Abstract
Observations were made in eight cases of complete heart block; and the findings in five cases, admitted previously to Bellevue Hospital, were used as material. Over 300 electrocardiographic tracings of one minute duration were analyzed.
Epinephrine was selected as a stimulant for the sympathetic end apparatus in the heart. Subcutaneous doses of 1 to 2 mg. increased the ventricular rate considerably. This increase persisted from 15 minutes to several hours. The auricular rate and the blood pressure showed no, or moderate, increase. Change in the auricular rate did not go parallel, as a rule, with the change in the ventricular rate. The experimental findings suggest that the ventricles have direct and rich sympathetic nerve supply.
Atropine sulfate was administered in doses of 5.0 mg. and 3.5 mg. respectively. The results of these observations indicate that the influence of the vagus on the sinus node is the same in complete heart block as in normal individuals. The effect of atropine on the auricular rate lasted over three hours. The maximal increase was reached as early as 10 minutes and as late as 50 minutes after the injection. The ventricular rate was slightly but distinctly increased, indicating that the vagus exerts a slight inhibitory influence on the ventricles in complete block.
If a certain amount of epinephrine, which increased the ventricular but not the auricular rate, was given after the vagus had been paralyzed; there was an increase in the rates of both the auricules and the ventricles.
Following and probably during exercise there was a marked increase in the auricular rate. The ventricles showed but slight increase as late as 15 to 25 minutes after exercise.
The normal ventricular rate in the cases studied varied from 9 to 84 per minute.
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