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Transtelephonic 12-Lead-ECG-Service Centers in the Netherlands. H.A. Holtkamp and N.H. van Boxel. Sophia Ziekenhuis, Zwolle, The Netherlands.

A new and practical ECG modem was developed for transtelephonic transmission of 12 lead standard ECGs. The ECGs were made at the primary health care level (general practitioner's office or patient 's home}. The interpretation was done by a cardiologist in a general hospital. The study measured positive and negative effects on diagnostics and referral. I t was shown that: �9 it is a reliable, simple and widely applicable method, �9 diagnostic efficiency is greatly improved, �9 negative side effects are hardly present, �9 the ECG should be accompanied by patient 's case his-

tory and personal data, �9 the cooperation between general practitioner and car-

diologist benefits through the method, and �9 incidence of myocardial infarction may be 30 percent

greater than indicated by official statistics. In the Netherlands ECG service centers are quickly

expanding. In the Netherlands ECG service centers are quickly expanding. The method is now also in use to obtain earlier, i.e., at the patient 's home--intervention with thrombolytic therapy like tPA.

Wide QRS-T Angle--an Indicator of Coronary Artery Disease or Not? F.U. Huwez and P.W. Macfarlane. University Dept. Med- ical Cardiology, Royal Infirmary, Glasgow, Scotland.

Repolarisation abnormalities are recognized features of coronary artery disease {CAD) when associated with pathological Q waves and/or ST segment deviations. However, isolated T wave inversion in the inferior leads particularly aVF is not uncommon but its significance as a probable sign of CAD requires clarification. I t has been suggested that a QRS-T angle >60 ~ is an indicator of CAD while an angle <60 o is not abnormal.

21 patients (11 male. 10 female, age range 41-67) with symptomatic coronary artery disease and isolated T wave abnormalities in aVF underwent coronary arteriography. I t was found tha t the QRS-T angle exceeded 60 ~ in 11 (50%) patients, all of whom had significant CAD. Their mean QRS and T axes were 23 ~ and -32.3 ~ respectively. In the remaining 10 patients with QRS-T <60 ~ there was also found to be significant coronary artery disease. In this group, the mean QRS axis was 19.9 ~ and the mean T axis was -25.7 ~ The criterion of QRS-T :>60 ~ was also assessed in a population of 375 apparently normal indi- viduals >/40 years and was found to be 94% specific.

I t is concluded that a QRS-T angle >60 ~ has a high predictive value in patients with suspected coronary artery disease, is relativley specific but is insensitive. Conversely, a narrow QRS-T angle <60 ~ in the presence of an inverted T in aVF, does not exclude coronary artery disease. This finding was present in only 3/375 normals. T inversion in aVF therefore appears highly abnormal irrespective of QRS-T angle in subjects over 40 years.

Body Surface Mapping of PR-Segment. Distribution and Direction of His-Purkinje Potentials on the Body Surface. Jin Jie* and G. Schoffa. Inst i tute of Biophysics, Univer- sity of Karlsruhe" FRG.

*Permanent address: Medical University, Xian, China. The non-invasive measurement of His-Purkije signals

is made more difficult by the very small amplitudes of the His signals and by the superimposition of atrial depolarization potentials. The first problem was solved by constructing a specially low-noise 64-channel BSPM System and through averaging of 38 heart beats using an IBM AT. The synchronization of individual heart beats was first of all carried out on a rough basis by shift- ing of the QRS segment to the uniform intersection point of the zero line between R and S, followed by a second process, performed to a high degree of precision, involv- ing timelag crosscorrelation of the QRS complex. Sub- straction of the atrial depolarization potential was done by a special method of regression analysis in t ime space for the separate points on the body surface. By this, we obtained maps with pronounced His-onset signals, from which the propagation of the His signals out to the body surface could be determined. Thanks to the special method of space difference averaging, it was possible to represent the His signals in the form of voltage difference signals within the PR segment of the electrocardiogram.

Application of a Bedside Microcomputer System for ECG Mapping Analysis after Myocardial Infarction M. Knorre, H. Knorre, V. Wiechmann, I. Assmann, P. Kassel and I. Porstmann. Medical Academy Erfurt, Erfurt, GDR.

A microcomputer system for analysis of multiple elec- t rocardiogram regis t ra t ions is described. D a t a from 1-100 simultaneous ECG leads can be collected. Special hardware and software permit on-line data acquisition and processing at the patient 's bedside. The analogue part of the ECG mapping system consists of change- able arrangements of electrodes, the ECG-amplifiers, the multiplexer and the high-speed AD-converters. For data acquisition, processing and control operations the digi- tal part of the ECG mapping system is used with a Z 80 microcomputer as the main part. This computer inter~ acts with an alpha-numeric keyboard, with a floppy-disk memory and with a colour graphic display. Using the sys- tem for praecordial ST-mapping or the body surface map- ping isopotential maps are calculated and represented at the colour graphic display a few seconds after the end of data acquisition. The isopotential maps and the origi- nal ECG data can be stored on a floppy disk. By this novel diagnostic procedure the physicians get a lot of new information about the function of the heart from the body surface First results of clinical applications of the diagnosis of myocardial infarction will be introduced.

JOURNAL OF ELECTROCARDIOLOGY 21 (1), 1988