mortality,2,27
ischemic stroke,4 thromboembolism,5 heart failure,5 and bleeding28,29 after CABG. The question
arises regarding whether POAF is causally related to these negative outcomes or whether a further
driver (eg, AF recurrence) may be the substitute associated with worse prognosis. We were unable to
identify an association between early AF recurrence and all-cause mortality, ischemic stroke, or any
thromboembolism. Conversely, we identified an association between early AF recurrence and heart
failure hospitalization after discharge.
In an analysis of data from the Framingham Heart Study, researchers reported that “AF occurs in
more than half of individuals with heart failure, and heart failure in more than one-third of individuals
with AF.”30 The association between heart failure and AF is further underpinned by the similarity of the
risk factors of the 2 conditions. When these conditions co-occur, they confer substantially increased
mortality31 compared with independent occurrence. In a previous analysis of patients in the SWEDEHEART registry who underwent CABG, which was based on partly the same study population as our
study, POAF was associated with an increased risk of heart failure hospitalizations (AHR, 1.35 [95% CI,
1.21-1.51]).5 In this study of patients who underwent CABG, we observed that early AF recurrence after
POAF was associated with heart failure hospitalizations (AHR, 1.80 [95% CI, 1.32-2.45]). Note that in our
analysis, only heart failure events occurring after recurrence events of AF were included in the calculation of hazard ratios. Analogously, researchers in the Framingham Heart Study found that AF more frequently antedated heart failure events than the reverse.30 Our results suggest that patients with clinically relevant early AF recurrence after CABG constitute a risk group who need close surveillance with a
focus on preventing and treating heart failure.
Current guidelines propose that it is reasonable to treat patients with POAF with oral
anticoagulation in a similar manner as nonsurgical patients.32 Furthermore, guidelines recommend
that the benefits and risks of anticoagulation therapy should be weighed individually.33 However,
studies investigating oral anticoagulation in patients with POAF after CABG in the Society of Thoracic
Surgeons Adult Cardiac Surgery Database suggest no net clinical benefit28 and even a possible
increased mortality risk.29 In this study, we observed, as expected, that patients were more likely to
receive oral anticoagulation therapy after recurrence events. Three months after recurrence, 90.0%
of patients with early AF recurrence had been dispensed an oral anticoagulant compared with 31.9%
of patients without AF recurrence. Furthermore, we observed an association between AF recurrence
and major bleeding events, likely attributable to oral anticoagulation, often in combination with
antiplatelet therapy.
Strengths and Limitations
To our knowledge, this study represents the first investigation of the association between early AF
recurrence and outcome events in patients with POAF after CABG. Strengths of this study include the
large study population, the long follow-up, the use of validated registries, and the completeness of
the data. Like all studies investigating POAF, a key limitation is the definition of POAF. Although the
present definition is valid and verifiable within the registry used, a comparison with other studies
must be performed carefully because of variability in the definition. We acknowledge that this study
only investigated patients with symptomatic AF recurrence, and patients with silent recurrence were
not included. An investigation of patients with silent AF necessitates the use of continuous
monitoring devices. Use of administrative data may underestimate the incidence of AF. However, it
has previously been shown that the sensitivity and specificity for detecting AF in registries based on
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ICD codes is reasonable.34 A small portion of the patients investigated may have been in AF at
discharge; with the available data, it was not possible to determine whether or when conversion
occurred. Patient-level data on combined antiplatelet and oral anticoagulant use, as well as use at the
time of the investigated outcome events, was not available within our database. Multiple
comparisons increase the risk of false-positive findings; however, this was unlikely in our study, given
the robust P values for heart failure hospitalization and major bleeding. Finally, as in all observational
studies, there remains a risk for selection bias and residual confounding in our study (although the
E-value analysis indicated moderate robustness).
