CCORT ATLAS PAPER Cardiac procedures after an acute myocardial infarction across nine Canadian provinces

Transcription

1 CCORT ATLAS PAPER Cardiac procedures after an acute myocardial infarction across nine Canadian provinces Louise Pilote MD MPH PhD 1, Patrick Merrett BSc 1, Igor Karp MD MPH 1, David Alter MD PhD 2, Peter C Austin PhD 2,6, Jafna Cox MD 3, Helen Johansen PhD 4, William Ghali MD MPH 5, Jack V Tu MD PhD 2 L Pilote, P Merrett, I Karp, et al. Cardiac procedures after an acute myocardial infarction across nine Canadian provinces. Can J Cardiol 2004;20(5): BACKGROUND: Geographical variations in the use of invasive cardiac procedures have been documented. It remains unclear to what extent these variations exist across the Canadian provinces. OBJECTIVE: To describe variation in the use of invasive cardiac procedures and waiting times for these procedures across nine Canadian provinces. METHODS: Using longitudinal, de-identified patient data from the Canadian Institute for Health Information, records of patients who had suffered an acute myocardial infarction (AMI) in each of nine Canadian provinces between 1997/1998 and 1999/2000 were selected. Rates and median waiting times for percutaneous coronary intervention and coronary artery bypass graft surgery were calculated by age, sex and health region. RESULTS: There was a large variation in the use of and waiting times for invasive cardiac procedures across the Canadian provinces studied. In general, cardiac procedure rates in Western provinces were higher than in Eastern provinces, most notably higher than in the Maritime provinces and Ontario. In addition to interprovincial variation, there was also significant regional variation in the rates of revascularization and waiting times. Rates of percutaneous coronary intervention increased over the study period, whereas rates of bypass surgery remained relatively stable. CONCLUSIONS: Significant variation in the use of cardiac procedures after AMI exists across Canada and this may represent potential inequalities in the treatment of AMI across Canada. Key Words: Acute myocardial infarction; Canada, Revascularization Acute myocardial infarction (AMI) is the leading cause of mortality in Canada and its treatment places a large financial burden on the health care system. Large regional variations in the use of cardiac procedures after AMI, such as percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery, have been documented across North America (1-3) and Europe (4,5). Similarly, large variations in the use of revascularization procedures after AMI have been identified within Canadian provinces, notably Manitoba (6,7), Ontario (8,9) and Quebec (10). Les interventions cardiaques après un infarctus aigu du myocarde dans neuf provinces canadiennes HISTORIQUE : Les variations géographiques dans l utilisation des interventions cardiaques envahissantes ont été documentées. On ne connaît toutefois pas la mesure de ces variations au Canada. OBJECTIF : Décrire la variation dans l utilisation des interventions cardiaques envahissantes et les délais d attente à l égard de ces interventions dans neuf provinces canadiennes. MÉTHODOLOGIE : Au moyen de données longitudinales de patients anonymes tirées de l Institut canadien d information pour la santé, des dossiers de patients ayant souffert d un infarctus aigu du myocarde (IAM) ont été sélectionnés dans chacune des neuf provinces canadiennes entre et Les taux et les délais d attente médians pour les interventions coronaires percutanées et les pontages aortocoronariens ont été calculés selon l âge, le sexe et la région sanitaire. RÉSULTATS : On a remarqué une forte variation dans l utilisation et les délais d attente des interventions cardiaques envahissantes entre les provinces canadiennes à l étude. En général, les taux d intervention dans les provinces de l ouest étaient plus élevées que dans celles de l est, et surtout plus élevés que dans les Maritimes et en Ontario. Outre la variation interprovinciale, on observait également une variation régionale marquée dans les taux de revascularisation et de