Methods Clinical Material Fifteen patients who had had an acute myocardial infarction within the preceding 24 hours were selected for treatment and investigation. The evidence of myocardial infarction was based on unequivocal electrocardiographic proof of recent transmural myocardial infarction. Six patients were considered to be in severe cardiogenic shock. The criteria used to define shock were a systolic blood-pressure on auscultation of less than 100 mm. Hg in the presence of cold, clammy, sweating, and cyanosed extremities, with mental apathy or restlessness. The other nine patients had had an acute myocardial infarction uncomplicated by either shock or manifest left-ventricular failure. The clinical details of each patient are summarised in table i. The patients were admitted direct to an intensive-care resuscitation room in the ward area, in which the apparatus essential for their continuous monitoring was already assembled. An emergency team of doctors, nurses, and technicians was also available on a 24-hour standby basis, which ensured immediate attention to the patient on arrival in hospital.