Postoperative atrial fibrillation predicts cause-specific late mortality after coronary surgery

Figures & data

Table I. Patient characteristics.

Variables	POAF n = 2152 (32%) %	No POAF n = 4669 (68%) %	p-value
Age (years), mean ± SD	69.0 ± 7.7	65.2 ± 9.1	< 0.0001
Male gender	79	77	0.08
Hypertension	52	50	0.2
Diabetes	21	22	0.4
Prior MI	56	52	0.006
Diseased coronary vessels			0.5
1	4	5
2	21	21
3	75	74
Left main stenosis	34	32	0.2
LVEF			0.2
Good (> 50%)	69	70
Reduced (30–50%)	26	26
Poor (< 30%)	5	4
NYHA class			0.008
I/IIIA	47	51
IIIB/IV	53	49
CCS angina grading scale			0.1
0–2	32	35
3–4	68	65
EuroSCORE, median (25th to 75th pctl)^a	3 (2–5)	2 (1–4)	< 0.0001

CCS, Canadian Cardiovascular Society; LVEF, left ventricular ejection fraction; MI, myocardial infarction; NYHA class, New York Heart Association functional classification; POAF, postoperative atrial fibrillation.

^aVariable only available for half of the patients, even distribution between groups.

Table II. Peri- and postoperative variables.

Variables	POAF n = 2152 (32%) %	No POAF n = 4669 (68%) %	p-value
Perioperative
Aortic cross-clamp time, min^a	35 (43–53)	34 (42–52)	0.3
CPB time, min^a	66 (82–97)	65 (80–96)	0.5
Use of IMA	93	92	0.6
Number of distal anastomoses^a	3 (3–4)	3 (3–4)	0.2
Perioperative myocardial injury^b	8.8	9.3	0.5
Postoperative
Re-operation, bleeding	3.5	2.3	0.005
IABP	0.9	0.6	0.2
Respiratory complication^c	4.1	2.2	< 0.0001
Infection^d	7.3	5.0	< 0.0001
Stroke^e	3.7	2.1	< 0.0001
Permanent pacemaker	0.8	0.7	0.6

CPB, cardiopulmonary bypass; IABP, intra-aortic balloon pump; IMA, internal mammary artery; POAF, postoperative atrial fibrillation.

^aMedian (25th to 75th pctl).

^bPlasma creatine kinase-band value > 50 μg postoperative Day 1.

^cProlonged mechanical ventilation > 24 h, or re-intubation.

^dTreatment with antibiotics, and/or positive blood culture.

^eSevere neurological symptoms lasting ≥ 6 h, verified by computer tomography.

Figure 1. Kaplan–Meier survival curve based on cardiac mortality (A), and survival curve adjusted for baseline characteristics, medical history, and preoperative status (B), by occurrence of POAF. The figure shows 95% CI at 5, 10, and 15 years. Log-rank p < 0.0001. POAF = postoperative atrial fibrillation.

Table III. Multivariable predictors of cardiac mortality after CABG. Follow-up 10 (6–13) years.^a

Variables	n	Dead	HR	95% CI
POAF
No	4669	548	1.0	ref.
Yes	2152	381	1.4	(1.3–1.5)
Age (years)
≤ 60	1629	113	1.0	ref.
61–70	2536	276	1.7	(1.5–1.9)
71–80	2458	489	3.9	(3.7–4.1)
> 80	198	51	8.2	(7.9–8.6)
Diabetes
No	5365	676	1.0	ref.
Yes	1456	253	1.8	(1.6–1.9)
Number of prior MIs
≤ 1	5925	710	1.0	ref.
2	682	159	1.4	(1.3–1.6)
3	163	42	1.5	(1.2–1.8)
≥ 4	51	18	3.0	(2.5–3.4)
LVEF
Good (> 50%)	4732	471	1.0	ref.
Reduced (30–50%)	1798	374	1.9	(1.8–2.1)
Poor (< 30%)	291	84	3.4	(3.2–3.7)

CABG, coronary artery bypass grafting; HR, hazard ratio; LVEF, left ventricular ejection fraction; MI, myocardial infarction; POAF, postoperative atrial fibrillation.

^aMedian (25th to 75th pctl). All variables in Table I were considered, and the final analysis adjusted for age, diabetes, number of prior myocardial infarctions, and left ventricular function.

