Puncture with visible calcification:

• Use the lock-in function to set the fluoroscopy dose.

• Collimate the beam so that the puncture site in the vessel is well visualized but the outer end of the cannula remains outside the fluoroscopic field of view.

• To better protect the fingers against radiation attach a syringe to the cannula.

• Under fluoroscopic control, advance the tip of the cannula toward the vessel until the calcification is seen to move with the cannula.

• Turn off fluoroscopy.

• Remove the syringe from the cannula.

• Advance the cannula until blood gushes out.

Puncture with Doppler Ultrasound

In the absence of visible calcification (occluded iliac artery or severe obesity), use a Doppler probe to locate the artery. Often one can locate the artery with Doppler ultrasound and mark its course on the skin prior to administering local anesthesia and before the patient is prepped and draped. If the vessel still cannot be punctured, proceed as follows: An assistant places the Doppler probe in a sterile bag that you hold open (after first applying acoustic gel to its tip; Fig. 3.12). Then the device is hung by its cord in the sterile puncture area. To ensure good acoustic coupling, sprinkle a few drops of saline solution on the skin. Then grasp the probe in its sterile bag and locate the artery. The narrower the probe, the more precise the localization will be. (Very fine Doppler probes that can be advanced within the cannula to its tip are also available. One model is the SmartNeedle (Vascular Solutions, Maple Grove, MN, USA). The author has no experience with such probes.)

Puncture with Doppler ultrasound (Fig. 3.13 ):

• Apply the Doppler probe perpendicular to skin.

• Move it laterally, seeking maximum signal strength.

• Apply local anesthesia and make the skin incision over the course of the vessel.

• Point the cannula obliquely at the vessel in the plane of the Doppler probe.

• Advance the cannula until blood gushes out.

Possible problem: A collateral may emit a stronger signal than the artery being searched for, especially if that artery is occluded.

Puncture Using Road Mapping

Whenever a catheter is already in place proximal to an impalpable artery, the artery can be reliably visualized by road mapping and punctured. Two examples are as follows:

• Retrograde catheterization of an occluded left iliac artery is planned in the presence of an abdominal aorta catheter placed via a right arterial approach.

• Antegrade catheterization of an occluded superficial femoral artery is not feasible; catheterization is to be attempted via the popliteal artery: Contrast agent should be injected via a sheath already in place in the common femoral artery.

Procedure:

• Focus on the region of interest.

• Collimate the beam (with lock-in function as for puncture with visible calcification).

• Activate road mapping, inject contrast.

• Puncture the contrasted artery under fluoroscopy (as with visible calcification).

Instead of road mapping it is occasionally possible to advance a wire from the other catheter into the artery to be punctured. Then under fluoroscopic control one simply aims the cannula at the wire.

Whenever one is unsure whether one has punctured an artery or vein in the inguinal region, one must first answer this question before making a larger hole in the vessel wall with a catheter or sheath. A small quantity of contrast agent can be injected through the cannula and observed as to whether it flows proximally or distally. The same degree of certainty can be achieved by advancing a guidewire cranially past the iliac region. If the wire courses to the right of the spinal column, one is in the vein; if it courses to the left, one is in the artery.

Introducing a Catheter or Sheath

Once the wire has been positioned securely far enough within the artery, withdraw the cannula and compress the puncture site with the ring and middle fingers (Fig. 3.14a). Grasp the wire with the thumb and index finger of the same hand to prevent it from sliding out of the vessel when the cannula is withdrawn (Fig. 3.14b).

An assistant now slips the sheath or catheter over the proximal end of the wire after the cannula is withdrawn. This will be easier if one holds the wire with the thumb and middle finger and supports the wire and catheter tip from behind with the index finger (Fig. 3.15).

Without Assistance

In the absence of an assistant, it is best to use a sheath. As one slips the sheath over the wire, one presses the short outer end of the wire against the drape with the thumb of the hand that is compressing the puncture site. This will prevent the wire from whipping through the air at random (Fig. 3.16). Then the wire can be more easily placed on the index finger of the other hand and directed into the tip of the sheath.

If you are working alone and want to introduce the catheter without a sheath for angiography, proceed as follows: Place the wire on the drape in a wide loop (Fig. 3.17a) so that you can compress the puncture site while holding the end of the wire so it can be inserted into the tip of the catheter. Then push the wire through the catheter, grasp the catheter tip with the left hand, and with the right hand pull the wire out of the back of the catheter (Fig. 3.17b) until the loop disappears and the catheter tip has been drawn up to the puncture site (Fig. 3.17c, d).

Resistance at the Vessel Wall

As one introduces the tip of the catheter or sheath, the external pressure one applies helps to guide it through the subcutaneous tissue (Fig. 3.18). This prevents the catheter or sheath from glancing off the vessel into the soft subcutaneous tissue when it encounters the resistance of the vessel wall (Fig. 3.19).

