Waiting time and mortality in coronary artery bypass grafting patients
Abstract: Coronary Artery Bypass Grafting (CABG) has emerged as one of the most common major surgical procedures worldwide. Unfortunately the capacity is still unable to meet the demand in many countries. This leads to waiting times before surgery, prioritisation between patients and ultimately to deaths among the patients on the waiting list.Aims: 1. To calculate mortality on the waiting list for CABG and to identify independent predictors of death while waiting for surgery. 2. To investigate the difference in risk of death on the waiting list between men and women. 3. To assess the impact of waiting time on per-, and postoperative mortality. 4. To construct a simple score to identify patients with an increased risk of death on the waiting list.Materials and methods: All patients accepted for elective CABG between January 1995 and June 1999 were included in the study (n=5864, 78% men, 66 b9 years). Preoperative data were registered prospectively in a data base. Waiting time and pre-, per-, and postoperative mortality were registered. Mean follow up was 24 b15 months. A Poisson regression model was used to identify independent predictors of death on the waiting list, to construct risk profiles for men and women on the waiting list, to analyse the impact of waiting time on per-, and postoperative mortality and to calculate the effect of a shortening of the waiting time. Based on these results a simple score to identify patients with an increased risk of death while waiting for surgery was constructed. The score was then validated in a new cohort of consecutive CABG patients (n=5167, 76% men, 66 b9 years).Results: Median waiting time was 55 days. Seventy seven patients died while waiting for surgery (1.3% or 5.8 deaths/100 waiting years). Unstable angina pectoris, concomitant aortic valve disease requiring surgery, imperative priority, male gender, increased peroperative risk, decreased left ventricular ejection fraction and waiting time were independent risk factors for death on the waiting list. Women on the waiting list were older, had a higher Cleveland Clinic risk score and a better left ventricular ejection fraction. More women had unstable angina pectoris, diabetes mellitus, chronic obstructive pulmonary disease, hypertension and planned concomitant aortic valve surgery, while more men had three vessel disease. Female gender was associated with a lower risk of death on the waiting list than male gender (hazard ratio 0.42, 95% CI 0.19-0.93). Postoperative mortality during follow-up was higher in patients operated on after the intended time (8.0 vs 6.2 %) but after correction for age, gender, operative risk and angina symptoms, waiting time was not an independent predictor of postoperative death. When the risk score was validated 47% of the patients were low-risk, 38% intermediate-risk and 15% high-risk. Mortality incidence was five times higher in the high-risk group than in the intermediate-risk group and 25 times higher than in the low-risk group (32, 7 and 1.3 deaths/100 waiting years respectively). Twenty-three percent of the patients in the high-risk group had not been prioritised at acceptance to the imperative group. Conclusions: Waiting for CABG implies a considerable risk of death. Unstable angina, concomitant aortic valve disease requiring surgery, impaired left ventricular function, increased peroperative risk, imperative priority, waiting time and male gender are independent risk factors for death on the waiting list. Women have a lower risk of death on the waiting list for CABG. Waiting time has no impact on mortality after CABG. The risk score adequately identifies patients with an increased risk of death while waiting for CABG.
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