Abstract The evolution of spontaneous variations in the coagulability of the blood following myocardial infarction has been studied in seventy untreated cases by simultaneous estimations of the prothrombin time and the heparin tolerance test (in vitro). 1. 1. Starting from the acute attack, three phases succeed one another with great regularity: 1.1. (a) Period of hypercoagulability, often extreme, occupying the first twenty-four to forty-eight hours. Very constant. 1.2. (b) Period of spontaneous, secondary hypocoagulability from second to third to eighth to fifteenth day, usually lasting about seven days. Occurred in 81.4 per cent of cases in the series. 1.3. (c) Period of late hypercoagulability, variable in degree, starting on about the eighth or tenth day and lasting usually a few weeks but possibly several months. 2. 2. The demonstration of these spontaneous fluctuations of coagulability have enabled us to elaborate a rational system of anticoagulant treatment which has been applied to seventy-one cases of infarction with good results (over-all mortality: 9.8 per cent, thrombo-embolic complications: 2.8 per cent), and a small incidence of inconsequential bleeding (12 per cent). 3. 3. Frequent studies of blood coagulability are essential to any treatment with coumarin substances. The prothrombin time by itself is not enough; measurements of the heparin tolerance in vitro must always be made at the same time.
J. Beaumont, H. Chevalier, J. Lenègre
American heart journal