Access options for transcatheter aortic valve implantation

Introduction

Transcatheter aortic valve implantation (TAVI) is now the standard treatment for older adults with symptomatic severe stenosis of a trileaflet aortic valve regardless of surgical risk who do not warrant a mechanical valve. A key component in case planning for TAVI involves selecting the appropriate access for delivery of the transcatheter aortic valve (TAV).

• Although there are numerous access options for TAVI ( Fig. 7.1 ), transfemoral (TF) access is preferred and usually feasible in over 85% of cases; however, despite advances in TAV size and deliverability, the ability of the heart team to perform TAVI using alternative (nonfemoral) access remains relevant.

  

• In the early TAVI experience when sheath sizes were comparatively large, transthoracic access routes such as transapical (TA) and transaortic (TAo) were the predominant options for alternative access. ^,

• As sheath sizes decreased, less invasive alternate access options including subclavian, ^, axillary, carotid, and transcaval have been increasingly used with preference often driven by local heart team expertise.

This chapter reviews the current access options available for TAVI, including important technical and procedural details.

Transfemoral access

TF access is the most commonly used approach for TAVI.

• Imaging is an integral aspect of TAVI with computed tomography (CT) being the primary modality to evaluate access vessel caliber and degree of calcification to determine the suitability for TF access.

• TAV manufacturer’s guidelines provide a good resource for determining suitable vessel diameter for a given device; however, calcification and whether that calcification is circumferential are additional important considerations.

In the early TAVI experience, sheath sizes were comparatively large (22–24 French) and effective large-bore arterial closure devices were just emerging, making surgical exposure of the femoral vessels a common practice. With sheath sizes now 14 to 18 French, most TF TAVIs are performed percutaneously with local anesthesia and/or conscious sedation. Fig. 7.2 illustrates our current practice to ensure precise femoral access.

• Ultrasound guidance has emerged as a useful adjunct to minimize the number of punctures, to keep the access above the femoral bifurcation and on the anterior surface of the common femoral artery, and to avoid areas of calcification.

• The addition of a micropuncture technique in conjunction with femoral angiography before sheath placement also facilitates less traumatic access.

• Finally, the emergence of effective large-bore vascular closure devices has reduced the vascular complication rate and expanded the ability to perform cases percutaneously.

Increasingly TAVI is performed through iliofemoral arteries that fall below quality and manufacturer’s size criteria by taking advantage of improvements in sheath technology or using advanced endovascular techniques.

• The in-line delivery sheath for CoreValve (Medtronic, Minneapolis, MN) is an example of a sheath technology that is true 14 French and integrated with the TAVI delivery system.

• Another example is the eSheath (Edward, Irvine, CA), which has a flexible seam that can expand and then contract as the TAV is passed through it.

• Focal stenotic areas can often be successfully dealt with by using serial dilation with sheath introducers, dilated carefully with appropriately sized angioplasty balloons or prepped using intravascular lithotripsy.

When intrathoracic access sites (TA and TAo) were the only nonfemoral access available, the limits of TF access were often stretched using endo-conduits with a “pave and crack” technique.

• A covered stent(s) is first deployed in the iliac vessel followed by aggressive dilation with a noncompliant balloon allowing the larger TAV to be delivered.

• Today, endo-conduits using covered stents are primarily used to treat vascular injury during TF TAVI.

• Although vascular injury during TAVI has declined, its consequences can be devastating. With the advent of less invasive nonfemoral access options the need to push the limits of TF access should be tempered.

• Transseptal access for mitral transcatheter procedures is standard, but the transseptal approach for TAVI has largely been abandoned because of the complex manipulation required through the mitral valve and associated risk of complications.

• Although initial studies showed feasibility and low major bleeding complications with balloon-expandable sheaths during TAVI procedures, these devices now have been removed from the market for what are now obvious safety issues.