Rethinking Routine Testing of Chest-Pain Patients

Reed Miller

September 27, 2012

September 26, 2012 (Chicago, Illinois)A provocative opinion piece published online September 17, 2012 in the Archives of Internal Medicine calls for a randomized trial comparing the current routine testing protocols vs no testing in chest-pain patients presenting to the emergency department [1].

In the article, Dr Vinay Prasal, Dr Michael Cheung (Northwestern University, Chicago, IL), and Dr Adam Cifu (University of Chicago, IL) ask: "Does our current practice lead to the stenting of asymptomatic patients in the inevitable cases where the inciting pain was noncardiac? And, most importantly, does our practice improve outcomes?" They believe the results of such a trial could "reverse" current practice.

The current clinical-practice guidelines from the American Heart Association and American College of Cardiology recommend that patients presenting to the emergency department with a resolved isolated episode of chest pain and no electrographic or biomarker abnormalities should undergo noninvasive testing to make sure that an MI is not overlooked. Patients with negative stress-test results have extremely low 30-day event rates, while those with positive stress-test results have higher 30-day event rates.

The time has come to assess whether stress testing or CCTA can be omitted entirely.

However, Prasal et al argue that although avoiding false negatives is a noble aim, the frequently cited statistic that 2% of patients presenting with chest pain are inappropriately discharged from the emergency department is based on 1993 data collected prior to recent advances in biomarker testing. "Thus, the historical circumstances that provide impetus for our current practice may no longer be applicable."

Stress testing or coronary computed tomography angiography (CCTA) testing can identify patients at higher risk for unfavorable outcomes, but Prasal et al argue that clinical trials have yet to demonstrate that the interventions based on these tests improve outcomes overall. Interventions based on positive noninvasive test results may fail to yield better outcomes because the chest pain that prompted the patient to come to the hospital may be noncardiac but nevertheless launch a "cascade" of events leading to the diagnosis of coronary disease and revascularization of asymptomatic lesions, the authors explain.

Unanswered Questions

"The most important question facing any recommended testing program is whether the test improves outcomes, [and] in the case of resolved chest pain, no trial has examined this question," Prasal et al explain. Prasal et al cite the results of a recent study from the American College of Radiology Imaging Network (ACRIN) that showed that CCTA testing leads to a diagnosis of coronary disease and revascularization three times more often than with traditional care, but that trial did not show improved outcomes associated with that increased revascularization rate. Also, although some of these patients have both angina and significant, but stable, coronary lesions, major trials beginning with COURAGE have shown that that medical management is usually the best initial strategy for these patients, the authors point out.

Commenting on the article by Prasal et al, Dr Thomas Gerber (Mayo Clinic, Rochester, MN) told heartwire that patients who appear to be at intermediate or high risk of death or nonfatal MI based on history, pain, physical examination, and ECG and biomarker findings should "default" to treatment under the non-ST-segment-elevation-MI guidelines. However, for the patients who appear to be low risk after this initial evaluation, "there could and should be some discussion about further testing. However, it should first be recognized that prediction rules for excluding acute coronary syndromes in the emergency department are imperfect."

Dr Michael Kontos (Virginia Commonwealth University, Richmond) told heartwire , "What's happened over time is that how we evaluate these patients has shifted somewhat in that we're including lower- and lower-risk patients in all of the chest-pain protocols, and the lower the risk of the patient, the less overall value you're going to have to be able to demonstrate it." Meanwhile, there's been a shift toward more expensive testing methods like CCTA or perfusion testing, and "probably a lot of these patients do not need further imaging after they've had biomarker [tests] done, particularly with the more sensitive biomarkers.

"But we still don't have a good test for diagnosing ischemia alone. That's where the provocative [stress] testing comes form. You can fairly conclusively say that someone is not having a myocardial infarction, but we don't know if they've actually got unstable angina," Kontos said. "If you exercise somebody and they get chest pain, we're hoping that we're identifying somebody with an unstable lesion, but unfortunately you're probably picking up a lot of 'true-true-nonrelated': true they have chest pain, and true they have mild coronary disease, but they are not necessarily related."

So Kontos agrees with Prasal et al that "by doing all of this testing, maybe we're identifying a bunch of people with stable coronary disease and we're intervening on them, and all we're doing is adding costs without any value."

"But one of the reasons why the [emergency-department] doctors like CCTA so much is that it's fast--you can get the results in a few hours--and it takes away any of the uncertainty of what's going on. You can see if they've got normal coronaries and know that you don't need to really evaluate the chest pain that much if you know they're not having an MI," Kontos explained. "That's one of the reasons these things have taken off. They make the triage process a whole lot easier."

Is a New Randomized Trial Viable?

To test the benefit of the current ACC/AHA guidelines for management of patients with isolated chest pain and no electrographic or biomarker abnormalities, Prasal et al propose a randomized trial comparing routine stress testing and/or CCTA with a strategy of no further intervention. "The time has come to assess whether stress testing or CCTA can be omitted entirely."

Gerber believes such a trial may be possible depending on "how well the rationale is put forth" and if "buy-in from the various constituencies--cardiologists, [emergency-department] physicians, etc--is ascertained." He also pointed out that several large randomized studies comparing functional testing against anatomic imaging, such as ISCHEMIA, RESCUE, and PROMISE, will shed more light on the prevalence of high-grade coronary artery disease in chest-pain patients with normal ECG and biomarkers, and the outcomes data from these trials, including the frequency of revascularization, could help to estimate the sample size needed for a trial comparing current testing strategies with no testing at all, Gerber said.

Kontos believes that such a trial will be difficult to complete. It will require a standardized chest-pain scoring system to provide a rational way to identify patients with atypical symptoms and limit the trial to the lowest-risk patients--ie, patients under 50 years old with a normal ECG--he said, and "the problem with doing a randomized trial is that I don't know how many people would feel comfortable saying, 'Oh, you have chest pain and your ECG normal, so we can do a stress test or we can send you home and hope you don't have an MI.' I think you'd want to do some kind of intermediate step in between, like treadmill testing alone vs CCTA, for example."

In lieu of conclusive evidence from this proposed randomized testing, Kontos believes that treadmill stress testing, following the current guidelines, is a reasonable and fairly inexpensive way to evaluate these patients. He also suggested using an accelerated rule-out protocol that keeps the patient in the hospital only three or four hours instead of eight hours. Kontos also expects biomarker tests to become increasingly sensitive, which will identify patients who may not have unstable coronary plaque. But as the tests become more sensitive, they will also be less specific.

"When you do have an abnormal test, particularly if you're using CCTA, take a step back and say, 'What am I really trying to diagnose here?' " he suggested. "When you get one test that's abnormal, it can become a cascade of things that go downstream that lead to the patient being revascularized when they didn't really need it."

The authors report no potential conflicts of interest.