Geographic and temporal variation in the treatment and outcomes of atrial fibrillation: a population-based analysis of national quality indicators

Derek S. Chew; Flora Au; Yuan Xu; Braden J. Manns; Marcello Tonelli; Stephen B. Wilton; Brenda Hemmelgarn; Shiying Kong; Derek V. Exner; Amity E. Quinn

doi:10.9778/cmajo.20210246

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Figure 1:
Crude rates of initiation of oral anticoagulant therapy among patients with nonvalvular atrial fibrillation at high risk for stroke by Health Status Area, April 2008 to March 2016. Online map available at https://bit.ly/3fOXJq3.
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Figure 2:
Crude rates of initiation of oral anticoagulant therapy among patients with nonvalvular atrial fibrillation at moderate risk for stroke by Health Status Area, April 2008 to March 2016. Online map available at https://bit.ly/3fOXJq3.

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Table 1:

Baseline characteristics of patients with nonvalvular atrial fibrillation by stroke risk and oral anticoagulant use

Characteristic	No. (%) of patients^*

	Entire cohort n = 64 093	High stroke risk^† n = 36 199		Moderate stroke risk^† n = 14 411

		Oral anticoagulant n = 20 180	No oral anticoagulant n = 16 019	Oral anticoagulant n = 6448	No oral anticoagulant n = 7963
Age, mean ± SD, yr	69.0 ± 15.9	76.9 ± 10.3	77.0 ± 12.3	64.9 ± 8.4	61.3 ± 11.0

Age group, yr

18–64	22 720 (35.4)	2694 (13.3)	2671 (16.7)	2464 (38.2)	3997 (50.2)

65–74	14 983 (23.4)	3874 (19.2)	2618 (16.3)	3984 (61.8)	3966 (49.8)

≥ 75	26 390 (41.2)	13 612 (67.4)	10 730 (67.0)	0 (0.0)	0 (0.0)

Sex

Female	29 074 (45.4)	9710 (48.1)	8024 (50.1)	2414 (37.4)	3406 (42.8)

Male	35 019 (54.6)	10 470 (51.9)	7995 (49.9)	4034 (62.6)	4557 (57.2)

Health care zone

Calgary	21 391 (33.4)	6824 (33.8)	4695 (29.3)	2150 (33.3)	2568 (32.2)

Central	9424 (14.7)	3116 (15.4)	2591 (16.2)	1035 (16.0)	1047 (13.1)

Edmonton	21 076 (32.9)	6268 (31.1)	5675 (35.4)	2027 (31.4)	2830 (35.5)

North	6806 (10.6)	1851 (9.2)	1756 (11.0)	682 (10.6)	976 (12.3)

South	5396 (8.4)	2121 (10.5)	1302 (8.1)	554 (8.6)	542 (6.8)

Residence

Urban	54 707 (85.4)	17 247 (85.5)	13 648 (85.2)	5356 (83.1)	6754 (84.8)

Rural	9272 (14.5)	2906 (14.4)	2345 (14.6)	1077 (16.7)	1186 (14.9)

Missing	114 (0.2)	27 (0.1)	26 (0.2)	15 (0.2)	23 (0.3)

Pampalon deprivation index score

Material deprivation

5 (most deprived)	13 100 (20.4)	4142 (20.5)	3409 (21.3)	1390 (21.6)	1659 (20.8)

4	13 434 (21.0)	4328 (21.4)	3283 (20.5)	1378 (21.4)	1653 (20.8)

3	11 354 (17.7)	3492 (17.3)	2591 (16.2)	1190 (18.5)	1490 (18.7)

2	10 054 (15.7)	3094 (15.3)	2368 (14.8)	1031 (16.0)	1305 (16.4)

1 (least deprived)	10 631 (16.6)	3116 (15.4)	2458 (15.3)	1109 (17.2)	1432 (18.0)

Not defined	5520 (8.6)	2008 (10.0)	1910 (11.9)	350 (5.4)	424 (5.3)

Social deprivation

5 (most deprived)	17 147 (26.8)	5594 (27.7)	4492 (28.0)	1390 (21.6)	1659 (20.8)

4	14 473 (22.6)	4740 (23.5)	3582 (22.4)	1378 (21.4)	1653 (20.8)

3	10 851 (16.9)	3332 (16.5)	2573 (16.1)	1190 (18.5)	1490 (18.7)

2	7384 (11.5)	2189 (10.9)	1588 (9.9)	1031 (16.0)	1305 (16.4)