délais d attente. Les taux d interventions coronaires percutanées ont augmenté pendant la période de l étude, tandis que ceux de pontage sont demeurés relativement stables. CONCLUSIONS : Il existe une variation significative dans l utilisation d interventions cardiaques après l IAM au Canada, ce qui peut représenter des inégalités potentielles dans le traitement de l IAM au Canada. Variations in waiting times for coronary revascularization have also been identified across Europe and the United States (11). However, few studies to date have examined to what extent these variations exist among the Canadian provinces (12). To document variation in the treatment of AMI across Canada, we compared temporal trends in treatment rates and waiting times for two common cardiac procedures, PCI and CABG, among patients suffering from an AMI across nine Canadian provinces. 1 McGill University Health Centre at the Montreal General Hospital, Montreal, Quebec; 2 Institute of Clinical Evaluative Sciences, Toronto, Ontario; 3 Dalhousie University, Halifax, Nova Scotia; 4 Statistics Canada; 5 University of Calgary, Calgary, Alberta; 6 Department of Public Health Sciences, University of Toronto, Toronto, Ontario Correspondence and reprints: Dr Louise Pilote, Division of Clinical Epidemiology, Montreal General Hospital, 1650 Cedar Street, Montreal, Quebec H3G 1A4. Telephone ext 44722, fax , louise.pilote@mcgill.ca Received for publication January 23, Accepted February 12, Pulsus Group Inc. All rights reserved 491

2 Pilote et al Percent METHODS Encrypted records of patients who had suffered an AMI between the fiscal years 1997/1998 and 1999/2000 were selected. The coding system from the International Classification of Diseases, ninth revision (13) was used to identify the most responsible diagnosis of AMI (code 410) at the time of discharge. To ensure comparability between the study populations from different provinces, several exclusions were made. The records of patients who had been admitted for AMI within one year before their index AMI or who died within one hour of admission were excluded (because British Columbia hospitals routinely code patients who die in the emergency room as hospital admissions) (14). Records of patients who were discharged alive with a total length of stay of less than three days, suggesting an erroneous initial diagnosis of AMI, were also excluded. Records were also excluded if the patients had been transferred from another acute care facility (so that only the first admission would be counted), if they were not admitted to an acute care facility or if they were admitted to a noncardiac surgical service (so that patients with, for example, postoperative AMI complications would not be included). For each index admission, length of stay was defined as the total length of stay over all contiguous admissions. Finally, if patients were aged less than 20 years or greater than 105 years, or if AMI was coded as an in-hospital complication, the records were not included in the study population. Use of PCI and CABG was defined by examining the procedure fields in the Canadian Institute for Health Information (CIHI) discharge abstracts. The following Canadian Classification of Procedures (CCP) codes (15) were used for percutaneous transluminal coronary angioplasty: 48.02, and The following CCP codes were used for CABG: to Procedures that were coded as out of hospital, before admission or cancelled were excluded. Data were obtained from the CIHI for encrypted patient records in each of the Canadian provinces for which comparable data were available. Although data were available for Newfoundland, that province was not included due to variations in coding practices (14). Primary PCI was defined as PCI performed on the same day of admission as the AMI admission. Data Quebec Ontario Nova Scotia British Columbia 1997/ / /2000 Overall Figure 1) Primary percutaneous coronary intervention rates between 1997 and Data from Regie de l Assurance Maladie du Quebec and registre des hospitalisations (Quebec), Ontario Health Insurance Plan and Canadian Institute for