Contrast injection rate and injection volume.
Angiography has been historically used to image the peripheral artery system and still remains the gold standard for diagnostic and endovascular treatment. There is no standardized method for lower limb artery angiography. In this chapter, the basic standard technique for angiography of peripheral artery is described from aortoiliac, femoropopliteal and below the knee arteries. To obtain a good image, adequate contrast dose and image size must be determined with the appropriate catheter. For puncture, echo-guided approach is becoming popular; each lab needs to have echo machine to minimize the vascular complication. In cases of renal dysfunction, CO2 angiography is suited. However, care must be taken to deliver gas into arterial system and to know the merit and demerit of CO2 angiography.
- peripheral artery
- peripheral artery disease
- contrast angiography
- echo-guided puncture
- CO2 angiography
1. Angiography-suite for endovascular therapy of peripheral artery disease (PAD)
1.1. Detector size
High resolution, accurate imaging is the key to success in endovascular therapies. In recent years, most machines provide fairly good images. An important point is the detector size of the angiography machine. Some physicians still use a coronary lab for peripheral artery intervention, however, when considering the vessel length and area, at least a 30 cm detector is needed. In Figure 1 , two types of detectors are shown.
In peripheral artery angiography, the 30 cm system on the left (INNOVA 3100, 30 cm, GE healthcare, Uppsala, Sweden) ( Figure 1A ) is basically used while the 20 cm coronary system (INNOVA IGS620, 20 cm, GE healthcare, Uppsala, Sweden) ( Figure 1B ) is too small for peripheral artery angiography. For example, the superficial femoral artery (SFA) is the longest vessel and difficult to visualize in its entirety. In Figures 1 and 2 , two SFA short lesions are shown.
In the 30 cm panel, about 26 cm of the SFA can be visualized and intermediate stenosis around the culprit lesion ( Figure 2A ) can be discerned. On the other hand, the coronary detector could visualize only 13 cm of the SFA in 20 cm mode ( Figure 2B ). In a coronary lab, to visualize the SFA or below the knee (BK) arteries, the table is panned but a good static image of the lesion is difficult to obtain.
1.2. Extra monitor
In an angiographic suite, operators usually stand on the right side of the table. Most labs use one monitor and all medical staffs rely on this one screen. In right limb angiography via the left femoral artery approach, the operator who is standing on the right side has difficulty manipulating the catheter. In this situation, one operator needs to stand on the left side of the table to manipulate the catheter and hold the sheath. For this purpose, an extra-monitor should be installed ( Figure 3 ).
A typical right superficial artery (SFA) intervention is shown in Figure 3 . The main operator is standing on the left side of the table and watching the extra-monitor while the assisting operator keeps an eye on the central monitor. Without moving the central image monitor, the main operator is able to perform the procedure. This extra-monitor is useful in the left brachial approach as well. It is a convenient way to intervene in the right femoropopliteal artery or cross-over approach for right below the knee arteries. In the left below the knee artery procedure via the cross-over approach, the C-arm is rotated to the left side. The cranial side operator may not see the central image. In this situation, the extra monitor can be placed on the left cranial side.
For most of the small vessels in selective angiography, hand injection of the contrast dye is adequate. However, for optimal opacification of high-flow blood vessels like the aorta, the use of a power injector is mandatory. A constant and high volume of dye should be injected through an electronically calibrated power injector. There are two types of injectors: one is a conventional power injector and the other is an assisted device that introduces small or large amounts of dye by an injector attached to the catheter table. The contrast volume is adjusted manually so that even a small dose of dye can be injected. However, the space on the left side of the table is occupied by this assisted device. Thus, a conventional power injector mounted to the ceiling is preferable since it affords more space around the catheter table. Furthermore, the distance allows a significant reduction in radiation exposure during dye injection. With the assisted device, radiation exposure is difficult to prevent since the operator has to be beside the table during dye injection ( Figure 4 ).
