The acute phase of myocardial infarction.

During the acute phase of myocardial infarction, two groups of patients are observed. Patients in the first group have no significant complications, and approximately 95 per cent of these patients recover fully without any specific therapy. Patients in the second group may have various complications, some of which are benign, whereas others may lead to a fatal outcome. The complications may be divided into four major types: 1. Cardiac arrhythmias and conduction defects. The tachyarrhythmias and bradyarrhythmias are the most frequently encountered complications in patients with acute myocardial infarction. Tachyarrhythmias include ventricular premature beats, ventricular tachycardia, ventricular fibrillation, supraventricular tachycardia, atrial flutter, and atrial fibrillation. Bradyarrhythmias include sinus and junctional bradycardia and various degrees of heart block. Those patients who are unable to reach a hospital and die suddenly presumably succumb to ventricular fibrillation. 2. Left ventricular failure and cardiogenic shock. In more than 33 per cent of patients with acute myocardial infarction, a third heart sound and pulmonary rales may be heard. If they are present for only 24 hours, the physical findings may indicate an alteration of left ventricular failure. However, if they persist for a few days and disappear after medical therapy, mild left ventricular failure may be present. About 12 per cent of patients have acute pulmonary edema, and 10 per cent of patients develop cardiogenic shock. These two complications carry a high mortality rate (40 per cent and nearly 100 per cent respectively). 3. Rupture of the heart. Cardiac rupture may occur in the free wall, ventricular septum, and papillary muscles. These complications, although less frequently encountered, cause a number of deaths in patients with acute myocardial infarction. 4. Thromboembolism. Under this category are included pulmonary embolism, systemic arterial embolism, and systemic venous thrombosis.