Miriam E. Tucker

June 04, 2013

NATIONAL HARBOR, Maryland — Stress myocardial perfusion imaging is not very helpful in evaluating syncope in patients without known heart disease, even those at high risk for it.

These are the findings of a retrospective database analysis presented here at Hospital Medicine 2013 by M. Chadi Alraies, MD, a staff hospitalist at the Cleveland Clinic in Ohio. The results were also published in the May issue of Circulation: Cardiovascular Imaging.

The Appropriate Use Criteria for Cardiac Radionuclide Imaging, issued by an number of organizations, including the American College of Cardiology and the American Heart Association, recommend performing stress myocardial perfusion on patients who are at intermediate to high risk for coronary artery disease. The guidelines don't address low-risk patients, Dr. Alraies noted.

But in real-life hospital practice, stress tests are routinely ordered for patients who present with syncope, even when they have no risk factors for coronary artery disease and, in many cases, even when there's another more logical explanation for the fainting episode, Dr. Alraies told Medscape Medical News.

"There's a knee-jerk [reaction that] syncope is heart disease until proven otherwise," he said. "The practice is stress testing for everyone."

The study by Dr. Alraies and colleagues — the first to evaluate the yield of diagnostic stress testing in patients who present with syncope without known heart disease — adds support to the notion that such testing is inappropriate.

 
If someone with syncope comes in without risk factors for heart disease, they don't need stress testing.
 

"I can absolutely, confidently say that if someone with syncope comes in without risk factors for heart disease, they don't need stress testing," Dr. Alraies said. "This is where the imaging studies are used inappropriately, and overused."

"I think this study really confirms research that has shown that technology is not the answer when we work up syncope," said session comoderator Eduard Vasilevskis, MD, from the Vanderbilt University Medical Center in Nashville, Tennessee.

Previous studies have shown that a simple assessment for orthostatic hypotension — checking vital signs when the patient lies down and sits up — is a better initial evaluation for assessing syncope, Dr. Vasilevskis told Medscape Medical News.

"Probably the highest-yield test we can do is orthostatics by the bedside," he noted. "That's the lowest cost, most underutilized diagnostic method, whereas myocardial perfusion imaging is higher cost without a lot of yield or benefit," he explained.

Inappropriate Testing

Dr. Alraies and his team identified 700 consecutive patients from the Cleveland Clinic stress perfusion imaging database who underwent stress testing. Patients 18 years and older with syncope as an indication were included in the analysis, and those with a history of coronary artery disease, myocardial infarction, or cardiac revascularization were excluded.

Mean age of the participants was 62 years, 55% of the cohort was female, and 63% was white. Comorbidities were common; 62% had hypertension, 54% had hyperlipidemia, and 20% had diabetes mellitus. Just under half, 45%, were smokers.

Patients were stratified by risk for coronary artery disease (low, intermediate, or high) on the basis of their Framingham score. Patients in the high-risk group had more cardiovascular risk factors and were taking more cardiac medications.

Of the 339 low-risk patients, 13 had abnormal stress test results, defined as a summed score of at least 3. Of the 10 low-risk patients who underwent subsequent left heart catheterization, just 3 were found to have coronary artery disease, giving a diagnostic yield of 0.88%.

 
Many of these patients have a typical presentation and history of syncope that is noncardiac, yet they still go for a stress test.
 

Diagnostic yield wasn't much higher in the other 2 groups; it was 1.3% for the 234 intermediate-risk patients and 2.4% for the 127 high-risk patients. In contrast, the Cleveland Clinic's overall stress test yield performed for all indications is 33.0%.

"For folks who are not coming in with active chest pain, clearly the yield is incredibly low," Dr. Vasilevskis told Medscape Medical News. "Even in the positive ones, we don't know that's what caused their syncope. It could have been something else."

As expected, there was more 3-year mortality in the high-risk group than in the intermediate-risk and low-risk groups (20.0% vs 4.3% vs 2.9%; log-rank P < .0001). However, the annual mortality rate was not significantly different between patients with normal results on the stress test and those with abnormal results (2.3% vs 3.3%; log-rank P = .3).

More than half of all patients with abnormal test results did not undergo catheterization. Nonetheless, there was no difference in outcome between those who underwent left heart catheterization and those who didn't, Dr. Alraies noted.

Table. Causes of Syncope in the Study Cohort

Cause Percent
Idiopathic 35.0
Neurologic 19.3
Vasovagal 13.7
Pulmonary embolism or hypoxia 9.8
Arrhythmia 7.5
Anemia or hypovolemia 6.7
Hypoglycemia 4.1
Active ischemia or coronary artery disease 1.3

 

Both Dr. Alraies and Dr. Vasilevskis emphasized that these findings do not apply to a patient who comes in with chest pain, dyspnea, or other clear signs of a heart attack. However, stress testing isn't appropriate in those cases either, because they'll likely show changes on ECG and be sent straight to catheterization, Dr. Alraies told Medscape Medical News.

Patients who don't present so obviously but have a history of syncope, are elderly, or have another likely explanation — such as low blood glucose in the diabetic patient or dehydration in someone who has spent time outside in the summer — often end up undergoing inappropriate stress testing.

"Many of these patients have a typical presentation and history of syncope that is noncardiac, yet they still go for a stress test. This is a big chunk of patients for whom we're wasting money."

He advised going back to basics and doing a thorough history, physical exam, laboratory tests, and an ECG to ascertain risk factors.

"Use your clinical sense, the very basic tools. First and foremost is history, and history of syncope is most important," Dr. Alraies told Medscape Medical News.

He also recommended asking questions about the episode: When did it happen? How long were you unconscious? Has it happened before? Did you see black spots? The answers to these questions will point to the next appropriate step.

"We are doing extra things that are unnecessary because we don't have time to just sit and interview the patient properly," Dr. Alraies said.

Drs. Alraies and Vasilevskis agree that the low diagnostic yield even in the high-risk group suggests that current guidelines need to be re-examined.

"These data even call into question doing myocardial perfusion imaging for high-risk patients. Even they didn't get any benefit from perfusion testing," Dr. Vasilevskis pointed out. "They had more coronary disease, but the outcomes were the same."

Dr. Alraies concluded his presentation by stating that "reaffirmation and revision of the appropriateness criteria should be considered."

Dr. Alraies and Dr. Vasilevskis have disclosed no relevant financial relationships.

Circ Cardiovasc Imaging. 2013;6:384-391. Full text

Hospital Medicine 2013: Society of Hospital Medicine (SHM) Annual Meeting. Presented on May 18, 2013.

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