INTRODUCTION: Ventricular tachycardias (VT) are commonly associated with structural heart disease. However, 10% of VTs have no identifiable cause. Right ventricular outflow tract ventricular tachycardia (RVOT VT), a small subgroup of idiopathic VTs localized in the right ventricular outflow tract is highly sensitive to adenosine (ADO). Only 11% of RVOT VT is ADO-insensitive, posing a diagnostic challenge. We present a peculiar case of an ADO-insensitive RVOT-VT storm and the challenges of recognizing and managing it in a resource-limited setting.
CASE SUMMARY: A 15-year-old female, asthmatic, complained of palpitations, lightheadedness, chest pain and dyspnea a few hours prior to admission. She had a similar episode a month ago, which necessitated ER admission, electrical cardioversion and amiodarone.
On admission, she was tachycardic but normotensive. She had diffuse wheezes. Cardiac exam was normal. ECG revealed a wide complex tachycardia (WCT). Work-up revealed a normal chest x-ray, thyroid function tests and electrolytes. Echocardiogram showed a structurally normal heart. She was managed as a case of viral myocarditis and SVT with aberrancy. Vagal maneuvers and adenosine was given which slowed down the tachycardia. She was then started on IV anti-arrhythmics however, sustained symptomatic VT recurred on the same day. ECG analysis showed a WCT, LBBB, AV dissociation with positive QRS complexes in inferior leads suggestive of VT originating from the RVOT. RVOT VT storm was considered and adenosine (maximum dose) was given. The patient did not revert to sinus, hence, ADO-insensitive RVOT VT was considered. Cardioversion terminated the VT storm.
On electrophysiology study, the VT was induced/ localized at the RVOT via 3D mapping. Ablation of the RVOT focus was performed, immediately terminating the VT. Post ablation, the patient was asymptomatic and was discharged improved with excellent prognosis.
DISCUSSION: This case report highlights two things. The ECG remains a reliable tool in recognizing and localizing VTs clinically. Secondly, it highlights the importance of prompt recognition of ADO-insensitive RVOT VT because its management and prognosis is very different from the common causes of VT.