Stijn De Buck

Cardiac Three-Dimensional Magnetic Resonance Imaging and Fluoroscopy Merging A New Approach for Electroanatomic Mapping to Assist Catheter Ablation

Background— Modern nonfluoroscopic mapping systems construct 3D electroanatomic maps by tracking intracardiac catheters. They require specialized catheters and/or dedicated hardware. We developed a new method for electroanatomic mapping by merging detailed 3D models of the endocardial cavities with fluoroscopic images without the need for specialized hardware. This developmental work focused on the right atrium because of the difficulties in visualizing its anatomic landmarks in 3D with current approaches. Methods and Results— Cardiac MRI images were acquired in 39 patients referred for radiofrequency catheter ablation using balanced steady state free-precession sequences. We optimized acquisition and developed software for construction of detailed 3D models, after contouring of endocardial cavities with cross-checking of different imaging planes. 3D models were then merged with biplane fluoroscopic images by methods for image calibration and registration implemented in a custom software application. The feasibility and accuracy of this merging process were determined in heart-cast experiments and electroanatomic mapping in patients. Right atrial dimensions and relevant anatomic landmarks could be identified and measured in all 3D models. Cephalocaudal, posteroanterior, and lateroseptal diameters were, respectively, 65±11, 54±11, and 57±9 mm; posterior isthmus length was 26±6 mm; Eustachian valve height was 5±5 mm; and coronary sinus ostium height and width were 16±3 and 12±3 mm, respectively (n=39). The average alignment error was 0.2±0.3 mm in heart casts (n=40) and 1.9 to 2.5 mm in patient experiments (n=9), ie, acceptable for clinical use. In 11 patients, reliable catheter positioning and projection of activation times resulted in 3D electroanatomic maps with an unprecedented level of anatomic detail, which assisted ablation. Conclusions— This new approach allows activation visualization in a highly detailed 3D anatomic environment without the need for a specialized nonfluoroscopic mapping system.

Biplane three-dimensional augmented fluoroscopy as single navigation tool for ablation of atrial fibrillation: Accuracy and clinical value

BACKGROUND We developed new methods for real time biplane integration of three-dimensional (3D) left atrial models with fluoroscopic images to assist in catheter ablation of atrial fibrillation (AF). OBJECTIVE The purpose of this study was to quantitatively assess the accuracy of 3D fluoroscopy integration and to evaluate its clinical value when used as a single navigation tool for AF ablation. METHODS Sixty patients underwent AF ablation under biplane fluoroscopic guidance after selective angiography of the four pulmonary veins. Computed tomography [CT]-based 3D models were integrated in the fluoroscopic framework using visual matching and landmark-based registration approaches. Integration accuracy was quantitatively assessed according to registration approach and different CT acquisition parameters (electrocardiogram [ECG] gating, respiratory phase). In 30 of the 60 patients (3D+ group), the integrated 3D model was used for real time 3D-augmented fluoroscopic catheter navigation, and the effects on procedural parameters and patient radiation dose were evaluated. RESULTS Landmark-based registration resulted in superior 3D fluoroscopy integration accuracy compared with the visual matching approach (P <.001 for alignment error and alignment score). The effects of ECG gating and respiratory phase during CT acquisition on integration accuracy were small and clinically irrelevant. The use of 3D-augmented fluoroscopy in the 3D+ group was gauged as extremely helpful by the operator. It resulted in a significant reduction of fluoroscopy time (61 +/- 18 minutes vs. 77 +/- 26 minutes; P = .009) and a trend toward shorter procedure duration (230 +/- 67 minutes vs. 257 +/- 58 minutes; P = .06) versus conventional procedures. The systematic use of nongated cardiac CT in the 3D+ group resulted in an important reduction in total effective patient radiation dose due to CT+fluoroscopy (4 + 14 = 18 +/- 8 mSv vs.17 + 16 = 33 +/- 13 mSv; P <.001). CONCLUSIONS Biplane 3D-augmented fluoroscopy can be used as a safe and accurate stand-alone method to guide AF ablation procedures. The use of nongated cardiac CT substantially reduces total patient radiation dose without a relevant reduction in integration accuracy.

