Contrast Angiography

Fluoroscopic angiography with use of contrast remains the first‐line tool for the endovascular operator. Digital subtraction imaging (DSA) is utilized and enhances vascular visualization by subtracting the bony or dense structures from the image [7].

DSA can also reduce the amount of dye required for image acquisition. Even with less contrast delivered, full‐strength contrast injections into the extremity tend to be painful. A 50/50 mix of contrast and saline with DSA can allow for diagnostic images while reducing patient discomfort.

CO₂ Angiography

Peripheral arterial disease is prevalent in the chronic kidney disease populations [8, 9]. CO₂ angiography presents an attractive alternative to enable successful peripheral arterial disease intervention without the need for contrast dye exposure. Furthermore, CO₂ can be useful in patients with severe contrast allergies [10].

CO₂ angiography has important limitations. First, it may require specialized software to visualize the CO₂. Second, medical grade CO₂ cannot be delivered via mechanical power injection; and therefore, manual injection must be performed to achieve imaging. Third, in order to prevent erroneous air injection into the arterial system, one must create a separate system of tubing and syringes to allow for purging of atmospheric air and the creation of a closed CO₂‐filled circuit. Importantly, caution should be observed if a patient complains of abdominal pain after a CO₂ injection, as this could be a sign of intestinal ischemia related to successive injections of CO₂ [11]. Therefore, one should generally have a delay of two to three minutes between subsequent CO₂ injections [12]. Finally, imaging of the infratibial vessels is generally limited with CO₂ and may require switching the system to contrast or utilizing direct injection of CO₂ with a catheter placed in the below‐the‐knee popliteal artery [13].

Extravascular and Intravascular Ultrasound

Extravascular ultrasound (EVUS) has become a critical tool in safe arterial access and efficient vascular access [14]. Intraprocedural use of EVUS can also be useful in achieving procedural success by allowing controlled intraluminal wire reentry for complex chronic total occlusion crossing [15].

Intravascular ultrasound (IVUS) is a valuable tool in endovascular assessment of accurate vessel sizing, stenosis area determination, and visualization of the composition of arterial plaque (Figure 9.2). Preintervention IVUS precisely determines vessel size. This may be particularly important for self‐expanding stents with less radial force than balloon‐expandable scaffolds and can avoid both under‐ and over‐sizing [16–18]. IVUS may also inform atherectomy, angioplasty, or lithotripsy device selection by evaluating the degree of calcification within a stenotic segment.

Steps to IVUS Use

Three IVUS sizes are available: standard 0.014″ IVUS, which is also useful in the coronaries, is produced by multiple companies. There are 0.018″ and 0.035″ IVUS systems available from both Boston Scientific and Phillips. The 0.035″ IVUS is useful for large vessels and veins and is typically not necessary for the femoropopliteal segment.

1. Ensure adequate anticoagulation and administer vasodilators prior to use, typically 100–200 mcg nitroglycerin intraarterially (as long as no contraindication exists).
   
2. Place the IVUS catheter beyond the lesion. Prior to entering the body perform adequate catheter flushing and ensure functionality.
   
3. Manual pullback is generally performed given the length of imaging runs required in the femoropopliteal segments. Radiolucent measuring tape placed on the leg is used to coregister the IVUS with the angiogram. Bookmarks can be captured every 100 mm during pullback to correspond with marking tape measurements.
   
4. After pullback is completed, one may reintroduce the IVUS and fluoro‐store the catheter tip location to determine the exact location of the vessel ostia (if pertinent to the case) or lesion segments. This technique can be useful in reducing contrast in patients with chronic renal insufficiency.
   
5. Next remove the catheter from the body and bleed back from the sheath to prevent introduction of air.
   
6. Measurements can then be performed and include the distal reference diameter, proximal reference diameter, and minimal lumen area (Figure 9.2a–c). There is currently insufficient data to recommend exactly how reference measurements should be taken based on lumen measurement or based on external elastic lamina.
   
7. One may also utilize IVUS images to assess severity, arc, and length of calcification. This may aid in decision‐making regarding pretreatment with atherectomy or the potential need for specialty/lithotripsy balloons [19].
   
8. After treatment, repeat IVUS passes are used to assess for dissection, posttreatment minimal lumen, or stent diameters [20].

Steps for Crossover “Up and Over” technique

The “Up and Over” Crossover technique for peripheral intervention is the most common and traditional form of access and method of crossing.

1. Obtain common femoral access contralateral to the symptomatic side or lesion of interest based on noninvasive testing. Place a short sheath typically 4–6 Fr using modified Seldinger technique over the access wire.
   
2. Perform ipsilateral runoff if needed. One can place the image intensifier at 30° ipsilateral to the access site to open the bifurcation of the SFA and profunda arteries.
   
