Cardiac I-123-MIBG uptake in idiopathic ventricular tachycardia and fibrillation

Patients with idiopathic Ventricular tachycardia or fibrillation have no ad ditional structural or functional myocardial abnormalities. However, the in ducibility of typical tachyarrhythmias by physical or mental stress or by c atecholamine infusion suggests the involvement of the adrenergic system in the pathogenesis of these potentially life-threatening diseases. Methods: 4 5 patients with idiopathic right ventricular outflow tract tachycardia (RVO -VT), 25 patients with idiopathic left Ventricular tachycardia (ILVT), 15 p atients with idiopathic Ventricular fibrillation (IVF) and 10 age-matched c ontrol patients were investigated in this study. Diagnoses were made on the basis of detailed evaluation of the results of two-dimensional echocardiog raphy, left and right ventricular angiography, coronary angiography and end omyocardial biopsy. Local presynaptic norepinephrine re-uptake was assessed using the norepinephrine analog I-123-metaiodobenzylguanidine (MIBG), SPEC T and semiquantitative 33-segment bull's-eye analysis. Results: Locally red uced I-123-MIBG uptake was found in 27 of 45 RVO-VT patients (60%), 5 of 15 ILVT patients (33%) and 17 of 25 IVF patients (68%). Unlike ILVT patients, RVO-VT and IVF patients bad significantly reduced segmental I-123-MIBG upt ake of the posterior wall compared with control patients. Conclusion: Patie nts with idiopathic tachycardia and fibrillation show;abnormal I-123-MIBG u ptake, which indicates presynaptic sympathetic dysfunction. RVO-VT and IVF patients exhibit significantly reduced I-123-MIBG uptake in the posterior l eft Ventricular wall, whereas ILVT patients do not.