Interventions in Vascular Occlusive Disease

Arterial Occlusion

Checklist:

Arterial Occlusion

As all angiographies are dedicated tests undertaken exclusively by specialists, nobody will seriously expect you to interpret the results in your real clinical life as a nonradiol-ogist. You should , however, know the potential treatment options afforded by each modality and be familiar with the most important interventions, their preparation, and their complications. What is true everywhere remains valid here: Technology and new procedures develop extremely rapidly. Problems that seem impossible to solve today will perhaps be dealt with elegantly and ingeniously a year later by some bright brain—come to think of it, it could well be your bright brain!

In all interventions the risks of complications and the potential benefits of the procedure, time requirement, cost, and therapeutic efficiency must be carefully considered. One principle always applies: Inflicting controlled damage on a patient who trusts the physician must only be done with an appropriate indication (Table 7.1). Just assume the worst possible complication happens and you have to explain to a grieving relative of the patient (or worse, a judge) why you did what you did. Now let us have a look at the first intervention.

Is the vessel compressed extrinsically or owing to an intrinsic abnormality of the vessel wall? Are you dealing with generalized or focal vessel disease?

Is there a history of diabetes mellitus or tobacco abuse? Is there reconstituted blood flow distally through preexisting anatomical collateral vessels or newly formed collaterals?

What is the normal vessel caliber at the stenotic site?

A Window Shopping Bonanza

Gary Sweetblood (45) has had problems walking for quite a while. After just a short stride he regularly experiences cramps in his right calf and must pause for them to cease. That turns his beloved visits to the tobacco shop into a lengthy affair, forcing him to stop at every shop window on the way. His general practitioner has had difficulties finding his foot pulses on the right side and has sent him for diagnosis and potential therapy. Senior consultant Poznansky has sensed Joey's special gift for and his sincere interest in intervention. He looks on as Joey examines Mr. Sweetblood and tries to feel the arterial pulses: the foot pulses are gone and the popliteal artery is barely palpable. Poznansky lets Joey puncture the left femoral artery and advance a catheter into the vessel.

• Procedures

Arterial puncture and sheath insertion: After the patient is positioned comfortably on the angiography table and the left groin has been disinfected properly, Joey localizes the pulse of the left femoral artery below the inguinal ligament (Note: If possible, gain access on the healthy side!) with the fingertips of the index finger (D2, for the distal pulse) and the middle finger (D3, for the proximal pulse) of his left hand (Fig. 7.2a). Having thus determined the course of the vessel with certainty, he injects 10-20 ml of a 1% local anesthetic (lidocaine) subcuta-neously; he then incises the skin with a pointed scalpel. Still feeling the arterial pulse with the fingertips of his left hand, he now advances a hollow needle toward the vessel, the hub angled down toward the patient's feet by approximately 45°. As the needle tip gets close to the vascular wall it transmits the pulsation of the wall ("dancing needle"). Now the vascular wall is perforated with diligence. The squirting flow of bright red blood proves the arterial source. If the blood is too dark and

the flow is slow, the needle has been directed too far medially—this is where the vein is located. Puncturing just the anterior wall of the vessel is the preferred method. (Alternatively, employing the technique after Seldinger, one can also stick the needle straight through the vessel in one swift motion, remove the trocar, and then slowly pull back the hollow needle until it pops into the vessel lumen and blood starts to squirt back.) After correct puncture a short guide-wire with a floppy soft tip is introduced through the needle into the vessel and, if possible, advanced into the abdominal aorta. While fixing the wire position, the needle is carefully retracted over the wire and removed, and a plastic sheath is advanced over the wire into the vessel. The sheath has a silicone diaphragm at its end, which prevents blood from flowing back and at the same time permits the introduction and removal of catheters into and out of the vessel as a temporary access route without the need to repuncture.

As Poznansky watches him closely, Joey proceeds to push the catheter into the distal aorta. Injecting contrast at a high flow rate, he performs several contrast series, assessing contrast flow in the main arteries of the pelvis and both proximal legs. The main finding—an obstructing ar-teriosclerotic plaque—is located at the right iliac level (Fig. 7.2b). "Well done, Joey," says Dr. Poznansky respectfully and takes over. "We'll dilate and stent that now. Was the patient briefed yesterday evening and did he consent?" Mr. Sweetblood and Joey nod: "Of course—we discussed the whole thing for half an hour—all the details were covered," Joey claims.

Do You Know the Pioneer of Balloon Dilation?

Andreas Gruntzig was the ingenious developer of the balloon dilation catheter in Switzerland. But he also was a lucky guy. It has been said that in the beginning his balloons tended to expand in an unpredictable fashion, bulging eccentrically and following the path of least resistance. These balloons were useless for his purposes. He lamented about this to his department's secre-

| Interventions in Arterial Occlusion_

a Technique of arterial puncture in the groin

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Inguinal ligament

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Femoral artery

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"Dancing" needle

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b Angiography c Stent implantation

Do You Know What a Sheath Is?

