Current and Future Aspects of Multimodal Imaging, Diagnostic, and Treatment Strategies in Bicuspid Aortic Valve and Associated Aortopathies.

Bicuspid aortic valve (BAV) is the most frequent congenital cardiac abnormality leading to premature aortic valve apparatus dysfunction and is often associated with aortopathy. Therefore, current guidelines recommend a surgical aortic valve replacement (SAVR), even if many patients are deemed inoperable owing to their comorbidities and require alternatives such as transcatheter aortic valve replacement (TAVR). However, BAV variations remain challenging for procedural success. Therefore, the latest development in different imaging modalities (echocardiography, multislice-computertomographie, cardiovascular magnetic resonance) allows in-depth analysis for preprocedural risk stratification, follow up, and patient selection. Furthermore, we shed light on the latest developments in pre- and periprocedural fusion imaging as well as on current and future treatment options.

Echocardiographic and Fluoroscopic Fusion Imaging for Procedural Guidance: An Overview and Early Clinical Experience.

There has been significant growth in the volume and complexity of percutaneous structural heart procedures in the past decade. Increasing procedural complexity and accompanying reliance on multimodality imaging have fueled the development of fusion imaging to facilitate procedural guidance. The first clinically available system capable of echocardiographic and fluoroscopic fusion for real-time guidance of structural heart procedures was approved by the US Food and Drug Administration in 2012. Echocardiographic-fluoroscopic fusion imaging combines the precise catheter and device visualization of fluoroscopy with the soft tissue anatomy and color flow Doppler information afforded by echocardiography in a single image. This allows the interventionalist to perform precise catheter manipulations under fluoroscopy guidance while visualizing critical tissue anatomy provided by echocardiography. However, there are few data available addressing this technology's strengths and limitations in routine clinical practice. The authors provide a critical review of currently available echocardiographic-fluoroscopic fusion imaging for guidance of structural heart interventions to highlight its strengths, limitations, and potential clinical applications and to guide further research into value of this emerging technology.

Novel System for Real-Time Integration of 3-D Echocardiography and Fluoroscopy for Image-Guided Cardiac Interventions: Preclinical Validation and Clinical Feasibility Evaluation.

Real-time imaging is required to guide minimally invasive catheter-based cardiac interventions. While transesophageal echocardiography allows for high-quality visualization of cardiac anatomy, X-ray fluoroscopy provides excellent visualization of devices. We have developed a novel image fusion system that allows real-time integration of 3-D echocardiography and the X-ray fluoroscopy. The system was validated in the following two stages: 1) preclinical to determine function and validate accuracy; and 2) in the clinical setting to assess clinical workflow feasibility and determine overall system accuracy. In the preclinical phase, the system was assessed using both phantom and porcine experimental studies. Median 2-D projection errors of 4.5 and 3.3 mm were found for the phantom and porcine studies, respectively. The clinical phase focused on extending the use of the system to interventions in patients undergoing either atrial fibrillation catheter ablation (CA) or transcatheter aortic valve implantation (TAVI). Eleven patients were studied with nine in the CA group and two in the TAVI group. Successful real-time view synchronization was achieved in all cases with a calculated median distance error of 2.2 mm in the CA group and 3.4 mm in the TAVI group. A standard clinical workflow was established using the image fusion system. These pilot data confirm the technical feasibility of accurate real-time echo-fluoroscopic image overlay in clinical practice, which may be a useful adjunct for real-time guidance during interventional cardiac procedures.

Extended-field-of-view three-dimensional transesophageal echocardiography using image-based X-ray probe tracking.

The use of ultrasound imaging for guidance of cardiac interventional procedures is limited by the small field of view of the ultrasound volume. A larger view can be created by image-based registration of several partially overlapping volumes, but automatic registration is likely to fail unless the registration is initialized close to the volumes' correct alignment. In this article, we use X-ray images to track a transesophageal ultrasound probe and thereby provide initial position information for the registration of the ultrasound volumes. The tracking is possible using multiple X-rays or just a single X-ray for each probe position. We test the method in a phantom experiment and find that with at least 50% overlap, 88% of volume pairs are correctly registered when tracked using three X-rays and 86% when using single X-rays. Excluding failed registrations with errors greater than 10 mm, the average registration accuracy is 2.92 mm between ultrasound volumes and 4.75 mm for locating an ultrasound volume in X-ray space. We conclude that the accuracy and robustness of the registrations are sufficient to provide useful images for interventional guidance.

Coronary sinus anatomy by computerized tomography, overlaid on live fluoroscopy can be successfully used to guide left ventricular lead implantation: a feasibility study.

