The Influence of Digitalis on the T Wave of the Human Electrocardiogram

Abstract

PLATES 59 TO 64.The modifications in the form of the T wave of the electrocardiogram which we report in this communication were observed in the course of detailed studies on the action of digitalis in patients ( I ) , It has been noticed frequently that the time when digitalis takes .effect is a matter of uncertainty, so that in a given instance doubt is often entertained as to whether the drug itself is active, and if active, whether it is effective in producing a result. To be certain that the drug is effective, it has been considered necessary to administer it until an alteration in the rhythm of the heart occurs. In our treatment of patients we have, therefore, looked for evidences of altered heart rhythm to indicate that the heart is really digitalized. During the period of treatment, electrocardiograms were made almost daily, and often more than o.nce a day. In examining these records we found the changes in the T wave which we describe in this report.Other observers have published studies dealing with the effect of a number of agents, including digitalis, on the electrocardiogram. The only investigation dealing with this subject in human beings has been made by Nicolai and Simons (2). Seven ambulatory patients were given powdered digitalis, o.3 gin. daily, for five days. In two women the treatment was not completed; in one normal man the T wave did not increase in height, but decreased instead (" verschlechterte sich') ; and in the other four the T wave increased. They limited the taking of records to the first lead (right arm to left arm). Even if the * A preliminary report was made to the Section on Medicine at the Seventeenth International Congress of Medicine, London, I913, Section VI, 255--258. Re-

Studies on the Effect of the Action of Digitalis on the Output of Blood From the Heart. Iii. 12

“…They were frequently the earliest effects observed. The alterations were not uniform; the most characteristic and usual one was negativity of T3 (21); in certain cases T1 and T2, however, also became negative; T1 or T2or T8 sometimes became diphasic. On the other hand, waves which were negative became positive, and finally changes in amplitude only, occurred.…”

Studies on the Electrical Systole (“Q-T” Interval) of the Heart

“…The shortening occurs at least as early as any other known effect of digitalis. It takes place simultaneously with the lowering of the " T " wave (7) and precedes a change of " T" to a diphasic or negative form and a sagging of the "Q-T" level (cf. Tables 1 and 2).…”

Intestinal Necrosis Due to Digoxin Intoxication

“…Digoxin decreases the duration of the action potential, shortens the refractory period, and prolongs the AV-conduction. Electrocardiographic manifestations of the electrophysiologic effects are characterized by ST-segment depression, T-wave inversion, a shortened QT-interval, and prolongation of the PR-interval ( Figure 2) [11,12].…”