Not only may the inguinal artery be difficult to locate precisely; there may also be strong mechanical resistance to introducing a cannula, catheter, or sheath. Often hard subcutaneous scar tissue from previous surgery will be encountered. Large chronic hematomas can also lead to scarring and induration. The vessel wall itself may be indurated, calcified, and very hard as a result of arteriosclerosis. The scar tissue at an older anastomosis is almost always very firm. Finally, very firm scar tissue usually forms around a plastic bypass.

As one punctures the artery, the lumen can collapse before the cannula has passed through the proximal wall (see Fig. 3.8, p. 44). When that happens, one will have punctured the distal wall as well without the tip of the cannula having been within the open lumen. Solution:

• During the puncture procedure, one slightly withdraws the cannula several times to allow the arterial lumen to reopen.

• One withdraws the needle very slowly while maintaining pressure on the surface of the skin.

• As soon as blood gushes out of the cannula, it is best to introduce a short Amplatz wire (Boston Scientific, Natick, MA, USA). Inserted far enough, this will almost always provide a secure track suitable for introducing a sheath through indurated tissue (Fig. 3.19).

After initially using a normal guidewire, one may occasionally find that it is not possible to introduce a sheath over the wire without kinking it. This is especially true of a hard vessel wall with soft overlying tissue (Fig. 3.19). In this case, one first introduces the catheter of a long 18 gauge catheter cannula or a 4 French dilator over the normal wire and then replaces it with an Amplatz wire.

In this situation the sheath must meet certain special requirements: It must be made of very sturdy plastic, it must be in close contact with the guidewire, and the transitions between guidewire and dilator and between dilator and sheath must be smooth transitions without a pronounced step-off (see Chapter 2, Sheaths, p. 13). There must also be a firm connection between dilator and sheath. Otherwise only the sheath will move forward, and the dilator will be pushed out of the back of the sheath.

Acute Occlusion of the Common Femoral Artery Induced by Catheter or Sheath

Rarely a patient will complain of severe pain in the ipsilateral leg shortly after catheterization of the inguinal artery. The most common cause of this is that the catheter or sheath has completely blocked a high-grade stenosis, usually due to posteromedial plaque (Fig. 3.20). This results in ischemia of the entire leg. The pain can be so severe and so difficult to control that an anesthesiologist will have to be called in to help.

However, it is essential to perform angiography of the inguinal region and of the entire leg if possible to visualize the causative stenosis and to exclude acute embolism. A vascular surgeon must be alerted immediately.

Catheterization Via a Plastic Bypass

Even a plastic bypass can be punctured and catheterized (an aortofemoral, femoropopliteal, or axillofemoral bypass or a dialysis shunt). Especially in the vicinity of an anastomosis, a plastic bypass is often enveloped in very hard scar tissue that renders catheterization difficult. Then an extra stiff wire (Amplatz) is often required to introduce a catheter or sheath.

Caution: The following is the most important difference between this puncture and the puncture of an artery or vein: A bacterial infection of a bypass cannot be controlled by medication alone. Therefore the procedure should always be performed under strict aseptic conditions. To be on the safe side, the patient should also be given a broad-spectrum antibiotic prior to any puncture and catheterization of a plastic bypass.

Successful catheterization of arteries of the lower leg via the posterior tibial artery at the level of the ankle or the dorsalis pedis artery has recently been described as well (Huppert et al 2010, Schmidt and Montero-Baker 2008).

Translumbar Approach

During the 1970s the technique of percutaneous catheterization with guidewire and catheter introduced by Seldinger only gradually supplanted the previously predominant techniques of direct puncture of major arteries (common carotid artery, abdominal aorta, and femoral artery) with rigid cannulas. Up to that time translumbar aortography had been the standard procedure used in the diagnostic workup of peripheral arterial occlusive disease.

The patient (usually under general anesthesia) was positioned prone. A steel cannula ~ 2 mm wide was advanced toward the aorta from the left side, one hand width from the midline at the level of the L2–3 vertebra. At the time there was no tomographic imaging modality such as computed tomography (CT), magnetic resonance imaging (MRI), or ultrasonography. At best one could recognize the calcification of the aortic wall on the fluoroscopic image. And of course the aorta was not always punctured on the first attempt.

Today it is hard to imagine a situation that would require this approach. Nonetheless it would be less risky today than it used to be. CT, MRI, or ultrasound images could be used to plan the approach with a high degree of precision (Fig. 3.21). Local anesthesia of the cannula track would suffice. The puncture would be performed with an 18 gauge catheter cannula (1.2 mm in diameter). Then the catheter could be pointed cranially or caudally over a guidewire, or an angiography catheter of the appropriate size could be introduced.

Antegrade Catheterization of the Femoral Artery

Endovascular interventions involve many complex tasks. Some of them are rarely required, whereas others represent a daily challenge. Antegrade catheterization of the common femoral artery is undoubtedly the most common of these. Performed correctly, antegrade catheterization has several advantages over the crossover technique:

• It is quicker.

• It requires less material.

