on a VerifyNow (Accumetrics) device. Aspirin resistance was defined by an aspirinresistance unit (ARU) value �550.

Results: Prevalence of aspirin resistance at all sites combined averaged 14% with a95% confidence interval of 11-17%. There was no correlation between age or sex andresistance to aspirin, but African American and Hispanic patients showed significantlyhigher rates of aspirin resistance (p�0.03). Patients with current or past drug abusewere more likely to exhibit aspirin resistance (p�0.01). A history of congestive heartfailure (CHF) was associated with increased risk of aspirin resistance (p�0.03), as wasa final ED diagnosis of CHF exacerbation (p � 0.001). There was no significantdifference in the rate of aspirin resistance between patients on outpatient aspirintherapy and those who received their first dose in the ED (p�0.06).

Conclusion: Aspirin resistance is a prevalent condition among patients whopresent to the ED with chest pain. Certain factors such as race and history of CHFincrease the relative risk of aspirin resistance. Aspirin resistance testing may be animportant adjunct to the acute assessment of these patients and may be helpful inoptimizing anticoagulation therapies.

6 Discordant Cardiac Biomarkers: Frequency and Outcomes inEmergency Department Patients with Chest Pain

Storrow AB, Lindsell CJ, Han JH, Slovis CM, Miller KF, Gibler WB, Hoekstra JW,Peacock WF, Hollander JE, Pollack CV, on behalf of the EMCREG iTRACSInvestigators/Vanderbilt University, Nashville, TN; University of Cincinnati,Cincinnati, OH; Wake Forest, Winston-Salem, NC; The Cleveland ClinicFoundation, Cleveland, OH; University of Pennsylvania, Philadelphia, PA;Pennsylvania Hospital, Philadelphia, PA

Study Objective: We evaluate specific problematic associations among cardiacbiomarkers (CKMB with normal CK, or discordant CKMB and cardiac troponin)with the presence of acute coronary syndromes (ACS) in emergency department (ED)chest pain patients.

Methods: This was a secondary analysis of a prospective registry. Data wereobtained from the multi-center Internet Tracking Registry of Acute CoronarySyndromes (i*trACS), which included 17,713 ED visits for possible ACS betweenJune 1999 and August 2001. First visits and first ED cardiac biomarker results fromthe nine sites, 8 in the US and 1 in Singapore, were included. Subjects were excludedfor incomplete information or an initial ECG consistent with ST-segment elevationmyocardial infarction. Acute coronary syndrome was defined by DRG codeindicating myocardial infarction, positive invasive or non-invasive diagnostic testing,revascularization or death during hospitalization or within 30-days.

Results: Of 8,769 eligible patients, 1,614 (18.4%) had ACS. The CKMB andcTn results were discordant in 7% of patients (CKMB�/cTn�, 4.9%, CKMB�/cTn� 2.1%), while elevated CKMB with normal CK occurred in 239 (3.1%)patients. Compared to the reference groups of CKMB� / CK(� or �) and CKMB�/ cTn�, the unadjusted odds ratios for ACS were:

Conclusion: Among the spectrum of ED patients with chest pain, an elevatedCKMB with a normal CK identifies patients at increased risk for ACS. Similarlyan elevated troponin, regardless of CKMB level, and an elevated CKMBregardless of troponin level identifies patients at higher risk for ACS than thosewith uniformly normal cardiac biomarkers. Discordant marker sets should berecognized as true predictors of risk, rather than dismissed as “false” elevations inone of the markers.

7 Utility of the Charlotte Criteria and the Liatest D-DimerAssay in the Exclusion of Pulmonary Embolism in theEmergency Department

Mason PE, Gonzalez MG/Wilford Hall Medical Center and The San AntonioUniformed Services Health Education Consortium, Lackland AFB, TX

Background: The Charlotte criteria are objective questions that identify a groupof patients who can safely be evaluated for pulmonary embolism (PE) using a d-dimerassay. Those deemed “safe” by the criteria have a pre-test probability of disease of

13%. The Liatest® turbidimetric d-dimer assay has a LR- of 0.04 - 0.16. Patientsdeemed safe by the Charlotte criteria that also have a negative Liatest® should have apost-test probability of PE of two percent or less.

Study Objective: The objective of this study is to determine if a combination ofthe Charlotte criteria and the Liatest® can exclude PE in the emergency departmentwith a false negative rate of two percent or less.

