Four million stress tests are conducted each year on patients with stable chest pain, and yet the cardiology community has reached little consensus about how best to identify patients who will benefit from a trip to the cath lab. That may be changing, however, as cardiologists consider new data indicating the value of coronary computed tomographic angiography (CCTA) for diagnosing these patients.
Cardiologists have long struggled with the thorny problem of evaluating chest pain. In general, the physicians “do not do very well in having the right patient go to the cath lab with the underlying diagnosis of suspected coronary artery disease [CAD],” says Ralph G. Brindis, MD, MPH, clinical professor of medicine at the University of California, San Francisco, and senior medical officer of external affairs at the American College of Cardiology (ACC) National Cardiovascular Data Registry.
The root of the diagnostic dilemma is lack of evidence. Only about 1 percent of the more than 700 recommendations related to cardiovascular imaging in ACC/American Heart Association guidelines are classified as Class I Level of Evidence A because relatively few large, randomized, controlled trials have examined the issue. One recent study found only a weak correlation between most noninvasive diagnostic tests and the likelihood of obstructive CAD (Am Heart J 2014;167:846-852). The researchers reported that about 58 percent of patients who had elective angiography did not actually have obstructive CAD.
Cardiologists are in “a primitive age of evidence when we talk about stable chest pain,” Valentin Fuster, MD, PhD, said in a Journal of the American College of Cardiology
audio-commentary on an article reviewing the implications of SCOT-HEART and PROMISE, the two largest and most comprehensive cardiovascular imaging trials of stable angina (2016;67:843-52). Fuster underscored the review author’s conclusion: “Both trials show that coronary computed tomography angiography should have a greater role in the diagnostic pathway of patients with stable chest pain.”
Clearer pathway with CCTA?
The SCOT-HEART (Scottish COmputed Tomography of the HEART) trial compared the effectiveness of CCTA along with usual care with conventional stress testing alone (usually including exercise electrocardiography) to evaluate suspected angina due to coronary heart disease (Lancet 2015;385:2383-2391). The investigators found that adding information obtained from a 64-slice CCTA to standard clinical care clarified the diagnosis of angina due to coronary heart disease. The strategy resulted in reduced need for further stress testing and a modest net increase in the use of invasive coronary angiography. Event rates were low in both arms of the trial. At 20 months, there was a 38 percent reduction in cardiovascular death and nonfatal myocardial infarction (MI) in the CCTA arm compared with standard care, but the finding was not statistically significant.
The PROMISE (PROspective Multicenter Imaging Study for Evaluation of Chest Pain) trial randomized 10,003 patients who had symptoms suspicious for significant CAD that required non-emergent noninvasive testing to either an anatomic strategy using 64-slice CCTA or a functional strategy that included exercise electrocardiography, exercise or pharmacologic nuclear stress testing, or stress echocardiography (N Engl J Med 2015;372:1291-1300). The investigators found no significant differences in outcomes related to death, MI, unstable angina or major procedural complications between patients randomized to the initial anatomic strategy vs. the functional testing strategy. Use of the initial CCTA strategy was associated with fewer catheterizations showing no obstructive CAD when compared with catheterizations performed on patients in the functional testing groups.
In statements issued after the PROMISE and SCOT-HEART trials were presented at the ACC.15 Scientific Sessions, Ricardo C. Cury, MD, then-president of the Society of Cardiovascular Computed Tomography (SCCT), said, “PROMISE appears to demonstrate that coronary CTA uniquely identifies patients who have non-obstructive atherosclerosis and who will benefit from medical therapy” and “SCOT-HEART demonstrated that CCTA provided a clearer and more precise diagnosis of coronary heart disease [compared with conventional stress testing], reclassifying the diagnosis in one of every 4 patients.”
Cost & radiation tradeoffs?
Also at the ACC.15 Scientific Sessions,