Studies on Cardiotoxin and Vasoactive Substance Releasing Component(s) of Cobra Venom. Comparison of Hemodynamic Effects of Cardiotoxin with those of Cobra Venom

Abstract

The effects of crdiotxr on the cardiovascular system hat been studied in comarison with tboe& 'of crude yeanm of Formosan cobra. The intravenous injection of cardiotozin (1.0 mg/kg) usuaflly produces an iummdate rise in systemic arterial esefolowed by a progressive decline leaing to cardiac arrest, whereas a preiptos 11in systemc arterial pressure is usually obser ve with crue yea 105-1.0 wak). A very marked increase in both pulmonary artery pressure and pulonryvascua resistance is *ioduced foloning the injection of crueo venoma, wfras the increase is far loe conspicuous with cardiotin. Cardiac output as w4 as stroke volus is decreased by both crude veo and cardiotoxi.The early decree in cardiac output with crude veam appears to be resulted frca the marked ibcrease I pulmonary vascular resistance, whereas the progressive decrease leading to circulatc failuz% is due to the direct off ofAndox~ on the heart. Ventricular contractile force is depmessed by an apT c~ltqa smI rcded byc initial augmntation of varying Z V± AI1 01ine.s asSdprui inverted -T, nodal. rhythm, A-V block A-V dissociation, idiovent cLa rhythm a vmsnrcu1&r tachycardia are ao.ere with oardiotxist-as well as zrue venom. V. ca Pren=w in inareased with crude vono probablj as a result of dilation of the ASM * beart, tres no appeclahle change In caval pressure is frwd with oardletada ma lIe" oardlac fumcticss are seriously Impaired at.a later stags. Approved for public releaBe-, distribution unlimited. I:ABSTRACT -The effects of cardiotoxin on the cardiovascular system has been studied in comparison with those of crude venom of Formosan cobra. Tne intravenous injection of cardiotoxin (1. 0 mg/kg) usually produces an. immediate rise in systemic arterial pressure, followed by a progressive decline leading to cardiac arrest, whereas a precipitous fall in systemic arterial pressure is usually observed with crude venom (0. 5 -1. 0 mg/kg). A very marked increase ih both pulmonary artery pressure and pulmonary vascular resistance is produced following the injection of crude venom, whereas the increase is far less conspicuous with cardlotoxin. Cardiac output as well as stroke volume is decreased by both crude venom and cardiotoxin. The early decrease in cardiac output with crude venom appears to be resulted from the marked increase in pulmonary vascular resistance, whereas the progressive decrease leading to circulatory failure is due to the direct effect of cardiotoxin on the heart. ) Ventricular contractile force is depressed'by both crude venom and cardiotoxin, usually preceded by an initial augmentation of varying duration. Abnormal ECG changes such as ST depression, inverted T, nodal rhythm, A-V block, A-V dissociation, idioventricular rhythm and ventricular tachycardiaare observed with cardiotoxin as well as crude venom. V. cava pressure is increased with crude venom probably as a result of dilatation of the right heart, whereas no appreciable change in caval pressure is found with cardiotoxin unless cardiac functions are seriously impaired at a later sta...