Global and Regional Myocardial Innervation Before and After Ablation of Drug-Refractory Ventricular Tachycardia Assessed with ¹²³I-MIBG

Abstract

Cardiac innervation is a critical component of ventricular arrhythmogenesis that can be noninvasively assessed with 123 I-MIBG. However, the effect of ventricular tachycardia (VT) ablation on global and regional left ventricular sympathetic innervation and clinical outcomes has not been previously assessed. Methods: In this prospective, single-center feasibility study, 13 patients with cardiomyopathy (n 5 9 ischemic, n 5 4 nonischemic) who were scheduled to undergo ablation of drug-refractory VT underwent 15-min and 4-h 123 I-MIBG scans before and 6 mo after the ablation procedure. Planar and arrhythmia-specific 757-segment analysis of short-axis SPECT images was performed in all datasets. Results: Global innervation assessed with heart-to-mediastinal ratio and washout rates was preserved in all patients at baseline (1.8 [continuous variables are expressed as median and quartile: Q1-Q3, 1.7-2.4] and 54% [Q1-Q3, 47%-67%]) and did not change significantly at the 6-mo follow-up (1.9 [Q1-Q3, 1.6-2.2], P 5 0.9; and 56% [Q1-Q3, 41%-62%], P 5 0.6). However, segmental analysis demonstrated that ischemic patients had larger areas of abnormal innervation at baseline (52.1% vs. 19.6%, P 5 0.011) and at the 6-mo follow-up (56.7% vs. 27.5%, P 5 0.011) than the nonischemic patients. Innervation defects affected 40% of the inferior segments in all ischemic cardiomyopathy patients, whereas they affected only 10% of inferior segments in 75% of nonischemic patients. When segmental data were further analyzed in denervated (DZ), transition (TZ), and normal (NZ) zones, there were changes in these designated innervation categories from baseline to the 6-mo follow-up for ischemic (19% DZ, 59% TZ, 22% NZ) and nonischemic (6% DZ, 45% TZ, 15% NZ) patients. In ischemic patients, relative changes were significantly greater in the TZ segments than in the DZ, which demonstrated the second highest proportional changes (P 5 0.028). Receiver operating characteristic curves defined best cutoffs of DZ, TZ, and NZ as less than 30.5%, 30.6%-47.1%, and more than 47.1%, respectively. Conclusion: Patients with ischemic cardiomyopathy have larger areas of abnormal innervation than those with nonischemic cardiomyopathy. Although VT ablation did not change global innervation, a novel arrhythmia-specific segmental analysis demonstrated significant dynamic changes in innervation categories and allowed quantitative definitions of DZ, TZ, and NZ.These findings provide novel insights into the mechanics of sympathetic innervation in patients undergoing VT ablation and may have diagnostic and therapeutic implications.

Left ventricular function assessment using 123I/99mTc dual-isotope acquisition with two semi-conductor cadmium–zinc–telluride (CZT) cameras: a gated cardiac phantom study

“…The dual-isotope acquisition protocol using 201 Tl and 123 I-mIBG is well documented on conventional Anger cameras, using the triple-energy window [25] for scatter and crosstalk correction. Simultaneous perfusion and sympathetic innervation imaging with 123 I-mIBG and 99m Tc-labelled tracers enables the evaluation of innervation-flow mismatch and may provide valuable information to target the trigger zone in the setting of ventricular arrhythmia [4, 26]. In a recent study, Gimelli et al [11, 27] using sequential 123 I-mIBG and 99m Tc-tetrofosmin myocardial SPECT demonstrated a relevant association between innervation derangement ( 123 I-mIBG) and myocardial synchronicity ( 99m Tc-tetrofosmin).…”

Ventricular Tachycardia (VT) Substrate Characteristics: Insights from Multimodality Structural and Functional Imaging of the VT Substrate Using Cardiac MRI Scar, 123I-Metaiodobenzylguanidine SPECT Innervation, and Bipolar Voltage

“…3D reconstructions of myocardial innervation were created using Amira 5.4.2 software (Visage Imaging). On each 2-dimensional 123 I-MIBG SPECT slice, areas of abnormally innervated myocardium (,50% tracer uptake) were determined visually by 2 masked, experienced cardiac nuclear medicine physicians with previously demonstrated intraobserver or interobserver variability of less than 10% (8). From the sequential 2-dimensional datasets, individual 3D innervation maps were created for each of the patients in the Amira environment (Figs.…”

“…Both structural imaging and functional imaging demonstrated a good to moderate correlation with the voltage-defined VT substrate. However, small to moderate degrees of mismatch between structural imaging (CMR/CT) or functional imaging ( 18 F-FDG PET/ 123 I-MIBG innervation) and EAM suggested that postischemic adaptation may be a more complex, heterogeneous process affecting structural and functional properties of the VT substrate to variable degrees (1,3,(7)(8)(9)(10). To our knowledge, a comparison of structural and functional imaging properties and determination of their correlation with EAM/VT substrate data have not yet been performed.…”

Imaging the heart’s brain: Simultaneous innervation/perfusion analysis in the era of new CZT cameras

“…4,6,11,12 Accordingly, it has been recently reported that the specific geographical distribution of 123 I-MIBG uptake at myocardial SPECT can be used to guide the performance and predict the results of the procedures of transcatheter ablation of ventricular arrhythmias. 18,19 Until now, despite the obvious appeal of a dualisotope myocardial innervation/perfusion imaging protocol, most of the studies in whom it was employed have performed two separate acquisitions to obviate the development of possible scatter artifacts due to the crosstalk between the photons of the two radionuclides. 11,12 In fact, current scatter correction algorithms may consistently reduce the count statistics of a SPECT scan by rejecting the photons that fall in the predefined energy sub-windows of the ''lower energy'' isotope (i.e., 201 Tl), thus reducing the overall image quality obtained with tradition cardiac cameras.…”