Spontaneous rupture of one or more cardiac chambers following open heart surgery is not common. A case is reported of a 45 year-old woman who sustained a spontaneous rupture of the right atrium in the intensive care unit after mitral valve replacement. Exsanguination of the patient was very rapid. On the basis of clinical and experimental convincing studies in this case a high dose of ACTH was used to prevent the damaging effect of haemorrhagic shock. During the reopening manoeuvre and initial conventional management, 10 mg ACTH (1-24) was injected into a peripheral vein. Although the blood lost was 93% of her circulating blood volume and a lot of fluid transfused via the central venous catheter was lost into the pericardium and hemithorax, the patient's condition improved rapidly after the occlusion of the atrial tear with initial small volume of transfusion. Based on the review of recent investigations the use of ACTH is emphasized.