The incidence, significance and prognosis of arrhythmias in acute myocardial infarction.

Concepts of the incidence, significance and prognosis of almost all cardiac arrhythmias during acute myocardial infarction have changed greatly in the last 15 years. In some cities facilities are available to reach patients in the very earliest phases of ischaemia or infarction. As previously suspected but now confirmed, ventricular fibrillation occurs commonly at this time and depending on whether ischaemia or infarction is the basis of its occurrence, has a variable long-term prognosis. In the coronary care unit ventricular arrhythmias are more frequent than was originally believed and current research suggests that they have little if any predictive value in defining individuals who would develop ventricular fibrillation. Such events, however, appear related to the severity of myocardial or coronary artery disease. Similarly, asystole and heart block in acute myocardial infarction are important causes of mortality through their association with severe underlying disease. Other cardiac arrhythmias are not infrequent in acute myocardial infarction. They may carry an immediate prognostic implication for the patient but rarely have long-term implications. Autonomic nervous system disturbances may underlie many arrhythmias occurring particularly in the earliest phases of infarction.