Methods: This was a prospective, observational study of patients having a d-dimer level measured in the emergency department to exclude pulmonary embolism.Patient demographics, d-dimer values and the five components of the Charlottecriteria were recorded prospectively on standardized data collection sheets. The studydid not dictate the diagnostic strategy, treatment decisions or disposition.

Ninety days after enrollment each patient’s electronic medical record wasreviewed for new diagnosis of pulmonary embolism or imaging studies revealingpulmonary embolism. If the diagnosis was not made during this record review thepatient was contacted by telephone and a standard questionnaire was administered todetermine if they had received the diagnosis of pulmonary embolism since enrollingin the study.

Results: One hundred-twenty nine patients have been enrolled, 82 of which havecompleted the 90 day follow-up period. Three enrolled patients were lost to follow upleaving data on 79 patients for analysis. Four patients [5%] were diagnosed with PE,all at the time of study entry. Four patients died during the 90 day follow-up period,all of non-PE causes. The mean age of study participants was 53 years and 62% werefemale.

The median d-dimer level was 0.44 [Range � 0.22 - 20.0] ng/ml. Fifty-sixpercent of d-dimer measurements fell below 0.5 ng/ml and were considered negative.No patient with a normal d-dimer had a PE yielding a sensitivity of 100%. A positived-dimer had a specificity of 57%.

Of the 78 study patients, 72% were categorized as “safe” by the Charlotte criteria;none of these patients had a PE. The combination of a “safe” designation by theCharlotte criteria and a negative d-dimer gave a sensitivity of 100%.

Conclusions: Emergency department patients in whom the diagnosis of PE isconsidered can be evaluated using the Charlotte criteria and the Liatest®

turbidimetric d-dimer assay. In this small study, a d-dimer less than 0.5 ng/ml inpatients deemed “safe” by the Charlotte criteria yielded no false negative results.

8 Results From the Rescue-ACS Study: An ED-Based Study ofAnticoagulation Therapy in Patients with Non-St-Segment-Elevation Acute Coronary Syndrome

Pollack CV, Hollander JE, Hoekstra JW, Emerman C, Spinler SA/PennsylvaniaHospital, Philadelphia, PA; Hospital of the University of Pennsylvania,Philadelphia, PA; Wake Forest University, Winston-Salem, NC; The ClevelandClinic, Cleveland, OH; University of the Sciences in Philadelphia, Philadelphia,PA

Background: Antithrombin therapy (AT) is often initiated empirically in the EDfor patients with non-ST-segment elevation acute coronary syndrome (NSTE ACS).Options for treatment include unfractionated heparin (UFH), low-molecular-weightheparins such as enoxaparin (ENOX), and direct thrombin inhibitors such asbivalirudin. Studies such as SYNERGY have highlighted the possible adverseconsequences of “switching” or “stacking” AT, as sometimes occurs wheninterventional cardiologists prefer to use different AT from that started in the EDwhile the patient is being medically managed.

Methods: An industry-funded, randomized, open-label study, RESCUE-ACS,was developed to compare ENOX and UFH initiated in the ED for patients withNSTE ACS and a TIMI Risk Score � 4, who were unlikely to undergo diagnosticangiography and interventional management for the first 24-48 hours ofhospitalization. Primary results were to be the 30-day triple ischemic endpoint (death,myocardial infarction, urgent revascularization) plus TIMI major bleeding.Telephonic follow-up for ischemia was planned at 6 months. The trial intended toenroll 3,000 eligible patients.

Results: The trial was terminated prematurely due lower-than-expected eventrates and slower-than-expected accrual. Of 1,131 patients enrolled, 560 wererandomized to receive ENOX and 571 to UFH. Patients randomized to ENOX wereolder and were more likely to undergo PCI during the index hospitalization (24.6%vs 13.7% for UFH, p � 0.0260); otherwise the baseline and managementcharacteristics of the two groups were similar. In this open-label study, 9% of patientsrandomized to ENOX were switched to UFH in a violation of protocol, most (82%)at the time of intervention. Only 0.6% of patients randomized to UFH also receivedENOX. In the ITT population, patients randomized to ENOX were more likely to

Research Forum Abstracts

Volume , . : October Annals of Emergency Medicine S3