The "hidden" concealed left‐sided accessory pathway: An uncommon cause of SVT in young people. Issue 4 (23rd February 2018)

• Record Type: Journal Article
• Authors: Pass, Robert H.; Liberman, Leonardo; Silver, Eric S.; Janson, Christopher M.; Blaufox, Andrew D.; Nappo, Lynn; Ceresnak, Scott R.
• Is Part Of: Pacing and clinical electrophysiology. Volume 41:Issue 4(2018)
• Page Start: 368
• Page End: 371
• Publication Date: 2018-02-23
• Subjects: accessory pathway -- orthodromic reciprocating tachycardia -- pediatrics -- supraventricular tachycardia; Cardiac pacing -- Periodicals; Electrophysiology -- Periodicals; 617.4120645
• DOI: 10.1111/pace.13279
• Languages: English
• ISSNs: 0147-8389

Abstract

Abstract: Background: Concealed left‐sided accessory pathways (CLAP) are a cause of supraventricular tachycardia (SVT) in the young. Most are mapped with right ventricular (RV) apical/outflow pacing. Rarely, alternative means of mapping are required. We review our experience from three pediatric electrophysiology (EP) centers with a rare form of "hidden" CLAP. Methods: All patients <21 years undergoing EP study from 2008 to 2014 with a "hidden" CLAP (defined as an accessory pathway [AP] for which RV pacing at cycle lengths [CL] stable for mapping did not demonstrate eccentric retrograde conduction) were included. Exclusion criteria: preexcitation. Demographic, procedural, and follow‐up data were collected. Results: A total of 23 patients met the criteria (median age, 14.3 years [range 7–21], weight, 51 kg [31–99]). 21 (96%) had SVT and one AFIB (4%). APs were adenosine sensitive in 7/20 patients (35%) and VA conduction was decremental in six (26%). CLAP conduction was demonstrable with orthodromic reentrant tachycardia in all patients, with RV extrastimulus testing in seven (30%) and with rapid RV pacing (<CL 300) in three (13%). Left ventricular (LV) pacing demonstrated CLAP conduction in 17/17 (100%) patients in whom it was used. All 23 CLAPs were successfully ablated (100%) via transseptal approach with radiofrequency energy. Specific ablation techniques included: 16 (70%) during LV paced rhythm, four (17%) during orthodromic reciprocating tachycardia (ORT; 3/4 ventricular entrained), and three (13%) with brief rapid RV pacing. There were no complications. At 18 months (range 3–96), there was one recurrence (4%). Conclusions: Some CLAPs are only demonstrable with LV pacing, entrained ORT, or rapid RV pacing. LV pacing facilitated preferential AP conduction, allowing for mapping while maintaining stable hemodynamics.