Analysis of T-wave alternans in ambulatory records using a new index : ADTWA

Cardiovascular diseases are the major cause of death in adults and the elderly in the majority of the developed countries and in many developing countries. A great part of these deaths occur suddenly, shortly after the onset of the first symptoms, and are related to malignant ventricular arrhytmias that lead to a heart attack. This kind of outcome is known as sudden cardiac death (SCD). Implantable cardioverter defibrillators (ICD) are the most effective way of preventing SCD. However, the implantation of an ICD is an invasive procedure with associated risks and a high cost. Therefore, it is necessary to determine non-invasive risk markers that identify patients at a higher risk of suffering malignant arrhytmias, so that invasive diagnostic test and treatments can be selectively applied only to those patients who will benefit the most, saving risk for the patients and also health-care costs. Various non-invasive indices have been proposed to predict the risk of arrhytmias. Most of them are based either on the analysis of echocardiographic images or on the analysis of electrocardiographic signals (QRS duration, QT dispersion, heart rate variability, etc.). The main limitation of existing indices is their low specificity and predictive value. One of the most promising non-invasive indices is T-wave alternans (TWA). Its prognostic value is being intensively studied and significant evidence of the relation between TWA and the susceptibility to ventricular fibrillation has been found in recent years. This Master's Thesis work presents and assets a new method for evaluating the presence of TWA in ambulatory records (Amplitude of Dominant T-Wave Alternans).