PO-05-147 RIGHT ON Q: WIDE-COMPLEX TACHYCARDIA IN SETTING OF DEXTROPOSITION

Dextroposition is a rare cardiac malformation defined as rightward displacement with leftward apex, vs. dextrocardia, which base-axis orientation. We report the second known case of dextroposition accessory pathway, presenting preexcited atrial tachycardia. Abnormal anatomy complicates ECG localization and pathway ablation. N/A A 50-year-old woman was admitted respiratory distress due to EBV infection. Chest X-ray showed right-sided heart. month later, she presented in wide-complex tachycardia, rate 205 bpm. She cardioverted after minimal response procainamide/adenosine. Post-cardioversion short PR interval preexcitation, confirming presence pathway. However, tachycardia had morphology identical baseline, supporting over AVRT. Despite findings reverse R-wave progression precordial leads, left axis deviation initial negative deflection aVR argued against dextrocardia. Moreover, T- P-waves, associated levocardia. Thus, suspected. Millstein Arruda criteria suggested posteroseptal but no data on their applicability heart exist. EP study performed. Eccentric VA conduction noted. Earliest activation at proximal coronary sinus. During isoproterenol infusion, patient went into cycle length 420ms. Multiple AT foci were identified, including right appendage tricuspid annulus. ablation, developed fibrillation RR <250ms, high-risk Given numerous high risk, it decided focus sites. Pathway successfully ablated ostia sinus middle vein. One prior ablation has been reported. This lateral multiple congenital abnormalities lung hypoplasia. While our found have multifocal clinical or radiographic disease. changes are less predictable than dextrocardia; they vary rotation, position, lead position. Comorbid rare; ECG-anatomy relationship ill-defined. Structural pose individual challenges during electrophysiologic procedures.