Myocardial contractility after injection of prolonged infusion of magnesium sulphate.

The effect of magnesium sulphate administration on myocardial inotropism has been evaluated by means of the noninvasive indexes of myocardium contractility in 18 patients affected by myocardiosclerosis associated with signs of cardiac impairment of different degree. Magnesium has been administered via either a prolonged infusion (30-50 mg/min) or a single injection (2.5 g/30 sec). It is emphasized that the influence of this agent on systolic time intervals (STI) is dependent upon its route of administration. Thus, prolonged infusion does not modify significantly these parameters, whereas a single injection induces marked variations, i.e., decrease of LVET, increase of PEP, ICT and PEP/LVET ratio, which are all more marked in cases of severe cardiac impairment. In view of the strict correlation established between the STI and the invasive indexes of myocardial contractility, it is suggested that administration of magnesium sulphate via prolonged infusion does not induce a decrease of cardiac performance, while a single injection of this agent leads to this effect.