document: The use of the SPSA method in ECG analysis The classification , monitoring , and compression of electrocardiogram -LRB- ECG -RRB- signals recorded of a single patient over a relatively long period of time is considered . The particular application we have in mind is high-resolution ECG analysis , such as late potential analysis , morphology changes in QRS during arrythmias , T-wave alternants , or the study of drug effects on ventricular activation . We propose to apply a modification of a classical method of cluster analysis or vector quantization . The novelty of our approach is that we use a new distortion measure to quantify the distance of two ECG cycles , and the class-distortion measure is defined using a min-max criterion . The new class-distortion-measure is much more sensitive to outliers than the usual distortion measures using average-distance . The price of this practical advantage is that computational complexity is significantly increased . The resulting nonsmooth optimization problem is solved by an adapted version of the simultaneous perturbation stochastic approximation -LRB- SPSA -RRB- method of J. Spall -LRB- IEEE Trans . Automat . Contr. , vol . 37 , p. 332-41 , Mar. 1992 -RRB- . The main idea is to generate a smooth approximation by a randomization procedure . The viability of the method is demonstrated on both simulated and real data . An experimental comparison with the widely used correlation method is given on real data
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