Overview of structural heart disease interventions

Introduction

Catheter-based structural heart interventional therapy has rapidly emerged and evolved over the past 15 years, with these treatments now established as the standard of care for many patient subsets. This chapter provides an overview of commercially available therapies and a glimpse into the future of the field.

General considerations

For patients being considered for transcatheter valve interventions, evaluation by a multidisciplinary heart team (i.e., clinical cardiologist, imaging specialist, interventional cardiologist, and cardiac surgeon) for determination of indications and the procedural plan is strongly recommended. The purpose of the heart team is to determine the optimal therapy, particularly when multiple or complex options are available. Preoperative dental clearance is recommended to reduce likelihood of endocarditis. For all procedures, we also prepare the subxiphoid area in the event that emergent pericardiocentesis is needed and have perfusionists on call in case there is a need for peripheral support (i.e., extracorporeal membrane oxygenation).

Transcatheter aortic valve replacement and balloon aortic valvuloplasty

For patients with severe symptomatic aortic stenosis, transcatheter aortic valve replacement (TAVR) is a life-saving procedure. Success rates for TAVR are greater than 95%, with procedural risks of mortality in 1% to 2%, stroke in 2% to 3%, and bleeding in 5% to 7%. The need for a permanent pacemaker varies according to underlying conduction disease, as well as type and implant depth of the TAVR prosthesis, ranging from 5% to 25%. The two principal TAVR prostheses types are balloon-expandable (e.g., Sapien 3 Ultra) and self-expanding (e.g., Evolut R Pro, Portico, Acurate Neo-2, JenaValve) ( Fig. 17.1 ). Transfemoral arterial access is used for TAVR in more than 95% of cases, although vessel requirements vary according to prosthesis type, size, and whether the device is to be placed with or without a sheath. TAVR can be performed for either native aortic stenosis or degenerative aortic valve prostheses. Balloon aortic valvuloplasty (BAV), although in practice since the 1980s, is now mainly used to facilitate TAVR placement when needed. In other cases, BAV can be used as standalone therapy for bridging, such as for a patient in cardiogenic shock or for the temporary relief of heart failure caused by aortic stenosis. Standalone BAV is palliative and not shown to improve survival because of the high rate of restenosis that occurs within approximately 6 months of the procedure.

Once the diagnosis of severe aortic stenosis and indications for TAVR have been established, gated contrast-enhanced computed tomography (CT) of the cardiovascular anatomy is needed to assess suitability for the procedure. The aortic valve is examined for area (primarily for balloon-expandable) and perimeter (primarily for self-expanding), with sizing calculations that are then matched to device manufacturer recommendations. Typical ranges covered by balloon-expandable prostheses (i.e., 20–29 mm Sapien Ultra) are 273 mm ² to 680 mm ² . For self-expanding protheses (i.e., 23–34 mm Evolut R Pro), the typical ranges are 56 mm to 94 mm. Other, less commonly used valves have sizes within these ranges. Clearance to the coronary arteries is important, not just for native aortic stenosis but especially for valve-in-valve therapy where the degenerated leaflets are permanently fixed and could impair flow. The peripheral arteries are studied for minimal lumen diameter (MLD), tortuosity, and disease to assess suitability for passage of the sheaths and delivery catheters. Typically, dimensions for MLD are 5.0 mm to 6.5 mm, with variation according to size and type of TAVR prosthesis. Vascular sheaths for TAVR include expandable 14 French (F) to 16F versions and ones with fixed diameters up to 22F, and some devices contain a built-in sheath (e.g., InLine for Evolut R Pro).

The TAVR procedure is frequently performed with conscious sedation, although some cases may require general anesthesia for patient comfort or transesophageal imaging. Ultrasound-guided vascular puncture facilitates percutaneous transfemoral procedures, with the preclose technique commonly employed for the large bore access site. A standard pigtail catheter placed in the contralateral access is used for aortography and to guide implant depth of the TAVR prosthesis ( Figs. 17.2–17.4 ). A cerebral protection device (i.e., Sentinel) for potential prevention of stroke may be used via the right radial artery. For deployment of balloon-expandable prostheses, a temporary venous pacemaker is used to create temporary ventricular standstill by pacing at rates of 160 to 180 beats per minute. A temporary pacemaker is also often used to create regular rhythm at 120 beats per minute for deployment of self-expanding prostheses.

After implantation of the TAVR prosthesis, routine monitoring on telemetry is advised. The temporary pacemaker may be removed or left indwelling according to electrocardiogram (ECG) disturbances and the patient’s risk for complete heart block. Most patients are discharged on postoperative day one with either single- or dual-antiplatelet therapy.

Transcatheter mitral valve repair and replacement

As a relatively less invasive therapy, percutaneous treatment for mitral regurgitation (MR), either as a repair or valve replacement, is an attractive option that may help address unmet clinical needs for patients with MR. The field of percutaneous MR treatment is highly active, with several options commercially available in clinical practice and dozens of technologies under development developed. To have outcomes comparable to surgery, percutaneous therapy requires proper patient selection through comprehensive preoperative imaging and implantation in partnership with an expert interventional imager.

Transcatheter mitral valve repair

Transcatheter repair approaches can be grouped broadly into treatments that target the leaflets (e.g., MitraClip [Abbott Vascular, Santa Clara, CA]; Pascal [Edwards Lifesciences, Irvine, CA]), mitral annulus (e.g., Cardioband [Edwards Lifesciences, Irvine, CA]; Millipede [Boston Scientific, Maple Grove, MN]), chords (e.g., Neochord [St. Louis Park, MN], Harpoon [Edwards Lifesciences, Irvine, CA]), or left ventricle (e.g., Accucinch [Ancora Heart, Santa Clara, CA]).

MitraClip is the most widely available percutaneous therapy for native MR, with over 125,000 patients treated worldwide thus far. Using a 24F transvenous, transseptal system, one or more clips are used to permanently appose the anterior and posterior leaflets to recreate and promote coaptation reserve. The MitraClip device comes in four sizes (NT, NTW, XT, and XTW) with device choice based on leaflet length, jet width, location of regurgitation, and size of the mitral valve. Frictional elements (i.e., “grippers”) are implanted on the atrial side of the mitral leaflets after insertion into the device arms ( Fig. 17.5 ), with verification of adequate insertion using multiple views on transesophageal echocardiogram (TEE). Overall, procedural success with reduction in MR to less than or equal to 2+ occurs in approximately 90% of selected patients, with approximately 65% of patients having residual MR less than or up to 1+, in association with an in-hospital mortality of 2% to 3%. Although single-leaflet device attachment was an early concern, the rate of this adverse event is now 1% to 2%, with embolization being rare. A learning for the procedure is present, with greater achievement of optimal reduction in MR occurring with operator experience of more than 50 cases. In the most recent experience with the MitraClip G4 system, optimal MR reduction was achieved in 90% of patients.

The PASCAL device is a 22F steerable, transvenous, transseptal system with 10-mm clasps and spring-loaded paddles that span 25 mm when open. Similar to MitraClip G4, the PASCAL device enables the operator to independently grasp each mitral valve leaflet. PASCAL also contains a 10-mm central spacer to reduce MR. PASCAL has been found to be effective in more than 95% of patients with low procedural mortality. PASCAL is the subject of ongoing trials with randomization to MitraClip in degenerative MR (CLASP IID) and versus medical therapy in functional MR (CLASP IIF). Presently, other devices for transcatheter repair also remain under investigation in the United States.