• The decisive advantage is that without the long tortuous approach through the iliac arteries it is easier to steer the wire and catheter in the arteries of the leg (for details see Chapter 5, Superficial Femoral Artery, p. 159).

In antegrade catheterization, all of the instruments such as the guidewire and catheter lie somewhere close to the patient’s face. Because it is not possible to cover the entire face with sterile drapes, this could pose problems with respect to sterility (the same applies to uncontrolled arm movements by the patient).

This does not mean that it would be better to lay the wire and catheter over the patient’s legs and then conduct them to the inguinal region in a 180° curve. The operator’s arms would be unnecessarily close to the fluoroscopic field. This would also reduce the immediacy of every manipulation (even in the radiologist’s imagination), and a curved catheter and wire cannot be rotated as freely as straight ones. Deformations in the catheter wall create resistance to torsion (Schröder 1992).

Yet it is a very good idea to use an oblique bracket to keep the sterile drape off the patient’s face (Fig. 3.22). Another proven solution is to attach a small extension platform alongside the table on the operator’s side. This provides a tray for the guidewire, catheter, manometer syringe, and other materials (Fig. 3.23). Radiation shields attached to the side of the table are also helpful. The covering drape can be positioned so it forms a trough behind the shields which can be used to hold instruments.

Antegrade Puncture of the Common Femoral Artery

Everything that has been said about retrograde puncture also applies to antegrade puncture. However, the procedure involves a few additional difficulties:

• An obese abdomen often makes it very difficult to perform the puncture at the proper site and at the desired angle.

• The path through the subcutaneous fatty tissue to the vessel is significantly longer in many cases.

• The deep femoral artery will often be accessible to the wire as the direct continuation of the line of puncture (Fig. 3.27).

• In contrast, the superficial femoral artery courses horizontally and not in a favorable posterior direction like the external iliac artery in the retrograde puncture.

• And if the deep femoral artery is punctured instead of the common femoral artery, there will be no way to get from there to the superficial femoral artery.

A soft, mobile abdomen can be pulled in an obliquely cranial and contralateral direction and immobilized there with long strips of bandage. These strips should not be fastened to the contralateral abdomen but to the rail on the table instead. Otherwise one will merely draw the abdomen together slightly and it will slide back into its original position (Fig. 3.24).

In a patient with a firm potbelly, there is little you can achieve with bandages. An assistant must push the abdomen upward when vascular access is established, or one opts for crossover catheterization (p. 60).

A long path through the subcutaneous fatty tissue also means that the skin incision must be made farther cranial in order for an oblique cannula to puncture the common femoral artery at the proper location. This requires particularly careful planning of the puncture level and then advancing the cannula under fluoroscopic control. These imaging findings may reveal that a change in the puncture angle or an incision at a different site is indicated.

In antegrade catheterization, it will not always be possible to avoid a puncture angle steeper than 45°. However, such an angle has significant disadvantages:

• The guidewire can travel cranially into the iliac arteries (Fig. 3.25).

• The sheath can easily kink, making it very difficult to introduce a catheter and especially a vascular closure system into the sheath (Fig. 3.26).

As soon as blood gushes out of the cannula, introduce the wire and try to hold the cannula at an acute angle to the skin, if necessary by turning it slightly medially, before you advance the wire into the vessel.

From the Deep Femoral Artery to the Superficial Femoral Artery

The deep femoral artery will often be accessible to the wire as the direct continuation of the line of puncture (Fig. 3.27). Brief fluoroscopy will usually show whether the wire has entered the superficial femoral or deep femoral artery (Fig. 3.28).

Into the Superficial Femoral Artery with the Aid of the Cannula

The difference is more obvious on lateral oblique fluoroscopy: If the wire is in the deep femoral artery, it will often be possible to bring it into the superficial femoral artery by withdrawing it and advancing it again with the cannula at a more acute angle to the skin and at a slightly medial angle (Fig. 3.29).

Into the Superficial Femoral Artery with an 18 G Catheter Cannula (or 4F Dilator) and a Curved Glide Wire

The previous method may be unsuccessful and it may be doubtful that one has entered the common femoral artery far enough proximal to its bifurcation. In this case one must determine the precise location of the puncture before creating a larger hole in the vessel wall with a sheath.

The author cannot recommend withdrawing the wire and injecting contrast through the cannula for this purpose. Doing so may cause the cannula to slip out of its correct position. With the wire in place, replace the rigid cannula with a long 18 gauge catheter cannula or a 4 French dilator. This can be placed in a secure position within the vessel without greatly expanding the hole in the vessel wall. Then do the following:

• Use oblique projection (30% ipsilateral).

• Collimate the beam, focusing on the femoral artery bifurcation (lock-in function).

• Use road mapping over the catheter cannula.

• Fill the catheter with concentrated contrast agent so that its tip is clearly visualized.

• Withdraw it until proximal to the femoral artery bifurcation.

• Introduce a short curved, torqueable glide wire.

