Six mechanisms of supraventricular tachycardia in the same patient: report of a case.

An 18-year-old girl had been suffering from palpitations for 3 years. After a normal and asymptomatic pregnancy, she became highly symptomatic with more than 6 tachycardia paroxysms a week, many of them requiring emergency hospitalizations because of hemodynamic collapse. The electrophysiological evaluation revealed dual A-V nodal pathways and the presence of 4 accessory pathways (3 in the left A-V ring: lateral, posterior, and posteroseptal, 1 right posteroseptal) with 5 types of atrioventricular tachycardia and atrial flutter. The 4 accessory pathways and the slow A-V nodal pathway were successfully ablated, and the patient has been asymptomatic for 12 months without taking antiarrhythmic drugs.

Direct negative chronotropic and inotropic efects of curare on isolated and perfused frog's heart

It has been stated that curare has no direct effect upon the heart because the cardiac muscle is deprived of nicotine receptors. While performing an experimental work, we noticed that when high doses of curare were administered to frogs, a change in cardiac activity occurred. In order to elucidate whether the cardiac effects of curare wee the results of a direct action or a reflex response, we studie the effects of increasing doses of d-tubocurarine on the rate and contractility of 8 isolated and perfused frogs'hearts. After testing the d-tubocurarine effects on the heart rate and contractility, we added either acetylcholine, atropine, atenonol or verapamil in orden to find out whether any change ocurred in the cardiac effects produced byd-tubocurarine. Thirty seven measurements were carriet out and it wasfound that 1) high doses (between 1 and 15 micrograms) of d-tubocurarine produced a highly significant decrease in heart rate an contractility; 2) d-tubocurarine did not avoid the acetycholine effect; 3) atropine, atenonol and verapamil did not interfere with d-tubocurarine effects. We conclude that high doses of d-tubocurarine produce "dosis-dependent" heart rate and contratility reductions. These effects are not mediated by muscarinic receptors beta-1 receptors or the show calcium channels