A sheath in vascular intervention is a thin but rigid plastic tube with a tapered tip that is inserted into the vessel over a guide-wire. At the proximal end a valve is attached. The valve consists of a thick, soft silicone membrane with a central perforation through which a catheter may be advanced. If the sheath does not contain a catheter, this membrane seals the sheath off to the outside and the blood stays inside. Many sheaths have a side port that can be used to flush the sheath to prevent blood clots from forming. For port implantations, a special valveless sheath is used.

Balloon dilation: 5000 IU of heparin is administered via the sheath. Then another guide-wire is advanced from the left external iliac artery across the aortic bifurcation over to the right external iliac artery and well past the stenosis. The balloon catheter slides into position over this wire. The balloon resembles a sausage when inflated and has the diameter of a normal vessel segment in this location. It is filled with saline under pressure of up to 8-12 atmospheres and kept expanded for about a minute. The first contrast run after the dilation shows a residual stenosis. Of course Joey knows that intimal tears are a regular effect of balloon dilation and they may proceed to full-blown dissections with the danger of acute vascular obstruction. Poznansky asks for a metal stent.

b Angiography c Stent implantation

Fig. 7.2 a After positioning of the patient on the angiography table and disinfection of the groin, the arterial pulse of the femoral artery is palpated caudal to the inguinal ligament with the fingertips of the index and middle finger of the left hand. The index finger lies distal, the middle finger proximal (please modify if you are left-handed). Then 10-20 ml of 1 % lidocaine is injected subcutaneously and the skin is incised with a pointed scalpel. The needle is now advanced toward the vessel in dorsocranial direction with the right hand while the left fingers stay in place. When a pulse-synchronous movement of the needle is felt, the vessel wall has been reached and is perforated cautiously. The squirting flow of bright red blood proves the arterial source. b The primary angiography shows very irregular plaque that narrows down the right external iliac artery by more than 50%. c After the stent implantation, the stenosis has disappeared completely.

I Interventions in Arterial Occlusion

I Interventions in Arterial Occlusion

Peripheral Plaque Embolization

Fig. 7.2 d This is a stenosis in the internal carotid close to the bifurcation. Thrombus formed along this plaque may be dislodged into the brain. e Under special protection—a temporary umbrella device is inserted into the vessel to prevent embolization—a stent can be implanted in this location as well. Risks are higher than in peripheral interventions. A weathered top neurointerventionalist is an absolute must. f This close-up of a chest radiograph demonstrates nicely the wavy lower rib margins typical of aortic coarctation and due to the dilated and tortuous infracostal arteries serving as collaterals. g The contrast-enhanced MR angiography documents the chest wall collateral paths around the stenosis at the aortic isthmus. h A sagittal Tl-weighted MR image depicts the stenosis itself. i A stent is placed after dilation of the stenosis. j The CT reconstruction shows the final result.

tary, whose husband happened to work in a Swiss factory for pressure-proof garden hoses. From there came the important hint that made all the difference: a spirally woven net of plastic fibers in the balloon wall assured the retention of the form of the balloons. After that everything else was a breeze. Gruntzig had less luck later in his life—he died in the crash of his private airplane. At least he could afford one. (The source of this story we cannot remember and won't guarantee it is at all true. But that is what supposedly happened ...)

Stent implantation: The collapsed stent is mounted over the tip of the collapsed balloon catheter, advanced directly into the dilated segment, and expanded there with the help of the balloon. The expansile force of the balloon as well as the radial force of the stent makes it cling to the vascular wall, smoothes the plaque surface, and repositions any dissection membranes that may be present (Fig. 7.2c). Stents can also be used to treat carotid stenoses (Fig. 7.2d, e) or congenital stenoses such as in aortic coarctation (Fig. 7.2f-j). Fabric-coated stents, so-called covered stents, can also be used to stop bleeds of larger vessels or treat aneurysms (Fig. 7.3).

Joey is amazed about the final result and Sweetblood gives Poznansky and Joey a big smile after seeing the post-therapy angiography on the monitor: "Hey, Doc, that looks as good as new! I gotta go out and have a smoke." Poznans-ky sends the patient back to the ward with a grin on his

I Intervention in a Large Arterial Bleed

I Intervention in a Large Arterial Bleed

Fig. 7.3 a The primary angiography in this patient with an advanced gynecological tumor of the pelvic base shows acute contrast extravasation (arrow) arising from the external iliac artery. b The immediate implantation of a fabric-coated stent into the eroded vascular segment bypasses the leak and stops the bleeding immediately. c The final film demonstrates the structure of the stent (black arrows) and the contrast-enhanced free blood in the pelvic cavity (white arrows).