• Steer the wire into the superficial femoral artery under fluoroscopic control (Fig. 3.30).

It can be helpful to rotate the wire 180° as soon as its tip has reached the origin of the superficial femoral artery. The wire will hook into that artery instead of sliding back into the superficial femoral artery. Only when the wire has been positioned securely far enough within the superficial femoral artery the catheter cannula may be withdrawn and the sheath introduced.

Often the bend in the tip of the glide wire is too slight. Then the tip will fail to reach the origin of the superficial femoral artery (Fig. 3.31). In this case the wire should be given a more pronounced bend (see Chapter 2, Guidewires, p. 8).

Into the Superficial Femoral Artery with a Curved Catheter (Simplest Method)

The alternative to a curved wire is a curved catheter. This has a straight shaft but must have a 90° bend immediately behind its tip (ACN 1 from Cook Medical [Bloomington, IN, USA] or BERN from various suppliers). If one rotates the tip of this catheter anteromedially within the deep femoral artery, withdrawing the catheter will cause the tip to drop back medially as soon as one leaves the deep femoral artery (Fig. 3.32). “Road mapping” or continuous injection of small amounts of contrast as the catheter is withdrawn will verify proper positioning. This maneuver with the curved catheter will probably work more reliably than the one with the curved wire, and the distance to the femoral artery bifurcation is not as critical in this case. In a wide vessel one may not succeed in guiding the tip of the catheter along the medial wall of the deep femoral artery. In that case, road mapping will reliably show how far to withdraw the catheter.

Shortening the catheter to a length of ~ 30 cm will greatly facilitate this manipulation.

If the catheter is smaller than the sheath (e.g., 4 French as opposed to 6 French), then one should advance only the wire into the superficial femoral artery and then replace the catheter with a dilator. Otherwise the unprotected tip of the sheath could injure the vessel wall at the carina (Fig. 3.33).

The sheath must be long enough so that it extends at least 1 to 2 cm into the superficial femoral artery. Otherwise it can easily slip back into the deep femoral artery when one changes catheters.

Into the Superficial Femoral Artery Using the Cope Technique

Cope et al (1990) suggested introducing into the deep femoral artery a short catheter or dilator that has a side hole on the outside of a bend. Road mapping is used to place this catheter at the femoral artery bifurcation in such a manner that one can steer a 0.018 in. wire through the side hole into the superficial femoral artery (Fig. 3.34). Then the catheter is removed and the sheath is introduced into the superficial femoral artery over the wire. Unfortunately, the author has yet to find any company on the German market that supplies this catheter with a side hole.

When the road mapping shows that the puncture site is very close to the femoral artery bifurcation, it will often be impossible to introduce a curved wire or curved catheter into the superficial femoral artery. In that case one must withdraw the catheter cannula, compress the site for 2 to 3 minutes, and repeat the puncture.

Kink in the Sheath

Certain anatomical situations (such as a steep puncture through a thick layer of subcutaneous fatty tissue) are conducive to kinking of the sheath that could prevent insertion of a wire or catheter. Wherever there is a risk of kinking, always leave a stiff wire or catheter in the sheath. And with every new catheterization, have an assistant pull the abdomen upward!

The attempt to catheterize a kinked sheath will probably have the best chance of success if one uses a wire splinted by a dilator to within a short distance of its tip. (Use of a stopcock on the dilator ensures a firm connection between the dilator and the wire.) A fixed kink is best overcome by withdrawing the sheath slightly, advancing the wire and dilator up to the kink, and then advancing sheath, dilator, and wire together (Fig. 3.35).

High Bifurcation of the Common Femoral Artery

A high bifurcation of the common femoral artery or a prominent abdomen will occasionally preclude antegrade catheterization of the common femoral artery. In such cases one may consider crossover catheterization (see later discussion) or, rarely, a superficial femoral artery puncture. For a puncture of the superficial femoral artery (not palpable, use a Doppler probe!) its lumen should not be less than 5 mm so that a vascular closure system can be placed to seal the puncture after the intervention. This is particularly important because there is no solid structure deep to the superficial femoral artery that could be used as a buttress to achieve compression.

In extremely obese patients it is possible that the inguinal regions of both sides are unsuitable for catheterization, regardless of whether antegrade or retrograde. One possible access site in such cases is the left brachial artery. This artery usually lies just beneath the skin even in severe obesity (see Access via the Brachial Artery, p. 65).

Retrograde catheterization of the superficial femoral artery via the popliteal artery is an option primarily where occlusion of the superficial femoral artery precludes proximal access. Usually this is preceded by antegrade placement of a sheath via the common femoral artery (see Chapter 5, Superficial Femoral Artery, p. 159). In the rare case of chronic occlusion of the superficial femoral artery over a long segment, one may consider antegrade catheterization of the popliteal artery to treat the arteries of the lower leg (Schroeder 1989).

