CT coronary angiography (CTCA) can clarify the diagnosis of angina due to coronary heart disease, leading to a reduced need for further stress testing and enabling more targeted interventions.

Ultimately, changes in treatments stemming from the addition of CTCA to standard clinical care could reduce fatal and non-fatal heart attack rates, according to the SCOT-HEART study published online in The Lancet.

David Newby, MD, PhD, of the University of Edinburgh's Centre for Cardiovascular Science, and colleagues noted that while rapid clinical assessment of patients with suspected angina due to coronary heart disease is generally effective, misdiagnoses still occur. Studies have shown that about one-third of patients who die from cardiovascular disease or have an acute coronary syndrome within five years of follow up were originally diagnoses with non-cardiac chest pain.

For SCOT-HEART, Newby and colleagues tracked 4,146 patients referred for assessment of suspected angina due to coronary heart disease from Nov. 18, 2010, through Sept. 24, 2014. Baseline clinic diagnosis showed 47 percent of participants with coronary heart disease and 36 percent with angina due to coronary heart disease.

Half of the patients underwent CTCA in addition to standard diagnostic tests. Results showed that at six weeks, CTCA had reclassified the diagnosis of coronary heart disease in 27 percent of those patients and the diagnosis of angina due to coronary heart disease in 23 percent of patients in that group.

“We noted that although the certainty and frequency of the diagnosis of coronary heart disease increased, the overall diagnostic rate of angina due to coronary heart disease did not change or seemed to fall with the introduction of CTCA,” wrote Newby and colleagues. “This finding suggests clinicians tend to overdiagnose angina due to coronary heart disease, probably for fear of undertreatment. However, CTCA did diagnose many patients with angina due to coronary heart disease who had been misclassified in the clinic. Overall reclassification happened in one in four patients and this is clearly important for the subsequent investigation and treatment of these patients.”

In twenty months of follow up, the number of heart attacks that occurred in patients who received CTCA was reduced by 38 percent.

Future studies will investigate whether giving scans to all patients presenting at the emergency department with chest pain would help cut heart attack rates, according to the university.