The Site of Origin of Torsade de Pointes

Study Questions:

Where is torsade de pointes (TdP) most likely to originate?

Methods:

This was a retrospective analysis of 1,025 electrocardiograms that recorded the onset of TdP (n = 151) or QT-related ventricular extrasystoles (n = 874). The electrocardiograms were from 50 patients without structural heart disease who had either congenital or acquired long QT syndrome (LQTS). The site of origin of QT-related arrhythmias was classified as outflow tract, inferior left ventricle, or inferior right ventricle based on QRS morphology and axis.

Results:

The most common site of origin of TdP was the outflow tract (56%), followed by the inferior left ventricle (32%) and inferior right ventricle (12%). The most common site of origin of QT-related extrasystoles also was the outflow tract (70%), followed by the inferior left ventricle (17%) and inferior right ventricle (13%). There was no relationship between the etiology of LQTS and the arrhythmia site of origin. Among 34 patients with ≥2 episodes of TdP, the site of origin was consistent.

Conclusions:

The authors concluded that the most common site of origin of TdP and QT-related ventricular extrasystoles is the outflow tract.

Perspective:

The most common site of origin of catecholaminergic polymorphic ventricular tachycardia (VT), idiopathic ventricular fibrillation, and polymorphic VT associated with the Brugada syndrome also is the outflow tract. Furthermore, the outflow tract is the most common site of origin of idiopathic monomorphic VT and idiopathic premature ventricular depolarizations. The reason that the outflow tract is a common site of origin of ventricular arrhythmias in patients without structural heart disease is unknown. In any case, as demonstrated in some case reports, a reproducible site of origin can allow mapping and ablation of the triggers of TdP and other types of polymorphic VT.

Clinical Topics: Arrhythmias and Clinical EP, Congenital Heart Disease and Pediatric Cardiology, Implantable Devices, EP Basic Science, Genetic Arrhythmic Conditions, SCD/Ventricular Arrhythmias, Congenital Heart Disease, CHD & Pediatrics and Arrhythmias

Keywords: Brugada Syndrome, Tachycardia, Ventricular, Heart Conduction System, Ventricular Fibrillation, Long QT Syndrome, Electrocardiography, Heart Ventricles, Ventricular Premature Complexes


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