Procedural Image Guidance for Transcatheter Mitral Valve Repair Interventions
Srdjan Jelacic, MD FASE; G. Burkhard Mackensen, MD PhD FASE; Department of Anesthesiology and Pain Medicine, Division of Cardiothoracic Anesthesiology, University of Washington, Regional Heart Center, Seattle, WA
Mitral regurgitation (MR) as a result of degenerative, functional/ischemic, or mixed etiology has a high prevalence in developed countries and increases with age.1 Traditionally, mitral valve (MV) disease has been treated with surgical valve repair or replacement while percutaneous treatment has been limited to balloon mitral valvuloplasty in the case of mitral stenosis. The growing field of transcatheter interventions now includes percutaneous approaches for MR, including leaflet and chordae repair, indirect coronary sinus annuloplasty, direct annuloplasty, and valve replacement.2
The most established and the only Food and Drug Administration (FDA) approved transcatheter technique for MV repair in the United States is the MitraClip® system (Abbott, Menlo Park, CA), which mimics the surgical edge-to-edge repair by creating a double orifice valve.3 To date, more than 30,000 patients have been treated worldwide. Restoring coaptation between the anterior and posterior MV leaflets with satisfactory reduction of MR can generally be accomplished with the use of 1 or more MitraClips®, but in more than 40% of patients, at least 2 MitraClips® were required. Although the surgical MV repair is considered as a “gold standard” in the treatment of MR, a significant proportion of patients are at prohibitive risk for open heart surgery due to their age, reduced left ventricular function, comorbidities, and other reasons.4 The Endovascular Valve Edge-to-Edge Repair Study (EVEREST) I demonstrated the safety, feasibility, and efficacy of the MitraClip® procedure in patients with 3 to 4+ MR while the EVEREST II randomized cohort results revealed superior safety and similar improvements in clinical outcomes despite residual MR in many patients when compared to surgery.5,6 The FDA approved the MitraClip® system in October of 2013 for commercial use in patients with significant symptomatic degenerative MR (≥3+) who are at prohibitive risk for surgery.
In an effort to expand the limited FDA indications, the ongoing Clinical Outcomes Assessment of the MitraClip® Percutaneous Therapy for Extremely High-Surgical-Risk Patients (COAPT) evaluates the safety and effectiveness of MitraClip® in functional MR patients when compared to medical therapy (ClinicalTrials.gov Identifier: NCT01626079). In addition to the COAPT trial, several registries, including Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy registry with over 7000 MitraClip® patients, are continuing to enroll MitraClip® patients with functional MR.
The initial experience following commercialization in the United States demonstrated a favorable success rate that supports the effectiveness of the MitraClip® therapy in high-risk surgical patients with degenerative MR. The treatment of functional MR with the MitraClip® remains off-label use reserved for symptomatic improvement, but is currently the most common indication for the MitraClip® therapy in Europe with the international registry data showing good safety record and symptomatic improvement after 1 year.7-10 Until convincing effectiveness data of ongoing trials and registries are available, the long-term benefits of the MitraClip® therapy in patients with functional MR remain uncertain, a fact that is reflected in recent American Heart Association Heart Failure guidelines.11
The MitraClip® procedure requires careful planning and a dedicated team with expertise in cardiac imaging and transcatheter interventions. The structural heart valve team seeks input from an interventional cardiologist, a cardiac surgeon, a cardiac anesthesiologist (who may or may not serve as the interventional echocardiographer), or a dedicated interventional echocardiographer (with or without a sonographer). Cardiac anesthesiologists with experience in perioperative real-time two- (2D) and three-dimensional (3D) echocardiography are ideally positioned to serve as the interventional echocardiographer.
