Hourly variability versus ECG morphological criteria in predicting the site of origin of ventricular outflow tract ectopy.

Outflow tract ventricular arrhythmias (OTVA) are the most common form of idiopathic ventricular arrhythmias encountered in clinical practice. The 12-lead electrocardiogram (ECG) is a vitally important tool that allows rapid and non-invasive localization of the most likely site of origin (SOO) when planning ablation procedures. Different ECG criteria have been validated for this purpose.1 However, their accuracy may be reduced by variations in body habitus and cardiac orientation.2