Background Supraventricular tachycardia (SVT) is common in pediatric patients. During radiofrequency ablation, catheters (ventricle, V; coronary sinus, CS; high right atrium, HRA; his, H) are used to determine the properties and sidedness of the accessory pathway. The purpose of this study was to determine whether accessory pathway sidedness could be determined using the V-HRA interval. If the V-HRA interval is a valid predictor of sidedness prior to implanting a CS catheter, then the CS catheter may not be necessary in many electrophysiology studies.
Methods This retrospective, IRB approved study was performed using data collected from patients who underwent radiofrequency ablation for SVT due to an accessory pathway from 12-00 to 08-04. Data collected included age, intracardiac timing intervals, type of SVT, location and sidedness of the accessory pathway.
Results The study included 44 patients with SVT. Of those, 27 had right-sided accessory pathways (RSAP) and 17 had left-sided accessory pathways (LSAP). There were 21 males and 23 females and the mean age for both groups was 12 years. Comparisons between RSAP and LSAP revealed the average cycle length of the tachycardia for RSAP was 289 ms (range 231-376) versus 316 ms (range: 236-410) (p = NS), the V-HRA interval for RSAPs was 82 ms compared to 155 ms for LSAPs (p < .001). RSAPs (27/27) had V-HRA intervals < 160 ms, as did (8/17) LSAPs. Utilizing 160 ms to discriminate sidedness; all RSAPs had a V-HRA < 160 ms and 47% (8/17) of LSAPs. These figures yield a sensitivity of 100% and a specificity of 53% for RSAPs. Using a V-HRA of 120 ms to discriminate sidedness, all LSAPs were correctly identified. However, 6/27 (22%) of RSAPs had V-HRA of > 120 ms. The sensitivity for LSAPs was 100% and specificity 78%. A gray zone existed when the V-HRA was > 120 ms and < 160 ms. Fifteen patients fell in this area (8 LSAPs/7 RSAPs).
Conclusion The V to HRA interval is a useful predictor of sidedness of the accessory pathway in supraventricular tachycardia in pediatric patients. When the V-HRA was < 120 ms, all were RSAPs and when the V-HRA was > 160 ms, all were LSAPs. Determining this interval may obviate the need for a CS catheter. This will save vascular access, fluoroscopy time, and expense.