RT Journal Article
SR Electronic
T1 SLOWING AND BLOCK IN THE HEART UNDER DIGITALIS IN ANIMALS
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 1
OP 17
VO 26
IS 1
A1 A. R. CUSHNY
A1 K. Y. YU
YR 1925
UL http://jpet.aspetjournals.org/content/26/1/1.abstract
AB In the dog and cat, the digitalis series induces slowing and block more frequently than in man, probably because in the latter the drug has to be abandoned owing to its effects on other tissues, which in many individuals are more susceptible than the inhibitory cardiac center. These animal also vary in their response, apparently owing to varying susceptibility of the inhibitory cardiac center. When this is low, the spontaneous rhythmicity of the heart may be so much augmented by the drug that the rhythm becomes irregular from ectopic beats at a lower concentration of the drug than is necessary to arouse the inhibitory center. This unresponsiveness of the center is especially liable to occur from reflex "shock" during the operation, and unless this is carefully avoided, no slowing or block may be induced by digitalis or its allies. The more perfect the anesthesia, the greater is the inhibitory action as a general rule.2 The peripheral inhibitory mechanism is not at fault. In the rabbit there is little or no slowing from digitalis, probably from the weak activity of the center in these animals. When there is marked sinus slowing there may be no sign of impairment in the A-V conduction, but on increasing the demands on it by accelerating the rhythm even slightly, its weakness is made manifest in block.