1.4. Contrast dose
Contrast-related factors include the vascular access site, injection time duration, injection rate, contrast volume and dye concentration. The key factor is the injection rate. An increased rate of injection can induce a greater extent of vascular opacification but the safety and total volume of the contrast dose must be carefully monitored. The contrast volumes for opacification of the major arteries are shown in Table 1 . These are the injection volumes mainly used in our catheter laboratory although the actual contrast volume depends on the patient’s condition, the catheter size, amount of contrast and speed of injection. Therefore, the contrast dose should be individualized for each case.
|Location||Catheter||Injection rate (ml/s)||Total volume (ml)|
|Aortoiliac||5Fr Pig tail||14–16||15–25|
|CFA-SFA-Pop A||4–5Fr MP||5–7||16–20|
|Run: CFA-BTK||4–5Fr MP||4||9–12|
|Run: BTK||4Fr MP||3–4||10–12|
|Below the ankle||4Fr MP||3–4||5–7|
There is no universally agreed upon threshold in the degree of renal dysfunction beyond which intravascular iodinated contrast medium should not be administered. We use Visipaque 320 . Contrast-induced nephropathy (CIN) is an infrequent adverse reaction to iodinated contrast agents . In endovascular procedures, particular complex procedures are associated with CIN and larger doses of contrast are considered a risk factor. Thus, as a precaution against CIN, the use of contrast media at the lowest dosage possible is advised. To minimize the contrast dose, we dilute Visipaque 320 by adding 30 cc of saline solution in a 100 cc bottle. The key factor is the injection rate which indicates the amount of dye per second. In our experience, 1/3rd diluted contrast does not decrease image quality.
1.5. Radiation safety
Angiography machines which use fluoroscopy for endovascular work are equipped with pulsed fluoroscopy instead of continuous fluoroscopy and this, to a large extent, helps to reduce the radiation dose (three radiation pulse mode). During this procedure, both the patient and physician are exposed to a certain degree of radiation so that its dose needs to be minimized. Constant measurement of radiation doses in patients and personnel is vital. Above all, the shielding in the room is particularly important. We use a suspended ceiling shield as well as a floor installed shield ( Figure 5 ). During digital subtraction angiography (DSA) imaging, other comedical staffs are outside the angiosuite. The main operator besides the patient is protected by a ceiling-mounted radiation shielding glass. After the procedure, radiation exposure levels must be routinely recorded and archived.
2. Imaging techniques
2.1.1. 4Fr sheath
The 4Fr sheath is mainly used for the antegrade femoral approach. For initial access, a 4Fr sheath is placed from the common femoral artery (CFA) to the SFA. The reason is that an antegrade puncture is technically more demanding and if we fail to make the puncture, the sheath can be withdrawn or repositioned. While keeping the 4Fr sheath in the profunda femoris artery (PFA), we can even place an additional 4Fr sheath into the CFA. The long 4Fr sheath is for below the knee work. However, it is easily kinked and there may be an increased risk of hematoma formation. In interventions below the knee arteries, most occlusion balloons accept the 4Fr sheath with the use of a 0.014 or 0.018 in. guidewires. And to minimize sheath size in the ipsilateral CFA approach, a 4Fr long sheath is ideal for patients with critical limb ischemia (CLI) ( Figure 6A ).
2.1.2. 5Fr sheath
In ad hoc interventions, we have standardized the 5Fr sheath for the initial retrograde CFA approach. When stent implantation is planned, we start with a 6Fr sheath. Either a 4Fr or 5Fr pigtail catheter can be used for aortography. With a 4Fr pigtail catheter, the amount of dye is limited to around 10–13 cc/s. To opacity the terminal aorta to both the iliac and common femoral arteries, the rate of injection should be 15–20 cc/s and this flow rate can be achieved with at least a 5Fr pigtail catheter. Introducer sheaths are used for all angiography and endovascular procedures. The 5Fr 45 cm cross-over sheath is used for either the retrograde or antegrade approach. In a contralateral SFA intervention, a 5Fr 45 cm crossover sheath is used. However, when stenting is performed, the sheath should be replaced with a 6Fr crossover sheath. In the antegrade approach for BK interventions, a 5Fr 45 cm crossover sheath gives more back-up support to intervene on the tibial arteries ( Figure 6B ).
