Regional revascularization patterns after myocardial infarction in Ontario

Objective — To determine whether regional differences exist within Ontario in the use and timing of coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) among patients who have recently suffered an acute myocardial infarction (AMI).

Background — Regional variations have been documented in the use of CABG in Canada, but previous findings do not fully account for either an alternative procedure (PTCA) or the impact of geographic variations in disease incidence or severity. By following persons after AMI, one can address both issues simultaneously in a subpopulation of patients where substitution of PTCA for CABG may be occurring.

Patients and Methods — Hospital discharge abstracts were used to define an inception cohort of 6565 patients with a primary diagnosis of AMI in the first six months of fiscal 1990. Subjects were tracked longitudinally for subsequent CABG or PTCA over the remainder of the fiscal year. Procedures were attributed by site of patient residence to one of five major Ontario referral regions. Proportions of patients undergoing revascularization and time in days from AMI to intervention were compared by chi 2 tests and nonparametric analysis of variance, respectively.

Results — Overall, 9.7% of patients underwent revascularization, with regional rates ranging from 7.2 to 13.6% (P < 0.0001). Elapsed time to revascularization also varied by region (P < 0.01). Use of CABG and PTCA varied separately by region (both P < 0.0001). Two regions with significantly elevated CABG rates were statistically similar to the provincial mean for overall revascularization owing to proportionately lower use of PTCA.

Conclusions — Regional variations in use and timing of coronary revascularization were evident in this post-AMI cohort. Longitudinal tracking for substitutable procedures in a defined inception cohort may yield perspectives that complement conventional small area analyses.