Introduction
General Issues
Anatomy
While access sites such as the common femoral artery are easily accessible, sometimes alternative access may be needed as a result of the previous site being infected, scarred, or occluded. Preoperative planning by considering the patient’s anatomy, vessel to be accessed, location of intended treatment, positioning of the patient for comfort, and devices needed for treatment is paramount in making the procedure safe and efficient.
Depending on the area of access and body habitus, patients may need further adjustments or retraction of extra tissue, which can be done with tape. Full exposure of the site allows the clinician the ease of access and control.
For patients with heavily scarred access sites, a small incision at the area of access may help advance the sheath through scar tissue. The use of serial dilation is also helpful. In addition, the use of stiffer wires such as Amplatz or Rosen can help with trackability and ability to push forward.
The anatomy of the access site should also be taken into consideration. The diameter of the access vessel will determine the maximum size of sheath that can be placed ( Table 2.1 ). This will in effect determine which device can be delivered through the sheath. Vessel tortuosity can affect the placement of the sheath. It may preclude the full advancement of the sheath or the ability of the device to be able to navigate the curves and turns. If the vessel is very tortuous, use of a stiffer system (wire, guide catheter. and/or sheath) or an alternative access site should be considered.
| Artery | Diameter | Positioning |
|---|---|---|
| Superficial femoral artery | 6–8 mm | Supine, external rotation |
| Popliteal artery | 4–6 mm | Supine with flexion and external rotation, prone |
| Pedal artery | 1–3 mm | Supine |
| Graft | Various | Various |
| Radial | 2–2.5 mm | Supine with wrist extension |
| Brachial | 3–4 mm | Supine, arm extension |
| Axillary | 4.8–8.0 mm | Abduction, external rotation, flexion of elbow |
Pathology
Within the vessel, if the area of desired access is heavily calcified or has significant atherosclerotic plaque, it is difficult and potentially dangerous to insert a sheath through this area. It can cause rupture, dissection, thrombosis, or distal embolization. Preferably, a different access site that does not include the area of stenosis or occlusion should be chosen. If the lesion is not precisely at the access site, adjuncts such as balloon angioplasty with or without stenting can be used to allow the passage of the sheaths through the stenotic vascular segments.
Location
The location of the intended treatment area will help determine the possible access sites. A shorter working distance from the access site to the treatment site is favorable because of better deliverability, trackability, and torque ability. For longer distances, it may be difficult to navigate devices to the location of interest and to maintain enough support in the system to be able to perform the planned interventions. For access sites in the lower extremity, a lesion at the mid superficial artery or popliteal artery can be potentially accessed from the contralateral common femoral artery, the ipsilateral common femoral artery, pedal access, or brachial access. Brachial access is unlikely to reach tibial or pedal arteries. Patients are supine for most procedures, but popliteal access requires preferentially a prone position or, less frequently, supine position with flexion and external rotation of the leg. Brachial access requires the patient’s arm to be supinated and can be extended or abducted if needed ( Table 2.2 ).
| Advantages | Disadvantages | Pitfalls | Troubleshooting | |
|---|---|---|---|---|
| Common femoral | Antegrade and retrograde access, most common access site | Difficult in obese patients, previous history of surgery | Calcification, atherosclerotic plaque, anatomic variants | Ultrasound guidance for access, proper positioning of patient |
| Superficial femoral artery | Antegrade and retrograde access, large diameter, alternative site | Depth of vessel, comfort of positioning | Calcification, atherosclerotic plaque, anatomic variants, hemorrhage can be difficult to control | Ultrasound guidance, balloon occlusion during hemorrhage |
| Popliteal artery | Antegrade and retrograde access, alternative site | Comfort of positioning, small vessel, short distance for antegrade intervention | Calcification, atherosclerotic plaque, anatomic variants, nerve injury | Ultrasound guidance, balloon occlusion during hemorrhage |
| Pedal artery | Retrograde access, alternative site | Small vessel | Calcification, atherosclerotic plaque, anatomic variants, spasms | Ultrasound guidance |
| Graft | Large diameter | Risk of infection, scar tissue | Pseudoaneurysm, hematoma, back wall punctures | Antibiotic periop, suture closure |
| Radial | Alternative to transfemoral approach | Smaller vessel, spasms, hematoma, nerve injury, long distance | Ischemia to hand, embolism to carotid artery, thrombosis | Allen’s test, proper positioning of hand and wrist, ultrasound guidance micropuncture set, antispasmodic |
| Brachial | Alternative to transfemoral approach | Smaller vessel, spasms, hematoma, nerve injury, long distance | Ischemia to hand, embolism to carotid artery, thrombosis, need for open exposure | Proper positioning of arm, ultrasound guidance micropuncture set, antispasmodic |
| Axillary | Alternative to transfemoral approach | Smaller vessel, spasms, hematoma, nerve injury, long distance, discomfort with positioning | Ischemia to hand, embolism to carotid artery, thrombosis | Proper positioning of arm, ultrasound guidance micropuncture set, antispasmodic |
Guidance for Puncture
After choosing the appropriate site, there are various types of techniques for access. The preferred technique for obtaining access is with the use of B-mode ultrasound using the longitudinal or transverse view. The vessels are directly identified and the anterior wall is accessed under direct visualization with the needle. The benefits of ultrasound guidance are the visualization of the intended vessel and surrounding structures (adjacent vein, nerve, arterial branches, etc.). With severely calcified vessels, it can also alert the operator that there may be some difficulty with initial access or that another site may need to be considered.