2.1.3. 6Fr sheath
When an iliac artery stent is already planned, a 6Fr short sheath should be placed in a retrograde manner. In a cross-over approach, a 6Fr 45 cm cross-over sheath is employed. The advantage of the 6Fr system is that the closure device can be applied after the procedure. In some medical centers, the antegrade 6Fr short sheath is placed for SFA stenting. However, we do not routinely use the 6Fr sheath for antegrade work ( Figure 6C ) ( Table 2 ).
|Better wire control with short wire||Complication related to antegrade common femoral artery (CFA) puncture|
|Short distance to the lesion||Might miss proximal superficial femoral artery (SFA) lesion|
|Precise stent placement||Need caution of proximal end of stent|
|Access to below the knee arteries||Compression of ischemic side after procedure|
2.2.1. 0.035 in. wire
There are three types of tips for the 0.035 wire. We do not use a regular J-tip Radifocus wire (Terumo, Tokyo, Japan) ( Figure 7A ). The initial wire is always a 1.5 mm J-type Radifocus wire (Terumo, Tokyo, Japan) ( Figure 7B ). The tip of this wire has a 1.5 mm round shape and is quite safe when the wire migrates into the small branches or other vessels. Once the guidewire crosses the lesion, we change to a regular 0.035 in. spring wire ( Figure 7C ). The Radifocus wire is slippery and is difficult to keep in place while regular spring wires tend to stay in place. Thus, for stability, the wire should be changed to a spring wire once the lesion is crossed. These three types of 0.035 in. wires should always be at hand.
2.2.2. 0.018, 0.014 in. wires
Basically, we do not use the 0.018 in. wire as a regular wire. Chronic total occlusion (CTO), a 0.018 in. Treasure 12-g (Asahi Intec, Nagoya, Japan) wire is initially selected. It has a 12-g tip load and is best suited as a peripheral CTO wire. The V 18 (Boston Scientific, Cambridge, MA, USA) wire has a strong main shaft with a soft tip and can be used for cross-over ballooning or stent implantation. There are many 0.014 in. wires and their purposes vary. For below the knee artery work, the 0.014 in. wire is the basic wire used.
2.3. Digital subtraction angiography (DSA) vs. digital angiography (DA)
Digital subtraction angiography (DSA) has long been the gold standard for evaluation of atherosclerotic lesions in patients with PAD. Image quality has been further improved by replacing traditional image intensifiers with flat panel detectors so that regular digital angiography (DA) is now replacing DSA. When considering the high radiation doses, not all cases need imaging by DSA. Above all, critical limb ischemia is difficult to manage and some patients have difficulty staying still during injection of the contrast dye. Thus, adequate optimization with either DSA or DA should be employed to obtain accurate imaging of the diseased segments.
2.3.1. Aortoiliac artery
A typical DSA image of the iliac artery is shown in Figure 8 . In the 30 cm image, we can see from the terminal aorta to both common femoral arteries ( Figure 8A ). In the 20 cm image, a clearer view can be seen ( Figure 8B ).
DA is more practical for stent implantation since it provides the background image. In the aortoiliac artery segment, the image is hampered by bowel and gas movements. Aortoiliac artery angiography is basically taken by DSA, however, due to bowel and gas movements, the image is blurred ( Figure 10A ). In such a circumstance, we change to the DA image ( Figure 10B ). In Figure 10 , a left common iliac aneurysm with distal stenosis can be seen; the DSA image is blurred while the DA image clearly reveals stenosis.
2.3.2. Femoropopliteal artery
The initial angiographic image is the ipsilateral angled view. Either DSA or DA can provide a reasonable image ( Figure 11 ), although the DSA image ( Figure 11A ) is shown to be better than the DA image ( Figure 11B ). In the DA image, the background is shown and can be used as reference ( Figure 11B ).
