Left fascicular ventricular tachycardia characterized by right bundle branch block and left axis deviation. It typically presents in young male adults without structural heart disease.
A 13-year-old girl presented to our emergency department with one week history of fever and cough. She was found to be tachycardic on arrival with heart rate of 200 beats/min. She was normotensive with spiking temperature of 39C. There was no murmur or additional heart sound on cardiac examination. The electrocardiogram (ECG) revealed a narrow complex tachycardia with a RBBB pattern and left superior axis deviation. Successive intravenous adenosine was given but ineffective in reverting the arrhythmia. Intravenous amiodarone slowed down the tachycardia successfully but unable to terminate the abnormal rhythm. A diagnosis of fascicular ventricular tachycardia was made after consultation with cardiologist. The patient received intravenous verapamil 10mg and the tachyarrhythmia was terminated finally. The transthoracic echocardiography demonstrated normal cardiac structures with left ventricular ejection fraction of 60%. A subsequent electrophysiological study showed a scar over left ventricular posterior fascicle and catheter ablation was performed. She was discharged well after one week of admission.
Fascicular ventricular tachycardia often misdiagnosed as supraventricular tachycardia conducted with RBBB. The presence of atrioventricular dissociation in the ECG gives an important clue in reaching the diagnosis. It responds well to verapamil as the underlying mechanism depends on the slow entry of calcium in partially depolarised Purkinje fibers. Catheter ablation is recommended when symptoms are severe and pharmacologic treatment is not effective.
Prompt recognition of this arrhythmia is crucial as it can be terminated by administration of calcium antagonists. Clinicians should look for specific features of VT in the ECG to make an earlier diagnosis. The overall prognosis is excellent because it is curable with catheter ablation.
Left fascicular ventricular tachycardia