1 (least deprived)	8718 (13.6)	2317 (11.5)	1874 (11.7)	1109 (17.2)	1432 (18.0)

Not defined	5520 (8.6)	2008 (10.0)	1910 (11.9)	350 (5.4)	424 (5.3)

Location of initial atrial fibrillation diagnosis

Outpatient	52 969 (82.6)	16 886 (83.7)	11 460 (71.5)	5979 (92.7)	6786 (85.2)

Inpatient	11 124 (17.4)	3294 (16.3)	4559 (28.5)	469 (7.3)	1177 (14.8)

No. of comorbidities

0	9088 (14.2)	746 (3.7)	616 (3.8)	771 (12.0)	846 (10.6)

1	12 628 (19.7)	2447 (12.1)	1786 (11.1)	2402 (37.2)	2974 (37.3)

2	13 407 (20.9)	4600 (22.8)	3333 (20.8)	1819 (28.2)	2132 (26.8)

≥ 3	28 970 (45.2)	12 387 (61.4)	10 284 (64.2)	1456 (22.6)	2011 (25.2)

Comorbidities

Heart failure	12 219 (19.1)	6470 (32.1)	4803 (30.0)	526 (8.2)	420 (5.3)

Hypertension	40 849 (63.7)	17 453 (86.5)	13 536 (84.5)	4305 (66.8)	5555 (69.8)

Diabetes	14 718 (23.0)	7682 (38.1)	6070 (37.9)	415 (6.4)	551 (6.9)

Ischemic stroke or TIA	11 334 (17.7)	6307 (31.2)	5027 (31.4)	0 (0.0)	0 (0.0)

Chronic kidney disease	30 843 (48.1)	13 062 (64.7)	10 118 (63.2)	2124 (32.9)	2224 (27.9)

Pulmonary disease	15 861 (24.7)	6014 (29.8)	5098 (31.8)	1174 (18.2)	1464 (18.4)

Acute myocardial infarction	4593 (7.2)	1872 (9.3)	1631 (10.2)	341 (5.3)	352 (4.4)

Cancer	5066 (7.9)	1715 (8.5)	1513 (9.4)	376 (5.8)	602 (7.6)

Peripheral artery disease	2702 (4.2)	1126 (5.6)	926 (5.8)	146 (2.3)	165 (2.1)

Thyroid disease	9667 (15.1)	3672 (18.2)	3075 (19.2)	722 (11.2)	960 (12.1)

Cirrhosis	348 (0.5)	53 (0.3)	117 (0.7)	25 (0.4)	58 (0.7)

CHADS₂ score^‡

0	13 959 (21.8)	0 (0.0)	0 (0.0)	1454 (22.5)	1867 (23.4)

1	15 155 (23.6)	168 (0.8)	162 (1.0)	4994 (77.4)	6096 (76.6)

2	15 831 (24.7)	10 024 (49.7)	8304 (51.8)	0 (0.0)	0 (0.0)

3	9381 (14.6)	4932 (24.4)	3745 (23.4)	0 (0.0)	0 (0.0)

4	6044 (9.4)	3259 (16.1)	2300 (14.4)	0 (0.0)	0 (0.0)

5	2888 (4.5)	1403 (7.0)	1179 (7.4)	0 (0.0)	0 (0.0)

6	835 (1.3)	394 (2.0)	329 (2.0)	0 (0.0)	0 (0.0)

CHADS₂ score, median (IQR)	2 (1–3)	2 (2–4)	2 (2–3)	1 (1–1)	1 (1–1)

Note: IQR = interquartile range, SD = standard deviation, TIA = transient ischemic attack.
↵* Except where noted otherwise.
↵† Excludes patients who died within 90 days of nonvalvular atrial fibrillation diagnosis.
↵‡ A score of 0 = low risk of stroke, a score of 1 or 0 and age 65–74 years = moderate risk of stroke, and any score above 1 = high risk of stroke.