Fig. 7.3 a The primary angiography in this patient with an advanced gynecological tumor of the pelvic base shows acute contrast extravasation (arrow) arising from the external iliac artery. b The immediate implantation of a fabric-coated stent into the eroded vascular segment bypasses the leak and stops the bleeding immediately. c The final film demonstrates the structure of the stent (black arrows) and the contrast-enhanced free blood in the pelvic cavity (white arrows).

face after ordering a 24-hour perfusion with 25 000 IU of heparin, subcutaneous injections of a low-molecular-weight heparin formulation twice daily for two weeks, and 100 mg of acetylsalicylic acid daily as permanent medication for prophylaxis of restenosis. With Joey he discusses another potential vascular intervention that was fortunately unnecessary in Mr. Sweetblood's case.

Thrombolysis: If a fresh intravascular thrombus needs to be removed, local lysis is a possibility. For this procedure a catheter with side holes is advanced into the thrombus. Over the course of many hours, high doses of thrombolytic agents (for example, t-PA) are infused via this catheter. Thrombolysis may induce hemorrhage at other locations, especially intracranially, and must therefore be considered and monitored closely.

The described interventional techniques can also be applied—with some modifications—in hemodialysis shunts.

After a therapeutic vascular intervention in peripheral arteriosclerosis, the patient has to be put on a lifelong aspirin regimen (100 mg daily).

Venous Obstruction n w.

Here Is Another Kind of Pioneer: Felix Hoffmann

Felix Hoffmann was the guy who first synthesized acetylsalicylic acid (aspirin) on 10 August 1897 in Leverkusen, Germany. The drug has been proved to significantly lower the rate of coronary and cerebral infarctions in some of the best and largest studies in medical history. Hoffmann would have loved the success story of this invention, much less the story of his other major invention: on 1 August 1897 he was the first to synthesize heroin.

Checklist:

Venous Obstruction

Is the vessel extrinsically compressed or obstructed by thrombi in the vessel lumen?

Does injected contrast flow around the thrombi or are they adherent to the vascular wall?

Does the patient smoke or take contraceptives, is he or she significantly overweight, was the patient recently immobilized, postoperative, or pregnant?

Is there a known malignancy?

All of a Sudden the Leg Was Swollen

Georgina Truelove (52) noticed a swelling of her left leg yesterday evening that has increased overnight. Now she can only walk with pain. Her general practitioner has sent her for the suspicion of deep vein thrombosis in her left leg. Dr. Goolagong has Hannah working with him today. He explains the common procedure in case of suspected deep vein thrombosis. "Since the internists have stopped immobilizing patients with calf thrombosis, lower extremity venography has lost much of its relevance. Only with venography could one detect small thrombi in the veins of the lower leg. Apart from that, venography is not always trivial to perform in severely swollen legs. Ultrasound and Doppler ultrasound suffice for the confirmation of most clinically relevant thromboses. If pulmonary embolism is suspected you should go right ahead and perform a dedicated spiral PE protocol CT."

I Thrombosis: Venography

Occlusive Vasculitis

Fig. 7.4 a This view of the calf shows a thrombus (arrow) surrounded by flow of contrast in a vein just above a venous valve. b In the thigh, another, large thrombus is seen in the femoral vein that reaches up to the inguinal ligament. This finding requires immobilization of the patient to keep the chances of a pulmonary embolism low.

Fig. 7.4 a This view of the calf shows a thrombus (arrow) surrounded by flow of contrast in a vein just above a venous valve. b In the thigh, another, large thrombus is seen in the femoral vein that reaches up to the inguinal ligament. This finding requires immobilization of the patient to keep the chances of a pulmonary embolism low.

• Procedures

Venography: In venography, contrast medium is injected into a vein on the dorsum of the foot—preferentially close to the base joint of the large toe—while the superficial veins of the lower leg are compressed at the same time by a tourniquet just above the ankle joint. The examination table should first be tilted head-up at a 45° angle for the venous puncture and for the venography in order to fill the veins from below. As one reaches the level of the iliac veins and the inferior vena cava, the table is tilted slightly head-down quickly to get a rush of contrast from the leg veins into the larger proximal veins, resulting in good filling of these venous segments. Thrombi are depicted as intravas-cular filling defects surrounded by flowing contrast medium (Fig. 7.4).

Doppler ultrasound: In the Doppler ultrasound that Dr. Goolagong performs on Mrs. Truelove he follows the course of the veins from the popliteal level up into the pelvis. Normal veins are compressed with ease by the ultrasound probe, which is what is done every few centimeters along their course. A thrombosed vein is not compressible and does not show flow on Doppler ultrasound examination. Goolagong finds a long thrombosis in one of Mrs. Truelove's deep veins in the thigh that reaches up to the inguinal ligament (Fig. 7.5c). Goolagong turns to Hannah: "Here we have the diagnosis: Thrombosis of the superficial femoral vein." "You are going to relax comfortably in bed for a week: television, magazines, good music," he cheers up the patient.

I Thrombosis: Doppler Ultrasound

Veins Legs Compressed
Fig. 7.5 The healthy vein (a, large arrow)—dorsal to the artery on this image (a, small arrows)—is easily compressed (b). Compression of the adjacent artery requires a higher pressure. The thrombus (c) shows no flow in Doppler mode and hinders the compression of the vessel.
Quadrantanopia Mri
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