Electrocardiology 2014 - Proceedings of the 41 st International Congress on Electrocardiology 155 Impact of the Heart Rate on Normal STT Integral Body Surface Potential Maps 1 J. Svehlikova, 2 M.Kania, 2 R. Maniewski, 1 M. Tysler 1 Institute of Measurement Science SAS, Bratislava, Slovakia, 2 Nalecz Institute of Biocybernetics and Biomedical Engineering PAS, Warsaw, Poland Email: jana.svehlikova@savba.sk Abstract. We suggested a method for localization of ischemic lesions from difference integral body surface potential maps (IBSPMs) computed by subtraction of IBSPM without manifestation of ischemia from the IBSPM during ischemia that can be obtained at rest and during the stress test. In this work the possible changes in IBSPMs of healthy subjects with increasing HR were studied. BSPMs were measured during the stress test in 12 subjects (age 30-53). During the test, the HR of each subject increased from the rest value up to the value higher than 85% of the value (220-age) at the top of the load. The IBSPMs were computed for 5 HR values up to the highest one. Correlation and power of IBSPMs at subsequent values of the HR were evaluated. The correlation coefficient between the IBSPM at rest and IBSPM at the top HR was higher than 70%. The root-mean-square value of the IBSPM at the top HR varied from 43% to 128% of the root-mean-square value of the IBSPM at rest. The existence of remarkable differences in STT IBSPMs at rest and at stress in healthy subjects should be considered when the IBSPMs during the stress test are evaluated for ischemic patients. Keywords: STT integral body surface potential maps, stress test, heart rate, local repolarization changes 1. Introduction Local repolarization changes (e.g. during ischemia) are reflected in integral body surface potential maps (IBSPMs) of the STT interval [1]. In previous simulation study we suggested a method for identification and localization of local ischemic lesions from difference IBSPMs using the inhomogeneous torso model and the geometrical model of heart ventricles [2], [3]. The activation propagation was simulated by cellular automaton and ischemic lesions were modelled by shortening the action potential duration by 20% in selected areas of the ventricles. The difference IBSPM was computed by subtraction of IBSPM without manifestation of ischemia from the IBSPM during ischemia. It was supposed that for real patients such data can be obtained from ECG measurements performed before and during the stress test. However, in the simulation study all changes in IBSPMs were considered as the effect of repolarization changes. During a real stress test the HR considerably increases, so the question is how to compute the difference IBSPM correctly if each member of the subtraction is computed for significantly different HRs, thus for a different time interval. The aim of this work was to study the behavior of IBSPMs in dependence on the HR for subjects with no heart disease history, whether we can suppose, that the changes in IBSPM during the stress test reflect only pathological repolarization changes or there are some changes that can be considered physiological. 2. Subject and Methods Multichannel ECG recordings with 64 leads were performed during the stress test on 12 volunteers (age 30-53) with no heart disease history in Medical University Warsaw as it is described also in [4]. BSPMs from 64 measured leads were computed. Simultaneously, the 12-lead ECG was measured to evaluate the measured data in a standard way. During the test,