Are you using this new cardiac diagnostic test?

Find out if low-risk patients can go home safely

A 39-year-old man. Chest pain atypical for angina or myocardial infarction (MI). A completely normal electrocardiogram (ECG). When he arrived at the ED at Boston-based Tufts-New England Medical Center, this patient appeared to be at very low risk for an acute coronary syndrome diagnosis.

However, instead of being admitted or sent home, the man received acute myocardial perfusion imaging, a noninvasive radionuclide imaging test. The test revealed a pronounced perfusion defect in the inferolateral wall of the left ventricle — an area of the heart not clearly seen by the ECG.

The patient actually was having an MI and went straight to the cath lab for emergency angioplasty, reports James E. Udelson, MD, the facility’s associate chief of cardiology.

Without this additional imaging test, the man probably would have been admitted for observation, and all the cardiac enzymes would have come back positive, Udelson explains. "He would have had a good-sized MI and may or may not have been referred for cardiac catheterization the next day," he says. "Because he was treated much earlier, we were able to salvage a lot of heart that otherwise might have been damaged."

Use of test is growing

Are you using acute myocardial perfusion imaging in your ED? According to a new study, this diagnostic test can improve treatment of ED patients with suspected acute myocardial ischemia.1

Not many EDs are using this potentially lifesaving tool yet, but the number is increasing, says Udelson, the study’s principal investigator.

"Missed MI is one of the most common causes of litigation against ED personnel, and this test may also facilitate an earlier diagnosis in such patients," he underscores.

The goal is to make better decisions about who can safely go home from the ED, Udelson explains. "EDs are using this in low-risk patients who need more information to help decision makers decide what to do," he says.

ED physicians may think that the patients probably are not having an MI, but they are not sure enough to send them home, Udelson explains. "This test will help push that decision one way or the other," he says.

There is a huge problem with admitting patients for observation who don’t really need it, Udelson says. "Many hospitals are so full that patients will end up spending the night in the ED," he says. "This ties up beds that ED patients could go to, so the whole system backs up."

Here are items to consider:

• Understand how the test is used.

Nuclear imaging of the myocardium provides additional data during stress testing, with resting images compared with stress images, explains Steven D. Glow, RN, MSN, FNP, CEN, EMT-P, nursing faculty at Salish Kootenai College in Pablo, MT, and ED nurse at Community Medical Center in Missoula, MT. If resting images reveal an area that is not perfused, this provides evidence of myocardial infarction, he says.

If resting images are normal and stress images show decreased perfusion, this area of the heart is possibly being supplied by a narrowed coronary artery, says Glow. "Such data suggest the patient may be a candidate for invasive or surgical repair of the narrowed artery," he says.

If resting and stress images are normal, there is no evidence of significant narrowing of the coronary arteries, says Glow. "Remember that, even in the absence of significant narrowing, coronary artery vasospasm still can result in chest pain and ischemia," he says.

By implementing resting imaging in the ED, a more informed decision can be made about whether to admit patients with suspected MI, says Glow. These data would be used to supplement current diagnostic data including 12-lead ECG and cardiac enzymes, he says.

• Educate patients.

You’ll need to educate patients about this diagnostic tool, says Glow. He gives the following example: The patient should be informed that the ECG and first set of enzymes were normal, but an additional test is needed to determine if there has been any damage to the heart muscle.

The ED nurse would explain to the patient what will happen next, says Glow, who suggests you convey the following information: "A nuclear medicine technician from the medical imaging department will come and give you an injection of a short-acting radioisotope. You then will be taken to the nuclear imaging department where they will lay you on a table while a radiation sensor is passed over your chest. A computer will generate images that will be read by the radiologist, nuclear medicine physician, or cardiologist. The results will be used by the ED physician in consultation with the cardiologist to determine whether or not to admit you for further testing and treatment."

Glow says you should be ready for these common questions asked by patients:

  • "Will I feel anything after the injection?" (No.)
  • "Am I a hazard to others?" (No.)
  • "How long does the radiation last?" (Only a short time: fewer than six hours.)
  • "Should I take any special precautions after the test?" (No.)
  • "If the test is negative, does that mean I’m OK?" (The test may not reveal if you have narrowing of the heart arteries or other risk factors for a heart attack. It is important to follow up with the doctor to whom we are referring you.)

Glow suggests discussing risk factor modification with the patient at this point. If the index of suspicion is high enough to warrant nuclear imaging of the myocardium during an ED stay, patients should be instructed to follow-up for a complete stress test, he notes. Most cardiologists would prefer to schedule the stress images as soon as possible after the resting images, or else the resting images may have to be repeated, Glow adds.

• Understand that patients who are the most appropriate candidates for this test are low-risk.

ED nurses sometimes are uncomfortable with transporting potentially unstable patients for this diagnostic test, Udelson says. "But if you select the patients properly, this is generally a low-risk group," he says. "In fact, the majority of these scans are normal."

Reference

1. Udelson JE, Beshansky JR, Ballin DS, et al. Myocardial perfusion imaging for evaluation and triage of patients with suspected acute cardiac ischemia. JAMA 2002; 288:2,698-2,700.

Sources

For more information on myocardial perfusion imaging, contact:

Steven D. Glow, RN, MSN, FNP, CEN, EMT-P, Nursing Faculty, Salish Kootenai College, P.O. Box 117, 52000 N. Hwy 93, Pablo, MT 59855. Telephone: (406) 275-4922. Fax: (406) 275-4806. E-mail: steve_glow@skc.edu.

James E. Udelson, MD, Division of Cardiology, Tufts-New England Medical Center, 750 Washington St., Box 70, Boston, MA 02111. E-mail: judelson@Lifespan.org.