Validation of a novel CARTOSEG™ segmentation module software for contrast-enhanced computed tomography-guided radiofrequency ablation in patients with atrial fibrillation.

INTRODUCTION: Visualization of left atrial (LA) anatomy using image integration modules has been associated with decreased radiation exposure and improved procedural outcome when used for guidance of pulmonary vein isolation (PVI) in atrial fibrillation (AF) ablation. We evaluated the CARTOSEG™ CT Segmentation Module (Biosense Webster, Inc.) that offers a new CT-specific semiautomatic reconstruction of the atrial endocardium. METHODS: The CARTOSEG™ CT Segmentation Module software was assessed prospectively in 80 patients undergoing AF ablation. Using preprocedural contrast-enhanced computed tomography (CE-CT), cardiac chambers, coronary sinus (CS), and esophagus were semiautomatically segmented. Segmentation quality was assessed from 1 (poor) to 4 (excellent). The reconstructed structures were registered with the electroanatomic map (EAM). PVI was performed using the registered 3D images. RESULTS: Semiautomatic reconstruction of the heart chambers was successfully performed in all 80 patients with AF. CE-CT DICOM file import, semiautomatic segmentation of cardiac chambers, esophagus, and CS was performed in 185 ± 105, 18 ± 5, 119 ± 47, and 69 ± 19 seconds, respectively. Average segmentation quality was 3.9 ± 0.2, 3.8 ± 0.3, and 3.8 ± 0.2 for LA, esophagus, and CS, respectively. Registration accuracy between the EAM and CE-CT-derived segmentation was 4.2 ± 0.9 mm. Complications consisted of one perforation (1%) which required pericardiocentesis, one increased pericardial effusion treated conservatively (1%), and one early termination of ablation due to thrombus formation on the ablation sheath without TIA/stroke (1%). All targeted PVs (n  =  309) were successfully isolated. CONCLUSIONS: The novel CT- CARTOSEG™ CT Segmentation Module enables a rapid and reliable semiautomatic 3D reconstruction of cardiac chambers and adjacent anatomy, which facilitates successful and safe PVI.

Nuclear Imaging Guidance for Ablation of Ventricular Arrhythmias.

Due to an increase in the number of patients with heart failure and ventricular arrhythmias, ventricular tachycardia ablation has a growing clinical role. Long-term success rates remain suboptimal and require creating a detailed electroanatomic map during the procedure to identify fibrotic areas responsible for arrhythmias. Nuclear imaging can identify areas of abnormal myocardial perfusion, metabolism, and innervation, which all may enhance our ability to identify ablation targets, thus decreasing procedure time and improving success rates. Myocardial scar, as assessed by single-photon emission computed tomography (SPECT) perfusion imaging, has been shown to correlate with abnormal areas found during electroanatomic mapping. Abnormal metabolism as identified by (18)fluorodeoxyglucose-positron-emission tomography (PET) imaging has been shown to predict successful ablation sites and help correct errors made in the creation of the electroanatomic map. Abnormal cardiac sympathetic innervation can be identified using the purpose (123)I-meta-iodobenzylguanidine SPECT imaging, which may help in identifying triggers that initiate ventricular tachycardia and also predict successful ablation sites within an otherwise normal myocardium. In conclusion, these imaging modalities can not only offer new insights into the pathophysiology of ventricular arrhythmias but also have the potential to improve outcomes from ventricular tachycardia ablation procedures.

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

UNLABELLED: 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 = 9 ischemic, n = 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 = 0.9; and 56% [Q1-Q3, 41%-62%], P = 0.6). However, segmental analysis demonstrated that ischemic patients had larger areas of abnormal innervation at baseline (52.1% vs. 19.6%, P = 0.011) and at the 6-mo follow-up (56.7% vs. 27.5%, P = 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 = 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.