Alternative ways to access include direct pulse palpation combined with anatomic landmarks, fluoroscopy guidance, or the use of Doppler needle. The access needle at the surface of the artery can transmit pulsation, providing a tactile feedback to the operator indicating the access needle is upon the vessel. Alternatively, a Doppler needle will transmit arterial signals with proximity to the artery. These techniques are associated with higher incidence of access-related complication, as the vessels and branch points are not specifically identified. Multiple attempts are frequently needed, with increased risk of back wall injuries as well, subsequent risks of dissections, laceration of the vessel, and bleeding complications. Also, with blind access, the needle can roll off the anterior surface of the artery and enter either the medial or lateral wall instead of the intended anterior wall. This can cause difficulty where compression with direct pressure or closure devices can be misplaced with resultant increased risk of bleeding or pseudoaneurysm formation.
Troubleshooting Access Site Complications Applicable to all Sites
Most access site complications can be treated in relatively the same manner. The most common complication is bleeding, which can happen in a wide spectrum of severity from a small hematoma to significant hemorrhage. A balloon brought to the area of injury or even proximal to the injury site can be used to occlude the vessel to temporize while the situation is assessed for more profuse bleeding. Treatment for minor injuries to a vessel include balloon occlusion or a covered stent while open repair for larger injuries.
Arteriovenous fistulas (AVF) can occur whether from initial access through the artery and the vein creating the connection or through wire work. A small AVF can resolve spontaneously or with simple compression. Larger fistulas may need intervention as this can lead to edema of the extremity, high output cardiac failure, or aneurysmal degeneration of the vessel. Exclusion of the fistula may require a covered stent or open surgical repair. When treating AV fistulas, it is critical to size the vessel correctly if endovascular repair is planned. Intravascular Ultrasound (IVUS) is ideal in this manner because an undersized stent graft will continue to permit flow behind the graft and into the fistula. The stent graft can be placed in either the artery or the vein if placement in the artery would risk coverage of critical branches, such as the profunda.
Dissections can be treated with either conservative management, balloon angioplasty, or stent placement, depending upon the extent and disturbance to flow. Initially, a small dissection may be observed or treated with prolonged inflation of a balloon. In many cases, this will resolve small dissections. A dissection that persists and interferes with flow should be further treated.
Thrombosis is another common complication. When accessing smaller arteries, heparinizing the patient prior to sheath placement is important. Use of additional medications, including vasodilators, can be considered for accessing radial arteries, as discussed later. If thrombosis occurs, treatment includes mechanical thrombectomy, pharmacomechanical thrombolysis, or open thrombectomy with or without endarterectomy to remove dissected plaque or large atheroma. Additionally, closure devices should be used with caution in smaller vessels, as many have components that remain intraarterial, and can occlude small vessels.
Pseudoaneurysms can also occur when the puncture site is not adequately sealed initially. These can be identified immediately after the procedure or several days later. A duplex ultrasound is the diagnostic investigation of choice. Cross-sectional imaging such as CT scan and MRI can also be used. Pseudoaneurysms less than 2 cm in size usually resolve spontaneously and rarely need further intervention. Ultrasound-guided compression can be considered if it does not spontaneously resolve. For pseudoaneurysms larger than 2 cm, direct thrombin injection with ultrasound guidance is the current standard of care. However, care should be taken to assess for a small neck and the absence of AVF to have greater success and to avoid complications. Repeat ultrasound of the area for resolution can further help to guide treatment. For pseudoaneurysms that do not resolve or have wide necks, open repair may be needed ( Fig. 2.1 ).
