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A total of 266 patients entered into a study comparing the effect of intravenous magnesium and propranolol following acute myocardial infarction. Of these, 97 were able to receive either drug and were therefore randomized into the magnesium (n = 51) or propranolol group (n = 46). 88 patients were unable to receive propranolol and formed a third group (NR) while a further 81 patients could not receive either drug and formed a fourth group (N). The study showed that intravenous magnesium was as effective in preventing potentially lethal arrhythmias as propranolol and could be given to some 70 per cent of such patients whereas propranolol could only be given to 36 per cent.

Ninety-five patients with acute myocardial infarction were followed up for 6 months to 3 years (mean 25.4 months) in a preliminary study to compare the effects of intravenous magnesium (49 patients) with that of intravenous propranolol (44 patients) given immediately after admission to the intensive care unit. There were four cardiac deaths in the propranolol group and no deaths in the magnesium group (P0.046) and 27 per cent of patients who received propranolol subsequently developed cardiac failure as opposed to 12 per cent of those who had received magnesium (P0.04). Intravenous magnesium given in the early stages of myocardial infarction reduces the subsequent cardiac death rate possibly by reducing infarct size.

This study analyzes the use of PAC in a registry comprising 5,841 hospitalized patients with AMI. A total of 371 patients received PAC. In-hospital mortality was higher in patients with CHF who received PAC, while there was no difference in patients with cardiogenic shock or persistent hypotension. Mortality in patients receiving PAC was higher irrespective of the presence or absence of "pump failure." A separate analysis of discharge summaries of 364 patients with CHF showed that PAC was used more frequently in sicker patients and that when severity of CHF was assessed, no difference in mortality was found in patients with mild or moderate CHF. We conclude that while a higher in-hospital mortality is found in patients receiving PAC, this excess is likely related to difference in severity of CHF, which had not been assessed in every individual. It is unlikely that PAC increases mortality.

Two hundred and fifty patients admitted with acute myocardial infarction were treated with a continuous infusion of magnesium sulfate for 24 h (a total of 46 mmol of elemental magnesium). Only 1 patient had ventricular fibrillation; no patient had sustained ventricular tachycardia requiring cardioversion. Twenty-five patients had short runs of non-sustained ventricular tachycardia and did not need cardioversion. In 6 further patients, the infusion had to be discontinued because of a drop in blood pressure. The in-hospital mortality for the group was 3.4%.

The case of a two year old girl with anomalous origin of the left coronary artery from the pulmonary artery is described. She was never in heart failure but had cardiomegaly and anginal pain. The ECG showed a typical infarct pattern with left ventricular hypertrophy. An unusual finding was a prolonged QTc of 0.52. During cardiac catheterization and twice 24 hours later she developed ventricular fibrillation treated with electroshock and prevented later with propranolol. The QTc returned to normal after surgery. Echocardiography showed diastolic flutter and early systolic closure of the pulmonary valve. This disappeared after surgical correction. Transverse 2D echo of the aortic root showed a large right coronary artery which decreased in size after surgery. The left coronary artery was not seen on echocardiography. At cardiac catheterization the diagnosis of an anomalous origin of the left coronary artery from the pulmonary artery was established, with a large shunt to the pulmonary artery through the anomalous artery. Mild pulmonary hypertension and mild mitral regurgitation were present. At surgery, since direct implantation was technically impossible, the left coronary artery was successfully connected to the aorta via a 6 mm expanded Poly-Tetra-Fluoro-Ethylene (P.T.F.E.) graft.

Seven of 48 patients (14.6%) with acute myocardial infarction who were given 2.4 g of magnesium sulfate as a single intravenous dose had potentially lethal arrhythmias during the first 24 hours after admission, whereas 16 (34.8%) of 46 patients receiving placebo had similar arrhythmias. In addition, 14 of these 16 patients in the placebo group had their first arrhythmia (in the intensive coronary-care unit) within two hours after the start of the study, whereas in the magnesium-treated group, there were no such arrhythmias until some four hours later. The higher the lymphocyte potassium concentration, the greater the reduction in the incidence of arrhythmias. Serum magnesium levels increased by 16.5% and lymphocyte magnesium concentrations by 72% in the magnesium treated group. Intravenous magnesium reduces the incidence of serious arrhythmias after acute myocardial infarction.

The auscultatory signs in 90 subjects with hypertrophic obstructive cardiomyopathy are described. The late-onset ejection systolic murmur and its responses to vaso-active manoeuvres reflect a volume-dependent outflow tract obstruction. Late vibrations of the systolic murmur, not uncommonly recorded at the apex, are due to associated mitral incompetence. Non-ejection systolic clicks may occur, and the likely explanation is inequality of the functional length of the mitral chordae tendineae secondary to asymmetrical myocardial hypertrophy. The second heart sound is often abnormal, usually with delay in the aortic component. Some correlation was demonstrated between the relative degrees of left and right ventricular outflow obstruction and the pattern of splitting of the second heart sound. Reversed or partially reversed splitting is usually associated with a more severe left ventricular outflow obstruction. Ejection systolic clicks and early diastolic murmurs occur infrequently, but are not incompatible with the diagnosis of hypertrophic obstructive cardiomyopathy.