Investigation and Validation of Imaging Techniques for Mitral Valve Disease Diagnosis and Intervention

Mitral Valve Disease (MVD) describes a variety of pathologies that result in regurgitation of blood during the systolic phase of the cardiac cycle. Decisions in valvular disease management rely heavily on non-invasive imaging. Transesophageal echocardiography (TEE) is widely recognized as the key evaluation technique where backflow of high velocity blood can be visualized under Doppler. In most cases, TEE imaging is adequate for identifying mitral valve pathology, though the modality is often limited from signal dropout, artifacts and a restricted field of view. Quantitative analysis is an integral part of the overall assessment of valve morphology and gives objective evidence for both classification and guiding intervention of regurgitation. In addition, patient-specific models derived from diagnostic TEE images allow clinicians to gain insight into uniquely intricate anatomy prior to surgery. However, the heavy reliance on TEE segmentation for diagnosis and modelling has necessitated an evaluation of the accuracy of the oft-used mitral valve imaging modality. Dynamic cardiac 4D-Computed Tomography (4D-CT) is emerging as a valuable tool for diagnosis, quantification and assessment of cardiac diseases. This modality has the potential to provide a high quality rendering of the mitral valve and subvalvular apparatus, to provide a more complete picture of the underlying morphology. However, application of dynamic CT to mitral valve imaging is especially challenging due to the large and rapid motion of the valve leaflets. It is therefore necessary to investigate the accuracy and level of precision by which dynamic CT captures mitral valve motion throughout the cardiac cycle. To do this, we design and construct a silicone and bovine quasi-static mitral valve phantom which can simulate a range of ECG-gated heart rates and reproduce physiologic valve motion over the cardiac cycle. In this study, we discovered that the dynamic CT accurately captures the underlying valve movement, but with a higher prevalence of image artifacts as leaflet and chordae motion increases due to elevated heart rates. In a subsequent study, we acquire simultaneous CT and TEE images of both a silicone mitral valve phantom and an iodine-stained bovine mitral valve. We propose a pipeline to use CT as the ground truth to study the relationship between TEE intensities and the underlying valve morphology. Preliminary results demonstrate that with an optimized threshold selection based solely on TEE pixel intensities, only 40\% of pixels are correctly classified as part of the valve. In addition, we have shown that emphasizing the centre-line rather than the boundaries of high intensity TEE image regions provides a better representation and segmentation of the valve morphology. This work has the potential to inform and augment the use of TEE for diagnosis and modelling of the mitral valve in the clinical workflow for MVD

Perioperative and acute care transesophageal echocardiography (TOE)

In Pakistan perioperative transoesophageal echocardiography (TOE) during cardiac surgery is available in a few centers with reliance on cardiologists and cardiac technicians and its use in noncardiac surgery and intensive care units is very limited. In view of the increasing popularity of TOE based on obvious benefits this review is presented with an aim to evaluate the current indications and potential benefits of using TOE during anesthesia for cardiac and non-cardiac surgery and the intensive care units and compare TOE with pulmonary artery catheter (PAC) and transthoracic echocardiography (TTE) as an hemodynamic monitor in the acute care setting

Imaging in left-sided VHD

In terms of valvular heart disease (VHD) imaging, transthoracic echocardiography (TTE) is the preferred first choice because of its widespread availability. Other modalities, such as transesophageal echocardiography, computed tomography and magnetic resonance imaging, have played a supplementary role in diagnosis for severity, deciding the timing/type of treatment, detection of post procedural complications, and prognostic predictions. However, there are few consensuses on how to employ these modalities, as the evidence is not extensive as that for TTE. On the other hand, these imaging modalities also have their own unique strengths. If employed properly, these modalities have the potential to play a more prominent role in clinical decision making. In this review, we focus on the potential, limitations and application of current imaging modalities in the management of left-sided VH

Methods of estimation of mitral valve regurgitation for the cardiac surgeon

Mitral valve regurgitation is a relatively common and important heart valve lesion in clinical practice and adequate assessment is fundamental to decision on management, repair or replacement. Disease localised to the posterior mitral valve leaflet or focal involvement of the anterior mitral valve leaflet is most amenable to mitral valve repair, whereas patients with extensive involvement of the anterior leaflet or incomplete closure of the valve are more suitable for valve replacement. Echocardiography is the recognized investigation of choice for heart valve disease evaluation and assessment. However, the technique is depended on operator experience and on patient's hemodynamic profile, and may not always give optimal diagnostic views of mitral valve dysfunction. Cardiac catheterization is related to common complications of an interventional procedure and needs a hemodynamic laboratory. Cardiac magnetic resonance (MRI) seems to be a useful tool which gives details about mitral valve anatomy, precise point of valve damage, as well as the quantity of regurgitation. Finally, despite of its higher cost, cardiac MRI using cine images with optimized spatial and temporal resolution can also resolve mitral valve leaflet structural motion, and can reliably estimate the grade of regurgitation

