CT shines as cardiac triage tool in the ER

Multislice CT may someday save thousands of patients the worry and bother of a hospital stay to determine whether their chest pain is caused by acute cardiac syndrome.

Preliminary results from two studies provided convincing evidence that adding coronary artery CT angiography improves initial triage of patients normally evaluated with ECG and enzyme markers. The studies were presented Tuesday at the RSNA meeting.

Inaccurate testing for chest pain costs hundreds of millions of dollars in unnecessary hospitalization, according to Dr. Udo Hoffmann, director of cardiac CT research at Massachusetts General Hospital. Despite conservative practice, initial clinical and lab examinations miss 1% of acute cardiac syndrome (ACS) cases. Misdiagnosis constitutes 20% of emergency department malpractice costs, he said.

Hoffmann's study of 40 nonconsecutive patients with chest pain suggests that 64-slice CT is well suited for the role. CT findings were positive in seven patients. At least one significant stenosis was detected. The presence of stenosis was excluded in 26 patients, and results were inconclusive for seven patients. Five patients developed ACS during hospitalization. Thirty-five patients did not have ACS.

Investigators shifted from a 16-slice to a 64-slice device midway through the trial. The superior image quality made possible with 64-slice CT compared to 16-slice CT was reflected in the 100% sensitivity to ACS demonstrated with the 64-slice scanner, Hoffmann said. Specificity was 88%. Negative predictive value was 100%.

In 20% of the patients who underwent coronary angiography, CT correctly detected the presence of stenosis in four patients and ruled out a stenosis in two patients. Overall, only seven of the 30 patients would have been admitted to the hospital without missing a patient with ACS. Patients would have been discharged an average of 22 hours earlier because of the CT evaluation, and two angiograms would have been avoided, Hoffmann said.

Results from a similar trial conducted by Dr. Tamar Gaspar at Carmel Medical Center in Haifa, Israel produced equally encouraging findings. In her study of 54 patients who entered the emergency department with chest pain of unknown etiology, 64-slice CT altered the initial evaluation based on ECG and enzyme biomarkers in almost half of the patients.

Planned hospitalization was canceled for eight of 24 patients, and nine recommended interventions were postponed. However, coronary artery disease was found in four patients who were cleared on their clinical findings. In three cases, the CT results were confirmed during intervention. No adverse evidence was identified among any of the subjects after six months

"On a preliminary basis, it has been shown it is possible to study these patients in the emergency room on an outpatient basis," said session co-moderator Dr. Martin Lipton. "It is possible to determine whether they have significant stenosis of one or more vessels using 64-slice CT. That means the patients can either go home knowing they don't have coronary artery disease, or they can be admitted promptly to the hospital and follow the normal pattern of evaluation for ischemic heart disease."

Large randomized trials are needed to confirm these results before they may be integrated into routine practice, according to Hoffmann. Expanded protocols that include evaluation of plaque, for example, are also under consideration, and may extend the use of CT to triaging patients for suspected myocardial infarction, he said.