Cardiac anesthesiologists already are familiar with the procedure room environment and staff while also having expertise in the hemodynamic management of patients with severe MR and other cardiovascular comorbidities. Given the close working relationship between cardiac anesthesiologists and interventionists, effective and dynamic communication is easily accomplished and of outmost importance for the success of the MitraClip® therapy or any other procedure requiring echocardiographic guidance. Although the traditional role of the perioperative echocardiographer (often a cardiac anesthesiologist) includes the performance of a comprehensive transesophageal echocardiography (TEE) exam at baseline,12 the imaging during the cardiac surgery often is sporadic. In most cases, the perioperative echocardiographer will confirm the underlying pathology and mechanism of disease, and then repeat a comprehensive TEE exam with a particular focus on the actual surgical procedure at the end of the surgery. On the other hand, the interventional echocardiographer often provides continuous imaging guidance along with clear and ongoing communication and shared decision making with the interventionist, which can extend over many hours. Given the proximity of the interventional echocardiographer to the source of x-ray radiation and the length of exposure during transcatheter procedures, particular attention should be paid to radiation exposure and safety.13
The role of echocardiography in procedural planning and guidance is essential for the MitraClip® procedure. Screening patients for the procedure requires careful examination by either transthoracic echocardiography or TEE, including 3D imaging modalities to determine the severity and etiology of MR as well as suitability of MV morphology for MitraClip®. Similar to the surgical MV repair data, which indicate that the best outcomes are associated with experienced reference centers,14 the MitraClip® procedure should be performed by an experienced interventional cardiologist especially in cases with more challenging MV morphology. Some of the optimal MV morphological features for the MitraClip® procedure include regurgitation isolated to the middle (Carpentier’s classification 2) segment with minimal leaflet calcification, adequate MV opening area (≥4 cm2), sufficient posterior leaflet length (≥10 mm), a flail width of <15 mm, and a flail gap of <10 mm. Deployment of the MitraClip® is more challenging in Carpentier’s classification segments 1 and 3 (due to increased risk of entanglement of the device in the dense chordal apparatus in the commissures), mild leaflet calcification, suboptimal MV opening area (3-4 cm2), and mobile posterior leaflet length of 7-10 mm.15
After appropriate screening and determining that the patient is not a surgical candidate based on consultation with a cardiac surgeon, the MitraClip® procedure is performed with fluoroscopic and, more importantly, TEE guidance, including real-time 3D imaging. In some institutions, fusion imaging (where echocardiographic images and guidance tools are projected onto the fluoroscopy screen) may be available for procedural guidance, but the experience with such imaging is limited.16 During the procedure, TEE is essential in guiding safe transseptal puncture, advancement of the delivery system, and positioning of the MitraClip®. The MitraClip® has to be positioned perpendicular to the line of coaptation of the MV leaflets and ideally in the center of the regurgitant orifice and regurgitant jet. During leaflet grasping and closing of the device, the extent of leaflet insertion and grasp stability needs to be assessed. Following deployment of the MitraClip®, 2D and 3D TEE imaging is used to evaluate clip stability, coaptation surface length, residual MR, and mitral orifice area (Figure 1).17 In addition, any complications such as leaflet detachment from the MitraClip®, entanglement in the chordal apparatus, cardiac perforation (tamponade), and large postprocedural iatrogenic atrial-septal defect should be ruled out.
To date, our structural heart disease team at the University of Washington Regional Heart Center in Seattle has performed up to 150 MitraClip® procedures. For all of these procedures, cardiac anesthesiologists have provided procedural guidance with TEE. To facilitate optimal imaging with TEE and hemodynamic monitoring, all of our MitraClip® patients received general anesthesia with invasive arterial, central venous, and often pulmonary artery pressure monitoring. Based on our institutional experience, we highly recommend starting a new program with a small and consistent team. This helps to familiarize all team members with the procedural steps and builds trust and confidence among the team members.
Despite the expanding potential therapeutic targets for the MitraClip® procedure, the long-term sustainability of the national MitraClip® programs will depend on expanding the FDA indications and ensuring appropriate reimbursements for device and procedural costs. The Centers for Medicare & Medicaid Services has recently finalized their proposal to reassign the MitraClip® procedure to a new diagnosis-related group, which will result in a significant increase in the base payment rate. In November of 2016, Abbott plans to launch a new and updated equipment version termed the MitraClip® NT system. Amongst other features, this new system will offer grasping with a fully open MitraClip® and improved steering and handling of the delivery system.
Recent developments in transcatheter MV therapy offer new opportunities for treatment of MV disease (eg, combining a transcatheter annuloplasty with the MitraClip®).18 Advances in 3D echocardiography and hybrid imaging will continue to support the refinement of current technologies, the expansion of clinical applications, and the development of novel devices. Growing use of 3D echocardiography to improve patient screening, optimize implantation strategy, and identify potential complications offers a unique opportunity for cardiac anesthesiologists to be involved in preprocedural planning. Furthermore, cardiac anesthesiologists should take a leading role in procedural imaging, which is essential for interventional guidance and assessment of device effectiveness. In addition to expert imaging, the success of the MitraClip® therapy or any other transcatheter valve intervention depends on multidisciplinary input from a structural heart valve team with effective and continued communication among team members. Finally, continuous evaluation of relevant evidence from randomized studies, meta-analyses, and registries regarding the safety and short-term and long-term effectiveness of current and new transcatheter devices is critical in justifying the device and procedure costs in the current environment of diminishing reimbursements.
Three-dimensional transesophageal echocardiogram image of the mitral valve from the left atrial (A) and left ventricular (B) perspective showing the deployed MitraClip® (white arrow) bringing together the middle segments of the anterior and posterior leaflets while creating a double orifice during diastole. (C) Three-dimensional transesophageal echocardiogram image of MitraClip® in the left atrium above mitral valve prior to advancing the MitraClip® into left ventricle. (D) MitraClip® device (image provided by Abbott, Menlo Park, CA).
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- Eggebrecht H, Schelle S, Puls M, et al. Risk and outcomes of complications during and after MitraClip implantation: experience in 828 patients from the German TRAnscatheter mitral valve interventions (TRAMI) registry. Catheter Cardiovasc Interv. 2015;86(4):728-735.
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