Relation between initial treatment strategy in stable coronary artery disease and 1-year costs in Ontario: a population-based cohort study

Jaskaran S. Kang; Maria C. Bennell; Feng Qiu; Merril L. Knudtson; Peter C. Austin; Dennis T. Ko; Harindra C. Wijeysundera

doi:10.9778/cmajo.20150138

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Figure 1
Selection of patients for the study. Note: CABG = coronary artery bypass grafting, MI = myocardial infarction, PCI = percutaneous coronary intervention.
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Figure 2
Variation in individual- and hospital-level costs. The median is plotted for each centre as a horizontal line, the boxes represent the interquartile range, and the circles represent the mean.

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Table 1: Baseline characteristics of patients with stable angina, by initial treatment strategy Table 1: Baseline characteristics of patients with stable angina, by initial treatment strategy

Variable	% of patients*			p value (medical therapy v. revascularization)	% of patients*
Variable	Total n = 39 126	Medical therapy n = 15 138	Revascularization n = 23 988	p value (medical therapy v. revascularization)	PCI n = 15 601	CABG n = 8387
Patient-level factors
Demographics
Age, mean ± SD, yr	66.0 ± 10.3	67.0 ± 10.2	65.3 ± 10.3	< 0.001	65.0 ± 10.7	66.0 ± 9.7
Sex, male	75.3	74.3	75.9	< 0.001	72.9	81.3
Rural residence	14.5	14.4	14.5	0.7	14.6	14.5
Income quintile				< 0.001
1 (lowest)	18.6	19.6	17.9		18.4	17.1
2	20.4	20.4	20.4		20.4	20.6
3	20.2	20.3	20.2		20.3	19.9
4	20.7	20.2	21.0		20.8	21.3
5 (highest)	20.1	19.4	20.5		20.2	21.1
Medical comorbidities
PVD	9.4	11.5	8.1	< 0.001	7.6	9.0
Previous MI	28.1	35.8	23.3	< 0.001	24.8	20.4
COPD	6.9	8.6	5.8	< 0.001	6.1	5.1
Charlson Comorbidity Index score, mean ± SD	0.9 ± 1.3	1.1 ± 1.5	0.8 ± 1.2	< 0.001	0.7 ± 1.3	0.8 ± 1.2
Cardiac risk factors
Diabetes	44.0	48.0	41.4	< 0.001	40.5	43.1
Hypertension	86.7	89.5	84.9	< 0.001	84.9	85.1
Hyperlipidemia	80.8	83.0	79.5	< 0.001	79.9	78.7
History of smoking	31.6	33.2	30.5	< 0.001	30.3	31.0
Cardiac status/testing
Native stenosis†
LM	13.0	10.8	14.4	< 0.001	5.5	31.0
Proximal LAD	33.2	28.7	36.0	< 0.001	29.7	47.6
Mid/distal LAD	49.6	47.5	51.0	< 0.001	46.0	60.3
Circumflex	51.5	50.9	51.9	0.07	43.6	67.2
RCA	60.8	60.5	60.9	0.4	54.7	72.6
Had previous CABG				< 0.001
Yes	18.0	30.1	10.4		15.1	1.6
No	81.9	69.9	89.5		84.9	98.2
LV function				< 0.001
≤ 34%	5.4	8.4	3.5		3.3	4.0
35%-49%	12.9	16.0	11.0		10.6	11.7
≥ 50%	48.6	46.5	50.0		49.7	50.5
NA	33.0	29.1	35.5		36.4	33.8
Exercise ECG risk				< 0.001
High risk	27.7	21.3	31.7		28.8	37.1
Low risk	22.4	22.9	22.2		23.0	20.7
Uninterpretable	4.9	4.8	4.9		5.3	4.2
NA	45.0	51.1	41.2		42.9	38.0
Patient-level factors cont'd
Cardiac status/testing cont'd
Functional imaging risk				< 0.001
High risk	32.0	31.2	32.6		31.1	35.3
Low risk	23.0	25.1	21.7		23.2	19.1
Unknown/NA	44.9	43.7	45.7		45.7	45.7
CCS class				< 0.001
0	16.5	22.0	13.0		11.3	16.2
1	14.0	15.9	12.8		12.3	13.8
2	38.3	35.5	40.0		40.8	38.5
3	28.5	24.2	31.1		32.3	29.0
4	2.8	2.4	3.0		3.3	2.5
Physician-level factors
Referral physician				0.01
Family physician	25.7	26.1	25.5		25.6	25.3
Cardiology	41.4	40.5	14.9		42.1	41.6
Internal medicine	9.4	9.3	9.6		9.1	10.4
Other	6.6	6.8	6.5		6.2	7.0
Missing	16.9	17.4	16.5		17.0	15.6
Hospital-level factors
Annual no. of catheterization procedures, mean ± SD	4092.3 ± 1696.4	4031.3 ± 1684.3	4130.9 ± 1702.9	< 0.001	4120.9 ± 1702.6	4149.5 ± 1703.6
Hospital type				< 0.001
Catheterization only	13.2	13.6	13.0		13.4	12.2
PCI and catheterization only	6.1	7.2	5.4		5.0	6.1
CABG, PCI and catheterization	80.8	79.3	81.7		81.7	81.8

CABG = coronary artery bypass grafting, Cath = catheterization, CCS = Canadian Cardiovascular Society, COPD = chronic obstructive pulmonary disease, ECG = electrocardiogram, LAD = left anterior descending, LM = left main, LV = left ventricular, MI = myocardial infarction, NA = not done, PCI = percutaneous coronary intervention, PVD = peripheral vascular disease, RCA = right coronary artery.

