093 Ability of ST/HR index and ST/HR hysteresis during exercise testing to predict significant ischemia assessed by G-SPECT imaging

Purpose Heart rate adjustment of exercise-induced ST-segment depression (ST/HR index and ST/HR hysteresis) has been suggested as an accurate predictor of the presence of a coronary artery disease. Its powerful predictive value for proven coronary artery stenosis is now accepted. The objective of our study was to investigate the sentitivity and specificity of computerized ST/HR index and ST/HR hysteresis to detect significant ischemia. Methods We used a cross-sectional analysis of exercise test and myocardial perfusion stress-rest SPECT data. The study population comprised 710 consecutive patients referred for myocardial perfusion imaging. The threshold of significant ischemia was set above 10% reversibility hypoperfusion area from entire surface of left ventricle using gated-SPECT image analysis (QGS). Diagnostic performance of ST/HR index and ST/HR hysteresis was assessed by receiver operating characteristic (ROC) curve. Results Crude ST/HR hysteresis showed at the same 70% specificity, a sensitivities of 56% and 57%, respectively. Diagnostic performance of ST/HR hysteresis seems slightly better than ST/HR index (AUC = .668 vs .654) with the following cut points .038 mV and 1.625 μV/bpm. Adjusting these variables to body mass index does not improve the diagnostic performance. Combining an independant clinical judgement in the model yields a moderate increase of the diagnostic accuracy the prediction only for ST/HR index as suggested by the AUC (.688). Conclusions ST/HR index and ST/HR hysteresis have a good capability to detect a significant myocardial ischemia evaluated by SPECT, which has therapeutic implications.