Health Information (Ontario), Improving Cardiovascular Outcomes in Nova Scotia Registry (Nova Scotia), and the British Columbia hospitalization database and the Medical Service Plan (British Columbia) for primary PCI were obtained from the following sources: Regie de l Assurance Maladie du Quebec and registre des hospitalisations in Quebec; Ontario Health Insurance Plan and CIHI in Ontario; Improving Cardiovascular Outcomes in Nova Scotia Registry in Nova Scotia; and the British Columbia hospitalization database and the Medical Service Plan in British Columbia. The definition of primary PCI was similar across the data sources. Primary PCI data were not available for the other provinces. Statistical analyses For each province, yearly and overall rates of PCI and CABG use within 30 days and one year of admission were calculated. Overall revascularization rates within 30 days and one year were also calculated, capturing whether patients had received either PCI or CABG. Additionally, rates of primary PCI were calculated if PCI was performed on the day of admission. Procedure rates within 30 days of admission were stratified by age and sex, as well as by health region. All rates are reported as number of procedures per 100 patients, and are based on the patient s residence, not on location of admission or procedure. Yearly and overall median waiting times from admission to PCI, to CABG and to any revascularization procedure were also calculated for each province. Additionally, median waiting times were stratified by age, sex and health region. RESULTS Procedure rates Regional variation: Figure 1 and Table 1 illustrate the rates of PCI, CABG and overall revascularization during the fiscal years 1997/1998 to 1999/2000. There was considerable variation across Canada in the use of cardiac revascularization during the study period. This variation tended to align itself along an east-west axis across the country. Rates of cardiac revascularization were typically higher in Western provinces, notably Alberta and British Columbia, and lower in the Maritime provinces. The highest rates of revascularization at one year were observed in Alberta (36%) and British Columbia (32%). In contrast, Prince Edward Island had a rate of revascularization of 6% at one year post-admission. This east-west gradient was also observable for PCI alone. Alberta, for example, had the highest rates of PCI use, both at 30 days (23%) and at one year (26%), followed by British Columbia at 19% for 30 days and 24% for one year. An important exception to this trend was Ontario, which tended to have similar rates as the Maritime provinces in use of PCI (8% at 30 days and 13% at one year). Among the four provinces for which primary PCI data were available, Quebec had the highest rate of this procedure (3.6%), followed by British Columbia (2.5%), Nova Scotia (2.0%) and Ontario (0.9%) (Figure 1). The east-west gradient occurred to a lesser extent in the use of CABG. Again, Alberta and British Columbia had the highest 30-day rates, at 7% and 5%, respectively. A notable exception, however, was Nova Scotia, which had a low PCI rate but the highest one-year CABG rate (12%). In addition to interprovincial variation in revascularization rates, there was also significant regional variation during the study period (Figures 2 and 3). In Alberta, for example, only 5% of patients in the Peace Regional Health Authority received PCI compared with 39% in the Calgary Regional

3 Cardiac procedures after AMI across nine Canadian provinces TABLE 1 Rates of percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) surgery and overall revascularization between 1997 and 2000 PCI (%) CABG (%) Any revascularization (%) Province 1997/ / /2000 Overall 1997/ / /2000 Overall 1997/ / /2000 Overall Prince Edward Island 30 days year Nova Scotia 30 days year New Brunswick 30 days year Quebec 30 days year Ontario 30 days year Manitoba 30 days year Saskatchewan 30 days year Alberta 30 days year British Columbia 30 days year Data from the Canadian Institute for Health Information Health Authority. This was similar for CABG but