*Unless stated otherwise.

†LM if ≥ 50% stenosis, proximal LAD if ≥ 70% stenosis, mid/distal LAD if ≥ 70% stenosis, circumflex if ≥ 70% stenosis, RCA if ≥ 70% stenosis.

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Table 2: Components of 1-year mean costs

Category	Cost, $			p value (medical therapy v. revascularization)	Cost, $
Category	Total	Medical	Revascularization	p value (medical therapy v. revascularization)	CABG	PCI
Acute care hospital admission	11 373	7038	14 109	< 0.001	25 927	7755
Emergency department	372	367	375	0.3	403	361
Surgery	2691	2090	3071	< 0.001	1901	3699
Physician visits	5449	4079	6313	< 0.001	10 086	4284
Medication*	1810	1857	1780	0.004	1476	1944
Laboratory	194	195	193	0.3	217	180
Long-term care	54	93	29	< 0.001	47	19

Note: CABG = coronary artery bypass grafting, PCI = percutaneous coronary intervention.

*For patients > 65 years of age.

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Table 3: Predictors of 1-year cumulative health care costs Table 3: Predictors of 1-year cumulative health care costs

Covariate	Cost ratio (95% CI)
Treatment*
Medical management	Reference
PCI	1.27 (1.24-1.31)
CABG	2.62 (2.53-2.71)
Patient-level factors
Demographic characteristics
Age, yr	1.01 (1.01-1.01)
Sex, male	0.96 (0.95-0.98)
Rural residence	0.97 (0.95-0.99)
Income quintile
5 (highest)	Reference
1 (lowest)	1.10 (1.07-1.12)
2	1.04 (1.02-1.07)
3	1.02 (1.00-1.05)
4	1.02 (1.00-1.05)
Medical comorbidities
Peripheral vascular disease	1.25 (1.21-1.28)
Previous MI	0.95 (0.93-0.97)
COPD	1.10 (1.07-1.13)
Charlson score	1.17 (1.16-1.17)
Cardiac risk factors
Diabetes	1.00 (0.99-1.02)
Hypertension	1.11 (1.08-1.13)
Hyperlipidemia	0.95 (0.93-0.97)
History of smoking	1.00 (0.99-1.02)
Cardiac status/testing
Native stenosis†
LM	1.12 (1.09-1.15)
Proximal LAD	1.10 (1.08-1.11)
Mid/distal LAD	1.08 (1.06-1.09)
Circumflex	1.11 (1.09-1.12)
RCA	1.09 (1.07-1.11)
Previous CABG	0.83 (0.82-0.85)
LV function, %
≥ 50	Reference
35-49	1.03 (1.00-1.05)
≤ 34	1.14 (1.10-1.18)
NA	0.95 (0.93-0.97)
Patient-level factors cont'd
Cardiac status/testing cont'd
Exercise ECG risk
Low risk	Reference
High risk	1.04 (1.02-1.06)
Uninterpretable	1.09 (1.05-1.14)
NA	1.24 (1.21-1.27)
Functional imaging risk
Low risk	Reference
High risk	1.01 (0.99-1.03)
Unknown/NA	1.05 (1.03-1.08)
CCS class
0	Reference
1	0.90 (0.87-0.92)
2	0.88 (0.85-0.90)
3	0.90 (0.88-0.92)
4	0.86 (0.82-0.90)
Physician factors
Referral physician
Family physician	Reference
Cardiology	1.02 (1.01-1.05)
Internal medicine	1.00 (0.98-1.03)
Other	1.22 (1.19-1.27)
Missing	1.03 (1.00-1.05)
Hospital factors
Hospital revascularization ratio*
Low	Reference
Medium	1.03 (0.93-1.15)
High	1.08 (0.97-1.21)
Annual catheterization volume	0.99 (0.99-0.99)

Note: CABG = coronary artery bypass grafting, CI = confidence interval, COPD = chronic obstructive pulmonary disease, ECG = electrocardiography, LAD = left anterior descending, LM = left main, LV = left ventricular, MI = myocardial infarction, NA = not done or missing, PCI = percutaneous coronary intervention, RCA = right coronary artery.

*The 2 main covariates of interest: treatment type and hospital revascularization ratio.

†LM if ≥ 50% stenosis, proximal LAD if ≥ 70% stenosis, mid/distal LAD if ≥ 70% stenosis, circumflex if ≥ 70% stenosis, RCA if ≥ 70% stenosis.