Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine

<p>Abstract</p> <p>Background</p> <p>Real-time cardiovascular magnetic resonance (rtCMR) is considered attractive for guiding TAVI. Owing to an unlimited scan plane orientation and an unsurpassed soft-tissue contrast with simultaneous device visualization, rtCMR is presumed to allow safe device navigation and to offer optimal orientation for precise axial positioning. We sought to evaluate the preclinical feasibility of rtCMR-guided transarterial aortic valve implatation (TAVI) using the nitinol-based Medtronic CoreValve bioprosthesis.</p> <p>Methods</p> <p>rtCMR-guided transfemoral (n = 2) and transsubclavian (n = 6) TAVI was performed in 8 swine using the original CoreValve prosthesis and a modified, CMR-compatible delivery catheter without ferromagnetic components.</p> <p>Results</p> <p>rtCMR using TrueFISP sequences provided reliable imaging guidance during TAVI, which was successful in 6 swine. One transfemoral attempt failed due to unsuccessful aortic arch passage and one pericardial tamponade with subsequent death occurred as a result of ventricular perforation by the device tip due to an operating error, this complication being detected without delay by rtCMR. rtCMR allowed for a detailed, simultaneous visualization of the delivery system with the mounted stent-valve and the surrounding anatomy, resulting in improved visualization during navigation through the vasculature, passage of the aortic valve, and during placement and deployment of the stent-valve. Post-interventional success could be confirmed using ECG-triggered time-resolved cine-TrueFISP and flow-sensitive phase-contrast sequences. Intended valve position was confirmed by ex-vivo histology.</p> <p>Conclusions</p> <p>Our study shows that rtCMR-guided TAVI using the commercial CoreValve prosthesis in conjunction with a modified delivery system is feasible in swine, allowing improved procedural guidance including immediate detection of complications and direct functional assessment with reduction of radiation and omission of contrast media.</p

Development of a Surgical Assistance System for Guiding Transcatheter Aortic Valve Implantation

