Does coronary artery bypass surgery improve survival?

Figures & data

Table I. Patient characteristics. Mean ± standard deviation or number (%).

		Missing data (n, %)
Number of patients (n)	10657	0 (0)
Men	8344 (78)	0 (0)
Age (years)	66±9	0 (0)
Waiting time (days, median and interquartile range)	39 (13–89)	0 (0)
Waiting time (days)	64±74	0 (0)
Body mass index	27±4	245 (2.3)
Cleveland clinic risk score	1.67±1.61	287 (2.7)
Left main stenosis	2261 (21)	189 (1.8)
Unstable angina	3177 (30)	92 (0.9)
Chronic obstructive pulmonary disease	563 (5)	380 (3.6)
Previous stroke	535 (5)	363 (3.4)
with previous TIA included	858 (8)
Hypertension	4498 (42)	363 (3.4)
Atrial fibrillation	215 (2)	370 (3.5)
Diabetes mellitus	2107 (20)	260 (2.4)
Serum creatinine (µmol/L)	102±49	293 (2.7)
Blood hemoglobin (g/L)	140±13	179 (1.7)
NYHA-class		370 (3.5)
I	6792 (64)
II	1943 (18)
III	1395 (13)
IV	157 (2)
CCS-class		488 (4.6)
0	977 (9)
I	588 (5)
II	2162 (20)
III	4893 (46)
IV	1549 (15)
Priority group		54 (0.5)
Imperative	3909 (37)
Urgent	4774 (45)
Routine	1919 (18)
Number of vessels diseased		189 (1.8)
Three-vessel disease	7429 (70)
Two-vessel disease	2354 (22)
One-vessel disease	684 (6)
Unknown	189 (2)
Ejection fraction	58.0±12.9	351 (3.3)

CCS, Canadian Cardiology Society; NYHA, New York Heart Association; TIA, transient ischemic attack.

Table II. ‘Univariable’ analyses of hazard functions of death (‘univariable’ analysis of β–coefficients and hazard ratios is not truly univariable but includes time since TRIAGE and surgery respectively and age).

	Before surgery					After surgery
Variable (all variables are as known at triage)	β	SE	p–Value	HR	95% CI	β	SE	p–Value	HR	95% CI	p–Value (before vs. after surgery)
Gender	−0.0956	0.2778	0.7308	0.91	0.53–1.57	−0.0036	0.0628	0.9543	1.00	0.88–1.13	0.7467
Age	0.0334	0.0128	0.0091	1.03	1.01–1.06	0.0603	0.0033	0.0000	1.06	1.06–1.07	0.0419
Time on waiting list						0.3328	0.1154	0.0039	1.39	1.11–1.75
Body mass index	0.0135	0.0206	0.5123	1.01	0.97–1.06	−0.0033	0.0039	0.3975	1.00	0.99–1.00	0.4230
LVEF (left ventricular ejection fraction)	−0.0594	0.0075	0.0000	0.94	0.93–0.96	−0.0302	0.0019	0.0000	0.97	0.97–0.97	0.0002
Chronic obstructive pulmonary disease	0.7711	0.3370	0.0222	2.16	1.12–4.19	0.7045	0.0891	0.0000	2.02	1.70–2.41	0.8485
Preoperative stroke or TIA	0.8532	0.2851	0.0028	2.35	1.34–4.10	0.6678	0.0769	0.0000	1.95	1.68–2.27	0.5302
Hypertension	0.0900	0.2189	0.6810	1.09	0.71–1.68	0.3040	0.0523	0.0000	1.36	1.22–1.50	0.3417
Diabetes	0.9132	0.2224	0.0000	2.49	1.61–3.85	0.5542	0.0580	0.0000	1.74	1.55–1.95	0.1183
Smoker	2.2649	0.2466	0.0000	9.63	5.94–15.6	0.0571	0.0702	0.4160	1.06	0.92–1.21	0.0000
Preoperative heart failure	1.6694	0.2253	0.0000	5.31	3.41–8.26	1.0378	0.0667	0.0000	2.82	2.48–3.22	0.0072
Preoperative atrial fibrillation	1.3914	0.3717	0.0002	4.02	1.94–8.33	0.9432	0.1229	0.0000	2.57	2.02–3.27	0.2523
Preoperative unstable angina	1.6799	0.2285	0.0000	5.37	3.43–8.40	0.2934	0.0554	0.0000	1.34	1.20–1.49	0.0000
NYHA	0.5698	0.1303	0.0000	1.77	1.37–2.28	0.3315	0.0304	0.0000	1.39	1.31–1.48	0.0749
Se-creatinine	0.0025	0.0007	0.0004	1.00	1.00–1.00	0.0025	0.0003	0.0000	1.00	1.00–1.00	1.0000
Number of diseased vessels (1–3)	0.8188	0.2702	0.0025	2.27	1.34–3.85	0.3112	0.0501	0.0000	1.37	1.24–1.51	0.0647
Left main coronary disease	0.7868	0.2537	0.0019	2.20	1.34–3.61	0.1172	0.0615	0.0567	1.12	1.00–1.27	0.0103
Prox LAD-stenos	0.8777	0.2448	0.0003	2.41	1.49–3.89	0.1298	0.0519	0.0124	1.14	1.03–1.26	0.0028
3-Vessel disease	0.9212	0.3119	0.0032	2.51	1.36–4.63	0.3340	0.0612	0.0000	1.40	1.24–1.57	0.0647
3-Vessel disease + prox LAD	0.8928	0.2278	0.0001	2.44	1.56–3.82	0.2892	0.0516	0.0000	1.34	1.21–1.48	0.0098

Figure 1. To illustrate the difference between the pre- and postoperative risk models, we have chosen a moderately increased risk profile (age of 67 years at decision, EF =40%, diabetes, NYHA =2, S-creatinine =150 µmol/L, and stable angina operated 7 days after triage). The two curves give the preoperative (bold line) and postoperative (thin line) hazard function curves.

