Catheter angiography is the definitive method of evaluating arterial blood vessels for injury and of identifying active arterial hemorrhage. While CT angiography is frequently favored for imaging of many traumatic conditions, it has rarely been validated against the “Gold Standard” of catheter angiography. A notable exception is the screening of traumatic injury of the thoracic aorta that has replaced catheter angiography for many patients.
Advantages of catheter angiography are many. It allows simultaneous detection and treatment of a wide variety of traumatic vascular injuries. It is a very specific method of identifying bleeding at the submillimeter diameter of vessel. It can evaluate many sites of bleeding simultaneously. It has an excellent safety record, especially when using iso-osmolar nonionic contrast agents, coaxial micropuncture access, digital subtraction techniques, coaxial microcatheters, and steerable guidewires.
Disadvantages are cost, the delay necessary to assemble the team of radiologists, technologists, and nurses, the lack of suitability as a screening test, and the risks of radiation exposure. Technical expertise is limited to predominantly subspecialty-trained interventional radiologists (although endovascular surgeons and cardiologists may develop this expertise on an individual basis). These disadvantages are magnified when the likelihood of injury is low. Thus, noninvasive vascular techniques such as CT angiography should be explored under controlled studies to further assess their accuracy and appropriateness in such situations.
Transcatheter Endovascular Therapies
Endovascular techniques have become a broadly accepted way of controlling traumatic hemorrhage for a variety of reasons. Catheter-based hemostasis allows precise control from a remote site that avoids exacerbation of venous hemorrhage, introduction of pathogens, and hypothermia that may result from open exposure. It is especially valuable for hemorrhage that is remote or hidden from view and requires laborious time-consuming exposures or that is the result of multiple small bleeding sites that are not easily detected or controlled during operative exploration.
Endovascular techniques include embolization, stenting, stent grafting, and temporary balloon occlusion. They may be definitive or an adjunct to operative exposure. The methods of embolization include particulate or microcoil embolization of small vessels, proximal and distal large vessel isolation of a bleeding vessel, and conduit coil occlusion to cause selective temporary hypotension of the bleeding zone.
Stenting, which facilitates blood flow beyond an injury, has largely been replaced by covered stent grafts that exclude lacerations, transections, and arteriovenous fistulae while maintaining flow through the conduit. Endografts are made of a variety of porous materials such as expanded polytetrafluoroethylene and are reinforced by a metallic skeleton that apposes the stent graft to the native artery. Reports of midterm patency, while limited at this time, are beginning to show that these are durable options to vascular repairs.
Contraindications to endovascular techniques are highly dependent on skills, teamwork, and hemodynamics; however, there are some injuries that are difficult for rapid surgical control and endovascular techniques have a role, even in the unstable patient.
Arch Angiography for Acute Blunt-Force Traumatic Aortic Injury
Blackmore et al.59 have published a clinical prediction rule as an aid to determine which patients should be screened for traumatic aortic injury. Usual indications are either direct (pseudoaneurysm, intimal flap) (Fig. 15-42) or indirect (juxta-aortic hematoma) CT findings, especially if the abnormality involves the ascending aorta. If patients are going directly to angiography for evaluation of disruptions of the pelvic ring and the mediastinum is not normal on a chest x-ray, catheter arch angiography is the preferred “screening” modality; otherwise, CT is the preferred modality for patients at >0.5% risk for aortic injury.72 Modern CT angiographic techniques are quite exquisite in demonstrating aortic injuries as well as providing coronal and sagittal reformations that can illustrate the important relationships and variants necessary for surgeons to create a treatment plan.
Traumatic aortic pseudoaneurysm. A 30-year-old-male following high-speed motor vehicle accident. Left anterior oblique (LAO) digital subtraction arch aortogram shows traumatic aortic pseudoaneurysm extending proximal to the left subclavian artery. Of note, the aortic diameter and the distance from the left subclavian artery are important when considering endovascular therapy.
Among selected patients sustaining aortic injury who are not operative candidates, endovascular stent grafts have been advocated as either temporizing or definitive therapy.
Typically, a 5 French pigtail catheter is guided to the ascending aorta via a femoral arterial approach. Patients are positioned and imaged in both 35° right anterior oblique (RAO) and left anterior oblique (LAO) projections, using injection rates of approximately 25–30 mL/s for 40–60 mL volume (depending on hemodynamic status) and positioning to include the great vessels and diaphragm.