Development of image-guided interventional systems is growing up rapidly in the recent years. These new systems become an essential part of the modern minimally invasive surgical procedures, especially for the cardiac surgery. Transcatheter aortic valve implantation (TAVI) is a recently developed surgical technique to treat severe aortic valve stenosis in elderly and high-risk patients. The placement of stented aortic valve prosthesis is crucial and typically performed under live 2D fluoroscopy guidance. To assist the placement of the prosthesis during the surgical procedure, a new fluoroscopy-based TAVI assistance system has been developed. The developed assistance system integrates a 3D geometrical aortic mesh model and anatomical valve landmarks with live 2D fluoroscopic images. The 3D aortic mesh model and landmarks are reconstructed from interventional angiographic and fluoroscopic C-arm CT system, and a target area of valve implantation is automatically estimated using these aortic mesh models. Based on template-based tracking approach, the overlay of visualized 3D aortic mesh model, landmarks and target area of implantation onto fluoroscopic images is updated by approximating the aortic root motion from a pigtail catheter motion without contrast agent. A rigid intensity-based registration method is also used to track continuously the aortic root motion in the presence of contrast agent. Moreover, the aortic valve prosthesis is tracked in fluoroscopic images to guide the surgeon to perform the appropriate placement of prosthesis into the estimated target area of implantation. An interactive graphical user interface for the surgeon is developed to initialize the system algorithms, control the visualization view of the guidance results, and correct manually overlay errors if needed. Retrospective experiments were carried out on several patient datasets from the clinical routine of the TAVI in a hybrid operating room. The maximum displacement errors were small for both the dynamic overlay of aortic mesh models and tracking the prosthesis, and within the clinically accepted ranges. High success rates of the developed assistance system were obtained for all tested patient datasets. The results show that the developed surgical assistance system provides a helpful tool for the surgeon by automatically defining the desired placement position of the prosthesis during the surgical procedure of the TAVI.Die Entwicklung bildgeführter interventioneller Systeme wächst rasant in den letzten Jahren. Diese neuen Systeme werden zunehmend ein wesentlicher Bestandteil der technischen Ausstattung bei modernen minimal-invasiven chirurgischen Eingriffen. Diese Entwicklung gilt besonders für die Herzchirurgie. Transkatheter Aortenklappen-Implantation (TAKI) ist eine neue entwickelte Operationstechnik zur Behandlung der schweren Aortenklappen-Stenose bei alten und Hochrisiko-Patienten. Die Platzierung der Aortenklappenprothese ist entscheidend und wird in der Regel unter live-2D-fluoroskopischen Bildgebung durchgeführt. Zur Unterstützung der Platzierung der Prothese während des chirurgischen Eingriffs wurde in dieser Arbeit ein neues Fluoroskopie-basiertes TAKI Assistenzsystem entwickelt. Das entwickelte Assistenzsystem überlagert eine 3D-Geometrie des Aorten-Netzmodells und anatomischen Landmarken auf live-2D-fluoroskopische Bilder. Das 3D-Aorten-Netzmodell und die Landmarken werden auf Basis der interventionellen Angiographie und Fluoroskopie mittels eines C-Arm-CT-Systems rekonstruiert. Unter Verwendung dieser Aorten-Netzmodelle wird das Zielgebiet der Klappen-Implantation automatisch geschätzt. Mit Hilfe eines auf Template Matching basierenden Tracking-Ansatzes wird die Überlagerung des visualisierten 3D-Aorten-Netzmodells, der berechneten Landmarken und der Zielbereich der Implantation auf fluoroskopischen Bildern korrekt überlagert. Eine kompensation der Aortenwurzelbewegung erfolgt durch Bewegungsverfolgung eines Pigtail-Katheters in Bildsequenzen ohne Kontrastmittel. Eine starrere Intensitätsbasierte Registrierungsmethode wurde verwendet, um kontinuierlich die Aortenwurzelbewegung in Bildsequenzen mit Kontrastmittelgabe zu detektieren. Die Aortenklappenprothese wird in die fluoroskopischen Bilder eingeblendet und dient dem Chirurg als Leitfaden für die richtige Platzierung der realen Prothese. Eine interaktive Benutzerschnittstelle für den Chirurg wurde zur Initialisierung der Systemsalgorithmen, zur Steuerung der Visualisierung und für manuelle Korrektur eventueller Überlagerungsfehler entwickelt. Retrospektive Experimente wurden an mehreren Patienten-Datensätze aus der klinischen Routine der TAKI in einem Hybrid-OP durchgeführt. Hohe Erfolgsraten des entwickelten Assistenzsystems wurden für alle getesteten Patienten-Datensätze erzielt. Die Ergebnisse zeigen, dass das entwickelte chirurgische Assistenzsystem ein hilfreiches Werkzeug für den Chirurg bei der Platzierung Position der Prothese während des chirurgischen Eingriffs der TAKI bietet

3D Imaging for Planning of Minimally Invasive Surgical Procedures

Novel minimally invasive surgeries are used for treating cardiovascular diseases and are performed under 2D fluoroscopic guidance with a C-arm system. 3D multidetector row computed tomography (MDCT) images are routinely used for preprocedural planning and postprocedural follow-up. For preprocedural planning, the ability to integrate the MDCT with fluoroscopic images for intraprocedural guidance is of clinical interest. Registration may be facilitated by rotating the C-arm to acquire 3D C-arm CT images. This dissertation describes the development of optimal scan and contrast parameters for C-arm CT in 6 swine. A 5-s ungated C-arm CT acquisition during rapid ventricular pacing with aortic root injection using minimal contrast (36 mL), producing high attenuation (1226), few artifacts (2.0), and measurements similar to those from MDCT (p\u3e0.05) was determined optimal. 3D MDCT and C-arm CT images were registered to overlay the aortic structures from MDCT onto fluoroscopic images for guidance in placing the prosthesis. This work also describes the development of a methodology to develop power equation (R2\u3e0.998) for estimating dose with C-arm CT based on applied tube voltage. Application in 10 patients yielded 5.48┬▒177 2.02 mGy indicating minimal radiation burden. For postprocedural follow-up, combinations of non-contrast, arterial, venous single energy CT (SECT) scans are used to monitor patients at multiple time intervals resulting in high cumulative radiation dose. Employing a single dual-energy CT (DECT) scan to replace two SECT scans can reduce dose. This work focuses on evaluating the feasibility of DECT imaging in the arterial phase. The replacement of non-contrast and arterial SECT acquisitions with one arterial DECT acquisition in 30 patients allowed generation of virtual non-contrast (VNC) images with 31 dose savings. Aortic luminal attenuation in VNC (32┬▒177 2 HU) was similar to true non-contrast images (35┬▒177 4 HU) indicating presence of unattenuated blood. To improve discrimination between c