Especially in diabetic patients with trophic lesions in one foot and possibly renal insufficiency as well, it will occasionally be necessary to determine whether intervention is indicated using a slight amount of contrast. If indicated, intervention would then be performed immediately. (CO₂ should be used for contrast in the presence of renal insufficiency—see Chapter 2, CO₂ as a Contrast Agent, p. 36.)

It is recommended to begin with angiography via an 18 gauge catheter cannula (or 4 French dilator) immediately after puncture. This cannula need only be replaced with a sheath where angiography demonstrates findings requiring treatment.

Crossover Catheterization

The term “crossover” has come to be used for catheterization and treatment of the contralateral arteries of the pelvis and legs beyond the aortic bifurcation. The technique of crossover catheterization is a crucial element in the repertoire of every interventional radiologist. For example, after retrograde catheterization it can be used to treat not only the iliac arteries of one side but also the arteries of the contralateral pelvis and leg.

The crossover maneuver is performed in several steps:

• A catheter with a suitable bend is advanced past the aortic bifurcation and hooked into the contralateral common iliac artery.

• A guidewire is advanced through the catheter far into the contralateral iliac arteries.

• The first catheter is removed and replaced with a suitable sheath.

• The sheath is advanced over the wire into a stable position in the contralateral iliac arteries.

Catheters for Contralateral Access

Various catheters with a bend of < 180° are suitable for this purpose. The segment distal to the bend should not be longer than 15–20 mm to allow the catheter to be easily directed caudally within the aorta (Fig. 3.36). The UF catheters from Cordis (Miami, FL, USA); the Omni Flush, Sos Omni 0, 1, 2, or 3 from AngioDynamics (Latham, NY, USA); and the Contra from Boston Scientific are all very suitable designs. Several other catheters are also recommended in the literature for initial catheterization of the contralateral iliac arteries beyond the aortic bifurcation. These include a simple hook, a Judkins catheter for the right coronary artery, and even Cobra or pigtail catheters. This latter design is not really suitable (see Chapter 2, Angiography Catheters, p. 16); the Cobra catheter is useful only with an obtuse bifurcation angle. The other catheters mentioned have too wide a bend or insufficient strength to rotate the wire caudally nearly 180°.

The tighter bends recommended here (see Fig. 3.36) occasionally tend to slip back into the ipsilateral iliac artery. It is usually fairly easy to spread open the bend a little with the wire and then to guide the bend in the catheter across the bifurcation.

If one cannot find the bifurcation right away, road mapping with a small quantity of contrast will help.

The Wire’s Role in Crossover Catheterization

The wire must be soft near its tip to allow it to follow the bend in the catheter (Fig. 3.37). Gradually increasing stiffness (over a transition of at least 5 cm) is required to allow a relatively stiffsegment to pass through the bifurcation last. This is needed to extend the distal bend in the catheter so that it can be advanced across the bifurcation. An abrupt transition will cause the wire to push the catheter cranially into the aorta (Fig. 3.38).

Pulling the catheter downward onto the bifurcation to spread open the bend makes it a lot easier to advance the catheter into the contralateral iliac arteries (Fig. 3.37d). In difficult cases one can also apply external compression to try to hold the wire in its position within the common femoral artery. Then one can advance the catheter over the immobilized wire (Fig. 3.39). A spring wire with a very long soft tip (Bentson) is best suited for this purpose, not a “glide” wire.

If one does not succeed in introducing a normal J wire into the contralateral iliac arteries due to plaque or stenosis, a glide wire with a curved tip will almost always help. If this wire becomes caught on plaque, one can turn it and steer it past the plaque.

In patients with an acute-angle bifurcation and elongated iliac arteries, a normal wire will often be insufficient to guide the relatively stiff sheath. One will then need a stiffer wire (Amplatz or similar wire). However, it will only be possible to advance this wire across the bifurcation when the catheter lies far within the contralateral iliac arteries. This case requires one to do the following:

• Advance a normal wire far into the contralateral iliac arteries.

• Advance a catheter over the wire.

• Replace the first wire with a stiffer wire (Fig. 3.40).

An acute-angle bifurcation immediately followed by a medial curve in the common iliac artery may make it impossible to advance even a curved glide wire across the bifurcation. In such cases a long taper glide wire may be helpful. This wire with its long, increasingly stiff tip will only begin to spread open the bend in the catheter once it has reached a fairly stable position in the contralateral iliac arteries. Once it has been advanced far enough it is usually stiffenough to splint the bifurcation to allow passage of the catheter.

The bend in the catheter must be spread open as the catheter passes into the contralateral iliac artery. The force required to do this acts against the passage. Therefore, if the bend in the catheter prevents it from being guided around the curve (Fig. 3.41), it should be replaced with a straight 4 French catheter. This catheter will more easily follow the wire across the bifurcation. First the segment near the tip is softened with the fingers, and then the catheter is rotated as it is slowly advanced across the bifurcation. When this catheter has been advanced into the contralateral inguinal region, a stiff wire (stiff glide wire, Amplatz wire, or similar wire) is carefully inserted to spread open all the curves to allow passage of the sheath (Fig. 3.42).