The arteriographic appearance is classical. Linear filling defects indicate torn and ruffled intimal lining; expansion of the lumen, typically at the ligamentum arteriosum, indicates the presence of a pseudoaneurysm. This is sometimes associated with distal narrowing of the contrast column.
Associated injuries should also be identified. Injuries of the brachiocephalic branches may occur instead of or in association with aortic injury. Bleeding from the internal mammary or the intercostal arteries is easily overlooked without diligence.
Hepatic Angiography for Blunt-Force Lacerations
Visceral catheter angiography is appropriate to evaluate hepatic lacerations (Fig. 15-43), especially in patients with a labile hemodynamic status or those with active extravasation or vascular abnormalities on a contrast-enhanced CT. Gross hemodynamic instability and profound shock, however, usually mandate urgent celiotomy. Of course, angiography may have a role after a “damage control” operation.
Liver laceration. (A) CT of the upper abdomen reveals a Grade V liver laceration with pseudoaneurysm of the right hepatic lobe in this 18-year-old male status post-high-speed MVA. (B) Right hepatic angiogram identified the pseudoaneurysm. Note the size of the feeding vessel in relation to the 5 French diagnostic catheter. Selective coil embolization was performed through a microcatheter. When selective catheterization is not possible, the liver is quite tolerant of wide arterial embolization due to the dual blood supply provided the portal veins are patent.
Hepatic fracture lines seen on CT that traverse the hepatic triad more often result in bleeding than those fractures that are parallel to the triad. Extravasation of CT contrast tends to be associated with a positive arteriogram, but the decision to use angiography should primarily be based on clinical status rather than the CT appearance. Lack of enhancement of segments of the liver on CT is a very important finding. It represents a large hematoma in the liver, occlusion of the portal triad, or injury of the hepatic outflow from that segment. It is vital to distinguish nonenhancement from a hematoma. A large hepatic hematoma pushes the hepatic fragments away from each other, and unopacified or opacified hepatic vessels are not seen in a hematoma. If the area of nonenhancement has vessels running through it, it suggests an occlusion of the portal vein and hepatic artery or injury to a hepatic vein. Therefore, CT nonenhancement of the liver is a clear indication for urgent angiography if at all possible to confirm such injuries and to control arterial hemorrhage. As surgical exploration of damaged hepatic veins may be quite difficult, hepatic embolization and observation of a nonbleeding hepatic venous injury can be lifesaving. And, as noted above, hepatic angiography has an important role in the management of penetrating liver injuries that are isolated to the liver, as well as a secondary procedure.
Selective catheterization of both the celiac trunk and the superior mesenteric artery (SMA) is essential due to the high rate of hepatic vascular variants, particularly the aberrant replaced right hepatic artery from the SMA. Imaging should be continued through the late portal venous phase. Moreover, it is important to determine whether there is patency of portal flow prior to embolization of the hepatic artery.
Critical findings include arterial extravasation, spasm and occlusion, or shunting and fistula to portal or hepatic venous structures. Embolization of discretely abnormal vessels can be performed using a number of methods. A diffusely abnormal parenchymal injury with arterial bleeding may be safely embolized with Gelfoam due to the dual blood supply of the liver (hepatic arterial and portal venous). Embolization of hepatic arteries in the absence of portal flow increases the risk of developing an infarction or abscess. Depending on the location of bleeding and on the difficulty with catheterization, particulate embolization is the fastest technique; however, single microcoil embolization is preferred if time and circumstances allow. While formation of a postprocedure abscess is a complication of embolization, outcomes are favorable by integrating percutaneous image-guided drainage into the scheme.
Splenic Arteriography for Blunt-Force Lacerations
A patient who is hemodynamically unstable is not a candidate for angiography and embolization. Other patients who have an injury of the spleen diagnosed on CT are candidates for nonoperative therapy with good results. CT is not a reliable predictor, however, of which patients are best managed by bed rest compared to those patients who require hemostasis. When a CT demonstrates active arterial extravasation or a parenchymal vascular abnormality, one should consider angiography. Unfortunately, there is not good correlation between the CT grading system and outcome of treatment. Many Grade IV injuries can be observed and some Grade I injuries become worse, rebleed, and require definitive procedural therapy. The author and his surgical colleagues observe (i.e., bed rest) most Grade I injuries, but advocate liberal use of angiography for triage of most other CT-diagnosed splenic injuries, especially in those patients with a significant hemoperitoneum or transient hypotension. Patients with high-grade injuries on CT should be imaged by angiography early to avoid transfusion or delayed rupture. The absence of arteriographic extravasation is a highly reliable predictor of successful nonoperative therapy regardless of grade. Identification of active arterial extravasation is the standard indication for endovascular treatment.
