Examination by auscultation was performed on 286 heifers and 548 cows (consisting of 8 Japanese Black and 822 Holstein-Friesian cattle) in order to detect arrhythmia.
The results obtained are summarized as follows.
1) Eight cows with arrhythmia were found in 540 dairy Holstein cows. No arrhythmia was detected from the heiferes or Japanese Black cows.
2) The eight Holstein cows were noticed electrocardiographically to be affected with atrial fibrillation (AF).
3) One of the eight cows with AF died suddenly about one month after the electrocardiographic examination. A postmortem diagnosis of heart failure was made on it.
4) In the case of AF, RR intervals were absolutely irregular, rangeing from 0.4 to 1.1 sec. Heart rate usually exceeed 100 per minute.
5) The fibrillation wave rate was between 350 and 900 per minute.

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Changes in electrocardiographic measurements were studied in growing Holstein cows. These cows, including neonatal and 12-year-old ones, were kept on the Stock Farm, Faculty of Agriculture, University of Tokyo. Electrocardiograms were recorded in the A-B bipolar lead and the standard limb lead. Those recorded in the A-B lead were used to measure the intervals of RR, PQ and QT, the durations of P, QRS and T waves, and the amplitudes of P, QRS and T waves. The mean electrical axis of the QRS complex was calculated from those recorded in the limb lead. The results obtained are summarized as follows.
1) The RR, PQ and QT intervals and the P and QRS durations increased with growth.
2) No changes were observed in P wave amplitude with age. The amplitude of the R wave was rather high till 30 days of age. The wave form of the QRS complex was of rS type. Afterward, it shifted to the QS type with no R wave. The amplitude of the S wave decreased gradually until 3 or 4 months of age. It was stabilized in about 0.8 mV. The amplitude of the T wave was fluctuated from 0 to 0.5 mV through all the stages.
3) The mean electrical axis of the QRS complex changed with age. The QRS vector axis was oriented forward to the left till 100 or 200 days of age. After that, it was oriented backward to the left.
4) Prolongation of PQ and QT intervals and forward deviation of the QRS vector axis were observed in cows of over the 4th calving.

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Clinical and pathological findings of subvalvular aortic stensosis with ventricular septal defect (VSD) in a one-year-old female domestic short-haired cat were described.
The cat revealed laboured breathing, tachycardia, hepatomegaly, and ascites. A systolic murmur was heard on both sides of the chest. The chest x-ray demonstrated severe cardiomegaly (CTR:80%) and pleural effusion. Electrocardiogram and vectorcardiogram showed combined ventricular hypertrophy with a dominant right ventricular force and biatrial hypertrophy.
Subvalvular aortic stenosis was present about 2 mm below the aortic valve and immediately above the VSD. The obstruction of about 2 mm opening in the sub-aortic area was formed by a fibrous membrane and the anterior leaflet of the mitral valve adhered to the ventricular septum.

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A six-year-old male mongrel dog was reffered to Hidaka Pet Clinic 6 hours after having been hit by a car. The dog was received physical, radiographic, electrocardiographic and hematological examination, then diagnosed as contusion of the chest and abdominal wall, dislocation of the right hip joint and traumatic heart disease.
The electrocardiogram recorded, at the first clinical examination, abnormal ST segment depression and positive sharped T wave . These electrocardiographic changeswere suggested the heart contusion. The multifocal premature contraction was noted 4 hours later, then antirhythmic therapy was started . These multifocal premature contraction were gone at the 5th clinical days' recording, but abnormal ST segment was continued at the 8th clinical day when he leaved the hospital .The dog was reexamined after 5 months and electrocardiogram showed normal except diphasic T wave.

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