Vascular Access for Structural Heart Disease

3.1

Arterial Access

Most of the renewed interest in arterial access has coincided with the advent of transcatheter aortic valve replacement (TAVR). Similar to the devices developed for endovascular aneurysm repair (EVAR), 16F to 24F sheaths are required to deliver transcatheter heart valves (THVs) from a retrograde transfemoral approach. Early in the experience of TAVR, a surgical cutdown with arteriotomy was often used for femoral arterial access and closure given the significant morbidity and mortality associated with vascular complications. Smaller sheath sizes, advanced interventional techniques, and suture-mediated percutaneous closure devices have now made a completely percutaneous approach to TAVR and other structural heart disease procedures possible. This minimally invasive technique holds the most promise for the future of the procedure and, if done correctly, can dramatically decrease procedure time, postprocedure morbidity, and in some cases obviate the need for general anesthesia. Several steps are necessary to safely perform a completely percutaneous transfemoral TAVR: appropriate patient selection, proper procedural technique, and postprocedural management.

3.2

Patient Selection

Understanding which patients are candidates for a transfemoral approach to TAVR is the first step to a successful procedure. Large body mass index (BMI) or body surface area, high sheath–to–femoral artery ratio (SFAR), femoral artery calcification, peripheral arterial disease, and low operator experience have all been associated with high complication rates and poor outcome for a percutaneous transfemoral approach. Patient-specific factors like BMI and prior peripheral arterial disease are known at the time of a clinic visit, but imaging is crucial for evaluating the vessel-specific factors of size, calcification, and tortuosity.

Imaging of the femoral and iliac vessels is performed by invasive angiography, contrast and noncontrast computed tomography (CT), magnetic resonance (MR) angiography, and intravascular ultrasound (IVUS). Though there is no consensus on which imaging modality is superior for TAVR planning, there is consensus that at least two modalities should be used for evaluation. At the Emory University Hospital in Atlanta, Ga., a bilateral lower extremity angiogram and noncontrast CT of the chest, abdomen, and pelvis are performed on all patients. The angiogram identifies stenoses, tortuosity, and aneurysms and allows for measurement of the true lumen diameter. Angiography should be done with digital subtraction angiography and a marker pigtail catheter (Figure 3–1). Rotational angiography has been advocated by some centers, but often a straight anteroposterior angiogram will allow for accurate calibration and measurements in both legs. The CT also helps confirm vessel size but primarily adds essential information about the location and extent of calcification in a vessel (Figures 3–2 and 3–3). For this reason it does not need to be done with contrast. Contrast CT can be performed in patients with adequate renal function and adds additional certainty of vessel size when using a work station that can rotate images in three dimensions. MR angiography has been used, but the resolution is not as good as CT and invasive angiography. IVUS has been used to confirm lumen size in patients, but measurements may be confounded by catheter bias in tortuous vessels.

The next step in patient selection is to determine whether the available sheath/delivery system will pass through the patient’s femoroiliac arteries. It has been determined that a noncalcified vessel will stretch up to 1 mm without rupture, although dissections can occur. SFARs above 1.05 have been associated with increased complications and mortality. A vessel with circumferential calcification will act like a rigid pipe and will not stretch beyond its nominal size without a significant risk of rupture. Noncircumferential calcification can cause significant drag on the delivery sheath, particularly in areas of high tortuosity such as the external iliac artery. Patients are often rejected for transfemoral approach if the external iliac arteries are calcified and the SFAR is greater than 1.0. Calcium in the common iliac arteries is very common in transfemoral patients; the area is often straight with an SFAR of less than 1.0 and thus of no consequence.

Analysis of the angiography and noncontrast CT will usually reveal a preferred side for access, as well as the optimal part of the common femoral artery to puncture. The entry point into the common femoral artery should ideally be without calcification, even if this requires a “high” entry just distal to the inguinal ligament before the vessel dives into the pelvis. For patients over 100 kg, excessive scarring at or near the common femoral, or entry into the vessel at the area covered by the inguinal ligament, a surgical cut down should be considered. During preprocedure planning, the external or common iliac artery should be scrutinized for feasibility of an iliac conduit in case femoral access fails. If needed, this would be a Dacron graft anastomosis end-to-side to the external/common iliac artery, with the conduit externalized through the groin incision and the sheath inserted through the conduit. The minimum diameters accepted for 18F, 22F, and 24F sheaths are 6 mm, 7 mm, and 8 mm, respectively, in any part of the arterial tree. Alternatively, the patient should be considered for a transapical, transaortic, or subclavian approach.