Diagnostic angiography of the celiac trunk is followed by selective splenic artery catheterization with a 5 French catheter. If splenic artery anatomy permits, and a solitary pseudoaneurysm or focus of extravasation is seen, distal coil embolization at the site of injury can be attempted. This is especially true in a patient in whom the extravasation extends beyond the splenic capsule into the peritoneal cavity. It should be remembered that distal superselective embolization is associated with the development of more postprocedure splenic infarctions and abscess, though these are uncommon. Finally, most patients have tortuous splenic arteries and most extravasations are multiple.
Diffuse intrasplenic extravasation is far more common, and superselective occlusion of these multiple sites would be very time consuming and less effective. Also, the splenic tortuosity that results from medial displacement of the spleen by the perisplenic hematoma often prevents rapid catheterization (Fig. 15-44). In such cases, embolization of the proximal splenic artery by coils placed distal to the dorsal pancreatic branch and proximal to the pancreatic magna branches is advocated to reduce the arterial pressure head at the injury site while allowing perfusion through collateral vessels. Such collaterals prevent splenic infarction by maintaining splenic perfusion through connections between the left gastric and the short gastric arteries, between the dorsal pancreatic artery and the pancreatica magna branches, between the right and left gastroepiploic vessels, and others (Fig. 15-45).
Splenic intraparenchymal false aneurysms. Digital subtraction angiogram of the splenic artery reveals multiple focal extravasations in this 56-year-old male status post-MVA. Selective embolization is not desirable because so many vessels are injured and selective catheterization would be difficult due to splenic artery tortuosity. In such cases proximal splenic artery coil embolization proximal to the pancreatic magna branch is usually successful in controlling this hemorrhage.
Demonstration of long-term follow-up of splenic artery embolization. A 40-year-old female pedestrian sustained blunt splenic injury after being struck by a motor vehicle 10 years ago. She was treated by coil occlusion of the proximal splenic artery with good results. During admission 10 years later for stab wound to the neck, the coils were detected. Splenic arteriography was performed. This demonstrated marked enlargement of the pancreatic collaterals that bridged the occlusion. Flow was rapid through these very large collaterals.
Complications are uncommon when proximal splenic artery embolization is performed. A poorly selected coil size may result in hilar occlusion if the selected coil is too small and migrates distally. Too large coils may migrate proximally to occlude the celiac axis or embolize into the aorta. As noted above, distal microembolization bypasses the collateral circulation and results in more loss of immune function.
Interventions for Renal Trauma
Low-grade renal injuries are usually well tolerated and do not require angiography, especially when caused by blunt trauma. Initial nonoperative management of blunt renal injuries with an intact pedicle is the common practice. High-grade injuries that result in massive hemorrhage are usually managed by nephrectomy. In other patients who are hemodynamically stabilized, angiography with intent to embolize bleeding is appropriate. Angiography is recommended for patients with CT evidence of a major renal injury and ongoing blood loss or persistent gross hematuria. Areas of nonenhancement on CT suggest a renal vascular injury, such as a polar avulsion or intimal stretch of the main renal artery with distal platelet embolization.
Penetrating renal injuries are more aggressively approached by angiography if nonoperative management is undertaken. Large perinephric hematomas, areas of nonenhancement, and extravasations on CT warrant angiography.
Aortography is helpful to assess injury of the origin of the renal artery, to exclude renal parenchymal injury perfused by accessory renal arteries, and to look for associated intraperitoneal and retroperitoneal bleeding sites. A selective renal arteriogram using a 5 French catheter is then performed. Most injuries will require use of a coaxial microcatheter and embolization of small branches. Coils are preferred as they can be carefully placed to prevent infarction of adjacent noninjured renal tissue, but surgical gelatin pledgets can be used, as well. Because renal branches are end vessels with little collateralization, infarction is likely, and the goal is to reduce these infarctions to a minimum.
