Three cases of the single atrium (cor triloculare biventricularis) were operated upon successfully, and diagnostic and surgical aspects of this rare malformation were discussed.

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The effect of aldosterone on electrolytes and water diuresis was examined on 3 groups of human and dog, i.e. normal, mild heart disease and congestive failure.
In control group, the administration of d-aldosterone prior to mannitol or saline infusion led to a large amount of potassium diuresis but did not decrease sodium excretion in urine. This phenomenon is regarded as the initial effect of aldosterone for electrolytes and water diuresis.
In patients and dogs with heart disease without edema, however, aldosterone showed differential effects between mannitol and saline infusion. By mannitol, potassium excretion was unchanged despite reduced sodium excretion, but by saline the former was increased and the latter was unchanged.
In patients and dogs with congestive heart failure, whether on mannitol or on saline, the pre-treatment of aldosterone minimized the sodium excretion in urine, but the potassium excretion was almost as same as that in normal cases and in mild heart disease.
These observations lead to the following conclusions.
(1) The increased aldosterone secretion itself is not the only necessary cause of edema.
(2) The sodium in renal tubules is reabsorbed by 2 ways; one is through Na-K exchange and the other is effected by the sodium reabsorption independent of Na-K exchange, and aldosterone can act on both processes differently according to the condition of patient or animal.
(3) The second way will act in initial effect and escape phenomenon in normal human and dog, but it will show the strong sodium retaining effect in human and dog with congestive heart failure.
(4) Aldosterone may probably aggravate the edema in congestive heart failure, but it might not be the primary cause of edema and its primary cause is rather the altered tubular responsiveness to aldosterone.

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The vectorcardiographic patterns of tricuspid atresia, transposition of the great vessels with interventricular septal defect, endocardial cushion defect, and isolated pulmonary stenosis with venoarterial interatrial shunt, were analyzed.
(1) The vectorcardiographic feature of moderate to severe left ventricular hypertrophy was observed in all 6 patients with tricuspid atresia. The mechanism of such left ventricular preponderance was discussed.
(2) Two types of vectorcardiogram were recognized in transposition of the great vessels. Right ventricular hypertrophy or combined ventricular hypertrophy was noted in 6 patients on the one hand, and features characteristic for endocardial cushion defect were noticed in 4 on the other.
(3) Patients with endocardial cushion defect with severe cyanosis do not necessarily present its characteristics on the vectorcardiogram.
(4) On the basis of vectorcardiogram, there are no reliable ways to differentiate isolated pulmonary stenosis from tetralogy of Fallot.

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(1) The manner of the stimulus conduction was investigated for both left and right atria of the canine heart through analysis of the configuration of unipolar electrograms and the arrival times of the activation wave. Langendorff's method of irrigating the heart was used.
(2) In the right atrium, the stimulus spreaded from the S-A node to the orifice of the I.V.C. with higher conduction velocity along the sulcus terminalis. The stimulus coming along the sulcus terminalis spreaded over the atrium through the muscle bundles which branched from the sulcus terminalis. The apex of the atrial appendage was found to be the last portion to become activated.
(3) In the left atrium, the stimulus originating in the S-A node, spreaded through Bachmann's bundle, first of all. The stimulus coming along Bachmann's bundle spreaded over the atrium through the muscle bundles which branched from Bachmann's bundle. The region between the left lower pulmonary vein and the A-V ring was found to be the last portion of activation in both left and right atrium.
(4) In some cases, there was an area in which the stimulus originating in the S-A node might reach directly from the right atrium without passing through Bachmann's bundle. This area was located in a small region of the posteroinferior portion of the left atrium near the I.V.C.

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The effect of strenuous exercise (60 knee bends in 1min.) on the electrocardiogram was studied in 8 top class swimmers in Mexico City (altitude 2, 240M.). The electrocardiographic changes during the 3 week Mexico training were compared with the responses in Tokyo.
(1) Heart rate immediately after the exercise increased markedly on the second day in Mexico, and declined gradually. Heart rate before and immediately after the exercise remained at higher level during Mexico training than in Tokyo.
(2) Average amplitudes of P waves before and after the exercise in lead II were taller during Mexico training than in control study in Tokyo, the most prominent P waves after the exercise being observed on the second day in Mexico. P pulmonale at rest was observed in 2 cases. Right axis deviation of P waves was observed in 3 cases. These changes in heart rate and P waves returned to the control value after coming back to Tokyo.
(3) Amplitude of T waves in lead II decreased immediately after the exercise throughout the study. Decreased amplitude of T waves before and after the exercise was remarkable after 12 days of Mexico training.
(4) The junctional depression of ST segment after the exercise was remarkable in the first week of Mexico training, and disappeared gradually in the following week.
(5) Relative QT duration was increased 2 and 5min. after the exercise. Relative QT duration increased during the Mexico training both before and after the exercise.
These electrocardiographic changes during Mexico training and anginal chest pain experienced during and after the race indicated the need for the careful health examination of the athletes.

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Six cases of aneurysm of the membranous ventricular septum were obtainable in Japanease literature and additional 3 cases of our own were presented in the paper. An autopsy case disclosed various appearances of arrhythmias during life. Three cases showed bulges of the membranous portion of the ventricular septum with ruptures over the domes. A bulge into the right atrium was recognized in a case with hypoplasia of the aorta. The rest 4 cases were found in connection with ventricular septal defects during surgery.

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A 20-year-old female with proved patent ductus arteriosus of insignificant left-to-right shunt and intermittent continuous murmur was reported. Once auscultation and phonocardiography revealed a typical continuous murmur, but this was responded unusually by amyl nitrite and methoxamine. Amyl nitrite inhalation initially caused usual response (attenuation of the murmur), but it was followed by unusual intensification. Intravenous administration of methoxamine caused, contrary to the expectation, decrease (first test) or disappearance (second test) of the murmur. The cause of these unusual findings is discussed.

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