Experiments with calculated therapeutic and toxic doses of digitalis

Electrocardiographic Changes Produced in Rabbits by Vasopressin (Pitressin) and their Alteration by Prolonged Treatment with A Commercial Heart Extract

The electrocardiographic changes produced in rabbits by large doses of vasopressin are interpreted to arise from an initial, unstable, state of apical accelerated repolarisation followed by a more enduring state of subendocardial injury. When rabbits were treated, daily, with a commercial heart extract for two weeks and then given vasopressin two days after treatment had stopped, signs of apical accelerated repolarisation were unaltered but the signs of subendocardial injury were substantially suppressed.

Spontaneous and Stress-Induced Myocardial Infarction in Aged Atherosclerotic Dogs

Male, mongrel dogs, six to eight years of age, were placed on an atherogenic regimen which included I 131 administration and/or thiouracil with cholesterol feeding and, in some cases, the addition of 10 per cent lard to the diet. As is usually observed in such experiments, the degree of hypercholesterolemia and atheromatosis varied greatly. However, in nine out of ten dogs with blood cholesterol levels of 1,800 mg. per cent or above for over 16 weeks, myocardial infarction appeared (a) spontaneously, (b) after pitressin administration, and (c) after exposure to a stresser. Myocardial infarction has been noticed only rarely previously. Reasons are given for the belief that the advanced age of the animals which were used here played a role in the genesis of infarction.

The pathogeneis of spontaneous cardiac rupture

Twenty patients with cardiac rupture were compared with suitable control groups. In each ruptured heart there was an acute coronary artery occlusion and a recent, transmural myocardial infarction which was unprotected at the site of rupture by scar or anastomotic circulation. Clinically, rupture usually occurred during the first two weeks of an acute infarction in a hypertensive patient with no previous history of old infarction or congestive failure; persisting hypertension or excessive effort usually preceded rupture. The role of an increased intraventricular pressure in the pathogenesis of cardiac rupture has therapeutic implications.