Efficacy of radiofrequency catheter ablation in athletes with atrial fibrillation

AIMS Endurance sports activities have been associated with the development of atrial fibrillation (AF). Pulmonary vein isolation (PVI) by means of radiofrequency catheter ablation has been established as an effective treatment for AF. The aim of the present study was to analyse the efficacy of AF ablation in athletes. METHODS AND RESULTS We compared procedural outcome and median term follow-up in 94 consecutive athletes (>3 h of sports/week for ≥ 10 years or ≥ 1500 h lifetime) who underwent PVI (94% men, 51 ± 8 years, 87% paroxysmal AF, left atrial (LA) diameter 40 ± 8 mm, mean follow-up 41 months), and 41 contemporary controls. Sixty-three per cent of athletes performed endurance sports (running, cycling, swimming, and rowing). Documented focal induction of AF and failed treatment with ≥ 1 anti-arrhythmic drug were pre-requisites for selection of ablation treatment. Patients with long-standing persistent or permanent AF or an LA diameter ≥ 55 mm were not considered for ablation. Median lifetime cumulative hours of sports was 8638 (4175-13 688) in athletes vs. 450 (280-600) in controls (P < 0.001). Other baseline characteristics except for gender (94 vs. 66% men, respectively, P < 0.001) were comparable between both groups, as was the total number of ablation procedures per patient (1.2 ± 0.5, P = 0.62). Survival analysis showed similar AF recurrence rate after a first ablation for controls and endurance athletes, though non-endurance athletes had a significantly higher AF recurrence rate (48 vs. 46 vs. 34% freedom from AF at 3 year follow-up after a single ablation, P= 0.04). Final outcome after all ablations was similar (87 vs. 84 vs. 85% freedom from AF at 3-year follow-up, P = 0.88). No other independent predictor for AF recurrence was identified. CONCLUSION In patients with documented focal induction of non-permanent AF and absence of structural heart disease, PVI is as effective in endurance athletes as in other patients.

Changes in left atrial anatomy due to respiration: impact on three-dimensional image integration during atrial fibrillation ablation.

Introduction: Patient respiration influences the accuracy of image integration approaches used during atrial fibrillation (AF) ablation procedures. We assessed both absolute and relative changes in left atrial (LA) and pulmonary venous (PV) anatomy due to respiration and their implications for 3D image integration.

Three-dimensional cardiac rotational angiography: effective radiation dose and image quality implications

AIMS Three-dimensional rotational angiography (3DRA) is a promising new online tool for 3D imaging during cardiac ablation procedures. No precise data exist concerning its associated radiation dose. The current study evaluated the effective dose (ED) of cardiac rotational angiography and its relation to patient properties, imaging system input settings, and quality of reconstructed 3D images. METHODS AND RESULTS We performed Monte Carlo simulation-based radiation dose calculations in 42 patients referred for ablation of cardiac arrhythmias. Detailed tube setting information from the 3DRA system (Siemens Axiom Artis dBC with Syngo DynaCT Cardiac software) was used to provide an accurate input for dose calculations in all 248 frames used during image acquisition. Our calculations yielded an overall mean ED of 6.6 +/- 1.8 mSv (based on ICRP 103 weighing factors). Manual collimation of the radiation beam can reduce ED by more than 20%. Image quality did not significantly relate to patient body mass index (BMI), dose per frame setting, or dose-area product (DAP), but was rather explained by contrast filling, cardiac motion reduction, and absence of image reconstruction artefacts. In the system evaluated, DAP values are nearly independent from BMI (R(2) = 0.30), due to its technical specifications. Therefore, patient BMI showed an unexpected strong inverse relation to ED. CONCLUSION Three-dimensional rotational angiography can be performed with acceptable patient radiation dose, comparable to cardiac CT. With the 3DRA system studied (Siemens Axiom), slender patients may currently receive unnecessarily high radiation doses when compared with obese patients, so that further dose reduction seems feasible for many patients. Adequate collimation is imperative to limit patient exposure.

