Impact of technetium-99m sestamibi imaging on the emergency department management and costs in the evaluation of low-risk chest pain.

OBJECTIVES: To assess the impact of rest sestamibi scanning on emergency physicians' (EPs') diagnostic certainty and decision making (as assessed by the hypothetical disposition of patients) for 69 consenting stable patients with suspected acute cardiac ischemia and nondiagnostic electrocardiograms. The resultant impact on costs was examined as a secondary outcome. METHODS: Patients with suspected acute cardiac ischemia were injected with 25 mCi of sestamibi within two hours of active pain in one of three emergency department study sites. The probability of acute myocardial infarction (AMI) and unstable angina (UA), and hypothetical disposition decisions were recorded immediately before and after physicians were notified of scan results. Changes in disposition were classified as optimal or suboptimal. For the cost determinations, a cost-based decision support program was used. RESULTS: For the subgroup found to be free of acute cardiac events (ACEs) (n = 62), the EPs' post-sestamibi scan probabilities for AMI decreased by 11% and UA by 18% (p < 0.001 for both conditions). In seven patients with ACEs, the post-scan probabilities of AMI and UA increased, but neither was statistically significant. Scan results led to hypothetical disposition changes in 29 patients (42%), of which 27 (93%) were optimal (nine patients were reassigned to a lower level of care, two to a higher level, and 16 additional patients to "discharge-home" status). The strategy of scanning all patients who were low to moderate risk for acute cardiac ischemia would result in an increase of direct costs of care of $222 per patient evaluated, due to added cost of sestamibi scanning. CONCLUSIONS: Sestamibi scanning results appropriately affected the EPs' estimates of the probability of AMI and UA and improved disposition decisions. Scanning all low-risk patients would likely be associated with increased costs at this medical center.

Pretest probability assessment for selective rest sestamibi scans in stable chest pain patients.

The objective of this study was to determine whether pretest probability assessments permit more selective testing of chest pain patients with technetium-99m sestamibi scanning. Pretest probabilities of cardiac ischemia were measured both objectively (Acute Cardiac Ischemia Time-Insensitive Predictive Instrument [ACI-TIPI]) and subjectively (physician's estimate of the probability of unstable angina). Two groups were defined: patients whose postsestamibi scan led to a "downgrade" of the intensity of monitoring and those that resulted in no change in monitoring intensity. Sixty-five patients met study criteria; 25 had a disposition downgrade and 40 had no change. Pretest ACI-TIPI scores were similar in the two groups (29% +/- 18% versus 27% +/- 11%, mean +/- standard deviation; P = .95) as were the physician's assessment of unstable angina (39% +/- 22% versus 40% +/- 24%; P = .75). Objective or subjective pretest probabilities are not significantly different in patients who are likely to have their disposition altered by sestamibi scanning.

Resting sestamibi imaging for the prognosis of low-risk chest pain.

OBJECTIVE: To assess the prognostic value of resting Tc-99m sestamibi scanning for adverse cardiac events (ACEs) in ED chest pain patients with a low probability of acute cardiac ischemia (ACI). METHODS: Sixty-nine consenting, hemodynamically stable patients with chest pain and a nondiagnostic electrocardiogram received an injection of 25 mCi of sestamibi during or within two hours of active pain. Scans were interpreted locally by a nuclear cardiologist or radiologist. Interrater reliability was assessed. ACEs of myocardial infarction (MI), death, or revascularization were assessed during the index hospitalization and over a one-year follow-up period. RESULTS: For ACEs, rest scanning with sestamibi had a sensitivity of 71% (95% CI = 0.33 to 0.97), a specificity of 92% (95% CI = 0.82 to 0.97), and an accuracy of 90% (95% CI = 0.87 to 0.99). The positive predictive value was 50% (95% CI = 0.19 to 0.82) and the negative predictive value was 97% (95% CI = 0.87 to 0.98). Sestamibi scanning was highly discriminating, with 62% of patients with positive scans but only 3% with negative scans having ACEs (p<0.001, log rank test). CONCLUSION: In patients with low-risk chest pain, sestamibi scanning has good specificity and moderate sensitivity for ACEs over a 12-month period.

Dose-related response of centrally administered epinephrine on the change in aortic diastolic pressure during closed-chest massage in dogs.

The current recommendation of the American Heart Association is to give 0.5 to 1.0 mg (7.5 to 15 micrograms/kg in a 70-kg man) of epinephrine intravenously every five minutes during cardiac arrest. The optimal dose of epinephrine to augment the aortic diastolic pressure (ADP) is not known. The effect of various doses of central bolus epinephrine on the ADP during closed-chest massage was studied. A group of 25 large dogs was divided equally into five groups: control and 15, 45, 75, and 150 micrograms/kg. After three minutes of cardiac arrest, closed-chest massage was initiated, and the study drug was given two minutes later. The ADP and right atrial pressures were monitored for 15 minutes. Changes in ADP peaked at two minutes after injection in all groups receiving epinephrine, and the drop in ADP over time noted in the control group was prevented by increasing doses of epinephrine. Among the groups receiving epinephrine, however, there was no difference in the absolute ADP and diastolic coronary perfusion pressure.