Mitral paravalvular leak closure

Introduction

Paravalvular prosthetic leak (PVL) occurs in 6% to 15% of surgical prosthetic valves or annuloplasty rings secondary to degeneration and loss of integrity of the annular tissue. Moderate-to-severe PVL is associated with increased morbidity and mortality if left untreated. ^, PVL is more common with mitral prostheses and use of continuous sutures or sutures without pledgets. ^, Patients with chronic mitral PVL usually present with clinical heart failure related to increased volume in the noncompliant left atrium (LA) and left ventricle (LV) over time. Right-sided heart failure can develop due to an increase in pulmonary artery pressure. Hemolytic anemia is also frequently seen in mitral PVL due to turbulent flow and increased shear stress on the red blood cells leading to fragmentation as they cross the paravalvular defects. Patients with coexisting iron- or folate-deficiency anemia are more prone to hemolysis due to red blood cell fragility and more turbulent flow through the defect in the setting of high cardiac output.

Indications for paravalvular leak closure

American College of Cardiology/American Heart Association (ACC/AHA) valve guidelines call for percutaneous PVL closure in patients with intractable hemolysis and severe heart failure symptoms who are at high risk for surgical intervention, if they have suitable anatomy for a catheter-based approach. Patients with clinically significant mitral PVL have already undergone a previous sternotomy and usually have a moderate to high risk for surgical intervention; therefore the vast majority of these patients are offered percutaneous repair at our institution if their anatomy is suitable before consideration of redo surgery ( Fig. 17.1 ).

Contraindications for paravalvular leak closure

Important contraindications include (1) active endocarditis, (2) intracardiac thrombus or vegetation, (3) a defect involving more than one-third of annular tissue, and (4) a rocking/unstable prosthesis.

PVL closure can be performed in patients with a history of endocarditis who have negative confirmatory blood cultures after completion of an intravenous antibiotic course. Similarly, patients with a history of intracardiac thrombus can be treated with anticoagulation, and percutaneous PVL closure can be attempted after ensuring full resolution of the thrombus by cardiac imaging.

Preprocedural planning

Transthoracic echocardiogram (TTE) is usually inadequate for assessment of mitral PVL due to the presence of a shadowing artifact from the prosthesis that interferes with localizing the defect(s) and assessing Doppler flow across it. Transesophageal echocardiography (TEE) is essential for preprocedural planning, as it provides in-depth information about the atrial septum and helps rule out intracardiac thrombus or vegetations. Using TEE, the mitral annulus can be divided into eight sectors ( Fig. 17.2 ) to enhance communication between the echocardiographer and operator. ^, Comprehensive evaluation of the prosthesis annulus with 2D TEE can help provide the location of the defect and assess the degree of PVL. Three-dimensional TEE can further delineate the accurate location, size, shape, and circumferential extent of the defect, as well as identify the number of defects present.

Cardiac computed tomography (CT) angiography imaging can also help determine the location, size, and extent of PVL but is typically not necessary for mitral PVL, given the excellent visualization provided by TEE (in contrast to aortic PVL, where CT can provide important incremental data to TEE). CT can also help predefine the best working fluoroscopic angles during the procedure. Careful discussion between the imaging cardiologist, radiologist, and interventional cardiologist is essential in preprocedural planning to help understand the anatomy and aid in deciding the best approach and equipment needed for PVL closure.

The procedure

Mitral PVL closure is a complex procedure that requires multiple skills for successful execution, including transseptal access, catheter navigation in the LA, plug delivery and deployment, and wire snaring for creation of a wire rail. LV puncture may be necessary to create a rail system in cases with double mechanical prostheses. Table 17.1 includes some of the common equipment utilized for mitral PVL closure.

It is important to note that no specific devices are approved by the Food and Drug Administration (FDA) for PVL closure. The devices preferred for this procedure are the Amplatzer Vascular Plugs (AVP) (St. Jude Medical; St. Paul, MN) made of low-profile fine nitinol mesh, allowing easy deliverability through guiding catheters and sheaths. The AVP II and AVP IV are available in the United States, and the AVP III is available in Europe.

Mitral PVL closure is usually performed under general anesthesia for patient safety and comfort due to the length of the procedure and the need for intraprocedure TEE guidance. Biplane fluoroscopy is highly useful tool to facilitate 3D navigation along the mitral prosthesis annulus. The fluoroscopic views are set up at right anterior oblique and left anterior oblique-caudal angulation to provide simultaneous on side and en face views of the mitral prosthesis, respectively ( Fig. 17.3 ). To minimize radiation exposure, low-resolution biplane fluoroscopy at 7.5 frames/second is recommended. The average procedure duration is 2 to 3 hours.

Mitral PVL closure can be performed using multiple methods: (1) antegrade transseptal approach, (2) retrograde transaortic approach, and (3) retrograde transapical approach. The antegrade transseptal approach is the most commonly used technique.