Figure 2. Adjusted survival curves based on death related to: (A) arrhythmia, (B) cerebrovascular disease, and (C) heart failure, by occurrence of POAF. The figures show 95% CI at 5, 10, and 15 years. Log-rank p < 0.0001. POAF = postoperative atrial fibrillation.

Table IV. Multivariable predictors of death related to arrhythmia, cerebrovascular disease, and heart failure after CABG. Follow-up 10 (6–13) years.^a

Variables	n	Primary or contributing cause of death
		Arrhythmia^b			Cerebrovascular disease^c			Heart failure^d
		Dead	HR	95% CI	Dead	HR	95% CI	Dead	HR	95% CI
POAF
No	4669	228	1.0	ref.	224	1.0	ref.	408	1.0	ref.
Yes	2152	192	1.8	(1.6–2.0)	172	1.4	(1.2–1.6)	298	1.4	(1.3–1.6)
Age (years)
≤ 60	1629	50	1.0	ref.	21	1.0	ref.	54	1.0	ref.
61–70	2536	119	1.6	(1.3–2.0)	116	3.9	(3.4–4.3)	209	2.8	(2.5–3.1)
71–80	2458	230	4.2	(3.9–4.5)	231	9.9	(9.5–10)	402	6.9	(6.6–7.2)
> 80	198	21	8.9	(8.4–9.4)	28	24	(24–25)	41	15	(15–16)
Hypertension
No	3345	192	1.0	ref.
Yes	3476	228	1.2	(1.1–1.4)
Diabetes
No	5365	292	1.0	ref.	275	1.0	ref.	512	1.0	ref.
Yes	1456	128	2.1	(1.9–2.4)	121	2.2	(2.0–2.4)	194	1.9	(1.7–2.0)
Number of prior MIs
≤ 1	5925							533	1.0	ref.
2	682							127	1.4	(1.2–1.6)
3	163							33	1.5	(1.1–1.8)
≥ 4	51							13	2.9	(2.4–3.5)
Diseased coronary vessels
1–2	1726	70	1.0	ref.
3	5095	350	1.4	(1.1–1.7)
Left main stenosis
No	4602							470	1.0	ref.
Yes	2219							236	1.2	(1.0–1.3)
LVEF
Good (> 50%)	4732	211	1.0	ref.	226	1.0	ref.	329	1.0	ref.
Reduced (30–50%)	1798	171	2.1	(1.9–2.3)	150	1.7	(1.5–1.9)	310	2.3	(2.2–2.5)
Poor (< 30%)	291	38	4.0	(3.6–4.3)	20	1.8	(1.4–2.3)	67	4.1	(3.9–4.4)

CABG, coronary artery bypass grafting; HR, hazard ratio; LVEF, left ventricular ejection fraction; MI, myocardial infarction; POAF, postoperative atrial fibrillation.

^aMedian (25th to 75th pctl). All variables in Table I were considered, and the final analyses adjusted for ^bage, hypertension, diabetes, diseased coronary vessels, and left ventricular function, ^cage, diabetes, and left ventricular function, and ^dage, diabetes, number of prior myocardial infarctions, left main stenosis, and left ventricular function.

Table V. Effect of POAF on late mortality over time. Follow-up 10 (6–13) years.^a

	< 3 years after CABG				3–8 years after CABG				> 8 years after CABG
	POAF	No POAF	HR	95% CI	POAF	No POAF	HR	95% CI	POAF	No POAF	HR	95% CI
Patients at risk	2152	4669			2005	4480			1312	3018
Primary cause of death
Cardiac mortality	72	69	2.0	(1.7–2.3)	126	180	1.3	(1.1–1.5)	182	300	1.3	(1.1–1.5)
Primary or contributing cause of death:
Arrhythmia	17	24	1.5	(0.9–2.2)	63	66	1.8	(1.4–2.1)	111	139	1.8	(1.6–2.1)
Cerebrovascular disease	30	29	1.9	(1.3–2.4)	66	83	1.4	(1.1–1.8)	75	113	1.4	(1.1–1.7)
Heart failure	34	33	1.9	(1.4–2.4)	95	129	1.3	(1.0–1.5)	169	246	1.5	(1.3–1.7)

CABG, coronary artery bypass grafting; HR, hazard ratio; POAF, postoperative atrial fibrillation.

^aMedian (25th to 75th pctl).

Horwich P, Buth KJ, Légaré JF. New onset postoperative atrial fibrillation is associated with a long-term risk for stroke and death following cardiac surgery. J Card Surg. 2013;28:8–13.

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