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Table 2:

Crude outcomes at 1 year

Outcome	Year								p value^*
Outcome	2008/09	2009/10	2010/11	2011/12	2012/13	2013/14	2014/15	2015/16	p value^*
Overall cohort	n = 7070	n = 8128	n = 8763	n = 8690	n = 7203	n = 7353	n = 8315	n = 8571
Ischemic stroke	310 (4.4)	298 (3.7)	280 (3.2)	302 (3.5)	232 (3.2)	234 (3.2)	263 (3.2)	268 (3.1)	0.01
Major bleeding	359 (5.1)	341 (4.2)	379 (4.3)	395 (4.5)	351 (4.9)	341 (4.6)	408 (4.9)	422 (4.9)	0.3
High stroke risk	n = 4084	n = 4401	n = 4838	n = 5184	n = 4087	n = 4217	n = 4676	n = 4712
Initiation of oral anticoagulant therapy within 1 yr	2095 (51.3)	2258 (51.3)	2483 (51.3)	2944 (56.8)	2420 (59.2)	2217 (52.6)	2678 (57.3)	3085 (65.5)	0.02
Persistence with oral anticoagulant therapy	1283 (31.4)	1355 (30.8)	1500 (31.0)	1920 (37.0)	1607 (39.3)	1373 (32.6)	1472 (31.5)	1976 (41.9)	0.1
Moderate stroke risk	n = 1519	n = 1697	n = 1960	n = 1797	n = 1675	n = 1655	n = 2033	n = 2075
Initiation of oral anticoagulant therapy within 1 yr	680 (44.8)	670 (39.5)	769 (39.2)	899 (50.0)	828 (49.4)	676 (40.8)	855 (42.1)	1071 (51.6)	0.4
Persistence with oral anticoagulant therapy	380 (25.0)	356 (21.0)	422 (21.5)	538 (29.9)	488 (29.1)	375 (22.7)	392 (19.3)	595 (28.7)	0.9

↵* Mann–Kendall test for monotonic trends.

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Table 3:

Small-area variation analysis^*

Outcome; statistic	Year								p value^†
Outcome; statistic	2008/09	2009/10	2010/11	2011/12	2012/13	2013/14	2014/15	2015/16	p value^†
Initiation of oral anticoagulant therapy
High stroke risk
EQ	24.0	10.3	4.7	6.2	3.2	10.0	3.7	2.8	0.04
CV × 100	23.3	20.0	15.6	22.1	18.6	22.5	21.3	18.5	0.5
SCV × 100	175.1	44.0	28.0	12.8	14.3	26.1	14.5	12.1	0.04
p value^‡	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	–
Moderate stroke risk
EQ	16.9	5.8	7.5	8.3	7.7	6.9	3.9	14.9	0.7
CV × 100	31.0	31.5	30.2	28.0	25.9	31.4	29.2	30.8	0.5
SCV × 100	41.6	33.0	36.0	35.9	17.3	19.9	18.3	24.3	0.1
p value^‡	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	–
Persistence with oral anticoagulant therapy
High stroke risk
EQ	19.8	4.0	9.1	6.9	12.8	4.8	5.7	2.3	0.2
CV × 100	27.5	24.9	23.2	21.5	23.6	26.6	26.9	19.2	0.5
SCV × 100	24.1	11.2	25.7	2.8	21.9	7.0	6.6	7.0	0.2
p value^‡	0.008	< 0.001	0.004	0.09	< 0.001	< 0.001	< 0.001	< 0.001	–
Moderate stroke risk
EQ	16.2	14.2	8.4	7.0	17.9	17.1	8.5	23.2	0.5
CV × 100	45.0	47.2	39.5	40.1	38.1	44.7	53.5	41.8	1.00
SCV × 100	302.7	329.0	166.4	424.2	180.4	196.4	204.9	254.7	1.00
p value^‡	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	–
Ischemic stroke
EQ	9.3	16.5	31.6	14.5	8.7	39.1	13.5	10.9	0.9
CV × 100	49.5	53.0	48.7	48.2	62.5	61.8	57.7	52.2	0.7
SCV × 100	< 1	< 1	< 1	< 1	< 1	< 1	< 1	< 1	0.4
p value^‡	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	–
Major bleeding
EQ	32.3	27.5	7.3	12.7	12.5	19.8	16.6	7.0	0.2
CV × 100	51.0	51.3	38.5	49.5	55.5	44.7	47.0	41.8	0.4
SCV × 100	6	< 1	< 1	10.9	7.1	< 1	< 1	< 1	0.06
p value^‡	0.9	1.0	1.0	0.8	1.0	1.0	1.0	1.0	–

Note: CV = coefficient of variation, EQ = extremal quotient, SCV = systematic component of variation.
↵* Applied to age- and sex-standardized outcomes.
↵† Mann–Kendall test for monotonic trends.
↵‡ χ² test for small-area variation in outcomes.