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.

Die transfemorale Aortenklappenimplantation stellt für ältere Patienten mit einer symptomatischen, hochgradigen Aortenklappenstenose und einem erhöhten perioperativen Letalitätsrisiko eine Alternative zum konventionell-chirurgischen Aortenklappenersatz dar. In der vorliegenden Arbeit wurden die beiden aktuell in Europa zugelassenen transfemoralen Systeme in Bezug auf deren prozedurale Sicherheit, den klinischen Nutzen, die 1-Jahres-Letalitätsrate und die langfristige Klappenfunktionalität unter Anwendung der Kriterien zur standardisierten Komplikationsanalyse des Valve Academic Research Consortiums (VARC) verglichen. Jeweils 100 konsekutive Patienten, bei denen eine transfemorale Aortenklappenimplantation mit den Edwards SAPIEN™/SAPIEN XT™ Transcatheter Heart Valves bzw. dem Medtronic CoreValve ReValving™ System durchgeführt wurde, wurden in die Analyse eingeschlossen. Dies stellt das größte bisher publizierte Patientenkollektiv für den Vergleich der beiden Aortenklappenimplantationssysteme in einem Zentrum über den femoralen Zugangsweg dar. Es wurden mit beiden Systemen ähnlich gute postinterventionelle hämodynamische und klinische Ergebnisse erreicht. Ein signifikanter Unterschied bezüglich der prozeduralen Sicherheit und der 1-Jahres-Letalitätsrate zwischen den beiden Systemen konnte trotz signifikanter Unterschiede in Bezug auf bestimmte periinterventionelle Risiken nicht nachgewiesen werden. Die langfristige Klappenfunktion beider Systeme war exzellent.

Transcatheter aortic heart valve replacement (TAVR) is a procedure to replace a failing aortic valve and is becoming the new standard of care for patients that are not candidates for open-heart surgery [2]. However, this minimally invasive technique has shown to cause ischemic brain lesions, or “silent infarcts”, in 90% of TAVR patients, which can increase the patient’s risk for stroke by two to four times in future years [3]. Claret Medical Inc., a medical device company, has developed a cerebral protection system that filters and captures embolic debris released during endovascular procedures, such as TAVR. This thesis utilized CT scans from Claret Medical to create a physical construct of the aortic arch to experimentally validate a theoretical computer model through flow visualization. The hypothesis was that the empirical model can accurately mimic the fluid dynamic properties of the aortic arch in order validate an in silico model using the finite elements program COMSOL MultiPhysics® Modeling Software. The physical model was created from a patient CT scan of the aortic arch using additive manufacturing (3D printing) and polymer casting, resulting in the shape of the aortic arch within a transparent, silicone material. Fluid was pumped through the model to visualize and quantify the velocity of the fluid within the aortic arch. COMSOL MultiPhysics® was used to model the aortic arch and obtain velocity measurements, which were statistically compared to the velocity measurements from the physical model. There was no significant difference between the values of the physical model and the computer model, confirming the hypothesis. Overall, this study successfully used CT scans to create an anatomically accurate physical model that was validated by a computer model using a novel technique of flow visualization. As TAVR and similar procedures continue to develop, the need for experimental evaluation and visualization of devices will continue to grow, making this project relevant to many companies in the medical device industry.

No description available.

Background: Coronary artery disease (CAD) is a frequent comorbidity in patients undergoing transcatheter aortic valve implantation (TAVI). If significant CAD can be excluded on coronary CT-angiography (cCTA), invasive coronary angiography (ICA) may be avoided. However, a high plaque burden may make the exclusion of CAD challenging, particularly for less experienced readers. The objective was to analyze the ability of machine learning (ML)-based CT-derived fractional flow reserve (CT-FFR) to correctly categorize cCTA studies without obstructive CAD acquired during pre-TAVI evaluation and to correlate recategorization to image quality and coronary artery calcium score (CAC). Methods: In total, 116 patients without significant stenosis (≥50% diameter) on cCTA as part of pre-TAVI CT were included. Patients were examined with an electrocardiogram-gated CT scan of the heart and high-pitch scan of the torso. Patients were re-evaluated with ML-based CT-FFR (threshold = 0.80). The standard of reference was ICA. Image quality was assessed quantitatively and qualitatively. Results: ML-based CT-FFR was successfully performed in 94.0% (109/116) of patients, including 436 vessels. With CT-FFR, 76/109 patients and 126/436 vessels were falsely categorized as having significant CAD. With CT-FFR 2/2 patients but no vessels initially falsely classified by cCTA were correctly recategorized as having significant CAD. Reclassification occurred predominantly in distal segments. Virtually no correlation was found between image quality or CAC. Conclusions: Unselectively applied, CT-FFR may vastly increase the number of false positive ratings of CAD compared to morphological scoring. Recategorization was virtually independently from image quality or CAC and occurred predominantly in distal segments. It is unclear whether or not the reduced CT-FFR represent true pressure ratios and potentially signifies pathophysiology in patients with severe aortic stenosis.

