VARIANCE CARDIOGRAPHY FOR EMERGENCY DEPARTMENT EVALUATION OF CHEST PAIN PATIENTS

Objective: To determine the test performance of 24-lead variance cardi ography (VC), an ECG technique that measures QRS morphologic variabili ty, for ED evaluation of chest pain associated with coronary artery di sease (CAD). Methods: A prospective, single-blind study of VC was perf ormed in a community teaching hospital ED. All chest pain patients (>3 0 years of age) who, after initial emergency physician evaluation, wer e believed to have pain of potential cardiac etiology and were admitte d to the hospital were eligible. Exclusion criteria included obvious n oncardiac etiology for discomfort, bundle-branch block, atrial fibrill ation, and incomplete subsequent cardiac evaluation. After initial eva luation and stabilization, VC was obtained. The numerical output of VC was a CAD index (CADI). Serum myoglobin and creatine kinase (CK)-MB l evels were obtained at the time of presentation and after one, two, an d six hours. Hospital records were reviewed to determine final diagnos is and in-hospital evaluation results. Results: Fifty-two of 75 eligib le patients had complete data. Final diagnoses were as follows: 27/52 (52%), noncardiac; 13/52 (25%), acute myocardial infarction (AMI); and 12/52 (23%), unstable angina due to CAD. Twenty-three percent (12/52) of the patients had CADIs <75. Eleven of these were found to have non cardiac origins for their chest pain. The twelfth patient had a 12-lea d ECG revealing AMI and had been given thrombolytic therapy with subse quent reperfusion prior to VC. Using a CADI <75 as the cutoff for a ne gative study, VC alone had a negative predictive value of 92%, a sensi tivity of 96%, a positive predictive value of 60%, and a specificity o f 41%. Conclusion: A CADI <75, irt addition to clinical impression and initial ECG, may identify chest pain patients who do not have signifi cant CAD. Further prospective assessment of VC is warranted.