Clinical Pearls & Morning Reports
The DISCHARGE (Diagnostic Imaging Strategies for Patients with Stable Chest Pain and Intermediate Risk of Coronary Artery Disease) Trial Group conducted a randomized trial that compared computed tomography (CT) with invasive coronary angiography (ICA) as initial diagnostic imaging strategies for guiding the treatment of patients with stable chest pain who had an intermediate pretest probability of obstructive coronary artery disease (CAD) and who were referred for ICA at one of 26 European centers. Read the NEJM Original Article here.
Q: How often does ICA reveal obstructive CAD in patients who are referred for the procedure in the United States and Europe?
A: ICA is the reference standard for the diagnosis of obstructive CAD and enables coronary revascularization during the same procedure. However, elective ICA is associated with rare but major procedure-related complications and has been reported to reveal obstructive CAD in only 38 to 50% of the patients who are referred for the procedure in the United States and Europe.
Q: How did initial CT to guide therapy in patients with stable chest pain compare with ICA in terms of the primary outcome of major adverse cardiovascular events in the DISCHARGE trial?
A: In this trial, the authors found no significant difference in the primary outcome of major adverse cardiovascular events. Over a median follow-up of 3.5 years, the primary composite outcome of major adverse cardiovascular events (cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) occurred in 38 patients (2.1%) in the CT group and in 52 patients (3.0%) in the ICA group (hazard ratio, 0.70; 95% CI, 0.46 to 1.07; P=0.10).
A: Because only 22.3% of the patients in the CT group underwent ICA during initial treatment, as compared with 97.4% in the ICA group, major procedure-related complications were less common in the CT group than in the ICA group, occurring in 9 patients (0.5%) in the CT group and in 33 (1.9%) in the ICA group (hazard ratio, 0.26; 95% CI, 0.13 to 0.55). The frequency of coronary revascularization procedures was lower in the CT group than in the ICA group (256 patients [14.2%] vs. 315 patients [18.0%]; hazard ratio, 0.76; 95% CI, 0.65 to 0.90). Angina during the final 4 weeks of follow-up was reported in 8.8% of the patients in the CT group and in 7.5% of those in the ICA group (odds ratio, 1.17; 95% CI, 0.92 to 1.48). Quality-of-life outcomes that were assessed at follow-up were also similar in the two groups.
A: First, patients and their clinicians were necessarily aware of the group assignments, which might have influenced outcomes, especially patient-reported outcomes. Because the authors could not systematically identify silent events (especially procedure-related myocardial infarction or stroke), ascertainment bias might have favored the ICA group. Second, the incidence of nondiagnostic CT in this and previous trials was approximately 6%, which indicates the need for continuous quality control of the conduct and interpretation of CT. Third, because this was a pragmatic trial, diagnostic imaging results informed, but did not mandate, management decisions, which might have resulted in a departure from guideline-based care. Finally, the authors do not present results for a comparison of the cost-effectiveness of CT and ICA, a factor that is a crucial component of decision making and that warrants rigorous analysis.