A System to Support Laparoscopic Surgery by Augmented Reality Visualization

This paper describes the development of an augmented reality system for intra-operative laparoscopic surgery support.The goal of this system is to reveal structures, otherwise hidden within the laparoscope view. To allow flexible movement of the laparoscope we use optical tracking to track both patient and laparoscope.The necessary calibration and registration procedures were developed and bundled where possible in order to facilitate integration in a current laparoscopic procedure. Care was taken to achieve high accuracy by including radial distortion components without compromising real time speed.Finally a visual error assessment is performed, the usefulness is demonstrated within a test setup and some preliminary quantitative evaluation is done.

Cardiac three-dimensional rotational angiography can be performed with low radiation dose while preserving image quality

AIMS The effective radiation dose (ED) of three-dimensional rotational angiography (3DRA) is 5-8 mSv, leading to reticence on its use. We evaluated the potential of 3DRA with a reduced number of frames (RNF) and a reduced dose per frame. METHODS AND RESULTS Three-dimensional rotational angiography was performed in 60 patients (52.5 ± 9.6 years, 16 females) referred for ablation in the right (RA; n = 10) and left atrium (LA; n = 50). In a simulation group (n = 20), the effect of dropping frames from a conventional 248 frames 3DRA LA acquisition was simulated. In a prospective group (n = 40), RNF 3DRA were acquired of LA (n = 30) and RA (n = 10) with 67 frames (0.24 Gy/frame) and 45 frames (0.12 μGy/frame), respectively. Accuracy was evaluated qualitatively and quantitatively. Effective radiation dose was determined by Monte Carlo simulation on every frame. In the simulation group, surface errors increased minimally and non-significantly when reducing frames from 248 to 124, 83, 62, 50, 42, and 31: 0.49 ± 0.51, 0.52 ± 0.46, 0.61 ± 0.49, 0.62 ± 0.47, 0.71 ± 0.48, and 0.81 ± 0.47 mm, respectively (Pearson coefficient 0.20). All 3D LA images were clinically useful, even with only 31 frames. In the prospective group, good or optimal 3D image quality was achieved in 80% of LA and all of RA reconstructions. These accurate models were obtained with ED of 2.6 ± 0.4 mSv for LA and 1.2 ± 0.5 mSv for RA. CONCLUSION Three-dimensional rotational angiography is possible with a significant reduction in ED (to the level of prospectively gated cardiac computed X-ray tomography) without compromising image quality. Low-dose 3DRA could become the preferred online 3D imaging modality for pulmonary vein isolation and other anatomy-dependent ablations.

Asymmetric collimation can significantly reduce patient radiation dose during pulmonary vein isolation.

AIMS Current fluoroscopic and 3D image-guided treatment of atrial fibrillation (AF) by radiofrequency ablation is characterized by a substantial amount of X-ray radiation. We investigated the potential of an asymmetric collimation technique to reduce dose. METHODS AND RESULTS For 30 patients, referred for AF ablation, we determined the received fluoroscopy dose for various collimation scenarios: a single collimation window encompassing all veins as used in most labs (Sc 1), an optimal adjusted symmetric collimation window encompassing each two ipsilateral veins (Sc 2) or each individual vein (Sc 3) and an optimal asymmetric collimation window encompassing each two ipsilateral veins (Sc 4) or each individual vein (Sc 5). Twenty patients were studied retrospectively and 10 were studied prospectively. Total fluoroscopy effective dose for all collimation strategies amounted to 45 ± 31 mSv for a single collimation field (Sc 1), 36 ± 25 mSv (Sc 2), and 24 ± 14 mSv (Sc 3) for a symmetrically adjusted collimation window and 15 ± 10 (Sc 4) and 5 ± 3 mSv (Sc 5) for an asymmetrically adjusted collimation approach. Validation of symmetric (Sc 2) and asymmetric (Sc 4) collimation in 10 patients confirmed the retrospective analysis. CONCLUSIONS Implementation and effective application of an optimal asymmetric collimation approach would yield an average three- to nine-fold reduction of fluoroscopy dose during AF ablation procedures. This reduction exceeds what has been previously reported by implementing an electromagnetic catheter tracking approach. Furthermore, it can be easily integrated in the clinical workflow with limited additional one-time cost. Manufacturers of imaging systems should consider its implementation a priority, and physicians should adopt it in their workflow.