A calcified lesion is often seen in the common femoral artery. In such cases, DSA provides a clearer view than the DA image ( Figure 12 ). DSA clearly shows the calcified lesion ( Figure 12A ) while, in contrast, the lesion could not be determined in the DA image due to low contrast ( Figure 12B ).
In a SFA lesion, measurement of the lesion length is important to decide the interventional strategy and we prefer a DA image for the pre-interventional angiogram. The popliteal artery is located deep in the posterior fossa of the knee joint. Surrounded by a bony structure, the popliteal artery is very difficult to visualize by DA. Basically, a DSA image is taken for the popliteal artery ( Figure 14A ). In Figure 14A , tight stenosis of the mid-popliteal artery is well visualized with rich collateral circulation. In the DA view, stenosis is well observed but most of the collateral vessels are not visualized ( Figure 14B ).
2.3.3. Below the knee arteries
Diseases of below the knee arteries are closely associated with critical limb ischemia (CLI) and detailed anatomical information is required to plan intervention. Compared to other limb arteries, angiography remains the imaging method of choice in most cases of CLI. How to take a good image is the cornerstone of successful endovascular therapy. DSA is a must for imaging of below the knee arteries. In Figures 2 – 10 , comparisons of the DSA and DA images of the left proximal tibial arteries are shown. In the DSA image, posterior tibial artery occlusion is well observed ( Figure 15A ). On the other hand, the DA image failed to show the tibioperoneal trunk and occlusion of the posterior tibial artery ( Figure 15B ).
A similar case of the left proximal below the knee artery is shown in Figure 16 . In the DSA image, three tibial arteries are shown with multiple stenosis ( Figure 16A ). In the DA image, precise diagnosis cannot be made ( Figure 16B ).
Assessment of the distal tibial arteries is vital in evaluating below the ankle disease. Continuation from the anterior tibial artery to the dorsal artery and the posterior tibial artery to the planted artery must be clarified. However, due to the bony structure, the DA image could not show these distal tibial and below the ankle arteries ( Figure 17 ). In Figure 17A , the planter artery is not clearly visualized in the DSA image. In the DA image, most of the vessels remain un-visualized ( Figure 17B ).
2.4. Basic angiography for PAD
2.4.1. Angiography from the terminal aorta to below the knee artery
In an angiographic approach for PAD diagnosis, we need to assess three segments of the lower limb artery, that is, the aortoiliac, femoropopliteal and below the knee arteries. In Figure 18 , the basic angiography is shown. First, angiography of the aortoiliac artery was taken ( Figure 18A ). The second angiography is an ipsilateral view of the proximal femoral artery ( Figure 18B ). In the right leg, a 30° right anterior oblique (RAO) view was chosen to separate the proximal SFA and PFA. Third, angiography from the CFA to the distal below the ankle artery was taken by running the table ( Figure 18C ). After observing these three angiograms, we could assess in which segment stenosis or occlusion was located.
A typical claudication with SFA disease is shown in Figure 19 . Aortoiliac artery angiography showed no significant stenosis ( Figure 19A ). In the proximal femoral artery, there was no stenosis in the SFA and PFA ( Figure 19B ). Left limb angiography showed focal stenosis in the mid-SFA while the left anterior tibial artery was not visualized ( Figure 19C ). By using DA, left SFA angiography was taken and revealed focal tight stenosis in the mid-SFA ( Figure 19D ). This DA image was used as reference in interventional work ( Figure 19D ).
Figure 20 shows isolated below the knee artery disease. From the iliac to femoropopliteal artery level, no atherosclerotic changes could be observed ( Figure 20A and 20B). A lesion is located in the right below the knee arteries. Below the knee arteries showed a stenotic lesion of the anterior tibial artery, and the posterior tibial artery and peroneal artery are occluded ( Figure 20C ). This type of lesion, that is, “isolated below the knee artery disease” is often found in patients with critical limb ischemia.
