Use of Coronary CT angiography associated with reduced nonfatal myocardial infarction in adults with chronic stable angina at 5 years

EBM Focus - Volume 13, Issue 34

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Reference: N Engl J Med 2018 Sep 6;379(10):924 (level 2 [mid-level] evidence)

The SCOT-HEART trial was an open label trial that evaluated the use of coronary CT angiography (CTA) in the management of patients with chronic stable angina. Patients were evaluated in a cardiology referral clinic and therapeutic plan was determined. At that point patients were randomized to either standard care (the plan that had been set) or standard care plus CTA with any subsequent modification of the treatment plan at the discretion of the treating physician. Initial results showed that coronary CT angiography (CTA) improved the ability to diagnose coronary heart disease (CHD) and changed management in patients with stable angina. Recently, continuation data from this trial was published that included 98% of the original 4,146 participants with a median follow-up of 4.8 years (SCOT-HEART). Outcome data were collected from the National Health Service electronic database and the outcome assessors were not blinded to treatment group.

The results found a reduced rate of death from CHD or nonfatal MI in the adults who had standard care plus coronary CTA testing compared to those receiving standard care alone (2.3% vs. 3.9%; hazard ratio, 0.59, 95% CI, 0.41 to 0.84; p = 0.004; NNT 63). The primary driver of this finding was a lower rate of nonfatal MI in the CTA group (hazard ratio 0.60; 95% CI, 0.41 to 0.87). Rates of invasive coronary angiography and coronary revascularization were higher in the CTA group earlier in the study but there were no differences in the rates of these procedures at the 5-year mark. Participants who underwent CTA were also more likely to have been prescribed preventive therapies, such as aspirin or a statin, and antianginal therapies. There was no difference in all-cause mortality at 5 years between treatment groups.

As previously reported by the SCOT-HEART and PROMISE trials, coronary CTA was more likely to accurately diagnose obstructive CHD than standard care or functional testing, leading to earlier initiation of preventive and antianginal therapies, and more appropriate use of coronary angiography and revascularization. However, taken differently, adding CTA to the evaluation of adults with stable angina from the outset may simply accelerate diagnosis and hasten the time to invasive coronary angiography and coronary revascularization in a group of people who will eventually get these interventions anyway. With the differences found being primarily a small decrease in the rate of non-fatal myocardial infarction and no difference in all-cause mortality at five years, we should consider whether it is worth performing 70 CTAs to prevent 1 non-fatal myocardial infarction over 5 years.

FOCUS POINT: While adding coronary CTA to standard evaluation of adults with chronic stable angina may slightly reduce nonfatal MI at 5 years, more data is needed from a cost-benefit perspective.
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