Abstract
Summary
In the isolated heart of the dog in the form of the heart-lung preparation atabrine has a negative inotropic action which appears in some cases at concentrations of 1 mg per liter of blood and is always observed at concentrations of 1.5 mg per liter or above. As a result, the work capacity of the heart is impaired. Slowing of the heart rate sometimes occurs. Irregularities of cardiac rhythm are seen only with high and acutely toxic doses.
Injection of 10-15 mg of atabrine within 1 minute into a total blood volume of 500 to 900 cc leading abruptly to blood levels of several milligrams per liter of blood causes a severe heart failure, while the continuous infusion of the same amount at a rate of 0.5 mg per minute will barely reach the toxic concentration in the blood.
A severe myocardial failure of the isolated heart, once established, does not appear to be reversible. Epinephrine hydrochloride has a transient positive inotropic and chronotropic action, while the cardiac glycosides effect a prompt and long-lasting improvement of the work capacity of the failing heart in doses which do not change the heart rate and do not lead to irregularities of heart rhythm.
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