The treatment of vascular injury in the renal pedicle continues to be a vexing problem, especially since delays in revascularization usually result in a renal infarction. Partial wall injuries that result in a pseudoaneurysm, false aneurysm, and segmental infarction often went unrecognized prior to the use of CT. Such injuries are detected currently before complete arterial thrombosis and renal infarction occurs. Therefore, arteriography is indicated when an injury in the renal artery is suspected. When such injuries are detected, treatment options are many, including operative revascularization, antiplatelet therapy and observation, and the application of covered stent grafts. Stent grafts can effectively seal full thickness injuries and cover exposed media that results in embolic infarctions. While long-term follow-up of series of these patients is lacking, the midterm (1–5 years) patency of stent grafts throughout the body remains high (Fig. 15-46).
(A–D) Renal artery injury. A 56-year-old man fell from a height of about 10 m. (A) During CT evaluation inhomogeneous enhancement of the spleen was detected. Central perinephric hemorrhage (asterisks) and irregularity of the renal artery (arrow) were seen. (B) Coronal reformation shows irregularity of the renal artery and thickening of its wall. (C) Aortography showed irregular enlargement of the proximal renal artery near the ostium (circled). Slight extravasation was seen on the later images. (D) Therefore, a stent graft was placed over the area of injury. The vessel wall was then smooth, and no extravasation was seen. Two-year follow-up arteriography showed continued patency and no stenosis.
Blunt pelvic fractures with crushing or shearing tear the small branches of the internal iliac artery that accompany ligaments, muscles, and tendons. Injuries tend to be multiple and bilateral, and from several branches. In addition, bony fragments can penetrate or perforate vascular structures. Examples include a fracture of the superior pubic ramus injuring the internal pudendal or obturator artery, a fracture of the iliac wing through the sciatic notch injuring the superior gluteal artery, and disruption of the sacroiliac joints injuring the lateral sacral arteries.
Pelvic fractures are potentially life-threatening injuries that are caused by high-energy impact trauma and account for about 3% of skeletal injuries. They are the third most common lethal injury after motor vehicle crashes. The majority of patients with pelvic fractures do not require massive transfusion (greater than 6 U) as bleeding in most cases is likely to be venous or osseous in nature and is self-limited. Radiological intervention is not commonly needed in patients with routine pelvic fractures. Severe hemorrhage, however, occurs in 3–10% of patients, and mortality rates may be as high as 50% in patients with unstable pelvic fractures. Thus, the use of angiography in patients with pelvic fractures is highly dependent on the hemodynamic status, the type of fracture pattern, the transfusion requirements, and the presence or absence of hemoperitoneum.
Most of the indications for angiography in blunt pelvic trauma have remained the same for more than 30 years and are listed as follows:
Hemodynamic instability in a patient with a pelvic fracture with no or little hemoperitoneum detected by FAST or diagnostic peritoneal lavage
Pelvic fracture and transfusion requirement of greater than 4 U in 24 hours
Pelvic fracture and transfusion requirement of greater than 6 U in 48 hours
Pelvic fracture and a large or expanding hematoma identified during celiotomy
CT evidence of large retroperitoneal hematoma with extravasation of contrast
Need for detection and treatment of other injuries during angiography
With MDCT the detection of extravasation of contrast has been used as an indication for follow-up pelvic angiography. Of course, CT is not as reliable as clinical signs as extravasation may be venous in origin and not correlate with massive arterial hemorrhage. Although it should not delay angiography that is already indicated for pelvic hemorrhage, CT is helpful in localizing the vessels likely to be bleeding and in excluding associated abdominal and cerebrospinal injuries. Correlations of location of the hematoma and site of vascular injury include obturator space and obturator artery, presacral space and lateral sacral artery, space of Retzius and internal pudendal artery, and buttock and gluteal artery.
Femoral access is the preferred approach; however, catheterization may be difficult because of hypotension, tachycardia, and difficulty in palpating the vessels as the pelvic hematoma expands. Ultrasound or fluoroscopic guidance is very helpful in these situations. A 5 French aortic flush catheter is used for flush abdominopelvic aortography. This is valuable to screen the abdominal viscera and mesentery, to exclude aortoiliac and other retroperitoneal bleeding sources, and as a road map of the pelvic vessels. Bilateral internal iliac arteriography is mandatory to exclude bleeding sites since aortography may not identify all bleeding. From one access, both internal iliac arteries are sequentially catheterized and opacified. Then, external iliac arteriography is used to evaluate the external pudendal and external obturator vessels.