Background: Significant coronary artery disease (CAD) is a common finding in patients undergoing transcatheter aortic valve implantation (TAVI). Assessment of CAD prior to TAVI is recommended by current guidelines and is mainly performed via invasive coronary angiography (ICA). In this study we analyzed the ability of coronary CT-angiography (cCTA) to rule out significant CAD (stenosis ≥ 50%) during routine pre-TAVI evaluation in patients with high pre-test probability for CAD. Methods: In total, 460 consecutive patients undergoing pre-TAVI CT (mean age 79.6 ± 7.4 years) were included. All patients were examined with a retrospectively ECG-gated CT-scan of the heart, followed by a high-pitch-scan of the vascular access route utilizing a single intravenous bolus of 70 mL iodinated contrast medium. Images were evaluated for image quality, calcifications, and significant CAD; CT-examinations in which CAD could not be ruled out were defined as positive (CAD+). Routinely, patients received ICA (388/460; 84.3%; Group A), which was omitted if renal function was impaired and CAD was ruled out on cCTA (Group B). Following TAVI, clinical events were documented during the hospital stay. Results: cCTA was negative for CAD in 40.2% (188/460). Sensitivity, specificity, PPV, and NPV in Group A were 97.8%, 45.2%, 49.6%, and 97.4%, respectively. Median coronary artery calcium score (CAC) was higher in CAD+-patients but did not have predictive value for correct classification of patients with cCTA. There were no significant differences in clinical events between Group A and B. Conclusion: cCTA can be incorporated into pre-TAVI CT-evaluation with no need for additional contrast medium. cCTA may exclude significant CAD in a relatively high percentage of these high-risk patients. Thereby, cCTA may have the potential to reduce the need for ICA and total amount of contrast medium applied, possibly making pre-procedural evaluation for TAVI safer and faster.

No description available.