3. Next perform an inflow aortogram. Place an Omni Flush catheter (Angiodynamics, Latham, NY, USA), ImagerII catheters (Boston Scientific), or a pigtail at the T12 or L1 vertebrae. Have the patient perform an expiratory breath hold. DSA imaging is performed with the injection of about 20 cc of 50/50 contrast/saline for visualization. Keys to an ideal diagnostic aortogram are high field of view, vertical orientation of the image intensifier, raised table to decreased magnification by increasing the signal to object distance. The tip of the catheter should be positioned at the top of the screen so that the full field of view is used.
   
4. After the contralateral iliac is wired, bring down the catheter to the top of the femoral head and move the image intensifier to 30° ipsilateral of the vascular segment of interest. Often a contralateral shot should also be taken for further delineation of the anatomic segment of interest. If the decision is made to intervene, advance a soft tipped, stiff wire through the catheter into a safe distal vessel in the contralateral leg. For proximal SFA stenosis, one may place the wire carefully in the profunda to allow for adequate wire “purchase.” Next place a long‐braided sheath “up and over” to the desired segments. For proximal SFA interventions a 40–50 cm sheath is used. For more distal interventions, longer sheaths may be chosen to enhance pushability when crossing high‐grade stenoses.

Radial

The radial approach for endovascular interventions is an excellent alternative to femoral access. Unfavorable iliac tortuosity may be overcome more easily from the radial approach. Challenges to radial access remain especially in terms of available equipment, including adequate device length, compatible drug‐coated devices, and embolic protection filters [21].

Steps for Radial Approach:

1. Left radial access is preferred for these cases as it does not require traversal of the aortic arch thereby minimizing distance to the abdominal aorta. Ultrasound imaging may be useful to confirm the radial arterial diameter is at least 25 mm to accommodate long specialty sheaths commonly utilized for these procedures.
   
2. Once radial access is obtained place a radial specific short sheath into the proximal vessel.
   
3. Use a JR4 or similar shaped catheter to traverse the subclavian artery and engage the descending aorta with a 0.035″ wire.
   
4. Advance an exchange length wire followed by a catheter to the descending aorta.
   
5. Abdominal aortography may be performed with a long pigtail catheter or a sidehole multipurpose catheter (ensure the tip is free from small branches before performing large injections).
   
6. Complete bilateral diagnostic runoff angiography to assess for disease by cannulating bilateral iliacs with a long sidehole catheter.
   
7. Use a stiff 0.035″ guidewire (e.g. Supra Core [Abbott, Chicago, IL, USA], glidewire advantage [Terumo, Shibuya City, Japan], or a long stiff glidewire [Terumo]) to advance the radial intervention sheath (typically 119 or 149 cm R2P destination sheath, Terumo) proximal to the femoropopliteal segment of interest.
   
8. Once the sheath is positioned, various strategies can be deployed to cross the diseased vascular segment.

Tibio‐Pedal Approach

The tibio‐pedal approach for distal entry to a stenosis or occlusion is a necessary component for more complex peripheral intervention. Given the retrograde cap of chronic total occlusions is typically softer than the proximal cap, utilizing pedal access can significantly add to crossiblity of complex and long segment chronic occlusions.

Steps to retrograde access and wire crossing (Figure 9.3).

1. Ultrasound the tibial vessels to determine if retrograde access is feasible and the best vessel to initially attempt. Study of preintervention ultrasound is critical in determining vessel approach and runoff patency. In general, in patients with single vessel runoff, one may try to avoid tibio‐pedal access and sheath placement, as injury to this vessel could lead to acute limb ischemia.
   
2. If all three below‐the‐knee vessels are patent, one may access in the anterior tibial preferentially at or above the ankle joint for easiest closure after the procedure is complete (Figure 9.3a–c). Local anesthesia is given to anesthetize the access arterial segment (Figure 9.3c). The posterior tibial artery is our second choice followed by peroneal. The peroneal artery is typically done under fluoroscopic guidance by puncturing directly between the tibia and fibula distally.
   
3. After access using ultrasound guidance, one can wire under fluoroscopy and place a tibial access sheath. A radial access sheath (Figure 9.3e–f) may also be repurposed for pedal access. Give a vasodilator cocktail (i.e. 200 mcg of nitroglycerin, assuming no contraindication) and perform angiography distally through the pedal sheath.
   
4. Next utilize a 0.014″ or 0.018″ wire coupled with a crossing catheter to gain access to the distal cap of an occlusion or stenosis to facilitate distal crossing.

Antegrade Femoral Access

Antegrade femoral arterial access allows for ipsilateral intervention sparing the need for crossing‐over technique. Antegrade sheath location can enhance support to allow advancement of equipment and may be particularly useful for popliteal and below‐the‐knee occlusive disease.

Antegrade access may be obtained with ultrasound guidance with the probe in a transverse position allowing visualization of the femoral head, common femoral, and superficial femoral/profunda bifurcation. This will ensure safe entry in a compressible segment of the vessel and enable steering into the SFA [22]. Standard short sheaths can be utilized. Access into the common femoral rather than the superficial femoral access may help avoid vascular access complications such as pseudoaneurysms if closure devices are not utilized, however, may require more radiation and longer access times as the access wire tends to move toward the profunda [23].

Lesion Preparation