less pronounced. Temporal trends: With the exception of a few provinces, the data suggest that rates of total revascularization have increased over time (16). This trend was due to an increase in the use of PCI, in contrast to CABG, which remained stable over the three years. In 1997/1998, 11% of patients in Saskatchewan had received PCI within one year after admission, increasing to 27% in 1999/2000. In the case of CABG, the rate of use increased only very slightly from 8% to 10% between 1997/1998 and 1999/2000. Consequently, revascularization overall increased from 19% to 36% at one year in Saskatchewan. This trend also occurred in Eastern provinces. In Nova Scotia, for example, 13% of patients received PCI in 1997/1998, compared with 17% in 1999/2000. The use of CABG increased only slightly in Nova Scotia during the study period, from 12% to 13%. As a result, revascularization overall in Nova Scotia increased from 24% to 29%. Age-sex variations: Tables 2 and 3 present the total number of AMI cases and compare the age- and sex-specific revascularization rates aggregated over 1997/1998 to 1999/2000. There were almost twice as many AMI cases among men than among women in all provinces during those years. Among women, the incidence of AMI increased with age, whereas the number of AMI cases among men was the highest between the ages of 50 and 64 years. Despite these distributions, both men and women in the youngest age group had the highest rates of revascularization at one year. This was similar for PCI use in most provinces. With respect to CABG use at one year, both men and women in the age classes 50 to 64 years and 65 to 74 years generally received more procedures than any other age class. For the most part, men received more cardiac procedures than women within one year after admission for AMI. In Quebec, for example, 25% of men received PCI within one year after admission, compared with 18% of women. With respect to CABG, 11% of men received this procedure at one year, compared with 7% of women. Procedural waiting times Regional variations: Table 4 illustrates median waiting times from AMI to PCI, CABG or any revascularization during the fiscal years 1997/1998 to 1999/2000. There was large variation in waiting times for revascularization across Canada during the study period. Similar to procedure rates, an east-west gradient was observable across the country in waiting times for revascularization. The median wait for any revascularization was the longest in Nova Scotia (29 days), and the shortest in Alberta 493

4 Pilote et al Figure 2) Rates of use of percutaneous coronary intervention within 30 days of admission, per 100 acute myocardial infarction (AMI) survivors, by health region (HR), 1997/1998 to 1999/2000. Data from the Canadian Institute for Health Information. PEI Prince Edward Island Figure 3) Rates of use of coronary artery bypass graft surgery within 30 days of admission, per 100 acute myocardial infarction (AMI) survivors, by health region (HR), 1997/1998 to 1999/2000. Data from the Canadian Institute for Health Information. PEI Prince Edward Island 494

5 Cardiac procedures after AMI across nine Canadian provinces Figure 4) Median wait time from acute myocardial infarction (AMI) to percutaneous coronary intervention, by health region (HR), 1997/1998 to 1999/2000. Data from the Canadian Institute for Health Information. PEI Prince Edward Island Figure 5) Median wait time after acute myocardial infarction (AMI) to coronary artery bypass graft surgery, by health region (HR), 1997/1998 to 1999/2000. Data from the Canadian Institute for Health Information. PEI Prince Edward Island 495

