Echocardiography, perfusion imaging identify infarctions with equal accuracy
SPECT myocardial perfusion imaging and echocardiography are equally useful when it comes to identifying patients with symptoms of myocardial infarction, according to researchers at Virginia Commonwealth University.
Their study assessed 141 patients considered at low to moderate risk of suffering a heart attack who underwent echocardiography or gated myocardial perfusion imaging with technetium-99m.
Researchers considered an MPI study positive if it revealed a perfusion defect associated with abnormal wall motion or thickening. Positive echocardiograms were those identifying segmental wall motion abnormalities or an ejection fraction of less than 40%.
Both modalities showed high sensitivity in identifying myocardial infarction in the emergency department. Echocardiography had a sensitivity of 91%, compared with 89% for MPI.
"Given the similar diagnostic accuracy between the two techniques, logistical issues and local expertise should be more important for determining which to use in the ED," said Dr. Michael C. Kontos, an assistant professor of cardiology at VCU's Medical College of Virginia.
The similar sensitivities give imagers leeway to make the most of each modality's advantages, Kontos said. Echocardiography, for instance, can provide structural and functional data, such as valvular abnormalities, that can have important prognostic information and can indirectly identify other causes for chest pain, such as pericarditis and pulmonary embolism. It is also preferable for patients in whom information is needed immediately. But echo has limits.
"People with a poor echocardio window or who are overweight may not be suitable for echo reading," said Dr. Karen Kurdziel, medical director of VCU's molecular imaging center.
Many patients presenting with myocardial infarction symptoms are overweight, diminishing the diagnostic accuracy of echocardiography, Kurdziel said. Other potential limitations include availability of qualified personnel after hours. Emergency departments need to have an appropriately trained echocardiography technologist and a cardiologist or radiologist to read the echocardiogram.
"That's going to be critical to get the sensitivity required, because echocardiography is very operator-dependant," she said.
