Cardiac sympathetic innervation in patients with idiopathic right ventricular outflow tract tachycardia

Abstract

The findings of the present study suggest that myocardial beta-adrenoceptor downregulation in patients with RVO-VT occurs subsequently to increased local synaptic catecholamine levels caused by impaired catecholamine reuptake.

Abnormal Myocardial Presynaptic Norepinephrine Recycling in Patients With Brugada Syndrome

“…12 Studies using positron emission tomography (PET) with 11 C-hydroxyephedrine ( 11 C-HED) and 11 C-CGP (CibaGeigy product) 12177 have shown that both ARVC and RVO-VT were characterized by reduced presynaptic catecholamine recycling and downregulation of postsynaptic ␤-adrenoceptors. 13,14 In the present study, we aimed to further investigate and prove our previous observations made with SPECT and 123 I-MIBG in patients with Brugada syndrome by noninvasive quantification of myocardial presynaptic and postsynaptic sympathetic function, using PET with 11 C-HED and 11 C-CGP. The results in patients were compared with those obtained in 2 groups of age-matched normal volunteers.…”

“…13,14,19 Presynaptic Norepinephrine Recycling 11 C-HED was prepared and infused intravenously as described previously. 13 ing the volume of distribution (V d ) of 11 C-HED with the use of a single-tissue compartment model.…”

“…13 ing the volume of distribution (V d ) of 11 C-HED with the use of a single-tissue compartment model. 13,14 The arterial input function was obtained from a left atrial region of interest on the dynamic 11 C-HED scan for the first 15 minutes after tracer's infusion and by means of a peristaltic withdrawal pump and a bismuth germanate (BGO) detection system afterward. 19,20 Plasma metabolite concentrations from additional blood samples were determined by high-performance liquid chromatography and used with the measured whole blood to plasma ratios to provide the plasma 11 C-HED input curves.…”

“…To convert V d from units of milliliter per milliliter to milliliter per gram of tissue, all values were divided by the density of myocardial tissue (1.04 g/mL tissue). 13,14 Myocardial ␤-Adrenoceptor Density…”

Cardiac autonomic imaging with SPECT tracers

“…Mitrani et al 128 observed that in patients who presented with VT but had structurally normal hearts, 55% had regional sympathetic denervation compared with none of the control patients. Gill et al 129 found asymmetrical uptake of 123 ImIBG (less in septum) in 47% of patients with VT and ''clinically normal'' hearts, particularly obvious in patients with exercise-induced VT. Interestingly, PET autonomic tracer (i.e., 11 C-HED) imaging of particular primary arrhythmias, such as right ventricular outflow tract tachycardia 130 and Brugada syndrome, shows focal defects in specific myocardial walls. 131 Regional autonomic abnormalities can also be seen in nonischemic cardiomyopathies, such as Chagas disease in which the posterolateral, inferior, and apical walls are selectively affected.…”