IMPROVED EXERCISE TEST ACCURACY USING DISCRIMINANT FUNCTION-ANALYSIS AND RECOVERY ST SLOPE

The objective of the study was to optimize the accuracy of the exercis e test for predicting the presence of significant angiographic coronar y artery disease. A retrospective analysis of stored digital exercise electrocardiographic data on 147 men who had undergone exercise testin g and cardiac catheterization was performed. With significant coronary artery disease defined as less-than-or-equal-to 70% stenosis, 95 pati ents had one or more vessel (s) diseased. None were receiving digoxin, had a myocardial infarction or previous coronary artery bypass graft, or exhibited left bundle branch block, left ventricular hypertrophy, Q waves, or ST depression on their resting electrocardiogram. Analysis was performed using the authors' averaging and measurement software a t rest and at each 30 seconds throughout the exercise and recovery in leads II, V2, and V5. Discriminant function analysis was used to analy ze pretest variables, as well as hemodynamic and electrocardiographic changes and symptoms during exercise. A discriminant function score wa s developed and compared to other treadmill scores. The setting was a 1,000 bed Veterans Affairs Medical Center (Long Beach, CA). Discrimina nt function analysis chose age, smoking status, presenting chest pain characteristics, and lead V5 ST slope in recovery to have independent power for separating those with and without coronary artery disease. A discriminant function score using these four variables was used to fo rm a receiver operating characteristics curve (and derive receiver ope rating characteristics curve areas) for comparison to other exercise t est methods and scores: (discriminant function score = .81; slope 3.5 minutes into recovery in lead V5 = .73; traditional ST amplitude metho d = .72; ST60/HR index (amplitude of ST depression 60 ms after the J p oint/delta heart rate) = .66; traditional ST amplitude/HR index (tradi tional method/delta heart rate) = .75; Hollenberg score = .68; Hollenb erg areas only = .66; and ST integral = .66. Receiver operating charac teristics curve analysis revealed a trend for the discriminant functio n score to be superior to all other measurements and scores. Recovery ST slope in lead V5 performed as well as or better than all other elec trocardiographic criteria or treadmill scores except for the authors' discriminant function score.