[Electrical activity in the region of the sino-atrial node. Experimental study]

After finding the landmarks of the sino-atrial node in the dog by means of serial sections, the authors have recorded the electrical activity in the region of the sinus by means of bipolar and monopolar electrodes placed in contact with it. a)A preatrial wave has been recorded, and its origin is discussed. b) Mechanical destruction of the sino-atrial node is followed by the disappearance of this wave and the appearance of a slow junctional rhythm with a retrograde atriogram. c) When lignocain is applied directly to the sino-atrial node, the pre-atrial potential decreases and then disappears and the post-stimulation pause is prolonged. d) Clamping of the peri-sinus region gives rise to an incomplete block, followed by complete block, of the pre-atrial potential and the P wave. The post-stimulation pause remains normal. The disorders of rhythm which have followed these producedures may be regarded as constituting experimental models for sinus lesions and for sino-atrial block.

[Relationships between pheochromocytoma and obstructive myocardiopathy. Apropos of a case]

The authors report the case of a 45 year old man who presented with a combination of a phaechromocytoma and obstructive cardiomyopathy. They discuss the possible inter-relationships between hypertension, catecholamines, phaeochromocytoma, and outflow stenosis.

[Aneurysm of the ascending aorta and aortic insuffiency]

Basing themselves on 24 cases of aneurysm of the ascending aorta with gross aortic incompetence, the authors give an account of their personal experience of this condition. They emphasise: -- the problems of aetiology posed by this annular dilation of the aorta with its associated elastic tissue dystrophy which is seldom apparent except at histological examination of the aortic wall at percuaneous biopsy; --the operative problems which confront the surgeon, especially because the orifices of the coronary vessels are in the very centre of the aneurysm. The detail their modest surgical experience, and emphasise the advantages of using Bentall's operation systematically; it seems that this is likely to be the operation of choice in the future.

[Hemodynamic effects and effects on plasma renin activity of injectable acebutolol in arterial hypertension]

The purpose of the study was to determine the early haemodynamic effects of injectable acebutolol and to study in parallel the changes in plasma renin activity (P.R.A.) in 11 patients, most of whom were affected with labile arterial hypertension. The haemodynamic measurements and P.R.A. determinations were carried out before and 5 and 15 mn after very slow intravenous injection of 10 mg acebutolol. The results obtained under these conditions were as follows: 1) Decrease in cardiac index (I.C.). It was particularly significant after 5 mn, since the I.C. decreased from 4.43 to 3.75 1/mm (p less than .01). It was essentially due to a decrease in heart rate, that fell from 90.45 to 77 beats/mn (p less than .001), while stroke volume changed virtually not. 2) Decrease in blood pressure, more marked on systolic blood pressure (110 mm Hg after 15 mn as against 154 mm Hg before injection; p less than .001), associated with a decrease in left ventricular work (4.7 kgm/mn/m2 after 5 mn as against 6.2 kgm/mn/m2 before injection; p less than .001), without significant changes in total systemic arterial resistances. 3) Increase in diastolic pulmonary arterial pressure (10.4 mm Hg after 5 mn against 8.09 mm Hg before injection; p less than .001), testifying to a slight left ventricular myocardial depression. 4) Decrease in supine P.R.A. level (0.72 nanogram/1/mn after 5 mn as against 1.15 nanogram/1/min before injection; p less than .01). A significant correlation was found between this decrease in P.R.A. and that in I.C., testifying to a close parallelism between the inhibition of cardiac beta-1 receptors and that of the receptors involved in renine secretion. 5) The tolerance of injectable acebutolol appeared to us to be excellent.

[Aneurysms of the membranous septum. Apropos of 4 cases]

Three cases of aneurysm of the membranous septum were diagnosed in vivo. The fourth case was discovered at post-mortem examination in a patient who had a conductive disorder. These four cases give us reason to review the anatomical, clinical, radiological and haemodynamic features of this condition.

[Atrio-ventricular block in Steinert's disease. Electrophysioligic and histologic study of the conduction system]

An anatomical study of the conducting pathways was carried out in a case of Steinert's disease complicated by a complete atrio-ventricular block with syncope. Electrical study of the potentials in the bundle of His located the block within and below the bundle. When the patient died, an anatomical study of the conducting pathways was carried out. There were foci of fibrosis mainly within the conducting system, but these changes were moderately marked only, and seemed to be the final stage of a disorder which was not itself visible optically. The basic underlying pathological process is probably biochemical, and the lesions seen microscopically are simply a late sign of the disorder.