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Tips on AVNRT Ablation
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=OxH9yFX5eI0
Description at: https://johnsonfrancis.org/profession... • Tips on AVNRT Ablation, collected from experts during EP meetings. • Ablation of anterior inputs to the AV node: fast pathway – seldom done now. Ablation of posterior inputs to AV node: Slow pathway – the main target for ablation in AVNRT. • Area of interest for atrioventricular nodal re-entrant tachycardia ablation: Triangle of Koch bounded by Coronary sinus os, septal tricuspid leaflet and Tendon of Todaro. Compact AV node and His Bundle are at the apex of the triangle. • If the Koch’s triangle is small, there is a higher risk of complete heart block which is more likely in children. In elderly the CS os is higher and the triangle becomes smaller and there is a higher chance of CHB. • Left anterior oblique view is foreshortened while RAO view can pick up supero-inferior catheter tip movements better during slow pathway ablation. Slow pathway ablation is done near the superior lip of the coronary sinus. • Accelerated junctional rhythm is seen at successful AVNRT ablation site. Stop the ablation even when there is VA block in a single beat. • End point for slow pathway ablation: Complete elimination of slow pathway conduction or a single echo beat during isoprenaline stimulation is indicative of successful ablation. • Ideally, only those who need catecholamines for induction of tachycardia prior to ablation need re-stimulation after ablation to check for efficacy of ablation. However, if isoprenaline stimulation is used for documentation of success, the recurrence rate will be lower. • AVNRT ablation in elderly: Elderly are often more symptomatic, triangle of Koch is more horizontal, associated structural heart disease is more common. • AVNRT ablation in children: AV block incidence is slightly more, long term follow up has shown it to be a safe procedure. Cryoablation is being used more often in children and may replace RFA • Gradual power titration can reduce incidence of CHB. Linear posterior lesion from CS to tricuspid annulus is safe. • Cryo ablation has lower rates of CHB and there is no epicardial coronary injury with cryo. Fluoro time is also reduced with cryo as the catheter adheres (cryoadherence) to the site and repeat fluoro is not needed during the ablation period. • Non-contact mapping in AVNRT ablation is reserved for refractory cases. Magnetic navigation systems can be used but are not too relevant for AVNRT ablation. • Ablation at the floor of the CS can cause inappropriate sinus tachycardia due to injury to the ganglia. Vagal stimulation during ablation in floor of the CS can cause AV block with simultaneous sinus bradycardia. • This will not be an indication for stopping ablation. A shot of atropine can be given, and we can continue with ablation. • A large CS may make the ablation site closer to the compact AV node if we take a CS catheter going along the roof of the CS as a guide. CS angio can be used to delineate the CS size in this case. • CS floor can be delineated by a catheter introduced from above through the internal jugular vein. • During slow pathway ablation, RAO view is used to ensure that the catheter is on the septum, which is identified by the up and down movement of the tip. If it is away from the septum the tip will move side to side in this view. • Fast pathway ablation is done in fast – fast pathway AVNRT, a very rare form of AVNRT. Fast pathway ablation has also been done when an IVC stent prevents ablation of slow pathway. • Left sided extension of slow pathway can occur in atypical AVNRT, requiring ablation deeper in the CS or in the middle cardiac vein. This breaks the rule that CS ablation should be done nearer the CS ostium to prevent coronary injury. • Junctional acceleration during ablation may not be seen when the sinus rate is high. End point for ablation should be stricter for slow pathway ablation in atypical AVNRT. Otherwise the recurrence rate is high.
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