3D Imaging for Planning of Minimally Invasive Surgical Procedures

Novel minimally invasive surgeries are used for treating cardiovascular diseases and are performed under 2D fluoroscopic guidance with a C-arm system. 3D multidetector row computed tomography (MDCT) images are routinely used for preprocedural planning and postprocedural follow-up. For preprocedural planning, the ability to integrate the MDCT with fluoroscopic images for intraprocedural guidance is of clinical interest. Registration may be facilitated by rotating the C-arm to acquire 3D C-arm CT images. This dissertation describes the development of optimal scan and contrast parameters for C-arm CT in 6 swine. A 5-s ungated C-arm CT acquisition during rapid ventricular pacing with aortic root injection using minimal contrast (36 mL), producing high attenuation (1226), few artifacts (2.0), and measurements similar to those from MDCT (p\u3e0.05) was determined optimal. 3D MDCT and C-arm CT images were registered to overlay the aortic structures from MDCT onto fluoroscopic images for guidance in placing the prosthesis. This work also describes the development of a methodology to develop power equation (R2\u3e0.998) for estimating dose with C-arm CT based on applied tube voltage. Application in 10 patients yielded 5.48┬▒177 2.02 mGy indicating minimal radiation burden. For postprocedural follow-up, combinations of non-contrast, arterial, venous single energy CT (SECT) scans are used to monitor patients at multiple time intervals resulting in high cumulative radiation dose. Employing a single dual-energy CT (DECT) scan to replace two SECT scans can reduce dose. This work focuses on evaluating the feasibility of DECT imaging in the arterial phase. The replacement of non-contrast and arterial SECT acquisitions with one arterial DECT acquisition in 30 patients allowed generation of virtual non-contrast (VNC) images with 31 dose savings. Aortic luminal attenuation in VNC (32┬▒177 2 HU) was similar to true non-contrast images (35┬▒177 4 HU) indicating presence of unattenuated blood. To improve discrimination between c

Transcatheter Structural Heart Disease Interventions

This reprint focuses on the transcatheter treatment of the main structural heart diseases covering the latest innovations and hot topics on this subject. All the technological developments witnessed in recent decades have made structural heart disease interventions a growing field and have contributed to offering patients less invasive, more effective, and safe alternative approaches