Sheaths for Crossover Catheterization

The sheath must have the following characteristics to be advanced across an acute-angle bifurcation:

• Either the dilator and the sheath have a suitable bend (e.g., from Cook Medical, Figs. 3.43 and 3.44),

• or a flexible dilator projects a few centimeters beyond the tip of the sheath (e.g., Arrow International [Reading, PA, USA], Figs. 3.43 and 3.45).

The dilator is first advanced across the bifurcation. It splints the bifurcation so the stiffer sheath can be advanced. (This is the principle of gradually increasing stiffness.)

An acute-angle bifurcation can cause the sheath to kink, which may even make it impossible to withdraw the sheath. For this reason crossover catheterization should only be attempted using sheaths with spiral metal reinforcement in their wall.

Interventions in the arteries of the pelvis and legs may also be performed without introducing a long sheath into the contralateral vessels. However, this long sheath has two decisive advantages:

• It allows injection of contrast agent during the intervention (road mapping and evaluation of results with the guidewire still in place).

• Equally important: Without the sheath you will be unable to negotiate many stenoses and occlusions because it will not be possible to apply sufficient axial force with guidewire and catheter alone. Guidewire and catheter alone will be diverted into the abdominal aorta as soon as they encounter any significant resistance. A sheath will reliably prevent this.

Caution: In crossover catheterizations the guidewire and catheter often spontaneously seek the internal iliac artery. This will not always be obvious from the course of the artery on a posteroanterior (PA) view. When in doubt, and especially before any intervention, rotate the C-arm to obtain a medial oblique view: The internal iliac artery courses posteriorly, the external iliac artery anteriorly.

The goal of crossover catheterization is typically an intervention. However, a balloon catheter does not allow one to choose between the deep and superficial femoral arteries. However, a curved diagnostic catheter is not required if the wire and catheter pass into the contralateral deep femoral artery instead of the superficial femoral artery. Use a torqueable curved glide wire to steer the catheter under fluoroscopic control. Use an ~ 30° lateral oblique projection and road mapping (Fig. 3.46b). If the bend is not sufficient, withdraw the wire and increase the bend (put a kink in it ~ 3 cm behind the tip). The wire can be used like a straight wire for negotiating the artery if one then withdraws the kink into the catheter (see Fig. 5.48, p. 188).

Access via the Brachial Artery

Special Considerations with the Arm Approach

The left brachial artery is the most important alternative to the inguinal arteries as an approach to the arterial system. The left side has the advantage of shorter distance. The risk of cerebral complications due to embolism or vasospasm is also significantly lower because a catheter introduced on the left side only passes the origin of the vertebral artery on its way into the descending aorta. However, one must also consider the possibility of stenosis or occlusion of the subclavian artery. Both are encountered significantly more often on the left side than on the right. Therefore one should measure the blood pressure in both arms before performing the puncture.

The axillary artery was once favored for vascular access due to its size. However, it is significantly more difficult to puncture, and the difficulty in achieving effective compression significantly increases the risk of local complications.

Some cardiologists prefer the radial artery because of the availability of the ulnar artery in the event of occlusion. Note, however, that the probability of vascular occlusion is higher than in the brachial artery due to the radial artery’s relatively small caliber.

If one chooses the approach via the radial artery, the Allen test must be performed first to verify the function of the ulnar artery as a collateral: Simultaneously compress the radial and ulnar arteries while the patient makes a fist. Then release the ulnar artery as the patient opens the fist. A sufficiently functional ulnar artery will cause the hand to turn pink within 5 to 10 seconds.

Puncture and Catheterization

The brachial artery is punctured where it is best palpated. It occasionally exhibits a tendency to avoid the cannula. Therefore, it is essential to use a sharp cannula. At least in difficult cases, it is advisable to supplement the normal puncture cannula with a puncture set (Fig. 3.47) that includes a thin cannula (21 gauge) and a fine guidewire such as those supplied for radial artery puncture.

Yet, if arterial blood pressure is very low, such as can occur in a proximal brachial or subclavian artery occlusion, the thin cannula can pose too much resistance for the escaping blood, particularly in a long cannula. Filling a cannula 8 cm long requires twice the pressure needed to fill one 4 cm long!

An 18 gauge plastic cannula is also a viable alternative. Where the brachial artery is poorly palpable it is often helpful to use a Doppler probe (see p. 47). The probe should be as narrow as possible. The weak pulse can of course be due to a subclavian artery stenosis. Compare the blood pressure with the right side. In this case, one may consider dilating the subclavian artery in the same intervention. Even an impalpable brachial artery can be punctured with the aid of a Doppler probe, for example, where a proximal brachial artery stenosis or occlusion is to be treated. However, in such a case the artery would no longer provide a suitable approach for intervention in other vessels.