Conclusions
In this cohort study, early AF recurrence after discharge in patients with new-onset POAF after CABG
was associated with subsequent heart failure necessitating hospital care, an increased burden of oral
anticoagulation, and an increased risk of major bleeding events. These results suggest that close
follow-up of patients with POAF and early AF recurrence is required.
ARTICLE INFORMATION
Accepted for Publication: January 18, 2024.
Published: March 7, 2024. doi:10.1001/jamanetworkopen.2024.1537
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2024 Herrmann
FEM et al. JAMA Network Open.
Corresponding Author: Anders Jeppsson, MD, PhD, Department of Cardiothoracic Surgery, Sahlgrenska
University Hospital, SE-41345 Gothenburg, Sweden (anders.jeppsson@vgregion.se).
Author Affiliations: Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy,
University of Gothenburg, Gothenburg, Sweden (Herrmann, Taha, Nielsen, Martinsson, Hansson, Jeppsson);
Department of Cardiac Surgery, LMU University Hospital, LMU Munich, Munich, Germany (Herrmann, Juchem);
DZHK (German Centre for Cardiovascular Research) Partner Site Munich Heart Alliance, Munich, Germany
(Herrmann); Department of Cardiology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg,
Sweden (Taha, Martinsson); Department of Cardiothoracic Surgery, Region Västra Götaland, Sahlgrenska
University Hospital, Gothenburg, Sweden (Nielsen, Hansson, Jeppsson).
Author Contributions: Drs Herrmann and Jeppsson had full access to all of the data in the study and take
responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Herrmann, Juchem, Jeppsson.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Herrmann.
Critical review of the manuscript for important intellectual content: All authors.
Statistical analysis: Herrmann, Martinsson.
Obtained funding: Herrmann, Jeppsson.
Administrative, technical, or material support: Nielsen, Jeppsson.
Supervision: Taha, Nielsen, Juchem, Jeppsson.
Conflict of Interest Disclosures: Dr Taha reported serving as a medical advisor to and receiving personal fees from
Medtronic and receiving lecture fees from Abbott outside the submitted work. Dr Hansson reported receiving
personal fees from Pfizer outside the submitted work. Dr Jeppsson reported receiving grants from AstraZeneca
and personal fees from AstraZeneca, LFB Biotechnologies, Werfen, Novo Nordisk, and Bayer outside the
submitted work. No other disclosures were reported.
Funding/Support: This work was supported by grants from the Swedish Heart-Lung Foundation (20210433 to Dr
Jeppsson), the Swedish state under the agreement between the Swedish government and the county councils
concerning economic support of research and education of doctors (ALFGBG-942665 to Dr Nielsen, ALFGBG977905 to Dr Martinsson, and ALFGBG-966204 to Dr Jeppsson), the Västra Götaland Region (VGFOUREG969376 to Dr Jeppsson), the Nils Winberg Family Foundation, the German Research Foundation (413635475 to Dr
Herrmann), and the Munich Clinician Scientist Program of LMU Munich.
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Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection,
management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and
decision to submit the manuscript for publication.
Data Sharing Statement: See Supplement 2.
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SUPPLEMENT 1.
eTable 1. List of Diagnoses According to International Classification of Diseases, Tenth Revision (ICD-10) Codes
eTable 2. List of Medications According to ATC Codes
eTable 3. Variables Included in the Individual Multivariable Cox Proportional Hazards Models Investigating the
Association of Early Atrial Fibrillation Recurrence With Outcomes
eTable 4. Cumulative Incidence of Atrial Fibrillation Recurrence After Discharge in Patients With New-Onset
Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting
eTable 5. Sensitivity Analysis for the Association of Early Atrial Fibrillation Recurrence With Primary and Secondary
Outcome Variables
eMethods. Sensitivity Analysis
eFigure. Atrial Fibrillation Recurrence in Patients With New-Onset Postoperative Atrial Fibrillation After Coronary
Artery Bypass Grafting With Grouping by Year of Surgery
SUPPLEMENT 2.
Data Sharing Statement
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