Studies on Aconitine-induced Arrhythmias

Abstract

Aconitine induced the automatic activities in the isolated strip of the left superior vena cava in rabbit. In the left superior vena cava near the coronary sinus, action potentials with diastolic slow depolarization were recorded after the application of aconitine. When aconitine was applied to the left superior vena cava near the coronary sinus in situ, cardiac arrhythmias were recorded. From the above-mentioned facts, it was suggested that aconitine induced the ectopic pacemaker in the left superior vena cava proximal to the heart and that the impulse from the ectopic focus spread not only to the periphery but also to the atrium. In the patient with persistent left superior vena cava the ectopic pacemaker formation in the vena caval muscle may have the significance for the genesis of cardiac arrhythmias, especially supraventricular extrasystoles. CONITINE is a characteristic substance which induces cardiac arrhythmias. When locally applied to the cardiac muscle, it induces ectopic pacemakers at the area of application. However, the ectopic pacemaker formation in the left superior vena cava proximal to the heart has never been reported. Recently, it was found that the impulse which originated in the sinus node spread not only to atrial muscle but also to vascular muscle in vena cava (sino-caval conduction),1)-3) that the configuration of transmembrane potential of left superior vena caval muscle had close similarity to that of cardiac muscle,4) and that the contractile tension could be recorded.5) In connection with these facts, the ectopic pacemaker formation by aconitine in the left superior vena cava proximal to the heart was studied in rabbit. METHODSThe rabbits weighing 1.5 to 2Kg. were used. After intraperitoneal injection of pentobarbital sodium, the animals were thoracotomized. Experiments were carried out in vitro and in situ. In the in vitro experiment, after three venae cavae were cut at 2-3cm. from their cardiac orifices, the heart was excised. Then a large