The standard J wire may not be used for catheterizing the brachial artery because the curve at its tip is 6 mm in diameter, which is far too wide for the narrow vessel. The wire will cause vasospasms. A 0.035 in. glide wire with a slightly curved tip is recommended.

Especially in the axillary artery, a curved wire will often enter a branch. At the slightest resistance, the region should be examined under fluoroscopy, and the wire should be withdrawn and then rotated to advance it beyond the branch.

The guidewire will often spontaneously enter the left vertebral artery. This, too, must be immediately corrected or, better, avoided from the outset (use fluoroscopy!) because the catheter can trigger a vasospasm at that location.

The arm approach for interventions in abdominal, iliac, or leg arteries is thus associated with an increased risk and remains the exception. The risks include thromboembolic complications in the arteries supplying the brain and vascular occlusions in the arm. Thrombus deposition can occur on long catheters and sheaths. Withdrawing the instruments can then strip this material off and release it into the bloodstream where it can form emboli in the basilar artery or the arteries of the fingers. For this reason heparin must be administered immediately at the beginning of any intervention.

Approach to the Descending Aorta

Usually one must negotiate a sharp curve at the junction of the left subclavian artery and descending aorta. Often this is attempted with a pigtail catheter, which is rather poorly suited for this purpose (Fig. 3.48a). Instead, use a catheter with a short distal bend of 180° maximum (Fig. 3.48b), and perform this maneuver under fluoroscopic control using the 30° left anterior oblique (LAO) projection.

Long sheaths that can be introduced as needed into the vessel requiring treatment are very helpful for interventions via a brachial approach. The following maneuver is recommended to guide these sheaths into the descending aorta:

• The sheath is advanced as far as the origin of the subclavian artery.

• The dilator of the sheath is replaced with a catheter having a distal bend of 150 to 180°. (In the absence of the proper sort of catheter, one can take a long pigtail catheter and cut off the superfluous part of the bend.)

• This catheter is used to direct the guidewire into the descending aorta (Fig. 3.49).

• The wire is pushed far enough into the catheter to extend its distal bend (or one can withdraw the bend in the catheter into the sheath).

• Finally, the sheath is advanced with the wire and catheter into the abdominal aorta (Fig. 3.49).

For most interventions (those in the renal or iliac arteries), a slight bend close to the tip of the sheath is helpful. Because of the small caliber of the arteries of the arm, the diameter of the sheath becomes a critical dimension (6 French is maximum, 5 French is better). This makes it essential to work with slender systems.

Treatment of the Access Site

Requirements, Alternatives

Most complications in angiography and endovascular intervention are sequelae of insufficient or unsuccessful treatment of the arterial access site.

Since the introduction of Seldinger’s percutaneous catheterization technique in 1953, the opening in the vessel wall has been closed by external compression. Even after the introduction of systems such as Angio-Seal or StarClose (Abbott Vascular, Temecula, CA, USA) that close the opening immediately at the vessel wall, compression treatment has continued to dominate to this day and accounts for 70 to 90% of all cases (Turi 2008). The ongoing trend to smaller systems (4 French rather than 6 French) will presumably help compression treatment maintain its dominance in the future as well.

Common Femoral Artery

The first step toward correct treatment of the access site at the end of the intervention is at its very beginning: the careful choice of puncture site. In the inguinal region, this is at the level of the middle third of the femoral head, although the distal third is also acceptable. Here one has a solid structure that can be used as a buttress to achieve compression, and for a vascular closure system one will not normally have a problem with the origin of the deep femoral artery in this segment.

Closure by External Compression

If the catheter track is to be closed by compression, then the pressure applied to the skin must be high enough to press the sides of the oblique wound together and prevent any more blood from escaping. The residual blood in the cannula track will then coagulate and seal the track. On the other hand, the artery must remain patent or only collapse briefly under the pressure. If there is no palpable pulse distal to the compression site or the Doppler probe or pulse oximetry fail to demonstrate blood flow there, then the pressure must be reduced within 2 minutes at the latest.

There are two decisive criteria for the entire aftercare phase:

• There must be no bleeding at the puncture site.

• There must be blood flow in the arteries of the legs. There must be a palpable pulse distal to the compression site (in the common or superficial femoral artery immediately distal to the compression site, in the popliteal artery, in the posterior tibial artery, or in the dorsalis pedis artery). Where there is no palpable pulse, one must look for flow signals with a Doppler probe or detect them by pulse oximetry.

The pressure exerted on the skin above the punctured vessel decreases with the depth of the tissue. One can compensate for this decrease with depth by increasing the surface on which one exerts pressure. Yet applying the same pressure over a larger area requires more exertion, which is why manual compression can be very strenuous in obese patients.

A solid buttressing structure, like the bones of the hip, acts as counterpressure. This force vector is added to the direct pressure to create a field of largely homogeneous compression between the compression device and the buttress (Fig. 3.50). A certain loss of pressure in the deeper tissue may nonetheless occur under such conditions, but this is due to the larger area of the buttress over which the force is distributed. The less the pressure decreases with depth, the more favorable will be the conditions for achieving successful compression.