Incidence of intra and postoperative complications associated with transesophageal echocardiograms (TEE) in pediatric patients

The benefits of intraoperative transesophageal echocardiography (TEE) during cardiac surgery are well documented. Intraoperative TEE accurately confirms and in many cases refines delineation of congenital heart lesions, can be used as a means for establishing an intraoperative technical surgical score, and offers a low incidence of intraoperative complications. It seemed likely that the rate of perioperative complications in children would be congruent with the current available data in adults. After Institutional Review Board approval, a retrospective chart review of patients at Boston Children's Hospital who underwent the TEE procedure between May 2012 and December 2014 was conducted. The final study sample consisted of 129 patient charts. Adverse events related to TEE were documented and defined as follows: 1) those potentially attributable to TEE and 2) those with a high likelihood of being related to TEE; defined as dysphagia, esophageal perforation, gastrointestinal bleeding, and throat discomfort/pain. Of the 129 total cases, there was only one case reporting an intraoperative adverse event with a high likelihood of being related to TEE. This incidence rate of 0.77% is consistent with the literature existing on adult and pediatric TEE safety studies. Literature on postoperative adverse events related to intraoperative TEE use in pediatric patients was limited to the incidence of dysphagia. The sample included no incidence of dysphagia and the review enumerated six postoperative adverse events (4.65%) of which had a high likelihood of being related to TEE. Three of these events were classified as major and three were classified as minor. Major postoperative events included blood draining from nasogastric/orogastric tubes and blood tinged secretions suctioned from the endotracheal tube. Minor events were patient reported as sore throat and voice hoarseness. It was concluded that TEE use is not associated with an increased risk of adverse events in pediatric patients if performed according to institutional procedure and recommendations. Intraoperative TEE offers immediate assessment of the adequacy of surgical repair and presence of residual lesions. This information can be used to generate a surgical technical performance score. The ability to detect and correct residual lesions with information provided by intraoperative TEE allows the surgeon to improve technical performance thereby reducing postoperative morbidity

Role of computed tomography imaging for transcatheter valvular repair/insertion

During the last decade, the development of transcatheter based therapies has provided feasible therapeutic options for patients with symptomatic severe valvular heart disease who are deemed inoperable. The promising results of many nonrandomized series and recent landmark trials have increased the number of percutaneous transcatheter valve procedures in high operative risk patients. Pre-procedural imaging of the anatomy of the aortic or mitral valve and their spatial relationships is crucial to select the most appropriate device or prosthesis and to plan the percutaneous procedure. Multidetector row computed tomography provides 3-dimensional volumetric data sets allowing unlimited plane reconstructions and plays an important role in pre-procedural screening and procedural planning. This review will describe the evolving role of multidetector row computed tomography in patient selection and strategy planning of transcatheter aortic and mitral valve procedures

Echocardiography

The book "Echocardiography - In Specific Diseases" brings together contributions from well- known researchers from around the world, some of them specialized in imaging science in their clinical orientation, but also representatives from academic medical centers. Each chapter is structured and written to be accessible to those with a basic knowledge of echocardiography but also to be stimulating and informative to experts and researchers in the field of echocardiography. This book is primarily aimed at cardiology fellows during their basic echocardiography rotation, fellows of internal medicine, radiology and emergency medicine, but also experts in echocardiography. During the past few decades technological advancements in echocardiography have been developing rapidly, leading to improved echocardiographic imaging using new techniques. The authors of this book tried to explain the role of echocardiography in several special pathologies, which the readers may find in different chapters of the book

Towards comprehensive assessment of mitral regurgitation using cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) is increasingly used to assess patients with mitral regurgitation. Its advantages include quantitative determination of ventricular volumes and function and the mitral regurgitant fraction, and in ischemic mitral regurgitation, regional myocardial function and viability. In addition to these, identification of leaflet prolapse or restriction is necessary when valve repair is contemplated. We describe a systematic approach to the evaluation of mitral regurgitation using CMR which we have used in 149 patients with varying etiologies and severity of regurgitation over a 15 month period