The occurrence of adverse events in relation to time after registration for coronary artery bypass surgery: a population-based observational study

Boris G Sobolev 0 Guy Fradet 2 Lisa Kuramoto 1 Basia Rogula 1 0 The University of British Columbia , 828 West 10th Avenue, Vancouver, BC V5Z 1M9 , Canada 1 Centre for Clinical Epidemiology and Evaluation, Vancouver Coastal Health Research Institute , 828 West 10th Avenue, Vancouver , Canada 2 The University of British Columbia , 2251 Pandosy Street, Kelowna, BC V1Y 1T1 , Canada Background: Our objective was to evaluate the effect of delays on adverse events while waiting for coronary artery bypass grafting (CABG). Methods: An observational study that prospectively followed patients from registration on a wait list to removal for planned surgery, death while waiting, or unplanned emergency surgery. The population-based registry provided data on 12,030 patients with a record of registration on a wait list for first-time isolated CABG surgery between 1992 and 2005. Results: In total, 104 patients died and 382 patients underwent an emergency surgery before planned CABG. The death rate was 0.5 per 1000 patient-weeks in the semiurgent group and 0.6 per 1000 patient-weeks the nonurgent group, adjusted OR = 1.07 (95% confidence interval [CI] 0.69-1.65). The emergency surgery rate of 1.2 per 1000 patient-weeks in the nonurgent group was lower compared to 2.1 per 1000 patient-weeks in the semiurgent group (adjusted OR = 0.72, 95% CI 0.54-0.97). However, the nonurgent group had a greater cumulative incidence of preoperative death than the semiurgent group for almost all weeks on the wait list, adjusted OR = 1.92 (95% CI 1.25-2.95). The surgery rate was 1.2 per 1000 patient-weeks in the nonurgent group and 2.1 per 1000 patient-weeks in the semiurgent group, adjusted OR = 0.72 (95% CI 0.54-0.97). The cumulative incidence of emergency surgery before planned CABG was similar in the semiurgent and nonurgent groups, adjusted OR = 0.88, (95% CI 0.64-1.20). Conclusion: Despite similar death rates in the semiurgent and nonurgent groups, the longer waiting times in the nonurgent group result in a greater cumulative incidence of death on the wait list compared to that in the semiurgent group. These longer waiting times also offset the lower rate of emergency surgery before planned admission in the nonurgent group so that the cumulative incidence of the emergency surgery was similar in both groups. - Background Delaying access to surgical procedures is a common alternative to having surplus capacity available at all times [1]. As argued elsewhere, surgical wait lists have been accepted on the ground that they provide efficient use of resources in health systems that budget the number of surgical procedures [2]. For example, cardiac services across Canada use wait lists to manage access to coronary artery bypass surgery (CABG) in periods when demand exceeds funded capacity [3-5]. Explicitly queuing patients according to urgency of required treatment is used to facilitate access to care within a clinically appropriate time. However, despite the concern that delays in necessary treatment could lead to poor clinical outcomes, the point at which the delay for CABG becomes too long has not been established [6]. Our objective was to evaluate the effect of delays on the occurrence of adverse events while waiting for CABG. In particular, we conducted an observational study to achieve a better understanding of whether longer delays for coronary artery bypass grafting contribute to worsening of the condition in less urgent patients waiting for planned CABG, and to estimate the risk of unplanned emergency surgery among these patients. We prospectively followed patients from registration on a wait list for first-time CABG to removal for planned surgery, death while waiting, or unplanned emergency surgery. We used all relevant records from the population-based registry of patients with angiographically proven coronary artery disease identified as needing bypass surgery on a non-emergency basis between 1992 and 2005. Primary comparisons have been done across synthetic cohorts of patients defined by the urgency at the decision to proceed with surgery. Methods Data sources Data from the British Columbia Cardiac Registries (BCCR) were used to identify the study participants and their demographic, clinical and treatment characteristics. This population-based patient registry prospectively captures the date of booking request for operating room time, and the date of and reason for removal from the wait list, for all adult patients accepted for CABG in any of the four cardiac centers in the province [7]. To identify cardiac catheterization dates and coexisting medical conditions, we used each patients provincial health number to deterministically link BCCR records to the Canadian Institute for Health Information (CIHI) Discharge Abstract Database (DAD) [8]. To identify coexisting conditions, we used diagnoses reported in the DAD within one year prior to the booking request. Census data on the decile of median income in enumeration area were based on the postal code of the patients residence. Patients We studied patients who had a record of registration on a wait list for first-time isolated CABG surgery from January 1, 1992 to December 31, 2005, and who had a record of catheterization procedure in the DAD. The inception cohort had 14,049 records of registration for CABG from January 1, 1991 to December 31, 2005. We excluded 567 records of patients for various reasons: procedure at registration was not isolated CABG (312), procedure at registration or at surgery was not first-time CABG (62), emergency cases at the time of registration (34), missing operating room reports (4), removed on the registration date (101), registration was on a weekend and admission was day after (14), or the patient had multiple episodes (40). We also excluded 1,452 records of patients who were registered in 1991 (797) or did not have a catheterization date (655). The remaining 12,030 records had either the surgery date or the date and reason of removal from the list without surgery. Primary study variable The study variable was urgency group at registration categorized as urgent, semiurgent, and nonurgent. When placing patients on wait lists in British Columbia, Canada, all cardiac surgeons indicate the urgency of CABG according to angiographic findings, symptom severity, and left ventricular dysfunction (ejection fraction less than 50%) to ensure timing of revascularization according to the provincial guidelines: within one week for urgent procedures, within six weeks for semiurgent procedures, and within 26 weeks for nonurgent procedures [9]. Outcomes The primary outcomes were (1) preoperative death from all causes and (2) unplanned emergency surgery while awaiting a planned CABG. Surgeons on call made the decision to operate on patients who presented to the emergency or admitting department. All admissions from the emergency department and admissions from other locations bearing an emergency code were classified as unplan (...truncated)