With the sharp drop in pressure that typically occurs in the absence of a buttressing structure, the cannula track is often closed superficially, whereas there is insufficient pressure in the deep layer to close the puncture wound in the vessel. This can lead to a pseudoaneurysm : Blood continues to escape into the surrounding tissue through the puncture wound in the vessel wall. Because it moves back and forth with the alternating blood pressure, it does not coagulate (Fig. 3.51).

These are the typical conditions that give rise to a pseudoaneurysm when the puncture is performed too far distal, beyond the buttressing structure of the femoral head. A puncture performed proximal to the inguinal ligament will also lack this buttress for compression. The consequences can be far worse at this site because a circumscribed cavitation will fail to form in the sparse tissue. The blood tends to flow into the retroperitoneum and often forms a life-threatening retroperitoneal hematoma. (Caution: Ultrasound and CT studies are indicated at the slightest suspicion!) In a more favorable case it can spread out within the anterior abdominal wall, where it is less dangerous but very painful.

The decisive requirement for complication-free management of the arterial access site is to perform the puncture at the correct level. (Fluoroscopy is indicated to determine the puncture site.)

The compression applied during the first 2 minutes should be close to the systolic pressure. Once a thrombotic closure has formed within the cannula track, it will suffice to maintain a significantly lower pressure.

Manual Compression

External compression is still largely performed by hand these days. This is a time-consuming and often strenuous method. The time wasted is particularly great when the compression is performed on the angiography table and the next patient is kept waiting. There is another disadvantage. A patient with an indwelling catheter or sheath can be safely moved to a bed because the catheter seals the puncture site. Yet moving a patient after manual compression, with the puncture site protected only by a pressure bandage of variable efficacy, increases the risk of postprocedure bleeding. Therefore one should only perform even manual compression after the patient has been transferred to a bed.

Manual compression lasting 10 to 15 minutes must be immediately followed by application of a pressure bandage intended to prevent postprocedure bleeding for the next 4 to 6 hours (or up to 24 hours). The following scheme can be applied to patients treated with 4 or 5 French systems and given a single dose of 5,000 IU of heparin:

• Apply manual compression for 10 to 15 minutes, then apply a pressure bandage.

• During the first 2 hours take the peripheral pulse and check for possible bleeding every 30 minutes.

• Reduce the pressure after 4 hours.

• Remove the pressure bandage after 5 hours, slowly mobilize the patient, and allow walking after another 2 hours.

The gauze strips between the back and medial aspect of the thigh once commonly used as a pressure bandage are not recommended. They require extension in the hip to maintain their tension. A better solution is to use a pad of expanded polystyrene held in place and pressed onto the puncture site by an elastic abdominal belt with a Velcro closure (Fig. 3.52, available from Ernst Tischler, Roth, Germany). The Velcro closure allows a certain measure of subsequent correction of the compression. Another option is to use an elastic foam rubber roll held in place and pressed into the wound by an elastic bandage (Fig. 3.53). Applying the elastic bandage requires the patient to get up several times and fixing it later is very difficult.

All of these bandages have the disadvantage that the compression applied is not measurable and cannot be gradually decreased during the course of treatment. One can only measure the peripheral pulse at various sites for orientation. Bleeding is only detectable when the bandage has turned red or blood is observed running down the medial aspect of the thigh.

Most of the complications in endovascular interventions occur at the access site, and the majority of these develop during the poorly controllable phase of those first few hours following manual compression. This situation can only be improved by mechanical compression systems that cover the entire phase of compression, are applied and adjusted before the sheath is removed, allow inspection of the puncture site, and permit gradual and preferably measurable reduction of pressure.

Internal Compression with a Percutaneous Transluminal Angioplasty Balloon

Occasionally the proximal popliteal or posterior tibial artery is punctured using road mapping to provide vascular access for retrograde catheterization of an occlusion. Postprocedure management of this access site is difficult because there is no structure to provide a buttress for external compression. An elegant alternative to external compression has recently been described for this situation (Huppert et al 2010). In these cases, percutaneous transluminal angioplasty (PTA) is usually performed via a sheath introduced into the inguinal arteries in antegrade fashion. When the vessel is again patent, one can easily advance a balloon catheter of the appropriate size to the peripheral access site and usually achieve thrombotic closure of the narrow cannula track by maintaining slight pressure for 2 to 3 minutes (Fig. 3.54).

Mechanical Compression Systems

Various mechanical systems are available as substitutes for manual compression. Such systems should fulfill the following criteria:

• Exact placement of compression

• Reliable pressure control

• Good fit on the surface of the body with uniform pressure distribution

• Sterility at and around the skin incision

• Good visibility of the puncture site to allow prompt detection of bleeding

• Definitive treatment that does not require subsequent application of a pressure bandage

• Minimal impairment of the patient while ensuring compression for a period of several hours

• Low material costs

The compression devices that have been available to date leave much to be desired.

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