Variations in Auriculoventricular Conduction Time in Rheumatic Carditis with Salicylate Therapy.

Abstract

It is now generally believed that the drugs employed in the treatment of acute rheumatic fever (sodium salicylate, acetylsalicylic acid and neocincophen) probably exert an antisymptomatic rather than a specific action in this disease. Following their administration, the pain and exudation of arthritis are usually controlled, high fever is reduced, the heart rate becomes slower and there is often a concomitant fall in the leucocyte count. The mechanism by means of which these results are accomplished, is not understood.

No direct effect of medication upon the cardiac lesions of rheumatic fever has been demonstrated. Auscultatory signs do not afford an accurate index of slight modification in a valvulitis. Electrocardiographic evidence of myocardial involvement is frequent; and the most readily measurable graphic change is auriculoventricular conduction time (P-R interval).

In three cases of acute rheumatic carditis with arthritis, prolonged P-R interval (0.23-0.24 seconds) was found on admission to the hospital. No digitalis had been given to any of the patients. Fever, tachycardia and slight leucocytosis were present in all. Salicylate, in the form of sodium salicylate or aspirin, was administered in courses, with an interval of from six to nine days between them. During this interval all drugs were withheld. Following the institution of salicylate therapy, the usual effects on arthritis, temperature, pulse and leucocyte count were experienced. In addition, there was a gradual reduction in the duration of the P-R interval to within normal limits (0.20 seconds or less). On discontinuing salicylate, the conduction time increased beyond the upper limit of normal, in one instance becoming longer than on first examination. The reappearance of fever, tachycardia, leucocytosis, and in two instances, arthritis, afforded further evidence of the recrudescence of acute infection. A second course of salicylate was again followed by the subsidelice of these signs and by a shortening of A-V conduction. There appeared to be a definite relationship between variations in conduction time and salicylate medication.