Data from long-term electrocardiograms and their use in cardiac risk stratification

Long-term electrocardiographic recordings were originally introduced into clinical practice to trace occurrences of ventricular premature depolarisations and the presence of other forms of cardiac arrhythmias. Presently, the frequency of ventricular premature beats still remains one of the factors acquired from Holter recordings. However, sophisticated computerised processing enabled more substantial information to be revealed from long-term electrocardiograms. Data from Holter records are used to assist clinical management of individual patients as well as to approximate the risk of adverse cardiac events. The utilisation of Holter recordings for cardiac risk stratification has been predominantly studied in survivors of acute myocardial infarction. In these patients, both the risk of ischaemic episodes and of arrhythmic events may be assessed from 24-hour electrocardiograms. The risk of ischaemia is mainly related to episodes of ST segment depression or elevation. Some of such episodes may not be associated with clinical symptoms. The term `silent ischaemia´ describes such cases. Increased frequency and prolonged duration of silent or symptomatic ST segment changes indicate high risk of reinfarction. If related to specific physical activity, their appearance may suggest specific patient management. Risk of arrhythmic complications is generally believed to be related to three factors. These are described here