Defining the pattern of initiation of monomorphic ventricular tachycardia using the beat-to-beat intervals recorded on implantable cardioverter defibrillators from the RAFT study: A computer-based algorithm.

Arrhythmia onset pattern may have important implications on morbidity, recurrent implantable cardioverter defibrillator (ICD) shocks, and mortality, given the proposed correlation between initiation pattern and arrhythmia mechanism. Therefore, we developed and tested a computer-based algorithm to differentiate the pattern of initiation based on the beat-to-beat intervals of the ventricular tachycardia (VT) episodes in ICD recordings from the Resynchronization-Defibrillation for Ambulatory Heart Failure Trial (RAFT). Intervals on intracardiac electrograms from ICDs were analyzed backwards starting from the marker of VT detection, comparing each interval with the average tachycardia cycle length. If the morphology of the beat initiating the VT was similar to the morphology of the VT itself, the episode was considered sudden. If the morphology of the beat initiating the VT was not similar to the morphology of the VT itself, the episode was considered non-sudden. The capability of the algorithm to classify the pattern of initiation based only on the beat-to-beat intervals allows for the classification and analysis of large datasets to further investigate the clinical importance of classifying VT initiation. If analysis of the VT initiation proves to be of clinical value, this algorithm could potentially be integrated into ICD software, which would make it easily accessible and potentially helpful in clinical decision-making.

Pattern of initiation of monomorphic ventricular tachycardia and implications on tachycardia mechanism.

The incidence of sudden cardiac death, predominantly caused by ventricular tachycardia and ventricular fibrillation, is high in patients with congestive heart failure. Implantable cardiac defibrillators have improved survival in this population but defibrillator shocks can lead to low quality of life and heart failure progression. The current management of recurrent ventricular tachycardia includes ablation and anti-arrhythmic drugs and both are associated with high recurrence rates. Better understanding the mechanism of ventricular tachycardia allowing individualization of treatment may improve outcomes. Re-entry is currently accepted as the mechanism of the majority of monomorphic ventricular tachycardias in patients with congestive heart failure, being responsible for more than 90% of the ventricular tachycardia in patients with ischemic cardiomyopathy. On the other hand, some studies show a greater participation of focal arrhythmias in the genesis of ventricular tachycardia in this population. The pattern of initiation of ventricular tachycardia is divided into sudden, when the first beat of the tachycardia is morphologically similar to the rest of the tachycardia, and non-sudden, when its morphology is dissimilar. An association between the pattern of the initiation and the mechanism of ventricular tachycardia has been proposed. The pattern of initiation of ventricular tachycardia is a readily available from data stored in current generation implantable cardiac defibrillators. The association with tachycardia mechanism may allow individualization of the therapy, however evidence is lacking and further research is required.