In order to elucidate an aspect of the development of cardiac function during the growing process, heart rate and conduction time were measured in rats, mice and guinea pigs 1 to 90 days of age.
1) The heart rates in rats and mice were almost stable within a range of 300 to 400 beats per minutes from birth to 5 days of age. Over a period from 14 to 30 days of age they increased temporarily to 530-620 beats per minute (in rats) and about 750 beats per minute (in mice). On the contrary, the heart rate in guinea pigs tended to decrease slightly with the advance in age.
2) The PQ and QT intervals shortened in rats and mice and prolonged in guinea pigs with the advance in age after 5 days of age. They were correlated positively with the RR interval in these animals, except guinea pigs in which there was a relation between PQ and RR intervals.
3) The QRS complex duration prolonged slightly in each animal species with the advance in age.
4) In the mouse ECG, ST segment could not be discriminated even on the first day after birth. It shortened and disappeared in the rat ECG with the advance in age. On the contrary, it was recognized clearly in the guinea pig ECG throughout the growing stage and adulthood.

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An animal model of coronary artery disease was produced with the new method in closed-chest dogs. In the method with x-ray procedure, a new type cannula was inserted either into the paroconal interventricular branch or the circumflex blanch of the left coronary system.
The method was performed with the cannulation of the canine left coronary arterial system from the left common carotid artery and introduction of new type embolus through that new type cannula.
The embolus in the left coronary arterial system was stayed for 15-60 minutes, and then was pulled out for the purpose of reperfusion. Our method successfully could produce the ventricular ectopic rhythm.

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Development of an autodiagnostic electrocardiograph for canine use has apparently not been published to date, and there is no such product on the market. In the present study, modification of the conventional canine autoanalyzing electrocardiograph was tried with the purpose of performing computer assisted ECG diagnosis for dogs. Model 503 FB-D (Fukuda M-E Kogyo Co., Ltd.) of autoanalyzing electrocardiograph was used for the modification study. The system consisted of a Model 8086 computer as the CPU with 80 and 128 Kb memories, ECG amplifier, R wave detecter, A/D converter, ECG recorder, LED display, thermal printer and floppy disk drive. ECG and measurement data are recorded continuously for 10 to 20 sec as the database for analysis of heart rate, PR interval, QRS duration, QT interval, all the P, Q, R, S and T waves, ST segment and VAT time from each lead. These values were then used to calculate the QTc and QRS electric axes and VAT time. The above data were then used for diagnosis of abnormal ECG patterns and to analyze arrhythmia of dogs. The accuracy of this improved system was assessed by using 200 cases with abnormal ECG findings. The results suggested that the modified model 503 FB-D autodiagnostic ECG with the computer program, might be practically applicable to canine medicine.

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Arteriovenous fistula (A-V fistula) between brachiocephalic trunk and anterior vena cava in Japanese Black has been diagnosed and its clinical and autopsy findings are as follows. There was no previous history of illness or injury except its slow growth rate. The continuous murmur was heard best by auscultation at one cranial intercostale space of the tricuspid area and was radiating toward cranial portion of thorax. Systolic murmur was auscultated at the pulmonic and tricuspid valve areas, however no murmurs were auscultated at the aortic and mitral valve areas. The catheter in the right atrium from the carotid artery was confirmed by the catheterization and the echocardigraphy. The aortic blood pressure dropped suddenly when the catheter was passed into the fistula to a lower turbulent pressure. By the contrast echo-graphic study, the micro-bubbles injected into the left ventricle appered in right atrium right after the injection. Autopsy study revealed the presence of angioid fistula between branchiocephalic trunk immediately caudal to left subclavian artery and anterior vena cava which inner diameter was approximately 5 mm. The heart was normal except slight dilatation ofthe right ventricle. Histopathological evalnation of the fistula wall revealed that the fistula contained vasuculur structure. From there findings, this it that the first reported of the congenital A-V fistula in Japanese Black.

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