Three-dimensional rotational angiography fused with multimodal imaging modalities for targeted endomyocardial injections in the ischaemic heart

AIM Biological therapies for ischaemic heart disease require efficient, safe, and affordable intramyocardial delivery. Integration of multiple imaging modalities within the fluoroscopy framework can provide valuable information to guide these procedures. We compared an anatomo-electric method (LARCA) with a non-fluoroscopic electromechanical mapping system (NOGA(®)). LARCA integrates selective three-dimensional-rotational angiograms with biplane fluoroscopy. To identify the infarct region, we studied LARCA-fusion with pre-procedural magnetic resonance imaging (MRI), dedicated CT, or (18)F-FDG-PET/CT. METHODS AND RESULTS We induced myocardial infarction in 20 pigs by 90-min LAD occlusion. Six weeks later, we compared peri-infarct delivery accuracy of coloured fluospheres using sequential NOGA(®)- and LARCA-MRI-guided vs. LARCA-CT- and LARCA-(18)F-FDG-PET/CT-guided intramyocardial injections. MRI after 6 weeks revealed significant left ventricular (LV) functional impairment and remodelling (LVEF 31 ± 3%, LVEDV 178 ± 15 mL, infarct size 17 ± 2% LV mass). During NOGA(®)-procedures, three of five animals required DC-shock for major ventricular arrhythmias vs. one of ten during LARCA-procedures. Online procedure time was shorter for LARCA than NOGA(®) (77 ± 6 vs. 130 ± 3 min, P < 0.0001). Absolute distance of injection spots to the infarct border was similar for LARCA-MRI (4.8 ± 0.5 mm) and NOGA(®) (5.4 ± 0.5 mm). LARCA-CT-integration allowed closer approximation of the targeted border zone than LARCA-PET (4.0 ± 0.5 mm vs. 6.2 ± 0.6 mm, P < 0.05). CONCLUSION Three-dimensional -rotational angiography fused with multimodal imaging offers a new, cost-effective, and safe strategy to guide intramyocardial injections. Endoventricular procedure times and arrhythmias compare favourably to NOGA(®), without compromising injection accuracy. LARCA-based fusion imaging is a promising enabling technology for cardiac biological therapies.

Multi-phase rotational angiography of the left ventricle to assist ablations: feasibility and accuracy of novel imaging.

AIMS Interventional left ventricular (LV) procedures integrating static 3D anatomy visualization are subject to mismatch with dynamic catheter movements due to prominent LV motion. We aimed to evaluate the accuracy of a recently developed acquisition and post-processing protocol for low radiation dose LV multi-phase rotational angiography (4DRA) in patients. METHODS AND RESULTS 4DRA image acquisition of the LV was performed as investigational acquisition in patients undergoing left-sided ablation (11 men; BMI = 24.7 ± 2.5 kg/m²). Iodine contrast was injected in the LA, while pacing from the RA at a cycle length of 700 ms. 4DRA acquisition and reconstruction were possible in all 11 studies. Reconstructed images were post-processed using streak artefact reduction algorithms and an interphase registration-based filtering method, increasing contrast-to-noise ratio by a factor 8.2 ± 2.1. This enabled semi-automatic segmentation, yielding LV models of five equidistant phases per cardiac cycle. For evaluation, off-line 4DRA fluoroscopy registration was performed, and the 4DRA LV contours of the different phases were compared with the contours of five corresponding phases of biplane LV angiography, acquired in identical circumstances. Of the distances between these contours, 95% were <4 mm in both incidences. Effective radiation dose for 4DRA, calculated by patient-specific Monte-Carlo simulation, was 5.1 ± 1.1 mSv. CONCLUSION Creation of 4DRA LV models in man is feasible at near-physiological heart rate and with clinically acceptable radiation dose. They showed high accuracy with respect to LV angiography in RAO and LAO. The presented technology not only opens perspectives for full cardiac cycle dynamic anatomical guidance during interventional procedures, but also for 3DRA without need for very rapid pacing.