The interpretation of the electrogram of the cardiac ventricle

Abstracts and Reviews Selected Abstracts Rosenbluetb, Cardiac

means

The of

P. A., Ventricle.

and

-08, Arch.

J. Inst.

electric phenomena of a cathode-ray oscillograph

the

G.: Cardiol.

The Interpretation Mex. 14: 232, 1945.

cardiac and the

ventricles following

of

the

Electrogram

of cats and dogs were observations were made.

of

recorded

the

by

When the leads are applied directly to two intact regions of the muscle, a typical diphasic electrogram is obtained. If an extensive injury (ligature or burn) is made between the leads, the records are not modified, although the response recorded from the injury to either of these two intact regions tested originally are typically monophasie. The existence of an injured region can only be appreciated in records taken from a direct to a distant lead if the direct lead is in contact with the damaged tissue. If, instead of being applied directly, the near electrode is placed on a layer of cotton moistened with Ringer’s solution which covers the heart, so that the lead becomes diffuse and makes contact with both injured and intact tissue, then the existence of an injury can be appreciated in the records even when the electrode is moved over a relatively large area in front of the heart. The polarization with direct current of either of the two lead-off regions results in marked changes of the diphasic electrograms. Applications of direct current to other regions of the heart, including the zone intermediate to the leads, do not modify the electrograms. Similarly, the monophasic records are strikingly modified wlien the live lead-off region is polarized anodally or cathodally, but are unchanged by the application of direct current to the intermediate zones or to the injured region. From these data the following inferences are drawn. (a) The only regions in the ventricle that contribute significantly to the electrograms obtained with leads applied on the surface are those in direct contact with the leads; the electrical phenomena which occur in other regions, including those intermediate to the leads, contribute only minimally or do not (b) There are no potential changes at an injured region contribute to the electrograms. concomitant wit,h the activity of the heart. (c) The monophasic electrograms, therefore, show only the potential changes which take place at the intact region which is in contact as monotopic ; the diphasic electrowith the corresponding electrode ; they may be designated grams are ditopie since they correspond to the algebraic sum of the two monotopic responses. (d) When applications of direct current to the injured region do not modify the monophasic electrograms it may be concluded that the injury is complete for the purpose of the that the electrograms are strictly monotopic; record, and it may be concluded, therefore, these strictly monotopic records are not simple but complex, they exhibit several components (e) The existence of a cardiac injury which differ in amplitude, polarity, and time course. may be detected in the human electrocardiogram because the distant electrodes are prolonged by the conducting media of the organism and the real leads are diffuse and come in contact with the injury.

Alexander, ters.

The Effects R. S.: Am. J. Physiol. 143:

of Blood 698, 1945.

Flow

and

Anoxia

on

Spinal

Cardiovascular

Cen-

By employing the activity in the inferior cardiac nerve of the cat as a direct index of the activity in the sympathetic outflow to the cardiovascular system, the following conclusions have been reached: After removal of all possible sources of reflex inhibition, a rise in thoracic blood pressure produced by injections of adrenalin or pitressin or by sudden occlusion of the abdominal aorta still serves to inhibit the tonic activity in the thoracic sympathetic outflow to the cardiovascular system. 314