2.4.2. Magnification of images
The image size has two purposes: one is to see the whole vessel, for example, in the aortoiliac artery, visualization from the terminal aorta to both the right and left CFA ( Figure 21A ). The other is to better intervene on the target lesion utilizing appropriate magnification of the image size ( Figure 21B ). For wiring to this lesion, a 20 cm magnified image was taken and successful wiring was carried out using a 0.014 in. wire ( Figure 21B ).
In below the knee arteries, the whole image shows which vessels are diseased ( Figure 23A ). However, this running image does not give detailed information on the three tibial arteries. In the 30 cm image, the three proximal tibial arteries are well observed, and the peroneal and posterior tibial arteries are diffusely diseased ( Figure 23B ). The further magnified 20 cm image revealed that there is tight stenosis at the ostium of the right anterior tibial artery ( Figure 23C ).
2.4.3. Pre- and postinterventional image
Basically, all interventional work requires two images to be taken, that is, pre- and postintervention. These two images reveal the angiographic changes pre and post procedure. In Figure 24A , the femorofemoral bypass was occluded and a long total occlusion of the right iliac artery is seen. After successful recanalization and stenting, angiography of the exact same iliac artery was taken ( Figure 24B ).
In Figures 2 – 20 , typical left SFA occlusion was seen ( Figure 25A ). After balloon angioplasty, dissection and incomplete dilatation were observed ( Figure 25B ). Post stent angiography showed excellent dilatation of the left SFA lesion ( Figure 25C ). During the procedure, the table was frequently moved and oftentimes, post angiographic images were not taken in the different positions, giving a false impression of the postinterventional image.
3. Echo-guided puncture femoral artery puncture
The common femoral artery (CFA) remains the most widely accepted site for endovascular artery access. Vascular access site-related complications are a major cause of periprocedural morbidity among patients undergoing percutaneous endovascular intervention. In particular, patients with PAD may be more likely to have atherosclerosis affecting the CFA. Ultrasound guidance is an emerging trend for all percutaneous procedures and its use for femoral artery puncture has decreased vascular complications and improved first-pass success rates [4–6].
3.1. Retrograde common femoral artery puncture
The CFA is the main access site for angiography and interventional procedures. Among the various puncture sites, the retrograde CFA puncture is the most commonly employed and the basis of arterial punctures. We have described a safe and echo-guided technique for avoiding femoral access site complications.
3.1.1. Puncture point
The inferior border and upper border of the femoral head should be realized by fluoroscopy ( Figure 26A ). After checking the maximum arterial pulse ( Figure 26B ), Xylocaine is given 1 cm below the middle of the femoral head ( Figure 26C ).
A sheath and two types of wires were prepared. Once a puncture is performed, the wire should be ready to be inserted and if there is resistance, change to a different kind of wire is advised ( Figure 27 ).
3.1.3. Echo scanning
For an echo-guided puncture (NEMIO MS, Toshiba, Tochigi, Japan), first, echo scanning was carried out from the upper CFA to proximal SFA ( Figure 28 ). We could identify where the bifurcation is located. Either a long axis ( Figure 28A ) or short axis can be obtained ( Figure 28B and C ). A scan is basically made by a short-axis view. The ideal puncture site of the CFA can then be located ( Figure 28B ) and the bifurcation site can be identified ( Figure 28C ).
An echo image is best seen from the upper common femoral artery to the distal external iliac artery. When total reliance is on echo guidance, the puncture site locates higher than the middle femoral head. To avoid too low or high punctures, rechecking the puncture site by fluoroscopy is advised ( Figure 26A ).