6 Pilote et al TABLE 2 Total number of acute myocardial infarction (AMI) cases and comparison of age- and sex-specific revascularization rates aggregated over 1997/1998 to 1999/2000 Men (age [years]) Women (age [years]) Province Overall Overall Prince Edward Island Number of AMI patients * PCI (%) 30 days * year * CABG (%) 30 days * year * Any revascularization (%) 30 days * year * Nova Scotia Number of AMI patients PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year New Brunswick Number of AMI patients PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year Quebec Number of AMI patients , ,545 PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year Ontario Number of AMI patients , , ,640 21,088 PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year Manitoba Number of AMI patients PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year Saskatchewan Number of AMI patients PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year Alberta Number of AMI patients PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year continued on next page 496

7 Cardiac procedures after AMI across nine Canadian provinces TABLE 2 (continued) Total number of acute myocardial infarction (AMI) cases and comparison of age- and sex-specific revascularization rates aggregated over 1997/1998 to 1999/2000 Men (age [years]) Women (age [years]) Province Overall Overall British Columbia Number of AMI patients PCI (%) 30 days year CABG (%) 30 days year Any revascularization (%) 30 days year *Data not available. CABG Coronary artery bypass graft surgery; PCI Percutaneous coronary intervention. Data from the Canadian Institute for Health Information TABLE 3 Comparison of age- and sex-specific primary percutaneous coronary intervention rates aggregated over 1997/1998 to 1999/2000 Men (age [years]) Women (age [years]) Province Overall Overall Quebec (%) Ontario (%) Nova Scotia (%) British Columbia (%) Data sources: Quebec Conseil consultatif de pharmacologie du Quebec; Ontario Canadian Institute for Health Information and Ontario Health Insurance Plan; Nova Scotia Improving Cardiovascular Outcomes In Nova Scotia Registry; British Columbia British Columbia hospitalization database and Medical Service Plan TABLE 4 Waiting times from acute myocardial infarction to percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) surgery or any revascularization procedures from 1997 to 2000 Median waiting time (25th and 75th quantiles), days PCI CABG Any revascularization Province 1997/ / /2000 Overall 1997/ / /2000 Overall 1997/ / /2000 Overall PEI * 4 (3-5) 9 (4-59) 7 (3-34) * * 12 (9-57) 12 (10-84) * 5 (3-6) 10 (7-59) 9 (8-34) Nova Scotia 15 (7-72) 15 (5-74) 11 (4-62) 13 (5-68) 74 (26-143) 64 (17-140) 50 (16-137) 63 (20-139) 39 (11-123) 28 (8-100) 20 (7-96) 29 (8-108) New Brunswick 8 (3-24) 8 (4-16) 8 (3-17) 8 (3-18) 26 (11-145) 20 (11-78) 20 (10-94) 22 (11-107) 11 (5-52) 10 (5-22) 10 (5-25) 10 (5-27) Quebec 11 (4-25) 9 (4-19) 7 (3-15) 9 (4-19) 36 (19-92) 30 (17-83) 33 (16-80) 33 (18-85) 16 (6-41) 13 (5-32) 10 (4-29) 13 (5-34) Ontario 19 (8-92) 16 (6-83) 14 (5-63) 16 (6-78) 51 (17-165) 40 (16-154) 39 (17-140) 43 (16-154) 28 (11-127) 23 (10-112) 21 (9-94) 24 (10-110) Manitoba 7 (4-19) 5 (3-11) 4 (3-8) 5 (3-12) 37 (14-131) 24 (11-104) 19 (11-78) 24 (12-110) 16 (7-63) 10 (4-32) 8 (4-28) 11 (4-38) Saskatchewan 11 (5-25) 6 (3-21) 4 (2-13) 6 (3-18) 27 (12-127) 52 (13-117) 51 (13-116) 47 (13-118) 15 (7-82) 11 (3-61) 7 (3-39) 9 (3-52) Alberta 6 (2-14) 5 (3-11) 4 (2-9) 5 (2-11) 27 (13-135) 21 (11-91) 18 (11-63) 21 (12-97) 9 (3-28) 8 (3-18) 6 (3-15) 8 (3-18) British Columbia 8 (4-21) 6 (3-17) 6 (3-13) 7 (3-16) 31 (14-138) 23 (11-114) 22 (11-99) 25 (12-114) 11 (5-47) 9 (4-37) 8 (3-24) 9 (4-33) *Data not available. Data from the Canadian Institute for Health Information. PEI Prince Edward Island (eight days) and British Columbia (nine days). Again, Ontario was an important exception to this trend, with a median waiting time similar to those of the Maritime provinces (24 days). The east-west gradient in waiting time was less apparent in the use of PCI. The median waiting time for PCI over the three years of the study was the longest in Ontario (16 days) and the shortest in the Western provinces (five days in both Manitoba and Alberta, and six days in Saskatchewan). A certain east-west gradient in the median waiting time for CABG was also apparent. Again, however, Ontario had a notably long waiting period (43 days) compared with its neighbours, Quebec (33 days) and Manitoba (24 days). Saskatchewan was also an important