Comparing CT Angiography to Invasive Angiography for Stable Chest Pain Patients
By Michael H. Crawford, MD, Editor
SYNOPSIS: A trial of initial coronary CT angiography vs. invasive angiography revealed outcomes over a median 3.5-year follow-up were similar, but procedure-related complications were more common in the invasive group.
SOURCE: DISCHARGE Trial Group; Maurovich-Horvat P, Bosserdt M, Kofoed KF, et al. CT or invasive coronary angiography in stable chest pain. N Engl J Med 2022; Mar 4. doi: 10.1056/NEJMoa2200963. [Online ahead of print].
A coronary artery CT (CTA) diagnostic approach has been shown to produce equivalent outcomes at 25 months as stress testing in the PROMISE trial.1 However, little is known about the comparative value of an invasive coronary angiography (ICA) approach for preventing major adverse cardiovascular events (MACE), defined as myocardial infarction (MI), stroke, or cardiovascular (CV) death.
The authors of the Diagnostic Imaging Strategies for Patients with Stable Chest Pain and Intermediate Risk of Coronary Artery Disease (DISCHARGE) trial conducted a multicenter, randomized, superiority study to compare CTA with ICA in the management of stable chest pain at 26 centers in 16 European countries. Intermediate risk was defined as a 10% to 60% risk of obstructive coronary artery disease (CAD). Enrolled patients were at least age 30 years and in sinus rhythm. The authors excluded pregnant patients and those on hemodialysis. After imaging, the patients were treated according to guidelines. As a pragmatic trial, no biomarkers or brain imaging were used to detect asymptomatic outcomes. The primary outcome was MACE. Secondary outcomes included major procedure-related complications within 48 hours of CTA, ICA, or subsequent revascularization procedures.
Between 2015 and 2019, 3,667 patients were enrolled and followed for a median of 3.5 years. The mean age of the population was 60 years, and 56% were women. One-third of patients underwent noninvasive functional testing before enrollment. Obstructive CAD was discovered in 26% of both groups. The primary outcome occurred in 2% of the CTA group and 3% of the ICA group (P = NS). Procedure-related complications occurred in seven patients assigned to CTA and 30 in the ICA group. Only 22% of the CTA group subsequently underwent ICA. When ICA was associated with revascularization, the rate of MACE quadrupled vs. ICA alone (1% vs. 4%). During follow-up, more patients in the CTA group underwent functional tests than those in the ICA group (19% vs. 13%). Subsequent revascularization was lower in the CTA group (14% vs. 18%). Quality of life and angina assessments during follow-up were similar for the two groups. The authors concluded the frequency of MACE was similar in the initial CTA group vs. the initial ICA group in patients with an intermediate pretest probability of obstructive CAD. Nevertheless, major procedural complications were more common with the initial ICA approach.
COMMENTARY
The evaluation of patients with stable chest pain (present longer than two months; no change in frequency, severity, or duration) remains controversial. Guidelines have recommended noninvasive functional tests to detect ischemia before embarking on angiography. However, evidence (e.g., the PROMISE trial) indicates CTA might be more efficient since it directly addresses the coronary anatomy, preventing the occasional false-positive and negative results of functional testing.
Why not go directly to ICA? If one finds high-risk obstructive CAD, the clinician can proceed directly to a percutaneous intervention. Thus, the DISCHARGE study of CTA vs. ICA in the initial evaluation of patients with stable angina and intermediate risk of obstructive CAD is of interest. The authors showed there were more procedural complications with ICA, but no difference in the primary outcome of MACE after a median follow-up of 3.5 years.
However, there are several caveats. First, this was a low-risk group, with a MACE incidence of 2% to 3%. There are several reasons why this rate was so low. Most patients were women who are known to be less likely to develop obstructive CAD as an explanation for their chest pain compared to men of a similar age. Also, about one-third of patients reported atypical chest pain. In addition, only about one-third of patients underwent functional tests to confirm ischemia. Finally, only 22% of the CTA group went on to undergo ICA. One could argue these were low-risk patients in whom angiography is not usually recommended. Second, no asymptomatic events were sought, so there may have been an ascertainment bias that improved the results of the ICA group. Third, the authors reported only 6% of patients underwent non-diagnostic CTAs. This may be partially attributed to the relatively low age of the population (mean age, 60 years). The incidence of heavy calcium, which can obscure the lumen in CTA studies, probably was low. The authors did not address this issue.
There were other limitations. The treating physicians and the patients were not blinded to their groups; only the outcome assessors were blinded, which could have biased the management of patients. Also, management decisions were not mandated; the participating physicians were told only to follow guidelines. There was no cost effectiveness assessment, which is an important issue; many insurance companies balk at paying for CTA because of its expense. In addition, fractional flow reserve, which can be assessed with CTA or ICA, was not employed, nor were plaque characteristics sought with CTA. Either assessment could have enhanced patient management. Finally, CTA was performed earlier than ICA after enrollment (mean, 3 days vs. 12 days), perhaps permitting earlier revascularization and improved outcomes in the CTA group. Although flawed, the DISCHARGE trial adds further impetus to considering CTA in selected patients with chest pain.
REFERENCE
- Douglas PS, Hoffmann U, Patel MR, et al. Outcomes of anatomical versus functional testing for coronary artery disease. N Engl J Med 2015;372:1291-1300.
A trial of initial coronary CT angiography vs. invasive angiography revealed outcomes over a median 3.5-year follow-up were similar, but procedure-related complications were more common in the invasive group.
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