Arterial access was obtained with an 18-G needle (COOK Medical, Bloomington, Indiana) using the modified Seldinger technique. The needle was inserted at an angle of about 45° from the skin at a level just below the center of the femoral head. In viewing the short axis, the aim should be for the top of the vessel. During flash backs of blood, a gentle wire insertion must be made. When resistance is felt, change from a straight wire to round shaped wire is advised ( Figure 29 ). When the plaque in the CFA is found, a normal CFA puncture site should be located. In Figure 29A , the long-axis view showed the plaque in the CFA.
In Figure 31 , a puncture was made at the site of CFA disease and the wire went into false lumen, resulting in the total occlusion of the CFA.
3.2. Antegrade common femoral artery puncture
For treatment of femoropopliteal artery disease, the standard approach has been to access the contralateral common femoral artery (CFA). However, an ipsilateral, antegrade CFA approach has certain advantages. Compared to the contralateral approach, access to the lesion distance is short which in turn improves the responsiveness of the wire handling used to perform the intervention. In other clinical situations such as post aorto-bi-femoral surgical bypass, deployment of iliac kissing stents, post stent grafting and for aortoiliac occlusive disease, an antegrade approach is the method of choice to reach the lesion. The advantages and disadvantages are shown in Table 2 .
The CFA is approximately 4–5 cm in length and arises from the external iliac artery (EIA) as it passes below the inguinal ligament. It then bifurcates into the PFA and SFA. An anatomical knowledge of the level of origin for the PFA is important in avoiding retroperitoneal bleeding, iatrogenic femoral arterial-venous fistula and/or formation of a pseudo aneurysm. The most lethal complication of femoral access remains retroperitoneal hemorrhaging due to a high puncture. Thus, the best first step toward reducing the incidence of retroperitoneal bleeding is to prevent high punctures.
3.2.1. Preparation of an antegrade puncture
As we perform in a retrograde puncture, two kinds of wires should be at hand. The initial sheath we place is always the 4Fr size sheath ( Figure 32 ).
The main reason is, when obtaining access to the CFA fails, the sheath can be easily withdrawn or left in the PFA. Once placing the sheath in the SFA is successful, it can be changed to any sheath as desired. Pointing to the middle of the femoral head, local xylocaine should be given around the inguinal ligamentum ( Figure 33 ).
Echo was applied in the same way. However, the proximal CFA to external iliac artery is well observed by echo and may result in a very high puncture site. Under fluoroscopic guidance with echo assistance, point to the middle of the CFA.
A puncture should be made by aiming an imaginary line over the center of the femoral head. The maximum level of bifurcation should be at or below the inferior border of the femoral head ( Figure 34A ). In about 1/4th of cases, bifurcation locates in the CFA ( Figure 34B ). In Figure 34B , the bifurcation point is in the middle of the CFA and there is a short margin for the antegrade puncture site.
3.2.3. Two-wire technique
Even when the puncture site is above the bifurcation, the wire may go to the PFA. In this situation, we use a two-wire technique ( Figure 35 ). If the wire goes to the PFA, the first step is to place a 4Fr sheath into the PFA. Two short 0.025 in. wires are inserted into the RFA ( Figure 35A ). Withdrawing the sheath, one 0.025 in. wire should be manipulated into the SFA ( Figure 35B ). Once the SFA is accessed, leaving one wire in the PFA, the other wire should be advanced to the SFA ( Figure 35C ). After confirming the wire in the SFA, the other PFA wire is withdrawn and a 4Fr sheath should be placed into the SFA ( Figure 35D ). If the sheath comes out, it can be repositioned back into the PFA by a 0.025 in. wire.
3.2.4. High bifurcation case
After surveying the CFA by echo, we may find high bifurcation of the SFA and PFA. In these cases, high puncture carries the risk of retroperitoneal bleeding. The puncture point should be in the range of the femoral head. In this situation, puncturing the SFA is one option. In Figure 36 , there is high bifurcation and a CFA puncture is almost impossible. In this case, we decided to puncture the proximal SFA.