exception, with a median wait of 47 days for CABG across the three years of the study. In addition to interprovincial variation in waiting times for revascularization, there was also significant regional variation during the study period (Figures 4 and 5). In New Brunswick, patients waited between three and 16 days for PCI, depending on which region they lived in. Similarly, the wait for CABG in Saskatchewan ranged from 13 to 100 days. Temporal trends: In general, the waiting times across Canada for revascularization shortened over the study period. In Ontario, for example, the median waiting time for PCI decreased from 20 days in 1997/1998 to 15 days in 1999/2000, the median wait for CABG decreased from 53 to 497

8 Pilote et al TABLE 5 Age- and sex-specific waiting times from acute myocardial infarction to percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) surgery or any revascularization procedures aggregated over 1997/1998 to 1999/2000 Median waiting time (25th and 75th quantiles), days Women (age [years]) Men (age [years]) Province Overall Overall Prince Edward Island PCI * * * 5 (1-10) 7 (3-10) * 74 (9-120) 4 (3-34) * 5 (3-37) CABG * * * * 10 (5-21) * * 12 (8-84) * 12 (9-84) Any revascularization * * * 5 (1-10) 8 (5-11) * 74 (9-174) 10 (5-47) * 9 (5-59) Nova Scotia PCI 12 (8-99) 11 (4-61) 8 (5-29) 13 (5-38) 12 (5-56) 18 (4-107) 12 (5-61) 16 (6-65) 24 (8-78) 15 (5-77) CABG 113 (38-200) 54 (25-132) 49 (16-125) 41 (12-88) 50 (17-125) 46 (13-148) 74 (20-160) 72 (31-148) 51 (20-117) 66 (21-146) Any revascularization 16 (8-128) 28 (7-105) 20 (8-83) 18 (7-66) 21 (7-92) 24 (6-128) 21 (8-120) 48 (13-112) 37 (10-88) 32 (9-116) New Brunswick PCI 5 (2-9) 8 (4-30) 8 (4-18) 8 (4-19) 8 (3-18) 7 (3-15) 8 (3-20) 9 (4-18) 8 (3-15) 8 (3-18) CABG 37 (9-133) 14 (11-119) 20 (16-54) 25 (12-115) 21 (12-97) 23 (9-158) 17 (11-117) 23 (9-93) 34 (10-107) 22 (10-110) Any revascularization 6 (2-10) 9 (5-32) 13 (5-26) 10 (5-34) 9 (5-25) 8 (4-21) 11 (5-33) 12 (6-28) 10 (5-34) 10 (5-28) Quebec PCI 7 (3-18) 8 (4-20) 9 (4-20) 10 (5-21) 9 (4-20) 8 (3-22) 8 (4-18) 9 (4-19) 9 (4-18) 9 (4-19) CABG 37 (15-160) 39 (21-106) 34 (18-80) 32 (18-66) 34 (19-89) 32 (16-105) 34 (18-97) 31 (16-69) 34 (18-87) 33 (17-84) Any revascularization 9 (4-26) 11 (4-32) 14 (6-34) 13 (6-31) 12 (5-32) 10 (4-30) 12 (5-34) 15 (6-37) 16 (7-38) 13 (5-35) Ontario PCI 14 (5-71) 16 (7-72) 17 (7-59) 14 (6-38) 15 (6-62) 15 (5-79) 17 (6-90) 17 (7-79) 15 (5-57) 16 (6-82) CABG 65 (18-204) 38 (16-161) 39 (17-144) 31 (16-96) 37 (16-147) 60 (15-179) 48 (17-163) 44 (17-147) 35 (16-123) 45 (17-156) Any revascularization 19 (7-95) 21 (9-104) 24 (11-101) 19 (8-62) 21 (9-91) 19 (7-106) 26 (10-122) 27 (12-118) 25 (11-93) 25 (10-116) Manitoba PCI 6 (4-18) 5 (3-11) 6 (4-43) 7 (4-14) 6 (3-16) 4 (2-8) 4 (2-9) 6 (3-15) 6 (4-14) 5 (3-11) CABG 22 (6-118) 18 (12-105) 25 (13-110) 31 (14-74) 25 (12-105) 26 (14-148) 23 (11-124) 21 (12-101) 25 (13-84) 23 (12-114) Any revascularization 7 (4-32) 8 (4-31) 15 (5-56) 13 (6-33) 11 (5-37) 6 (3-23) 11 (4-40) 13 (6-42) 14 (7-49) 11 (4-39) Saskatchewan PCI 5 (3-14) 6 (2-19) 7 (3-30) 6 (3-16) 6 (3-18) 4 (2-32) 6 (3-27) 4 (3-12) 6 (3-13) 5 (2-18) CABG 64 (18-117) 79 (15-153) 59 (10-171) 39 (17-140) 59 (12-157) 78 (21-148) 55 (14-109) 37 (12-91) 29 (13-93) 43 (13-108) Any revascularization 7 (3-19) 10 (3-77) 1 (4-76) 9 (4-31) 9 (4-50) 7 (2-63) 10 (4-62) 9 (4-52) 11 (4-28) 9 (3-54) Alberta PCI 4 (2-8) 5 (3-10) 5 (2-11) 7 (3-14) 5 (2-11) 4 (2-8) 5 (2-10) 6 (2-13) 6 (2-14) 5 (2-11) CABG 70 (20-120) 19 (14-59) 20 (12-56) 26 (14-77) 22 (14-74) 22 (9-116) 25 (13-135) 19 (10-84) 18 (11-38) 21 (11-102) Any revascularization 5 (2-10) 6 (3-15) 9 (3-19) 9 (3-24) 8 (3-18) 5 (2-11) 7 (3-19) 10 (4-22) 11 (4-24) 8 (3-19) British Columbia PCI 6 (3-47) 7 (3-16) 8 (4-18) 6 (3-17) 7 (3-18) 6 (3-13) 6 (3-15) 7 (3-18) 7 (3-18) 6 (3-16) CABG 10 (7-62) 30 (13-142) 26 (13-119) 18 (12-70) 24 (13-108) 25 (11-136) 25 (11-126) 24 (12-109) 25 (13-87) 25 (11-115) Any revascularization 7 (3-47) 9 (5-23) 11 (5-31) 10 (3-24) 10 (4-27) 7 (3-21) 9 (4-36) 11 (4-41) 11 (4-40) 9 (4-35) *Data not available. Data from the Canadian