Translational cell based therapies to repair the heart

Cardiovascular disease comprising of Coronary Artery Disease (CAD) and Valvular Heart Disease (VHD) represents the leading disease in western societies accounting for the death of numerous patients. CAD may lead to heart failure (HF) and despite the therapeutic options for HF which evolved over the past years, the incidence of HF is continuously increasing with a higher percentage of aged people. Similarly, an increase of VHD can be observed and although valve replacement represents the most common therapy strategy for VHD, approximately 30% of the treated patients are affected from prosthesis-related problems within 10 years. While mechanical valves require lifelong anticoagulation treatment, bioprosthetic valves present with continuous degeneration without the ability to grow, repair or remodel. The concept of regenerative medicine comprising of cell-based therapies, bio engineering technologies and hybrid solutions has been proposed as a promising next generation approach to address CAD and VHD. While myocardial cell therapy has been suggested to have a beneficial effect on the failing myocardium, heart valve tissue engineering has been demonstrated to be a promising concept to generate living, autologous heart valves with the capability to grow and to remodel which may be particularly beneficial for children. Although these regenerative strategies have shown great potential in experimental studies, the translation into a clinical setting has either been limited or has been too rapid and premature leaving many key questions unanswered. The aim of this thesis was the systematic development of translational, cell-based bio engineering concepts addressing CAD (part A) and VHD (part B) with a particular focus on minimally invasive, transcatheter-based implantation techniques. In the setting of myocardial regeneration, in the second chapter the intrinsic regenerative potential of the heart is investigated. Myocardial samples were harvested from all four chambers of the human heart and were assessed for resident stem/progenitor cell populations. The results demonstrated that BRCP+ cells can be detected within the human heart and that they were more abundant than their c-kit+ counterparts. In the non-ischemic heart they were preferentially located in the atria while following ischemia, their numbers were increased significantly in the left ventricle. There were no c-kit+/BCRP+ co-expressing stem/progenitor cell populations suggesting that these two markers are expressed by two distinct cell populations in the human heart. Although these results provided a valuable snapshot at cardiac progenitor cells after acute ischemia, the data also indicated that the absolute numbers of cells acquiring a myocardial phenotype are rather low and further effort is needed to upscale such cells into clinically relevant numbers. In chapter three, it is demonstrated that human bone marrow and adipose tissue derived mesenchymal stem cells can be efficiently isolated via minimally invasive procedures and expanded to clinically relevant numbers for myocardial cell therapy. Thereafter, these cells were tested in a uniquely developed intrauterine, fetal, preimmune ovine myocardial infarction model for the evaluation of human cell fate in vivo. After the successful intrauterine induction of acute myocardial infarction, the cells were intramyocardially transplanted and tracked using a multimodal imaging approach comprising MRI, Micro CT as well as in vitro analysis tools. The principal feasibility of intra-myocardial stem-cell transplantation following intra-uterine induction of myocardial infarction in the preimmune fetal sheep could be demonstrated suggesting this as a unique platform to evaluate human cell-fate in a relevant large animal-model without the necessity of immunosuppressive therapy. In chapter four, adipose tissue derived mesenchymal stem cells (ATMSCs) were processed to generate three dimensional microtissues (3D-MTs) prior to transplantation to address the important issue of cell retention and survival. Thereafter, the ATMSCs based 3D-MTs were transplanted into the healthy and infarcted porcine myocardium using a catheter-based, 3D electromechanical mapping guided approach. The previously used MRI based tracking concept was successfully translated into this preclinical model allowing for the in vivo monitoring of 3D-MTs. To address Valvular Heart Disease (part B), in chapter five, marrow stromal derived cells were used to develop a unique autologous, cell-based engineered heart valve in situ tissue engineering concept comprising of minimally-invasive techniques for both, cell harvest and valve implantation. Autologous marrow stromal derived cells were harvested, seeded onto biodegradable scaffolds and integrated into self-expanding nitinol stents, before they were transapically delivered into the pulmonary position of non-human primates within the same intervention while avoiding any in vitro bio-reactor period. The results of these experiments demonstrated the principal feasibility of generating marrow stromal cell-based, autologous, living tissue engineered heart valves (TEHV) and the transapical implantation in a one-step intervention. In chapter six, this concept was then successfully applied to the high-pressure system of the systemic circulation. After detailed adaption of the TEHV and stent design to the anatomic conditions of an orthotopic aortic valve, marrow stromal cell-based TEHV were implanted into the orthotopic aortic position. The implantation was successful and valve functionality was confirmed using fluoroscopy and trans-esophageal echocardiography. While displaying an ideal opening and closing behaviour with a sufficient co-aptation and a low pressure gradient, there were no signs of coronary occlusion or mal-perfusion. In conclusion, the results of this thesis represent a promising portfolio of translational concepts for cardiovascular regenerative medicine addressing CAD and VHD. In particular, it was demonstrated that mesenchymal stem cells / multipotent stromal derived cells represent a clinically relevant cell source for both myocardial regeneration and heart valve tissue engineering. It was shown that the preimmune fetal sheep myocardial infarction model represents a unique platform for the in vivo evaluation of human stem cells without the necessity of immunosuppressive therapy. Moreover, the concept of transcatheter based intramyocardial transplantation of mesenchymal stem cell-based 3D-MTs was introduced to enhance cellular retention and survival. Finally, in the setting of VHD it could be shown that marrow stromal cell based issue engineered heart valves can successfully generated and transapically implanted into the pulmonary and aortic position within a one-step intervention

Cardiovascular imaging 2019 in the International Journal of Cardiovascular Imaging

Cardiovascular Aspects of Radiolog