Each year in the United States nearly 6 million people experiencing the symptoms of a heart attack —usually chest pain—go to emergency departments. Because emergency room physicians often cannot reliably rule out the possibility of acute coronary syndrome , a substantial number of these patients are admitted to the hospital for observation. Acute coronary syndrome is a serious condition characterized by ischemia of heart muscle due to restricted blood flow, and it can manifest itself as a heart attack or unstable angina , a condition posing great risk of a heart attack. However, most admitted patients do not ultimately prove to have ischemia. On the other hand, a small but important number of patients initially discharged from the emergency department actually do have ischemia.

In a recent study in the Journal of the American Medical Association (JAMA), researchers found that incorporating a heart imaging procedure into the initial evaluation strategy of patients suspected of having a heart attack could help physicians more accurately establish which patients were, in fact, suffering from acute cardiac ischemia. This, in turn, helped to cut down unnecessary hospitalizations, without decreasing appropriate admissions of patients with acute ischemia.

About the Study

Researchers from seven medical centers and community hospitals studied 2475 adult patients who came to their emergency departments between July 1997 and May 1999 with chest pain or other symptoms of acute cardiac ischemia, but who had normal or inconclusive electrocardiogram (ECG) results. Patients with a history of myocardial infarction were excluded from the study because these patients often have abnormal resting blood flow patterns.

1260 of the patients (who made up the control group) were randomly assigned to receive whatever evaluation strategy was standard for that particular emergency department. The other 1215 patients had a standard evaluation supplemented with single-photon emission computed tomography (SPECT) myocardial perfusion imaging. In this imaging procedure, a small amount of radioactive tracer is injected into the circulatory system and viewed with a special camera to observe blood flow in and around the heart. The physicians then made decisions about whether to admit or discharge the patients, based either on the standard evaluation or on the standard evaluation plus SPECT results.

The primary endpoint of this study was whether the emergency department physicians made the correct initial decision to admit or discharge the patients, assuming that patients with acute ischemia should have been admitted and that patients without acute ischemia should have been discharged. This was determined by a final diagnosis arrived at for all patients through follow-up ECGs, measurement of cardiac enzyme levels, and follow-up stress testing. Study investigators, who were blinded to the randomization assignment and initial SPECT results, confirmed the final diagnosis and compared the appropriateness of the initial decisions for patients who had the SPECT scan and those who did not.

The Findings

Among patients with acute cardiac ischemia, there was no difference in the admission and discharge rates between patients who did and did not receive a SPECT scan. Among patients with acute myocardial infarction, 97% of patients who received a standard evaluation were hospitalized versus 96% of those who had a SPECT scan. Among those with unstable angina, 83% of patients who underwent a standard evaluation were hospitalized versus 81% who had a SPECT scan. None of these differences were statistically significant.

Among patients whose final diagnosis was not acute cardiac ischemia, doctors admitted 52% of the patients who had a standard evaluation and 42% of patients who had a standard evaluation supplemented with a SPECT scan. In retrospect, all admissions of patients without acute cardiac ischemia could be deemed unnecessary. In this group, the SPECT scan brought about a significant reduction of unnecessary admissions; a 10% absolute reduction and a 20% relative reduction.

The reduction in hospital admissions for patients without acute cardiac ischemia held true for men and women, younger and older patients, and patients with and without risk factors for coronary disease. In addition, hospitals with little or no experience using SPECT scans used the imaging procedure as effectively as facilities with more experience.

Overall, the study results were quite promising. However, because the participating centers each used their own standard evaluation procedures, the impact of SPECT imaging compared to the standard strategies was not clear. In addition, it is not known whether SPECT scanning would work as well in smaller or more rural hospitals because these types of facilities were not included in this study.

How Does This Affect You?

This study showed that SPECT imaging could be a promising new tool for emergency department physicians making admitting decisions about patients suspected of having a heart attack. For patients, this technology—if adopted—could mean fewer hospitalizations to rule out heart attacks. However, it remains to be seen how the added cost of routinely doing SPECT scans on every patient suspected of acute coronary syndrome measures up against the cost savings of fewer hospitalizations.

In any case, the usefulness of SPECT imaging or any other diagnostic procedure for acute coronary syndrome is contingent on getting to an emergency room as quickly as possible. If you think you are having a heart attack, call 911 immediately.

Symptoms of heart attack include:

  • Squeezing, heavy chest pain, especially with:
    • Exercise or exertion
    • Emotional stress
    • Cold weather
    • A large meal
  • Pain in the left shoulder, left arm, or jaw
  • Shortness of breath
  • Sweating, clammy skin
  • Nausea
  • Weakness
  • Loss of consciousness

Unusual symptoms of heart attack (may occur more frequently in women):

  • Stomach pain
  • Back pain
  • Confusion
  • Fainting