CT Coronary Angiography More Accurate Than Exercise ECG in Stable Angina

By Will Boggs MD

June 12, 2020

NEW YORK (Reuters Health) - CT coronary angiography (CTCA) is more accurate than exercise ECG for detecting coronary-artery disease (CAD) and predicting future risk in patients with suspected stable angina, according to a post hoc analysis of the SCOT-HEART trial.

In the SCOTT-HEART trial, the addition of CTCA to stress ECG was associated with a 41% reduction in cardiovascular deaths and nonfatal myocardial infarctions after five years. This has been used as justification for the use of CTCA as a second test.

In the current study, Tricia Singh of the University of Edinburgh and colleagues assessed the diagnostic, therapeutic, and prognostic benefits associated with exercise ECG alone or in combination with CTCA in 3,283 patients with suspected angina due to coronary heart disease.

Two-thirds of exercise ECGs were normal, 16% had abnormal results, and 17% had inconclusive results.

For those with normal exercise ECG results, more than half had either obstructive (15%) or nonobstructive (41%) CAD on CTCA. Conversely, 39% of patients with obstructive CAD on CTCA had a normal exercise ECG.

Among patients who underwent invasive coronary angiography, obstructive disease was identified more frequently in those with abnormal exercise ECG results. But those with normal or inconclusive results of exercise ECG were more likely to have obstructive CAD identified in the CTCA group than in the exercise ECG-only group, the researchers report in JAMA Cardiology.

The rates of initiation and discontinuation of preventive therapy and referral for invasive coronary angiography were higher among patients who underwent CTCA compared with those who only underwent exercise ECG, particularly among those who had inconclusive or normal results of exercise ECG.

Abnormal results of exercise ECG were associated with a 14.47-fold increased risk of coronary revascularization at one near and a 2.57-fold increased risk of dying from coronary heart disease or suffering a nonfatal myocardial infarction at five years (both P<0.001).

Compared with exercise-ECG alone, however, results of CTCA had a stronger association with five-year coronary-heart-disease death or nonfatal myocardial infarction (a 10.63-fold increased risk, P=0.002).

"Although abnormal results of exercise electrocardiography are associated with coronary revascularization and future risk of adverse coronary events, coronary computed tomography angiography may identify additional undetected coronary artery disease and add to clinical decision-making and may be more strongly associated with future risk," the authors conclude.

In a linked editorial, Dr. Pamela S. Douglas of Duke University School of Medicine, in Durham, North Carolina, writes, "Although falling short of recommending the addition of CTA for every patient with normal or inconclusive results of exercise ECG, a strategy that was not tested here, the implication of this study is that exercise ECG alone, for most individuals, is not sufficient to optimize outcomes."

"Coronary computed tomography angiography, with its far more nuanced interrogation of multiple parameters, stimulates directional thinking about coronary disease and, over time, will allow us to consider other aspects of coronary disease beyond stenosis," she said. "Especially in light of the ISCHEMIA results, which upended whatever was left of the stenosis-revascularization paradigm, there is so much more to learn."

Dr. Raymond J. Gibbons of Mayo Clinic, in Rochester, Minnesota, who wrote a linked viewpoint article, told Reuters Health by email, "Not every patient needs a CT angiogram after an exercise ECG. Some of the apparent benefit of CT angiography in SCOT-HEART was due to (1) the protocol recommendations for preventive therapy and (2) the selection of patients for revascularization (which was not always due to the exercise ECG or coronary anatomy and is therefore not generalizable)."

"If a patient has an abnormal exercise ECG and the clinician feels that revascularization is a reasonable option, the patient can be sent to invasive coronary angiography without doing a CT angiogram," he said.

"The use of preventive therapy for nonobstructive CAD in SCOT-HEART cannot be generally recommended without additional studies that include measurement of GI bleeding rates," Dr. Gibbons added.

Singh did not respond to a request for comments.

SOURCE: https://bit.ly/2MJBz8X, https://bit.ly/3cXuZq9 and https://bit.ly/2BUq2kZ JAMA Cardiology, online June 3, 2020.