The following are key points to remember from this review of catheter ablation of arrhythmias originating from the left ventricular outflow tract (LVOT):

1. Perspective: The LVOT is an important source of ventricular arrhythmias (VAs). Up to one-third of all idiopathic VAs in patients with structurally normal hearts may arise from the LVOT region. The local anatomy can present both opportunities and challenges for successful treatment. This state-of-the-art review provides an excellent overview complete with detailed figures on how to approach VA from the LVOT.
2. Anatomy of the LVOT: The complex LVOT anatomy has implications for mapping and ablation. The right aortic sinus of Valsalva and the aortomitral continuity are both myocardial targets within the aorta. The LV summit is the triangular region at the superior-most aspect of the LV ostium. The endocardial LVOT, the aortic root, the right ventricular outflow tract, and the great cardiac vein (GCV) and its branches offer multiple avenues for targeting VAs.
3. Targeting Aortic Root VA: Arrhythmias from the right-left commissure likely originate from the ventriculoarterial junction (VAJ). A transseptal approach may facilitate successful ablation in the region of the right-left commissure and has been adopted as a first-line approach by the authors. Transseptal access may decrease the risks of complications associated with instrumentation in the arterial circulation and lower the risk of brain emboli. Remote magnetic navigation may also facilitate mapping of the LVOT and aortic root while maintaining superior catheter stability.
4. Targeting Intramural and LV Summit LVOT Arrhythmias: LV summit VAs usually occur in the absence of structural heart disease. Identification of an intramural septal VA origin requires detailed study of the LVOT and adjacent structures from the endocardium, coronary venous system, and sometimes the epicardium. Mapping using the coronary venous system helps differentiate intramural from epicardial LV summit sources. Early activation in the distal GCV or proximal anterior intraventricular vein (AIV) implicates the LV summit as the site of origin. An early site in a septal perforating vein would point to an intramural source. Coronary angiography should be considered to ensure that the target site is not within 5 mm of a coronary branch. Power delivery is often limited due to low blood flow, and higher irrigation flow rates may be required.
5. One approach for ablating intramural and LV summit VAs that are not accessible via the coronary venous system is to ablate at the “next best” endocardial site(s), guided by local VA activation times and pace mapping. Prolonged application of radiofrequency energy and sequential ablation at multiple sites may be required with higher power and contact force.
6. Alternative techniques include simultaneous unipolar radiofrequency ablation, bipolar radiofrequency ablation, half-normal saline irrigation, retrograde ethanol ablation, and intramural needle ablation. Percutaneous or surgical epicardial approaches are potentially limited by proximity to the coronary arteries, epicardial fat, and position of the left atrial appendage.
7. Special Considerations for Structural Heart Disease: In patients with dilated nonischemic cardiomyopathy or with preserved LV function, LVOT VA can arise from scar involving the basal LV septum and the periaortic region. LVOT VA due to structural heart disease can be differentiated from idiopathic VA by: 1) late gadolinium enhancement on cardiac magnetic resonance imaging; 2) abnormal bipolar or unipolar voltage in the periaortic region; and 3) multiple inducible ventricular tachycardia morphologies, often associated with hemodynamic instability.
8. Scar-associated ventricular tachycardia is usually due to re-entry and is adenosine-insensitive, whereas most idiopathic ventricular tachycardia is due to triggered activity and is adenosine-sensitive. Ablation of scar-associated LVOT VAs has a higher recurrence rate. Alternative ablation strategies such as bipolar, ethanol ablation, or surgical ablation may be needed for scar-associated VAs.
9. Electrocardiogram (ECG) Analysis: The ECG can help localize likely sites of origin. However, published algorithms may be less reliable due to individual anatomic variations in the position of the heart. The presence of multiple exit sites can further complicate localization based on ECG criteria alone.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Vascular Medicine, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Adenosine, Arrhythmias, Cardiac, Atrial Appendage, Cardiomyopathies, Catheter Ablation, Coronary Angiography, Electrocardiography, Endocardium, Epicardial Mapping, Gadolinium, Hemodynamics, Intracranial Embolism, Magnetic Resonance Imaging, Pericardium, Sinus of Valsalva, Tachycardia, Ventricular

< Back to Listings