3.2.5. Sheath kinking
The angle of puncture should be more than 60° and almost vertical. After sheath insertion, care to avoid sheath kinking is advised. Once a hematoma is observed with sheath kinking, change to a larger size anti-kink sheath is necessary. In Figure 37 , the initial 4Fr sheath was kinked ( Figure 37A ) and hematoma formation was detected. After the 4Fr sheath was replaced with a 6Fr sheath, the hematoma was stabilized ( Figure 37B ).
4. CO2 angiography
The number of patients with chronic kidney disease (CKD) complicated with PAD is significantly increasing. In these patients, iodinated contrast may enhance the risk of contrast-induced nephropathy (CIN). CIN is an acute renal injury and may lead to irreversible loss of renal function. Carbon dioxide (CO2) gas angiography is indicated for those with renal insufficiency and high-risk patients who are allergic to iodinated contrast material . CO2 is imaged using digital subtraction equipment with a CO2 software program. Modern DSA equipment has a software program that allows integration of multiple images into a single composite image.
4.1. CO2 delivery system
The system consists of a medical grade CO2 gas cylinder with a regulator, a disposable sterile plastic tube with a bacteria-removal filter, and a 50-ml delivery syringe ( Figure 38 ).
Collection of CO2 to the syringe and injection system should be separated to avoid erroneous gas injection to an artery ( Figure 39 ).
The gas should be purged three to four times during collection to prevent room air contamination from the tube and delivery syringe in the circuit and then filled with gas at a stationary flow of 2 l/min. About 40 cc of aspirated gas was filled into the delivery syringe and 30–40 cm3 of CO2 gas was manually injected into the vessel leaving about 5 cm3 in the injection syringe ( Figure 40 ).
After gas injection, the remaining gas and blood were carefully aspirated into the syringe. Gas injections were spaced at least 30 s apart. Although we do not have experience in mechanical injection, manual injection is sufficient to inject 30–40 cc of CO2. However, the safety of injecting large amounts of CO2 is not guaranteed . If a patient complains of abdominal pain, further CO2 injection should be avoided. And if the angiogram shows a slow flow, further CO2 delivery by syringe should also be stopped ( Table 3 ).
|- Make a separate system with CO2 cylinder|
- Average dose of CO2 is about 30 ml by using 50 ml syringe
- Be sure complete air excretion
- Manual injection not a mechanical injection
- If patient complains of abdominal pain, avoid further injection
- When a slow flow are observed, avoid an further CO2 injection
4.2. Iliac artery angiography by CO2
The iliac artery is a large sized vessel and its inflow is the larger abdominal aorta. Moreover, there are two internal iliac arteries and two femoral arteries. CO2 angiography requires displacement of all or most of the blood to achieve adequate images. Due to such anatomical reasons, the iliac artery is not well suited for CO2 angiography. In Figure 41A , CO2 was administered from a 5Fr pigtail catheter at the terminal aorta and, in the left external iliac artery, CO2 was unfilled and there appears to be stenosis. With contrast angiography, no stenotic lesion is seen in the left external iliac artery ( Figure 41B ).
In Figure 42A , total occlusion of the left external iliac artery is observed. CO2 injection from the terminal aorta shows chronic total occlusion (CTO) of the left external iliac artery. To confirm CTO, a crossover sheath was positioned at the left common iliac artery and CO2 injection was repeated at a right anterior oblique (RAO) projection of 30° ( Figure 42B ). In this angiogram, CTO is clearly visualized and the left common femoral artery is well observed via the collateral flow from the deep circumflex artery. In CO2 angiography of the iliac artery, the angiogram is hampered by bowel and gas movements.
Generally speaking, when the iliac artery is not well visualized by CO2 angiography, increasing the volume of CO2 in the iliac abdominal aorta might be considered. However, there are important visceral vessels and the risk of various complications due to the injection of gas in these vessels must also be considered.
