Electrocardiology Adv. Cardiol., vol. 16, pp. 32-35 (Karger, Basel 1976)
The Electric Field of the Cardiac Repolarisation Physical Work E. SCHUBERT,
10
K. ECKOLDT and R. KASTNER 1
Institute of Physiology, Department of Cardiovascular Physiology, Humboldt University, Berlin
M.
In cooperation with
M.
ENGST and K.
MOHNIKE.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
Modern electronic techniques give the possibility of leading off and recording the reflection of the cardiac electric activity on the whole body surface simultaneously and with a high time resolution. This enables us to investigate the generation of the recovery pattern of the cardiac activity more exactly as before [1] and the expression of the influences of physical work onto this pattern. The increase of the frequency of beating produces changes of the plateau phase and of the repolarisation in the cardiac intracellular action potential [2]. From this we have to expect changes in the potential distribution on the chest surface during the ST and T times of the ECG under physical work. First investigations concerning the kind and possible reasons of these changes are the object of this paper. The method employed was demonstrated before by one of us [3]. By the use of this method we recorded the potential distribution at selected eight moments between the maximum of S and the descending side of the T wave simultaneously from 100 points on the body surface. In each experiment records were made during rest and immediately after a 5-min period of work on the bicycle ergometer with an intensity of 2 W/kg body weight. All registrations took place in end-expiratory position. This means an active expiration in work of maximum 500 ml. Out of the records maps were constructed for the eight moments during rest and for a corresponding number of moments after effort. In all cases this number of moments at work is smaller than at rest owing to the shortening of the QT period in increased heart frequency. The mean frequency after work amounted to 130 beats/min.
33
The correct correspondence of moments after work to the cycle at rest was evaluated from the known correlation between heart frequency and QT duration. Registrations took place in ten persons. Six of the experiments could be used for interpretation and construction of maps. The resulting maps showed three common features. In the records during rest the first one or two pictures, corresponding to the maximum and the end of the S wave, belong to the potential distribution of the QRS complex, i.e. the depolarisation pattern. The potential values decrease more and more. With the beginning of the ST interval in the third map a new positive maximum arises at the anterior surface in a place formerly covered by negative potential. In a number of cases this new positive maximum appears even when the QRS pattern has not yet completely disappeared. In the background a corresponding minimum arises. The maximum increases in potential until the time of the maximum of the T wave and moves to the left side of the anterior chest wall (fig. 1). After work we find the same potential pattern in the moments of the maximum and the end of the S wave as at rest. The following maps show in all parts an increase of the potential values for maxima and minima. Immediately after work the generation of the potential pattern of the repolarisation phase is delayed. The new positive maximum appears at a later time during the ST interval but its increase in potential is faster, so that it reaches similar or even greater potential values in the moment of the maximum of the T wave. The dynamics of the potential pattern during the ST interval and the T wave at rest agree with the findings of several other authors [4, 5]. The maximum and minimum pattern appearing at the beginning of ST confirms its interpretation as the expression of an independent repolarisation pattern generated after the disappearance of the QRS distribution [1]. It reflects the repolarisation pattern, owing to the recovery front, which runs over the myocardium more or less distinctly contrasted with the depolarisation front [6]. The increase of potentials after work may be interpreted as the consequence of a better summation or a smaller cancellation of single fibre potentials in the myocardium owing to the shortening of the repolarisation phase of the action potential [2] and to improved dromotropic conditions of the whole excitation under effort. Influences of a deeper expiration with dislocations of the heart and the lungs cannot explain these effects, as verified by mapping in the same probands at rest with additional deep expiration.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
SCHUBERT/EcKOLDT/KAsTNER
34
SCHUBERT{EcKOLDT{KAsTNER
After work ~
.......... ,...-J
____
Fig. I. Changes in surface potentials during the ST-T period at rest (left column) and immediately after work (right column). Left part of each column demonstrates the front; right part the back of the thorax.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
t£IU
The Electric Field of the Cardiac Repolarisation in Physical Work
35
The delay of the development of the repolarisation pattern during the ST phase at work also may be a consequence of the change of the course of the cellular action potential, especially the prolongation of the plateau phase and the acceleration of the repolarisation. Also the better summation conditions in the myocardium for depolarisation and repolarisation during physical work may improve a distinction between the depolarisation pattern and the recovery picture in maps.
References
2 3
4 5 6
ACHENBACH, H. und SCHUBERT, E.: Zur Problematik des kardioelektrischen Feldes als Grundlage der Elektro- und Vektorkardiografie. II. Arch. Kreislaufforsch.59: 228-234 (1969). TRAUTWEIN, W.; KASSEBAUM, D. G.; NELSON, R. M., and HECHT, H. H.: Electrophysiological study of human heart muscle. Circulation Res. 10: 306-312 (1962). KASTNER, R.; ECKOLDT, K, and SCHUBERT, E.: The exploration of the cardioelectric field during physical work. Digest of the 10th Congr. MBE, Dresden 1973, vol. 2, p. 46. TACCARDI, B.: Recent data on the cardiac electric field. Neue Ergebnisse der Elektrokardiologie, pp. 23-29, G. Fischer Verlag, (Jena 1966). YOUNG, B. D.; MACFARLANE, P. W., and LAWRIE, T. D. V.: Normal thoracic surface potentials. Cardiovasc. Res. 8: 187-193 (1974). SCHUBERT, E.: The temporo-spatial evolution of activation and repolarisation of the heart and its relation to the electric field. Proc. 12th lnt. ColI. vectorcardiographicum, Brussels 1972, p. 506-511.
