David A. Rytand

The Circus Movement (Entrapped Circuit Wave) Hypothesis and Atrial Flutter

Excerpt In the half century of its existence, the circus movement hypothesis has been accepted and rejected, ignored and misunderstood. There seems to be some revival of interest in it now, but eve...

On the Path of the Excitation Wave in Atrial Flutter

Available data on the arrival times of excitation at various central and peripheral atrial sites during atrial flutter (in a number of dogs and in one patient) have been examined in relation to families of involutes of an arbitrary central obstacle. The degree of fit seems to be satisfactory and is superior to that made for the same data by central-centrifugal (mother-daughter) waves. The latter appear to be an erroneous corollary of the circus movement hypothesis. In contrast, the concept that successive wave fronts of an entrapped circuit wave in atrial flutter may be described by a family of involutes has an appropriate physiological basis in the construction of Huygens, as first suggested by Wiener and Rosenblueth.

Hereditary Obesity of Yellow Mice: A Method for the Study of Obesity.

In the course of studies on the hereditary obesity of yellow mice first described by Dan-forth, 1 , 2 the following observation was made. A group of S obese females was permitted unlimited amounts of water and Purina dog chow pellets throughout the experiment. Their food intake was measured at 2-6-day intervals, and the caloric intake per mouse per day calculated from a value (3.50 cal./g) obtained by chemical analysis. At varying intervals they were also allowed to drink for a few days one of the following at a time: 10% and 20% solutions of dextrose, 50% sucrose, olive oil, and human plasma with a protein concentration of 17.3%. The unrestricted daily caloric intake per mouse of each of these (excepting olive oil) was calculated. Simultaneously, identical steps were taken with a group of 3 normal albino female mice. Fig. 1 shows the results. Briefly, none of these substances caused a gain in body weight of the normal mice; within the limits of error their caloric intake remained practically constant (see below). But the obese mice gained weight in three 4-day periods: 2.2 g with 20% dextrose, 3.0 g with 50% sucrose, and 4.4 g with olive oil. The caloric intake during 2 of those periods increased by about 12 calories and 24 calories (20% and 50% sugar, respectively), enough to explain most or all of the increased body weight as fat deposition. Moreover, when the sugar or oil was withheld, body weight fell to the original level during a few days in which there was an appropriately reduced caloric intake; surprisingly, under the same conditions, there was also a transient reduction of caloric intake cf the normal mice without loss of weight.

The Midclavicular Line: Where Is It?

Abstract The midclavicular line, a landmark of some interest and importance in electrocardiography and physical diagnosis, has undergone changes in its definition and description. These are reviewe...

Pathogenesis of Arterial Hypertension in Coarctation of the Aorta

Conclusions Partial (or even complete) occlusion of the aorta rats produces hypertension only if there is living renal tissue distal to the occlusion, just as there must be a kidney beyond a partially occluded renal artery in order to produce hypertension in a Goldblatt dog. The same degree of mechanical obstruction due to stenosis of the aorta and the presence of a collateral bed never results in hypertension when all of the renal tissue is above the site of occlusion.

Renal Blood Flow After Subtotal Nephrectomy

Conclusions Rats which become hypertensive several months after subtotal nephrectomy do not have renal ischemia; the flow per gram of renal tissue is 19% less than in rats a few days after sub-total nephrectomy, but the same as that in rats with unilateral nephrectomy and without hypertension.

Normal and Prosthetic Atrioventricular Valve Motion in Atrial Flutter Correlation of Ultrasound, Vectorcardiographic, and Phonocardiographic Findings

In order to correlate the electrical and mechanical events occurring in atrial flutter, three patients have been studied using the standard electrocardiogram, a computer-processed vectorcardiogram, and reflected ultrasound recordings of valvular motion. Anterior motion of the mitral valve leaflet occurs in the region of the nadir of the atrial flutter wave in lead II of the electrocardiogram. In one patient in whom it was possible to obtain a tricuspid leaflet echocardiogram, anterior motion was also initiated close to the nadir of the flutter wave. The probable sequence of electrical and mechanical events in atrial flutter is discussed. In one patient with a prosthetic mitral valve, correlation of diastolic clicking sounds with respect to the poppet echocardiogram provided some insight into irregularities in timing of previously reported flutter sounds.

The Significance of Changes in Amplitude of the First Heart Sound in Children with A-V Block

Curves which relate the peak intensity of the first heart sound to the P-R interval have been obtained from seven children with complete A-V block. The first sound is accentuated with short P-R intervals, becomes faint when the P-R interval is in the neighborhood of 0.20 to 0.30 second, and becomes loud again with relatively long P-R intervals. Repeated observations over a number of years demonstrated the effects of growth and aging on these phenomena. The data appear to indicate that the variable intensity of the first sound in complete A-V block is related to the position of the mitral valve at the time of ventricular systole.

Simple Optical Methods for the Recognition of Atrial Flutter, Especially at Slow Atrial Rates

Simple optical methods, particularly the use of a cylindrical lens, are described which facilitate the examination of electrocardiograms and the differentiation of atrial flutter from atrial tachycardia with block. Results of utilizing the methods indicate that what may seem to be an isoelectric line of the latter is sometimes but an optical illusion, especially at slow atrial rates. Continuous atrial electrical activity of flutter has been detected at atrial rates as slow as 88 per minute. Some of these findings are relevant to certain considerations on the mechanisms of atrial arrhythmias.

A Simple Apparatus for Metabolic Measurements on Small Animals.

Summary A simple apparatus is described for measuring the metabolic rates of smaller laboratory anirnals. It requires no unusual materials and can be made in a few hours by anyone able to solder. Its accuracy and simplicity are derived from the fact that by keeping the size down to a minimum, the contained gas volume is very small and the necessity for rigorous temperature control and circulation of the air is thereby eliminated. The values reported in the literature, with more complicated apparatus and groups of animals measured over longer intervals of time, are reproducible in this simple apparatus using single animals and observation-periods of relatively few minutes.