OBJECTIVE: This study aims to optimize coronary sinus (CS) computerized tomography (CT) imaging and evaluate its utility for preprocedural planning and intraoperative guidance by overlay of 3D reconstructed CS images on live fluoroscopy. BACKGROUND: Optimal CS lead placement for cardiac resynchronization therapy (CRT) remains challenging. Preprocedural knowledge of CS anatomy can significantly affect procedural outcome. Optimal CS imaging protocols by CT have not been well defined. METHODS: Seventeen consecutive CRT recipients underwent contrast-enhanced functional cardiac CT on a 64-slice scanner. The CS target branch closest to the most dyssynchronous LV segment was identified. 3D volume rendered CS images were superimposed onto live fluoroscopy via EP Navigator (Philips Healthcare, Best, The Netherlands) to guide CS cannulation and lead placement. The imaging protocol was optimized. RESULTS: CT images were successfully reconstructed and overlaid on live fluoroscopy in 16/17 patients. The overlay facilitated CS cannulation and lead placement into a predefined target branch. Excellent correlation between CT and angiographic CS anatomy was noted. By using the overlaid 3D CS as a road map, average total fluoroscopy time (14.56 ± 4.22 min) was significantly shorter when compared to historical controls. Total radiation exposure was significantly higher in the CT-guided group. Images obtained using double bolus injection and gated acquisition at 40 % of the cardiac cycle contained the most anatomical detail of the CS. CONCLUSION: Overlay of 3D CS anatomy defined by preprocedural cardiac CT is feasible. It allows planning of CRT implantation and live guidance of CS lead placement into a predefined target branch. Limiting the CT imaging to 40 % of the cardiac cycle phase provides optimal CS images and reduces radiation exposure. This approach may result in shorter procedural time and more optimal CS lead positioning. However, the concept remains to be confirmed by future studies.

First experience with rotational angiography of the right ventricle to guide ventricular tachycardia ablation.

BACKGROUND: Rotational angiography with three-dimensional reconstruction (3DRA) is a new imaging tool recently introduced to guide mapping and ablation of the left atrium. OBJECTIVE: The purpose of this study was to determine the utility of 3DRA for imaging the ventricles and guiding ventricular tachycardia (VT) ablation. METHODS: Using the Philips Allura Xper FD10 system, 3DRA was performed in eight patients referred for right ventricular outflow tract (RVOT) VT ablation. The imaging protocol for right ventricular (RV) injection is described. IV contrast was injected at the RA/IVC junction over 4 sec and 3DRA was obtained immediately. Images were segmented manually on the EP Navigator workstation and registered on live fluoroscopy. Intracardiac electrograms were superimposed on 3DRA creating a true electroanatomic map (ElectroNav). CARTO mapping and echocardiograms were performed on all patients, cardiac computed tomography (CT) in 4, and magnetic resonance imaging (MRI) in 1. RESULTS: Three-dimensional rotational angiography was successful in 7 of 8 patients. Image interpretation was unsuccessful in one patient due to poor isocentering. RV imaging was performed with 82 ± 18 mL of contrast. RV image segmentation required 19 ± 5 minutes. CARTO maps of the RVOT required 43 ± 12 minutes and additional fluoroscopy. Three-dimensional rotational angiography was used to guide VT ablation by providing realistic anatomic images of the pulmonary valve plane, endo-views of the ventricle, and ablation point tagging. Anatomic detail provided by 3DRA was qualitatively superior to CARTO. VT ablation was acutely successful in all patients. Close concordance between echocardiographic, CT/MRI, and 3DRA measurements of the RVOT was observed (r = 0.9, P <.01). CONCLUSION: Three-dimensional rotational angiography of the RV and RVOT is a feasible imaging technique that utilizes a protocol of timed angiography, manual segmentation, image registration, and superimposition of intracardiac electrograms to create an angiogram-based electroanatomic model of these structures.

Influence of hydration and mechanical characterization of carious primary dentine using an ultra-micro indentation system (UMIS).

The conditions under which mechanical properties of dentine are tested influence the values recorded. The aims of this study were to examine the effect of hydration on the mechanical properties of primary carious dentine and to provide information on changes in hardness and modulus of elasticity change caused by the demineralizing caries process in dentine. Three primary molar teeth with untreated carious dentine were prepared for nano-indentation tests under both wet and dry conditions. Further tests were conducted on eight primary molars with untreated carious dentine under hydrated conditions. The mechanical properties of dehydrated carious dentine increased approximately 10-fold for hardness and 100-fold for the modulus of elasticity compared with hydrated dentine. The hardness and elastic modulus of the carious primary dentine deteriorated progressively toward the lesion cavity floor, ranging from 0.001 to 0.52 GPa and from 0.015 to 14.55 GPa, respectively, and could be fitted to a simple linear relationship when plotted in logarithmic scale vs. distance. The total depth of dentine affected was around 1100 microm parallel to the tubule direction. This depth was significantly greater than observed subjectively, implying that the demineralization process is more advanced than might be suspected on simple clinical examination.