Institute for Health Information 39 days, and the median wait for any revascularization decreased from 29 to 22 days. In Nova Scotia, the median waiting time for PCI diminished from 15 to 12 days, the median wait for CABG decreased from 77 to 53 days, and the median wait for any revascularization decreased from 39 to 23 days. Nevertheless, some exceptions to this trend occurred. In Saskatchewan, the median wait for CABG increased from 27 to 52 days. Age-sex variations: Table 5 compares age- and sex-specific waiting times from AMI to PCI, CABG or any revascularization aggregated over 1997/1998 to 1999/2000. In general, waiting times for revascularization were the longest among the elderly, particularly among women. In Alberta, for example, the median wait for PCI was seven days among women aged 75 years and older, compared with four days among women aged 20 to 49 years. In Quebec, the median wait for this procedure was nine days among women in the age classes 65 to 74 years and 75 years and older, compared with seven days among women aged 20 to 49 years. Waiting times for CABG also increased slightly with patient age. In most provinces, waiting times for invasive cardiac procedures were comparable between men and women during the study period. Of notable importance, however, women in Saskatchewan had longer waiting times for both cardiac procedures, whereas men in Nova Scotia and Ontario had longer waiting times. 498

9 Cardiac procedures after AMI across nine Canadian provinces DISCUSSION We studied variation in revascularization rates and waiting times for revascularization across nine Canadian provinces. We found considerable variability in procedure rates and waiting times across the country, both interprovincially and regionally. There was an apparent east-west gradient in the availability of cardiac care for AMI. Western provinces tended to treat AMI patients more aggressively: cardiac procedure rates were higher and waiting times were shorter. Eastern provinces, most notably the Maritime provinces, had lower rates of cardiac procedure use and longer waiting times. Ontario was an important exception to this trend, with procedure use rates and waiting times largely similar to those of the Maritime provinces. Although data for coronary angiography were not readily available in the present study, variations in overall revascularization PCI and CABG combined correlated highly with regional variations in angiography. This correlation has been described previously as the funnel effect, whereby the number of patients from a given region who are referred for angiography is proportional to the number of patients in that region who ultimately receive PCI or CABG (6,17). This model suggests that variation in the use of revascularization is attributable to variation in the use of angiography, and inequity in the access to cardiac care is greatest for angiography. Once a patient has received angiography, however, inequities in receiving revascularization are greatly reduced. Although our findings are important, representing significant discrepancies in the treatment of AMI across Canada, we do not have any information regarding the appropriateness of care for AMI. Accordingly, the significance of geographical variations in revascularization rates is difficult to interpret and we do not make any attempts to identify the optimal rates for procedure use. Primary PCI was used rarely across four Canadian provinces during the study period. Given recent evidence of the benefit of primary PCI compared with thrombolytic therapy among AMI patients (18), an increase in the use of this procedure could be of benefit. However, an increase in access to primary PCI has important cost implications, especially given that some Canadian provinces only have one hospital that offers the procedure, while some have none. The feasibility of rapidtransfer mechanisms or stand-alone PCI centres must be investigated in future research and health policy planning. We identified notable time trends in the use and waiting times for revascularization. Overall, waiting times for revascularization