DOES A PROMINENT AND HYPERECHOGENIC MODERATOR BAND MAY REPRESENT THE SUBSTRATE FOR IDIOPATHIC VENTRICULAR TACHYCARDIA?

F. Baldazzi, G. Bronzetti, A. Giardini, A. Donti, D. Prandstraller, R. Formigari, M. Bonvicini, M. Boiani, F.M. Picchio

Pediatric Cardiology and GUCH Unit, University of Bologna, Italy

Background: Idiopathic ventricular tachycardia (IVT) occurs in pts with no structural heart disease. As far as now, two specific forms of IVT have been clearly identified according to site of origin: the right ventricular outflow tract (RVOT) ventricular tachycardia (VT), with a QRS morphology similar to left bundle branch block ( LBBB) and inferior QRS axis, and the left ventricular tachycardia where the QRS morphology is similar to right bundle branch block (RBBB) with a superior QRS axis, indicating its origin from the posterior-inferior interventricular septum. Case report: we report on a newborn delivered at term who was referred to us at 4 days of age because of a wide QRS tachycardia. No signs of heart failure were noted at clinical examination. The ECG showed an incessant ventricular tachycardia (VT) with a LBBB morphology and superior axis at about 190 beats/min, with sporadic sinus and fusion beats. Echocardiography showed a normal intra-cardiac anatomy; In particular, right ventricular volume, thickness and contractility appeared to be normal. The, only abnormality noted was a prominent, hyperechogenic moderator band. A treatment with oral sotalol was started at the dose of 100 mg/m2/day, with complete resolution of the arrhythmia within three drug administrations. In the wake of this case, we retrospectively analyzed the 15 patients diagnosed at our institution to have an IVT. We found one more patient with a non sustained VT showing the same ECG morphology (LBBB and superior QRS axis) and a normal echocardiographic examination, except for a prominent, hyperechogenic moderator band. This pt. is asymptomatic, and since the arrhythmia is not incessant, the patient is not taking any medication. Conclusion: In this report we describe two patients with IVT showing an uncommon QRS morphology (LBBB with a superior axis), suggesting an origin from the inferior aspect of the right ventricle. It is worth noticing that both patients showed a prominent, hyperechogenic moderator band at echocardiography. As reported for left ventricular false tendon, which is well recognized anatomic substrate for IVT, we can speculate that the moderator band may represent the anatomic substrate of some forms of IVT originating from the right ventricle.