Einleitung: Die Implantation kryokonservierter allogener Aortenklappen stellt heutzutage eine effektive operative Technik dar, um in schweren Fällen einer floriden Aortenklappenendokarditis exzellente postoperative Ergebnisse zu erzielen. Diese Studie demonstriert die Langzeitergebnisse im Deutschen Herzzentrum Berlin über einen Zeitraum von 17 Jahren. Material und Methoden: Zwischen dem 1.Januar 1987 und 31.Dezember 2003 wurden bei 203 Patienten mit florider Aortenklappenendokarditis kryokonservierte Aortenklappenallografts implantiert (in subkoronarer Implantationstechnik n=107 und durch totalen Aortenwurzelersatz n=96). Das mittlere Alter der Patienten betrug 51,3 Jahre (2-82 Jahre). Darunter waren 42 Frauen und 161 Männer. 161 Patienten zeigten präoperativ eine anuläre Aortenwurzelabszeßbildung. Ergebnisse: Die 30-Tage-Mortalität (mit Anulusabszeß) betrug insgesamt 21,1% (23,6%): bei nativer Aortenklappenendokarditis 14,9% (17,5%) und bei Prothesen-endokarditis 29,2% (29,6%). Nach 17 Jahren waren 70,4+3,6% und 78,6+6,3% (p=0,24) der Patienten mit und ohne präoperativem Anulusabszeß am Leben. Bei 12 Patienten mit Anulusabszeß trat eine Allograft-Re-Infektion auf, die aktualisierte Freiheit von Reinfektion betrug 91,6+2,4% nach 17 Jahren. Insgesamt wurden 37 Patienten reoperiert, die aktualisierte Freiheit von Reoperation betrug 75,0+3,7% nach 17 Jahren. Die aktualisierte Freiheit von Explantation der Allografts wegen Strukturalteration betrug bei den Patienten mit Anulusabszeß nach 17 Jahren 96,0+2,0%. Thrombembolische Ereignisse traten nicht auf. Die Univarianzanalyse identifizierte die Allograft-Re-Infektion (p=0,0001) und zu klein bemessene Allografts (p=0,001) als Risikofaktoren für eine Reoperation sowohl bei nativer als auch Prothesenendokarditis. Schlußfolgerung: Aortenklappenallografts zeigen bei florider Aortenklappenendokarditis mit Anulusabszeß exzellente Langzeitresultate. Die 30-Tage–Mortalität wird hinsichtlich der Schwere der Erkrankung akzeptiert und Re-Infektionen sind selten. Zu klein bemessene Allografts und Re-Infektionen sind Risikofaktoren für Reoperationen. / Objective: Cryopreserved aortic valve homografts have become an accepted valve substitute in acute aortic valve endocarditis, but long-term studies of valve function are largely unavailable. This survey represents our observations over a period of 17 years. Material and methods: Between February 9, 1987 and October 30, 2003, 203 patients with infective aortic valve endocarditis underwent allograft replacement of the aortic valve (free-hand subcoronary technique, n=107 and root replacement, n=96). The patients’ age ranged between 2 and 82 years with a mean age of 51.3 years. The survey included 42 females and 161 males. 161 had infected aortic root with ring abscesses. Results: The hospital mortality of patients with native and prosthetic endocarditis complicated by periannular abscess was 14.9% (17.5%) and 29.2 % (29.6%) respectively making an overall hospital mortality of 21.2% (23.6%). 17 years patient survival in patients with and without periannular abscess was 70.4+3.6% and 78.6+6.3% (p=0,24) respectively. There were 12 events of recurrent endocarditis in patients with periannular abscess, giving an actuarial freedom of 91.6+2.4% at 17 years. Reoperation was performed in 37 patients for a variety of reasons, and overall freedom from reoperation was 75.0+3.7% at 17 years. Freedom from explantation for structural valve deterioration was 96.0+2.0% at 17 years for patients with periannular abcess. No thrombembolic event was evident. Univariable analysis identified recurrent endocarditis (p=0.0001) and undersized allograft (p=0.001) as risk factors for reoperation for both native and prosthetic aortic valve endocarditis. No risk factors for hospital mortality were found. Conclusion: Aortic allograft offers an excellent long-term clinical result in patients with infective aortic valve endocarditis with associated periannular abscess. Operative mortality is acceptable based on the severity of aortic pathology, with low evidence of recurrent endocarditis and no thrombembolic events. Undersized allograft and recurrent infection are risk factors for reoperation.

