The risks of waiting for cardiac catheterization: a prospective study

Abstract

Background: Few large, systematic, prospective studies have documented the characteristics and clinical outcomes of patients awaiting cardiac catheterization and the delays that they experience. The primary objective of this study was to quantify the waiting times, morbidity and mortality of patients waiting for catheterization. A secondary objective was to identify predictors of cardiac events that occur while patients are waiting.

Methods: A computerized, prospective, central waiting list registry was developed at a regional centre in Hamilton, Ont., serving 2.2 million people in southern Ontario. Between Apr. 1, 1998, and Mar. 31, 2000, 8030 consecutive patients (4725 outpatients and 3305 inpatients) were referred for cardiac catheterization. Major cardiac outcomes while on the waiting list (death, myocardial infarction and congestive heart failure) were documented prospectively and related to requested versus actual waiting time.

Results: Most of the referrals (7345 [91.5%]) were for a primary diagnosis of suspected coronary artery disease. The median waiting time was 6 (interquartile range [IQR] 4) days for inpatients and 60 (IQR 68) days for outpatients. Actual waiting times correlated with the waiting times requested by the referring physicians. However, only 37% of the procedures overall were completed within the requested waiting time. Of the 8030 patients, 50 (0.6%) died, 32 (0.4%) had a myocardial infarction and 41 (0.5%) experienced congestive heart failure. Overall, 109 patients (1.4%) had a major cardiac event, namely, death, myocardial infarction or congestive heart failure. These events occurred over a median wait of 27 days (2 days for inpatients and 35 days for outpatients), and over half (57%) occurred within the waiting time requested by the referring physician. In the multivariate analysis, predictors of the composite of death, myocardial infarction or congestive heart failure were increasing age (relative risk [RR] 2.39, 95% confidence interval [CI] 1.52-3.75) and New York Heart Association class III/IV symptoms (RR 2.86, 95% CI 1.11-7.33) in inpatients, and increasing age (RR 1.36, 95% CI 1.12-1.66), aortic stenosis (RR 3.70, 95% CI 1.93-7.08) and left ventricular ejection fraction less than 35% (RR 4.35, 95% CI 2.48-7.61) in outpatients.

Interpretation: Patients awaiting cardiac catheterization may experience major adverse events, such as death, myocardial infarction and congestive heart failure, which may be preventable. Our findings provide a benchmark by which to measure the effect of increased capacity and prioritization schemes that allow earlier access for patients at higher risk, such as those with aortic stenosis and reduced left ventricular function.

Fig. 1: Trends in numbers of patients referred for cardiac catheterization (squares), numbers who underwent the procedure (diamonds) and numbers on the waiting list (triangles) in quarter-year intervals, Apr. 1, 1998, to Mar. 31, 2000.

Fig. 2: Median number of days from referral to cardiac catheterization or cancellation of procedure, by requested waiting time, for inpatients and outpatients. The bottom of each box represents the 75th percentile; thus, the height of the box is the interquartile range (IQR). The white line represents the median. Values that lie more than 1.5 IQRs beyond the top or bottom of the box (outliers) are shown as individual lines. The square brackets connected by dotted lines to the top and bottom of the box represent the most extreme values not more than 1.5 IQRs beyond the box. For inpatients, the median waiting time and proportion who underwent catheterization within the requested waiting time were as follows: < 48 hours: 3 (IQR 4) days, 48%; < 7 days: 6 (IQR 4) days, 50%; < 14 days: 7 (IQR 7) days, 82%. The corresponding values for outpatients were: < 14 days: 21 (IQR 18) days, 28%; < 42 days: 56 (IQR 44) days, 29%; < 90 days: 133 (IQR 88) days, 29%.