shortened greatly across the study period. Accompanying this trend, we identified significant increases in the use of revascularization across the study period, a result of increased PCI use, but not CABG. This increasingly preferential use of PCI has previously been identified among European countries (5), with the ratio of PCI to CABG increasing markedly between 1992 and Additionally, we found important variations in procedure rates and waiting times among patient groups. In particular, revascularization rates correlated negatively with patient age, while waiting times correlated positively with patient age, particularly among women. Given that patient age is an unequivocal baseline risk factor for AMI outcomes, perhaps the elderly (or at least specific subgroups among them) would benefit from a more liberal use of revascularization (19). Several potential limitations to the study exist. Administrative data do not always capture the full extent of illness in a population. The accuracy of our conclusions rests on the correct diagnosis and coding of the AMI event. If an AMI event was incorrectly coded in the administrative data, then this represents a potential source of error in our analysis. Nevertheless, the coding system was uniform across the country for all revascularization procedures except primary PCI, and the use of administrative databases for the study of heart disease in Canada has previously been validated (20,21). However, because different data sources were used for primary PCI, the results regarding this procedure need to be interpreted with caution. We excluded from our analyses the records of patients who were discharged alive within three days after admission to avoid the possibility of using the data from patients with an incorrect initial diagnosis of AMI. However, we may also have excluded some AMI patients with a short length of stay, which might have lead to bias in our estimates of the procedure rates. We considered in our analyses only inpatient procedures. However, a certain proportion of the procedures are performed on an outpatient basis, which could be another potential source of underestimation of revascularization rates across the provinces, although during the study period, outpatient PCI was rare. Another potential limitation of our analysis is the measure of waiting time that was used. We identified waiting times for invasive cardiac procedures based on time since AMI. If, however, a patient was referred for a cardiac procedure by a specialist days or weeks after initial hospitalization for AMI, then our measure represents an underestimate of the true waiting time. Another limitation was the inability to follow the encrypted patient records across provincial boundaries to get out-of-province procedures. Finally, the relatively short length of the study period limited our ability to draw conclusions about time trends and more current practices. Nevertheless, relatively large changes in procedure rates, particularly for PCI, were observed over the three years of the study. CONCLUSION We observed significant interprovincial and regional variation in the use of revascularization procedures across Canada. Moreover, waiting times for revascularization procedures varied similarly across the country. Interpretation of appropriateness of procedure use is limited in the present study. However, the study highlights potential inequities in the treatment of AMI across the country that must be addressed in future research and policy planning. ACKNOWLEDGEMENTS: The authors acknowledge CCORT Research Coordinator Susan Brien for her work in the final production of this manuscript, and graphic designer Brian Graves for designing and producing the maps featured in the manuscript. Parts of this material are based on data and information provided by the Canadian Institute for Health Information. However, the analyses, conclusions, opinions and statements expressed herein are those of the authors and not necessarily those of the Canadian Institute for Health Information. 499

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