Examinations have been made to find out the suitable method of detecting the ECG from fish for the purpose of pathological physiology study. The results obtained can be summarized as follows;
Unipolar leads of ECG from the surface of the heart.
ECGs, directly recorded on the surface of the Carp heart, consisted of P wave followed by QRS complex and a T wave (Fig. 4). Other waves derived from the heart could not be detected.
Unipolar lead and bipolar lead of ECG from the body surface.
i) ECG could be recorded from almost all the body surface of Carp by using unipolar lead. The amplitude of the QRS complex was about 40 µV in the vicinity of the heart.
ii) ECGs obtained by using bipolar leads from pectoral fins of Carp were stable and the QRS complex appeared as a QS type ordinarily and exceptionally as a QR type. This method may be useful for the pathological physiology study of fish. The amplitude of QRS complex was 70 µV on the average.
Bipolar lead of ECG from within the body.
Electrodes were inserted into the chest with operation. ECGs by this method were easily detected from Carp, Crucian carp, Rainbow trout, Yellow tail, Sea bream under swimming condition in aquariums. The patterns of ECGs from the chest cavity were similar to those from pectoral fins of Carp. The amplitudes of the QRS complex were 1.12 mV in Carp, 0.40 mV in Crucian carp, 1.15 mV in Rainbow trout, 0.88 mV in Yellow tail, 0.12 mV in Sea bream.
From the above results, it is apparent that the bipolar lead from the chest cavity is the most useful and suitable method to study fish ECG pathophysiologically and ecologically.