L’hyperglycémie de stress et la variabilité glycémique, consécutives à la réaction inflammatoire péri opératoire, sont associées à une morbidité et une mortalité accrues en chirurgie cardiaque. L’insulinothérapie intraveineuse administrée à l’aide de protocoles complexes, dits « dynamiques », constitue à l’heure actuelle le traitement de référence de l’hyperglycémie de stress. L’intérêt du contrôle glycémique péri-opératoire est admis par tous, sans qu’il existe de consensus véritable quant aux objectifs à atteindre, et reste très exigeant en termes de charge de soins. Dans la 1ère partie de ce travail, nous avons voulu vérifier si, 7 ans après sa mise en place, l’observance du protocole d’insulinothérapie utilisé dans notre Unité de Soins Intensifs de Chirurgie Cardiaque était conforme à celle mesurée lors de son implantation. Nous avons constaté des dérives majeures dans l’application du protocole qui ont pu être corrigées par la mise en place de mesures correctrices simples. Dans une 2ème partie du travail, nous avons cherché à évaluer si, à l’instar de la chirurgie cardiaque classique, une variabilité glycémique accrue était associée à une altération du pronostic des patients bénéficiant d’une procédure moins invasive (remplacement valvulaire aortique percutané ou TAVI). Nous avons ainsi analysé les données des patients ayant bénéficié d’un TAVI dans notre centre, et inclus dans les registres multicentriques français France et France-2. Nos résultats suggèrent une association entre une augmentation de la variabilité glycémique et un risque accru de complications cardiovasculaires majeures dans les 30 premiers jours, indépendamment de la qualité du contrôle glycémique obtenu. Enfin, dans une 3ème partie nous avons voulu savoir si exenatide, analogue de synthèse de GLP-1, permettait d’améliorer le contrôle glycémique péri opératoire en chirurgie cardiaque. Nous avons conduit un essai randomisé contrôlé de phase II/III montrant que l’administration intraveineuse (IV) d’exenatide, ne permettait pas d’améliorer la qualité du contrôle glycémique ou de réduire la variabilité glycémique par rapport à l’insuline IV, mais permettait de retarder l’administration d’insuline et de diminuer la quantité d’insuline administrée. Notre étude suggère également une diminution de la charge en soins. Du fait des données rapportées chez l’animal et dans l’infarctus du myocarde, nous avons également conduit une étude ancillaire suggérant l’absence d’effets cardioprotecteurs majeurs d’exenatide sur les lésions d’ischémie-reperfusion myocardiques, ne permettant pas d’améliorer la fonction cardiaque gauche à court et à moyen terme. L’optimisation du contrôle glycémique en chirurgie cardiaque nécessite ainsi la recherche de stratégies visant à améliorer l’observance des protocoles de soins et à réduire la variabilité glycémique. La place des analogues du GLP-1 reste à définir dans cette indication. / Stress hyperglycemia and glycemic variability are associated with increased morbidity and mortality in cardiac surgery patients. Intravenous (IV) insulin therapy using complex dynamic protocols is the gold standard treatment for stress hyperglycemia. If the optimal blood glucose target range remains a matter of debate, blood glucose control using IV insulin therapy protocols has become part of the good clinical practices during the postoperative period, but implies a significant increase in nurse workload. In the 1st part of the thesis, we aimed at checking the nurse-compliance to the insulin therapy protocol used in our Cardiac Surgery Intensive Care Unit 7 years after its implementation. Major deviations have been observed and simple corrective measures have restored a high level of nurse compliance. In the 2nd part of this thesis, we aimed at assessing whether blood glucose variability could be related to poor outcome in transcatheter aortic valve implantation (TAVI) patients, as reported in more invasive cardiac surgery procedures. The analysis of data from patients who undergone TAVI in our institution and included in the multicenter France and France-2 registries suggested that increased glycemic variability is associated with a higher rate of major adverse events occurring between the 3rd and the 30th day after TAVI, regardless of hyperglycemia. In the 3rd part if this thesis, we conducted a randomized controlled phase II/III trial to investigate the clinical effectiveness of IV exenatide in perioperative blood glucose control after coronary artery bypass graft surgery. Intravenous exenatide failed to improve blood glucose control and to decrease glycemic variability, but allowed to delay the start in insulin infusion and to lower the insulin dose required. Moreover, IV exenatide could allow a significant decrease in nurse workload. The ancillary analysis of this trial suggested that IV exenatide did neither provide cardio protective effect against myocardial ischemia-reperfusion injuries nor improve the left ventricular function by using IV exenatide. Strategies aiming at improving nurse compliance to insulin therapy protocols and at reducing blood glucose variability could be suitable to improve blood glucose control in cardiac surgery patients. The use of the analogues of GLP-1 in cardiac surgery patients needs to be investigated otherwise.

Introdução: O recente aperfeiçoamento da ultra-sonografia permitiu a análise estrutural e funcional do vaso. Casuística e Métodos: 36 pacientes com insuficiência aórtica e indicação de troca valvar, divididos em grupos com pressão arterial diastólica (PAD) superior e inferior a 50mmHg, avaliados antes e seis meses após a cirurgia. A função arterial compreendeu a complacência, distensibilidade e a função endotelial pela dilatação fluxo-mediada e nitrato-mediada. Conclusão: A complacência e a distensibilidade foram maiores no grupo com menor PAD e diminuíram após a cirurgia. A disfunção endotelial foi presente em insuficiência aórtica crônica independente do nível da pressão arterial diastólica / Introduction: The recent improvement of ultrasonography made possible a functional and structural analysis of the vessel. Methods: 36 patients with aortic insufficiency and valve replacement need, divided in 2 groups with diastolic blood pressure (DBP) above and below 50mmHg. Checked twice: before and 6 months after surgery. The arterial function comprised compliance, distensibility and endothelial function through flow-mediated dilatation and nitrate-mediated dilatation. Conclusion: The compliance and distensibility were higher in the group with lower DBP and decreased after surgery. Endothelial dysfunction was present in chronic aortic insufficiency no matter the level of DBP