Catheter ablation of pulmonary sinus cusp-derived ventricular arrhythmias by the reversed U-curve technique

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Radiofrequency catheter ablation (RFCA) has evolved into a widely accepted treatment for patients with symptomatic ventricular arrhythmias (VA).1 The right and left ventricular outflow tracts (RVOT/LVOT) are the most common origin sites for idiopathic ventricular tachycardia (VT) and premature ventricular contractions (PVC) in patients without structural heart disease.1 With approximately 70–80% the RVOT is the most common site for idiopathic VA.1,2 Although the reported success rates are relatively high, a recent multicenter analysis found a recurrence rate of 18% after a mean of 20.2 months.3 Therefore, in some cases successful ablation of these VA may be difficult by current RFCA techniques. In these challenging cases, understanding of the electrocardiography (ECG), anatomical structures, mapping and RFCA with specific techniques should be taken into consideration, especially for unusual locations of VA-origin. While VA arising from the RVOT region are generally located 1 cm near the pulmonary sinus cusps (PSC),4 RFCA is successful below the pulmonary sinus cusp in the majority cases. However, the exact anatomical location is very limited due to no angiography performance and lack use of ultrasound during the ablation. Recently, only a few studies reported on the prevalence and RFCA of VA arising from the pulmonary artery (PA) (21–46%), most commonly in patients with previous failed ablation.5,6
More distinct areas within the PA are the PSCs. Previous studies including autopsies found that myocardial musculature sleeves from the RVOT are extending above the PV into the PA in up to 74% of specimens.5,7 These musculature sleeves are accompanied by connective tissue and where previously suggested to be possible substrates for VAs arising from the PSCs and PA by creating abnormal triggered activity.6,7,8
While VA arising from the aortic valve cusps has been previously described by many authors,9,10,11,12 a novel type of arrhythmia-designated PSC-derived VA was recently proposed by Liao et al.10 and ECG characteristics, prevalence, mapping, and ablation techniques were described. In 24/24 patients PSC-derived VA could be successfully ablated via a reversed U curve technique within the PSC.8 Concerning VA arising from this distinct region a relatively small prevalence has been reported (11%).8
Within this context Yang et al. report their experience on RFCA of PSC-derived VA by applying the reversed U curve technique.13 Via a retrospective analysis from 180 patients with symptomatic VA, left bundle branch block (LBBB), and inferior axis 15 patients underwent RFCA for PSC-derived VA. Four cases had a history of ablation failure. Among the 15 patients with PSC-derived VA, all originated from the lower region of the PSC. In four cases VA derived from the right PSC (RC), five from the anterior PSC (AC), and six from the left PSC (LC). The origin of the 15 cases reported in this study was consistent with those reported by Liao et al.8 Additionally, the ECG characteristics were mainly consistent: high R-wave amplitudes in inferior ECG leads, aVL/aVR ratios of Q-wave amplitude was >1, and most transitional zones of the precordial leads were presented in V3. V2 lead transition in patients with left PSC-derived PVCs was similar to that originating from the LVOT.8 It can be explained by the fact that the left PSC is anatomically related very close to the left coronary sinus cusp and relatively high position, and this explains the high R-wave amplitudes of the inferior leads and the R/S ratio on lead V2. In patients with VA from PSC, mapping and ablation within the PSC was achieved by using a reversed U curve technique8,14: By rotating the mapping catheter clockwise and counterclockwise the three individual PSCs has been reached, and PA angiography and ICE was used to determine the precise location of the catheter.
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