Percutaneous pericardial access for epicardial mapping and ablation of ventricular arrhythmias has expanded
considerably in recent years. After its description in patients with Chagas disease, the technique has provided relevant information
on the arrhythmia substrate in other cardiomyopathies and has improved the results of ablation procedures in
various clinical settings. Electrocardiographic criteria proposed for the recognition of the epicardial origin of ventricular
tachycardias are mainly based on analysis of the first QRS components. Ventricular activation at the epicardium has a
slow initial component reflecting the transmural activation and influenced by the absence of Purkinje system in the
epicardium. Various parameters (pseudodelta wave, intrinsicoid deflection and shortest RS interval) of these initial intervals
predict an epicardial origin in patients with scar-related ventricular tachycardias with right bundle branch block morphology.
Using the same concept, the maximum deflection index was defined for the location of idiopathic epicardial
tachycardias remote from the aortic root. Electrocardiogram criteria based on the morphology of the first component of
the QRS (q wave in lead I) have been proposed in patients with nonischemic cardiomyopathy. All these criteria seem to be
substrate-specific and have several limitations. Other information, including type of underlying heart disease, previous
failed endocardial ablation, and evidence of epicardial scar on magnetic resonance imaging, can help to plan the ablation
procedure and decide on an epicardial approach.
Keywords: Arrhythmia, catheter ablation, electrocardiogram, epicardium, ventricles, ventricular tachycardia.
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