Mapping and radiofrequency ablation of left ventricular outflow tract arrhythmias.
Abstract
Left ventricular outflow tract (LVOT) ventricular arrhythmias comprise one-third of outflow tract ventricular arrhythmias. The LVOT comprises the aortic cusps, infracuspal left ventricle, aortomitral continuity, great cardiac vein, intramural myocardium, and the left ventricular (LV) summit, each providing potential arrhythmogenic sites. Electrocardiographic features provide important initial clues to differentiate LVOT from RVOT origins and further localize arrhythmia sources within the LVOT. However, definitive localization relies on systematic electroanatomic mapping. Electroanatomic mapping involves stepwise mapping strategy incorporating assessment of the RVOT, great cardiac vein-anterior interventricular vein junction, aortic cusps, and left ventricular endocardium. The triangular mapping approach, integrating activation timing across epicardial, endocardial, and cuspal sites, is particularly useful in identifying intramural foci, which are a common cause of ablation failure Interpretation of electrograms is essential for accurate localization, with characteristic findings such as reversal of high-frequency components in aortic cusp arrhythmias and discordance between unipolar and bipolar signals in intramural origins. Ablation strategies depend on arrhythmia origin. Low-power ablation (≈15 W) is one of the ablation strategies for aortic cusp origin VAs near the left main ostium to reduce risk. Intramural or summit ventricular arrhythmias often require alternative methods, including sequential or simultaneous unipolar ablation, bipolar ablation, specialized irrigants (e.g., half-normal saline), needle-tipped catheters, or ethanol infusion. Even after acute failure, delayed suppression is common due to lesion maturation A structured approach integrating anatomical knowledge, electrocardiographic interpretation, structured mapping and tailored ablation strategies is key to improving success rates in LVOT ventricular arrhythmias.