Prof. Dr. med. habil. E. SCHUBERT, Physiologisches InstJtut der Humboldt-Universitiit, Hessische Strasse 3-4, DDR-104 Berlin (GDR)
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
2
The Electric Field of the Cardiac Repolarisation Physical Work E. SCHUBERT,
10
K. ECKOLDT and R. KASTNER 1
Institute of Physiology, Department of Cardiovascular Physiology, Humboldt University, Berlin
M.
In cooperation with
M.
ENGST and K.
MOHNIKE.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
Modern electronic techniques give the possibility of leading off and recording the reflection of the cardiac electric activity on the whole body surface simultaneously and with a high time resolution. This enables us to investigate the generation of the recovery pattern of the cardiac activity more exactly as before [1] and the expression of the influences of physical work onto this pattern. The increase of the frequency of beating produces changes of the plateau phase and of the repolarisation in the cardiac intracellular action potential [2]. From this we have to expect changes in the potential distribution on the chest surface during the ST and T times of the ECG under physical work. First investigations concerning the kind and possible reasons of these changes are the object of this paper. The method employed was demonstrated before by one of us [3]. By the use of this method we recorded the potential distribution at selected eight moments between the maximum of S and the descending side of the T wave simultaneously from 100 points on the body surface. In each experiment records were made during rest and immediately after a 5-min period of work on the bicycle ergometer with an intensity of 2 W/kg body weight. All registrations took place in end-expiratory position. This means an active expiration in work of maximum 500 ml. Out of the records maps were constructed for the eight moments during rest and for a corresponding number of moments after effort. In all cases this number of moments at work is smaller than at rest owing to the shortening of the QT period in increased heart frequency. The mean frequency after work amounted to 130 beats/min.
33
The correct correspondence of moments after work to the cycle at rest was evaluated from the known correlation between heart frequency and QT duration. Registrations took place in ten persons. Six of the experiments could be used for interpretation and construction of maps. The resulting maps showed three common features. In the records during rest the first one or two pictures, corresponding to the maximum and the end of the S wave, belong to the potential distribution of the QRS complex, i.e. the depolarisation pattern. The potential values decrease more and more. With the beginning of the ST interval in the third map a new positive maximum arises at the anterior surface in a place formerly covered by negative potential. In a number of cases this new positive maximum appears even when the QRS pattern has not yet completely disappeared. In the background a corresponding minimum arises. The maximum increases in potential until the time of the maximum of the T wave and moves to the left side of the anterior chest wall (fig. 1). After work we find the same potential pattern in the moments of the maximum and the end of the S wave as at rest. The following maps show in all parts an increase of the potential values for maxima and minima. Immediately after work the generation of the potential pattern of the repolarisation phase is delayed. The new positive maximum appears at a later time during the ST interval but its increase in potential is faster, so that it reaches similar or even greater potential values in the moment of the maximum of the T wave. The dynamics of the potential pattern during the ST interval and the T wave at rest agree with the findings of several other authors [4, 5]. The maximum and minimum pattern appearing at the beginning of ST confirms its interpretation as the expression of an independent repolarisation pattern generated after the disappearance of the QRS distribution [1]. It reflects the repolarisation pattern, owing to the recovery front, which runs over the myocardium more or less distinctly contrasted with the depolarisation front [6]. The increase of potentials after work may be interpreted as the consequence of a better summation or a smaller cancellation of single fibre potentials in the myocardium owing to the shortening of the repolarisation phase of the action potential [2] and to improved dromotropic conditions of the whole excitation under effort. Influences of a deeper expiration with dislocations of the heart and the lungs cannot explain these effects, as verified by mapping in the same probands at rest with additional deep expiration.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
SCHUBERT/EcKOLDT/KAsTNER
34
SCHUBERT{EcKOLDT{KAsTNER
After work ~
.......... ,...-J
____
Fig. I. Changes in surface potentials during the ST-T period at rest (left column) and immediately after work (right column). Left part of each column demonstrates the front; right part the back of the thorax.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
t£IU
The Electric Field of the Cardiac Repolarisation in Physical Work
35
The delay of the development of the repolarisation pattern during the ST phase at work also may be a consequence of the change of the course of the cellular action potential, especially the prolongation of the plateau phase and the acceleration of the repolarisation. Also the better summation conditions in the myocardium for depolarisation and repolarisation during physical work may improve a distinction between the depolarisation pattern and the recovery picture in maps.
References
2 3
4 5 6
ACHENBACH, H. und SCHUBERT, E.: Zur Problematik des kardioelektrischen Feldes als Grundlage der Elektro- und Vektorkardiografie. II. Arch. Kreislaufforsch.59: 228-234 (1969). TRAUTWEIN, W.; KASSEBAUM, D. G.; NELSON, R. M., and HECHT, H. H.: Electrophysiological study of human heart muscle. Circulation Res. 10: 306-312 (1962). KASTNER, R.; ECKOLDT, K, and SCHUBERT, E.: The exploration of the cardioelectric field during physical work. Digest of the 10th Congr. MBE, Dresden 1973, vol. 2, p. 46. TACCARDI, B.: Recent data on the cardiac electric field. Neue Ergebnisse der Elektrokardiologie, pp. 23-29, G. Fischer Verlag, (Jena 1966). YOUNG, B. D.; MACFARLANE, P. W., and LAWRIE, T. D. V.: Normal thoracic surface potentials. Cardiovasc. Res. 8: 187-193 (1974). SCHUBERT, E.: The temporo-spatial evolution of activation and repolarisation of the heart and its relation to the electric field. Proc. 12th lnt. ColI. vectorcardiographicum, Brussels 1972, p. 506-511.
Prof. Dr. med. habil. E. SCHUBERT, Physiologisches InstJtut der Humboldt-Universitiit, Hessische Strasse 3-4, DDR-104 Berlin (GDR)
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 6:42:57 PM
2
