Michał KANIA, Małgorzata FERENIEC, Roman MANIEWSKI OPTIMAL LEADS SELECTION FOR ISCHEMIA DIAGNOSIS.

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1 XI Conference "Medical Informaics & Technologies" - 26 Michał KANIA, Małgorzaa FERENIEC, Roman MANIEWSKI body surface poenial mapping, myocardial infarcion, discriminan index OPTIMAL LEADS SELECTION FOR ISCHEMIA DIAGNOSIS. Absrac: This sudy aimed o idenify he opimal leads locaions in body surface poenial mapping (BSPM) o deec acue ischemia, e.g. myocardial infarcion. Mehods: We sudied 16 healhy conrols and 12 myocardial infarcion paiens. The capabiliy of a recording locaion o separae he groups was quanified by Discriminaion Index (DI). I was calculaed by subracing he mean signal ampliude of he normal group from ha of he paien group during he STT segmen and dividing he resuling ampliude difference by he corresponding sandard deviaion wihin all subjecs. Resuls: Locaions of opimal recording sies are mosly on he precordial area and some poins are scaered on he righ back or lef low ches. Conclusion: The BSPM lead locaions for effecive deecion of myocardial infarcion by evaluaion of he ST segmen as well as he T- wave were proposed. These locaions are mosly ouside he convenional 12-lead ECG recording sies. 1. INTRODUCTION Sandard 12 lead ECG recording is a widely used mehod o diagnose ischemic hear disease and is acue phase myocardial infarcion. Despie undeniable imporance, he aforemenioned mehod does no always allow o ge complee informaion abou elecrical aciviy of he cardiac muscle. The usage of he increased number of ECG leads significanly exends his knowledge faciliaing diagnosis of differen cardiac diseases [1-4]. Unforunaely, muli-lead ECG sysems are oo cumbersome o be used in clinical condiions. Therefore finding he bes leads placemen which capure he mos ECG signal energy is of grea imporance. Many works in ha direcion have been done during las decades e.g. [-11]. There are wo differen rends in lieraure of opimizing number of ECG leads and is locaions on he surface of he body. One of hem focuses on finding he smalles number of leads, which allow for he bes approximaion of ECG poenials disribuion on he surface of he body, received from sysem wih large (more han 1) number of leads. This rend is represened mainly by Barr [] and Lux [6,7]. The oher rend of seeking opimal number of ECG leads and is bes spaial locaon is conneced wih he diagnosis of paricular cardiac disease. The represenaive of his rend is firs of all Kornreich [8-11], who searches minimal number and opimal leads locaion allowing o increase sensiiviy and specificiy of diagnosic mehods using chosen leads subses. Insiue of Biocyberneics and Biomedical Engineering, Ks. Trojdena 4, 2-19 Warsaw, Poland.

2 164 Michał Kania e al. / XI Conference "Medical Informaics & Technologies" MATERIAL AND METHODS The preliminary analysis of HR-ECG in he repolarizaion period was carried ou on he se of daa of 16 normal subjecs and 12 pos-infarcion paiens. The examinaion was carried ou in he elecrically shielded room using he high-resoluion ECG measuremen sysem. The sysem consiss of 64 low noise amplifiers wih 16-bi A/D converers (BIOSEMI, he Neherlands). Digial signals sampled wih frequency of 496 Hz were ransformed o he serial opical forma and hen were ransferred o he compuer via an opical fiber. The daa acquisiion was conrolled by he LabView measuremen sofware. To improve he signal-o-noise raio he cross-correlaion averaging and filering mehods were applied o 64 signals obained from he lead posiion on he orso according o he Universiy of Amserdam lead sysem. The posiions of leads are based on wo 32 leads subses seleced by Lux [6-7] from 192 ECG leads by sequence selecion algorihm [6] (Fig. 1). In BSPM daa baseline drif was eliminaed wih he use of he high-pass filer (f=.33hz) and he sampling frequency was decreased o 1 khz (decimaion filer). To obain averaged ECG signals he cross-correlaion funcion was calculaed beween manually chosen paern of QRS complex and he whole signal. For alignmen and averaging beas wih correlaion coefficien higher han.98 were chosen. Addiionally, beas wih higher values of noise were eliminaed. Fig. 1 The 61 lead sysem used in he analysis.

