Objective: Although supraventricular tachycardia (SVT) can be identified from any lead of the bedside monitor, the mechanism of tachycardia is not always obvious. We analyzed the 12-lead electrocardiogram (ECG) in SVT of pediatric patients with different mechanisms of SVT to determine if there is a consistent optimal lead for rhythm identification.
Methods: Twelve-lead ECGs during SVT were available for retrospective analysis in 54 patients. The tachycardia mechanism was determined either by intracardiac or transesophageal recording, or after cardioversion analysis of atrial flutter or fibrillation. Blinded analysis of each separate lead of the 12-lead ECG was done to determine the best lead to diagnose the mechanism of tachycardia. For statistical analysis, χ2 or Fisher exact test was used.
Results: From analysis of the surface ECG, the mechanism of SVT could be identified in 49 (91%) of 54 patients. Lead V1 was the most useful lead to determine the tachycardia mechanism. V1 identified the mechanism in 39 (80%) of 49 patients compared with 29 (59%) of 49 in lead III (P < 0.05), 22 (51%) of 49 in lead II (P < 0.01), and 12 (24%) of 49 in V6 (P < 0.001). Lead V1 identified accessory pathway-mediated tachycardia in 15 (68%) of 22 patients, atrial flutter in 12 (87%) of 14 patients, atrial fibrillation in 7 (70%) of 10, and atrioventricular nodal reentrant tachycardia in 5 (62%) of 8 patients. The mechanism of tachycardia was more readily diagnosed using a combination of V1 and lead III (47/49 patients, 96%) compared with V1 alone (P < 0.05).
Conclusions: A right precordial lead (V1) is the best single lead to diagnose the mechanism of SVT. Furthermore, a combination of V1 and lead III increases the number of patients in whom the mechanism could be identified. Therefore, we recommend that V1 should be combined with an inferior limb lead during cardiac monitoring for optimal identification of the mechanism of SVT in children.