Table III. Multivariable analyses (significant β–coefficients, age, and time since TRIAGE and surgery respectively were included).

Variable (as known at triage)	β	SE	p–Value	HR	95% CI
Before surgery
Constant	−3.0822	1.0482
Current age	0.0202	0.0135	0.1358	1.02	0.99–1.05
EF	−0.0548	0.0079	0.0000	0.95	0.93–0.96
Diabetes	0.8762	0.2345	0.0002	2.40	1.52–3.80
Unstable angina	1.3517	0.2544	0.0000	3.86	2.35–6.36
S–creatinine	0.0035	0.0008	0.0000	1.00	1.00–1.01
Prox LAD–stenos	0.7534	0.2622	0.0041	2.12	1.27–3.55
Time since decision	−0.2443	0.5762	0.6716	0.78	0.25–2.42
After surgery
Constant	−4.2938	0.3572
Min(time, 0.1)	−25.3185	2.2868	0.0000	0.00	0.00–0.00
Max(Min(time-0.1, 0.5–0.1), 0)	−1.9103	0.5793	0.0010	0.15	0.05–0.46
Max(Min(time-0.5, 2–0.5), 0)	0.1451	0.1025	0.1569	1.16	0.95–1.41
Max(time–2, 0)	0.1210	0.0175	0.0000	1.13	1.09–1.17
Current age	0.0550	0.0042	0.0000	1.06	1.05–1.07
Left ventricular ejection fraction (LVEF)	−0.0234	0.0025	0.0000	0.98	0.97–0.98
Chronic obstructive pulmonary disease	0.5623	0.1109	0.0000	1.75	1.41–2.18
Preoperative stroke or TIA	0.4488	0.0961	0.0000	1.57	1.30–1.89
Diabetes	0.4748	0.0725	0.0000	1.61	1.39–1.85
Preoperative heart failure	0.3645	0.0901	0.0001	1.44	1.21–1.72
Preoperative atrial fibrillation	0.4069	0.1360	0.0028	1.50	1.15–1.96
NYHA	0.1315	0.0377	0.0005	1.14	1.06–1.23
S–creatinine	0.0029	0.0003	0.0000	1.00	1.00–1.00

Figure 2. Predicted and observed deaths (absolute numbers) before (to the left) and after surgery (to the right) accumulated over time.

Table IV. Probability of death (Individual values of all patients were entered in the two hazard function and the probability of death for each patient is presented according to the criteria of table headings).

						Probability of death (%) in the interval within 4 months
Ejection fraction	Diabetes	Unstable angina	Prox LAD stenosis	Number of patients	Proportion of patients (%)	Not operated	Operated
EF ≤30	No	No	No	49	0.7	1.8	2.8
EF ≤30	No	No	Yes	75	1.0	3.9	3.0
EF ≤30	No	Yes	No	27	0.4	6.4	3.4
EF ≤30	No	Yes	Yes	66	0.9	13.9	4.0
EF ≤30	Yes	No	No	28	0.4	3.9	4.3
EF ≤30	Yes	No	Yes	24	0.3	8.4	4.9
EF ≤30	Yes	Yes	No	23	0.3	16.1	6.6
EF ≤30	Yes	Yes	Yes	21	0.3	32.2	6.1
30 < EF ≤50	No	No	No	416	5.8	0.7	1.6
30 < EF ≤50	No	No	Yes	483	6.7	1.5	1.7
30 < EF ≤50	No	Yes	No	203	2.8	2.7	1.9
30 < EF ≤50	No	Yes	Yes	305	4.2	5.8	2.0
30 < EF ≤50	Yes	No	No	110	1.5	1.9	3.1
30 < EF ≤50	Yes	No	Yes	168	2.3	3.7	2.8
30 < EF ≤50	Yes	Yes	No	74	1.0	6.1	3.5
30 < EF ≤50	Yes	Yes	Yes	97	1.3	13.4	3.3
EF >50	No	No	No	1413	19.5	0.2	0.8
EF >50	No	No	Yes	1619	22.4	0.5	0.9
EF >50	No	Yes	No	487	6.7	1.0	0.9
EF >50	No	Yes	Yes	620	8.6	2.0	1.1
EF >50	Yes	No	No	324	4.5	0.6	1.5
EF >50	Yes	No	Yes	353	4.9	1.2	1.5
EF >50	Yes	Yes	No	124	1.7	2.2	1.5
EF >50	Yes	Yes	Yes	122	1.7	4.9	1.8