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SAN DIEGO -- Using computed tomography coronary angiography (CTCA) in patients with suspected angina due to coronary heart disease (CHD) changed the diagnosis in one quarter of patients, researchers reported here.

One in four patients also had changes in their medical treatment, which included preventive therapies and antianginal medications, said , a cardiologist at the University of Edinburgh in Scotland, and colleagues at a late-breaking clinical trial session at the American College of Cardiology meeting. Results were also published simultaneously in the .

The use of CTCA gives a measure of certainty for patients presenting with chest pain, Newby said. “Now [doctors] can look people in the eye and say, ‘Your heart arteries are normal,’” he added. “What patients hate to hear is, ‘I think your heart arteries are normal.’”

The diagnosis of CHD increased, but the diagnosis of angina due to CHD did not. Most changes were based on the identification or exclusion of obstructive CHD.

The findings suggest that physicians tend to overdiagnose angina due to CHD, the authors wrote.

The Scottish Computed Tomography of the Heart (SCOT-HEART) trial is the first to assess the clinical impact of the addition of CTCA in patients with stable chest pain, authors added.

The technology may help clarify which patients have a true diagnosis of angina, and whether or not they should have further testing or targeted intervention, , a cardiologist with Carolinas HealthCare System in Charlotte, N.C., told MedPage Today.

The trial included 4,146 patients, ages 18 to 75, with suspected angina due to CHD. They had been referred for assessment by their primary care physician with suspected angina due to CHD.

Excluded were patients who could not undergo CT scanning, had renal failure, were allergic to contrast media, were pregnant, or had experienced acute coronary syndrome in the past 3 months.

There were no restrictions based on weight, calcium score, or arrhythmias.

After the initial consultation, patients were randomized into two groups: standard of care and standard of care plus CTCA.

At 6 weeks, the physician reviewed the original diagnosis in conjunction with all information gathered, including CTCA results, and then documented if there was a change in diagnosis.

Patients were followed for a median of 1.7 years.

The primary endpoint was the proportion of patients diagnosed with angina pectoris secondary to coronary heart disease at 6 weeks.

Other measured outcomes were death, myocardial infarction (MI), coronary revascularization procedures, hospitalization for chest pain, cerebrovascular disease, and peripheral vascular disease.

A total of 36% of patients were diagnosed with angina due to CHD after the initial consultation.

In the CTCA group, the diagnosis of angina due to CHD changed in 23% of patients compared with 1% in the standard care group (P<0.001).

The diagnosis of CHD changed in 27% of patients in the CTCA group, compared with 1% in the standard care group (P<0.001).

Changes in diagnosis were associated with changes in management, including stress testing and invasive coronary angiography (15% in the CTCA group versus 1% in the standard group), preventive medical therapies (18% versus 4%), and antianginal medications (9% versus 1%).

At 6 weeks, both the CTCA and standard care group had significant improvement in the stability and frequency of angina. There was no difference between groups.

There were also no significant differences between groups in hospitalizations for chest pain or coronary revascularization.

The use of CTCA was associated with a 38% reduction in death from CHD and nonfatal MI (adjusted HR 0.62, 95% CI 0.38-1.01, P=0.0527).

Of the patients who had CTCA, a total of 1.7% had adverse reactions that included contrast reactions, contrast extravasation, vasovagal reaction, and headache.

The median radiation dose was 4.1 (IQR 3.0-5.6) mSv, of which more than a third (37%) was due to the measurement of the coronary artery calcium score, authors wrote.

The authors noted several limitations. Since the trial was an open one, clinicians might have favored CTCA or functional tests. It was possible that management changes took more than 6 weeks to implement, so an effect on anginal symptoms could have occurred after then. Also, patients over age 75 were excluded. Finally, the cost-effectiveness of CTCA was not addressed.

In an accompanying commentary, , of the Duke Clinical Research Institute in Durham, N.C., wrote that "because randomized trials of cardiovascular imaging are fairly new, much can be learned from the well-done SCOT-HEART study to guide clinical care and future research."

She pointed out that the study results answered "many crucial questions" such as, "in the absence of a feasible placebo strategy, how can imaging studies prevent or control bias in favour of the intervention? In SCOT-HEART, CTCA created greater diagnostic certainty in CT readers than in nonreader clinicians."

She also asked if imaging findings should be prospectively linked to mandated care algorithms. "The failure to follow best practices, or the ineffectiveness of treatments, can be falsely attributed to the test," she explained.

Douglas cited the in which a cardiac PET viability scan did not change outcomes in patients with heart failure overall, but those who got PET-guided care did have fewer events.

"SCOT-HEART bypassed this issue by using the upstream outcome of diagnostic certainty, but clinical events remain the preferred evidentiary standard," she wrote.

Douglas concluded that SCOT-HEART "provides important data regarding the effect of the addition of a new technology to usual care," but added that "more work is needed in this new specialty before the value of cardiovascular imaging can be fully understood."

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