Cardiac sympathetic innervation in patients with ventricular arrhythmias:: an assessment by 123I-metaiodobenzylguanidine scintigraphy

The aim of this study was to determine the state of sympathetic innervation in patients with ventricular arrhythmias (VA) using I-123-metaiodobenzylguanidine (I-123-MIBG) scintigraphy. Fifty six patients (26 men and 30 women, mean age 37,4 +/- 11,6) underwent single-photon emission computed tomography (SPECT) imaging and planner scintigraphy after injection of I-123-MIBG (activity 148 MBq). They form three groups. Thirty patients with idiopathic VA (IVA) were included in group I: 14 patients with ventricular extrasystoles (VE) and 16 - with ventricular tachycardias (VT). Group II was formed by 17 patients (with dilated cardiomyopathy, n=7 and chronic myocarditis, n=10), 6 of them had VE and 11 - VT. The control group III was formed by 9 healthy subjects with structurally normal heart without VA. We analyzed early (30 minutes) and delayed (4 hours) images after I-123-MIBG administration. The global sympathetic activity (SA) was assessed by heart/mediastinum ratio and washout rate. Regional SA was assessed by extent and severity of defect. In group I 25 of 30 patients (83.3%) had regional SA abnormalities significantly different from controls (p < 0.001). At the same time global uptake of I-123-MIBG in this group was not affected. In group II regional SA abnormalities were revealed in all patients (100%) and global reduction of I-123-MIBG uptake - in 14 patients (82,4%). Regional and global SA abnormalities in group II were different from controls (p < 0,0001) and patients with IVA (p < 0.001). There was no difference in SA abnormalities between patients with VE and VT. Our results suggest that patients with different VA have abnormalities of sympathetic innervation, including patients with structurally normal heart.