4.3. Femoropopliteal artery angiography by CO2
Visualization by CO2 angiography is best suited for the femoropopliteal artery segment. The main reason is that the superficial femoral artery (SFA) is a straight vessel with small branches. The vessels sizes are about 4–7 mm and could easily be filled by CO2 gas. In Figure 44 , there are three kinds of SFA angiograms for the same patient. Digital angiography enabled visualization of the background ( Figure 44A ) while DSA could obtain the highest quality angiogram ( Figure 44B ). CO2 angiography has poor visibility of small distal branches. However, it could visualize SFA fairly well and can be used as a substitute for contrast angiography ( Figure 44C ).
Similarly, the popliteal artery could be well observed even with the CO2 angiogram ( Figure 45 ).
In the DA angiogram, distal SFA is not well visualized compared to the DSA image ( Figure 45A ). In fact, a perfect image was obtained by DSA ( Figure 45B ). The CO2 angiogram shows a fairly clear picture of the distal SFA and popliteal artery ( Figure 45C ) while the right femoropopliteal artery was visualized by CO2 ( Figure 46 ). In proximal SFA, separation between the SFA and deep femoral artery (DFA) is well observed ( Figure 46A ). In the mid-SFA, no stenosis is seen ( Figure 46B ). In the distal SFA and popliteal artery, moderate stenosis is detected ( Figure 46C ).
Comparisons between CO2 angiography and digital angiography for the diseased SFA are shown in Figures 47 and 48 . Stenosis is seen in the distal SFA in Figure 47 . Both CO2 ( Figure 47A ) and DA images ( Figure 47B ) could identify distal SFA stenosis.
The totally occluded left SFA was well visualized by CO2 angiography ( Figure 48A ). Although DSA shows a clearer image with a rich collateral network ( Figure 48B ), the CO2 image can also be used for interventional work.
The CTO of the left SFA was intervened using CO2 angiography ( Figure 49 ) in a patient with stage 4 CKD. The CO2 angiogram showed typical CTO of the SFA ( Figure 49A ). After successful wiring, balloon angioplasty was performed ( Figure 49B ). Contrast was only used in the final angiogram ( Figure 49C ).
4.4. Below the knee angiography by CO2
CO2 angiography cannot be applied in below the knee (BK) work. The arterial vessel size below the knee is between 1.5 and 3 mm in diameter and the accuracy of CO2 angiography is insufficient. Above all, in BK cases, most of the patients have critical limb ischemia and cannot tolerate large amounts of gas injection. In Figure 50 , proximal right below the knee angiography was performed by CO2 ( Figure 50A ) and DSA ( Figure 50B ). In the CO2 angiogram, stenosis of the peroneal trunk could be seen; however, the right anterior tibial artery and posterior tibial artery are not well visualized when compared to DSA.
4.5. Problems of CO2 angiography
CO2 angiography can be performed with minimal or no contrast media and can be used on CKD patients. However, CO2 angiography carries several potential risks (8). Gas delivery into the vessel is basically contraindicated. Moreover, erroneous injection of excessive volumes may result in catastrophic clinical consequences. There are many reports about transient lower limb pain and transient abdominal pain. Fujihara et al. have conducted a multi-center prospective CO2 study and have reported that two patients (2%) developed CO2-related non-occlusive mesenteric ischemia which resulted in death. These non-occlusive mesenteric ischemia cases were caused by the trapping of CO2 gas in the celiac, superior and/or inferior mesenteric arteries . The quality of CO2 angiography is still not clear enough in the iliac artery and should not be employed in below the knee arteries. It should be used for the femoropopliteal artery although, even in the femoropopliteal artery, precise lesion evaluation may be difficult in some cases. Other complementary modalities such as surface echo, IVUs and/or pressure measuring should also be employed to confirm lesion severity ( Table 4 ).
|- Cause abdominal pain and leg pain|
- Poor quality angiogram in iliac artery by bowel gas and movement
- Not applicable to below knee artery
- Rapid transition to venous circulation
- Risks of cerebral infarction
- Risk of nonobstructive mesenteric ischemia
In treating claudication, safety is the first priority so that CO2 use may be limited for most patients except those who have anaphylaxis to iodinated contrast media.