3 Michał Kania e al. / XI Conference "Medical Informaics & Technologies" ANALYSIS To find he bes locaion of 12 and 16 leads form all 61 leads o disinguish he conrol group and he group of paiens afer myocardial infarcion, he parameer called Discriminan Index (DI) proposed by Kornreich [8] was used. DI parameer was calculaed for every ime insan and in every ECG lead for STT segmen. STT inervals were normalized in boh groups o 2 samples, and hen parially inegraed i.e. every 1 samples were inegraed, so 2 segmens were received. Then he mean STT volage in each group, and in each elecrode was calculaed: k V _ STTk, i= V _ STT i = 1, k, (1) k (1,... N ) k (1... S), i (1,...64), (1,... T STT ), where V_STT is he poenial V genereed during repolarizaion phase in ime insan, in lead in examined person k (Fig 2). Fig. 2 V STT i, _ and sandard deviaions in lead number 2. Then he mean poenials V STT i, _ of normal group were subraced from MI group mean volage for each ime insan and each elecrode. Sequenial discriminan maps for each pairwise

4 166 Michał Kania e al. / XI Conference "Medical Informaics & Technologies" - 26 comparison were obained by furher dividing each resuling difference by he corresponding composie sandard deviaion compued from he pooled groups: DI V _ STT MI V _ STT N =, (2) sd _ STT where sd _ STT for small groups is defined as follows: sd _ STT = ( N 1) var_ STT + ( S 1) var_ STT N S N S 2 (3) Thus he values achieved were sricly proporional o es saisics and provided informaion on he capabiliy for each measuremen a each elecrode sie and a each insan o separae MI paiens from he normal group. The values of DI parameer calculaed for lead 2 are presened in Fig. 3: Fig. 3 Values of DI parameer as a funcion of each segmen of STT inerval in lead number 2.

5 Michał Kania e al. / XI Conference "Medical Informaics & Technologies" RESULTS During preliminary analyses of DI parameer calculaed in 61 surface leads and 3 limb leads, sequenially, 12 and 16 lead ses having maximal value of DI parameer were seleced, and are presened in figure 4. The four lead ses were chosen 12 and 16 lead ses for surface of he whole horax and 12 and 16 lead ses for ches only Fig. 4 Values of DI parameer in all leads. Filled circle firs 12 leads chosen for bes locaion around he horax, unfilled circle added 4 leads o creae 16 opimal lead subse; filled squares firs 12 leads on he ches, unfilled squares added 4 leads o creae 16 opimal lead subse on he ches. According o resuls from Barr s work [] mos leads are siuaed in he precordial area. Some leads are placed in more scaered poins e.g. on he righ back or lef low ches. The following conclusion can be drawn: (1) opimal leads for MI ( acue CAD) diagnosis are mos ofen locaed ouside he regions sampled by he sandard ECG leads, (2) he problem of opimal leads selecion has no unique soluion. I srongly depends on examined cardiac disease, (3) furher analysis is required especially wih larger (saisically significan) number of paiens suffered from coronary arery disease (CAD).

6 168 Michał Kania e al. / XI Conference "Medical Informaics & Technologies" BIBLIOGRAPHY [1] AMBROGGI L.D., T. BERTONI, M.L. BREIGH, Diagnosic value of body surface poenial mapping in old anerior non-q myocardial infarcion. J Elecrocardiol, 21: p. 313, [2] YABE, S. H. HAYASHI, T. ISHIKAWA, Diagnosic value of Q waves ouside sandard precordial lead poins in lef anerior myocardial infarcion undeecable by sandard 12-lead elecrocardiogram. J Elecrocardiol, 21: p [3] USUGI, J. T. OHTA, J. TOYAMA, Body surface isopoenial maps in old inferior myocardial infarcion undeecable by 12-lead elecrocardiogram. J Elecrocardiol, 17: p., [4] MONTAGUE J.T., D.E. JOHNSTONE, C.A. SPENCER, Non-Q-wave acue myocardial infarcion: body surface poenial map and venriculographic paerns. Am j Cardiol, 8: p. 1173, [] BARR R.C., M.S. SPACH, G.S. HERMAN-GIDDENS, Selecion of he Number and Posiions of Measuring Locaions for Elecrocardiography. IEEE Trans Biomed Eng, 18(2): p , [6] LUX R.L., e al., Limied Lead Selecion for Esimaion of Body Surface Penial Maps in Elecrocardiography. IEEE Trans Biomed Eng., 2(3): p , [7] LUX R.L., e al., Clinically Pracical Lead Sysems for Improved Elecrocardiography: Comparison wih Precordial Grids and Convenional Lead Sysems. Circulaion, 9(2): p , [8] KORNREICH F., e al., Idenificaion of Bes Elecrocardiographic Leads for Diagnosing Myocardial Infarcion by Saisical Analysis of Body Surface Poenial Maps. Am J Cardiol, 6: p , 198. [9] KORNREICH F., Idenificaion of bes elecrocardiographic leads for diagnosing acue myocardial ischemia. J Elecrocardiol, 31 supplemen: p , [1] KORNREICH F., e al., Idenificaion of Bes Elecrocardiographic Leads for Diagnosing Lef Venricular Hyperrophy by Saisical Analysis of Body Surface Poenial Maps. Am J Cardiol, 62: p , [11] KORNREICH F., T.J. MONTAGUE, P.M. RAUTAHARJU, Idenificaion of firs acue Q wave and non-q wave myocardial infarcion by mulivariae analyisis of body surface poenial maps, Circulaion, 84: p , 1991.