Some types of electrocardiograms, their relation to paroxysmal tachycardia

278

AMERICAN

HEART

JOURNAL

been presented. It is fully appreciated that the value of electrocardiography in diagnosing cardiac conditions is limited. However, the numbers of records showing axis deviation, abnormalities of the T wave in Leads I and II, and the occurrence of prolonged P-R and QRS intervals indicate the value of such recordings at least as an indication for more careful investigation before selection for aircrew duties. AUTHORS. Ohnell,

v. R. I?.:

Tachycardia.

Some Types of Electrocardiograms, Cardiologia 5: 321, 1941.

Their

Relation

to Paroxysmal

Some types of electrocardiograms (with abnormalities R wave) have been described and, further, their relation and to the Wolff -Parkinson-White (( ( WPW ’ ‘) syndrome

between the P and the to paroxysmal tachycardia has been discussed.

Type A.-Gradual ( ‘ Conduction-time

QRS

Type ventricular

B.-Gradual complex

rise of ’ ’ subnormal.

the

rise of the in one lead.

initial intermediate

part

of part

the

between

complex the

in

P wave

one

lead.

and

the

AUTHOR.

Segall, II. N., and Goldbloom, cardia in an Infant Treated 46:

A.: With

Atrio-Ventricular Nodal Paroxysmal TachyAcetyl Beta Methylcholine. Canad. M..A. J.

233, 1942.

Atrioventricular paroxysmal tachycardia in an infant, aged 1 month, was treated with acetyl beta methylcholine. The first dose, 5 mg., administered during the second hour of the attack failed to restore normal rhythm but caused changes in amplitude of QRS and depression of S-T interval. The last dose, 8 mg., produced bradycardia (rate 20 to 56) by slowing abnormal rhythm for about five minutes, then normal rhythm was restored, but there were no changes in QRS and T waves. Adrenalin seems to be preferable to atropine in controlling the disagreeable systemic effects of acetyl beta methylcholine. AUTHORS.

Kennedy, J. A., and Clark, S. L.: Observations on the Physiological the Ductus Arteriosus. Am. J. Physiol. 136: 140, 1942.

Reactions

of

The authors have established that the ductus arteriosus is a structure which It responds to local mechanical can actively close in response to certain stimuli. stimulation much the same as certain other hollow muscular structures by contracting. The authors do not believe that local mechanical stimulation has an essential role in its closure under physiologic conditions. Neither does a neurologic mechanism appear essential to closure following artificial inflation of the lungs. Their findings are at variance with those of Barcroft, Kennedy, and Mason (1938) with respect to the reaction of the ductus following stimulation of the vagus nerve, but they believe that the present observations have been adequately controlled. Of the stimuli causing closure of the duetus which the authors have explored, it seems likely that under physiologic conditions breathing is the most important. The actual filling of the lungs by just any gas is not sufficient. From their experiments it appears that oxygen is a necessary component of the gas mixture since inflation of the lungs with pure nitrogen will not cause closure. Oxygen by vein will also cause closure without the necessity of accompanying inflation of the lungs. It is quite possible that many of all of the unexplained closures (see sec. 7) could be due to an increased oxygenation of the fetal blood in response to painful stimulation, There are other possible sources struggling of the mother or fetus, hemorrhage, etc.