Anthony M. Heagerty

Intravenous infusion of magnesium sulphate after acute myocardial infarction: effects on arrhythmias and mortality

Two hundred patients with acute myocardial infarction were entered into a randomised double-blind trial where they received either intravenous magnesium sulphate or saline for 24 hours after admission to hospital. The incidence of ventricular arrhythmias necessitating treatment was reduced by more than half in the group receiving magnesium sulphate. There were two deaths in the group receiving magnesium sulphate and seven receiving saline placebo. Total cardiac events were significantly reduced in the magnesium treated group. These reductions cannot be attributed to differences in risk factors or therapy between the two groups, either before or during the period of study. These results suggest that magnesium administration reduces the incidence of serious tachyarrhythmias and death after acute myocardial infarction and that this simple regime warrants further study.

Leucocyte membrane sodium transport in normotensive populations: dissociation of abnormalities of sodium efflux from raised blood-pressure.

Sodium efflux rates were measured in leucocytes from eighteen normotensive subjects who had one or more first-degree relatives with essential hypertension and from twenty-four matched controls with no such family history. The total efflux rate constant was significantly lower in those with a family history of hypertension, owing to reduced ouabain-sensitive sodium pump activity. The presence of a membrane electrolyte handling abnormality characteristic of essential hypertension in normotensive individuals genetically predisposed to hypertension points to an underlying genetic factor. At the same time, the fact that blood-pressure was normal in these subjects indicates that the abnormality does not participate directly in blood-pressure elevation. Rather, the abnormality, like other red-cell changes in electrolyte handling, seems to be a marker for a genetically determined alteration in membrane structure, and thus only indirectly related to hypertension.