Multiple areas of extravasation are often identified. These may be bilateral and may involve multiple vascular beds. Extravasation is often punctate, but can be large, coarse, and extensive, also. The size of such extravasations may not correlate with the degree of blood loss. Vascular occlusions are common, as well. These can be due to thrombosis or vasospasm that often cannot be differentiated. Failure to treat these occlusions may result in recurrent hemorrhage when vasospasm resolves. Arteriovenous fistulas can occur, but are more common in penetrating trauma.
Because bleeding is usually multifocal and originates from multiple small blood vessels, embolization requires small particulate embolization. Large coil occlusion is as ineffective as surgical ligation of the internal iliac artery because bleeding soon resumes through numerous collateral circuits. Surgical gelatin pledgets are ideal because they are inexpensive, readily available, and often temporary lasting only a few weeks and allowing reestablishment of normal blood flow after the tissue has healed (Fig. 15-47A and B). Permanent particulate emboli, however, are often used because of their ease of use through a microcatheter (Fig. 15-48A and B). Embolization is technically successful in more than 90% of patients, and hemorrhage control is highly effective. Survival depends on many other factors including associated injuries, the presence of an open fracture, transfusion requirements, and delays to embolization.
(A and B) Multiple bleeds from pelvic fractures: 48-year-old male driver in a motor crash sustained pelvic fractures requiring transfusions. (A) Circles surround multiple bleeding sites from the region of the sacroiliac joint; from the pelvic side wall on the right hemipelvis emanate anterior and posterior branches of the right internal iliac artery and in the region (B) multiple points of extravasation were detected (circle). They are emanating from the left lateral sacral artery. Such diffuse hemorrhage is not amenable to superselective embolization because it would be too time consuming. Pledgets of surgical gelatin, 2–3 mm in size, can occlude these vessels effectively.
(A and B) A 26-year-old motorcyclist sustained unstable pelvic fractures during a crash. He developed expanding perineal and scrotal hematomas requiring red cell transfusion. (A) Left internal iliac arteriogram reveals a source of bleeding from the left internal pudendal artery (curved arrow). The more medial contrast stain (straight arrow) is a normal finding. It represents the blush of the perineal body and root of the ischiocavernosa muscle that is frequently seen on internal iliac arteriography of mails. (B) Because this was focal hemorrhage, selective embolization via 2.8 French catheter placed coaxially through the 5 French catheter was attempted and successfully achieved hemostasis.
Penetrating Pelvic Trauma
Penetrating trauma is an uncommon indication for pelvic angiography as most patients are hemodynamically unstable or have clear indications for exploratory celiotomy. Moreover, they are more likely to sustain injuries to large vessels. Because the retroperitoneum has been exposed by a penetrating wound, intraperitoneal bleeding is likely and direct exploration is warranted. Occasionally, angiography is valuable when operative control cannot be initially accomplished and damage control has been performed. Angiography and embolization prior to unpacking will avoid additional blood loss at a reoperation.
Large vessel conduit injuries require a very different endovascular strategy. When an injury to a noncritical internal iliac artery or branch has been missed at operation, but detected on postoperative angiography, coil occlusion of both the proximal and, whenever possible, the distal end of the vessel is the standard treatment.
Peripheral Vascular Injuries
A discussion of the use of interventional radiology in the treatment of extremity injuries must be preceded by a discussion of the use of imaging in the diagnostic workup of suspected vascular trauma in the extremities. The indications and contraindications depend on a variety of factors that are primarily related to clinical presentation and hospital course, and also to associated injuries, mechanism of injury, and signs of circulatory shock.
Vigorous or pulsatile external active hemorrhage, a rapidly expanding hematoma, or loss of pulses at the wrist or ankle mandates emergent operative exploration. Other patients with proximity wounds and stable hematomas, diminished pulses, or signs of an arteriovenous fistula may benefit from arteriography. The availability of stent grafts has also increased the utilization of angiography as a prelude to nonoperative management of some clinically significant vascular injuries.
While debatable to some, “proximity” angiography has value in asymptomatic patients with penetration that has passed close to the estimated path of major vessels. Vascular injuries occur in 3–8% of asymptomatic patients. Failure to diagnose arterial injuries may result in delayed hemorrhage or chronic arteriovenous fistulas with claudication, venous insufficiency, and congestive heart failure. Exclusion angiography avoids the time and effort needed to keep track of patients who are often negligent in their own follow-up.
The indications for the use of angiography in patients who have sustained fractures and dislocations are a more complicated matter. Vascular injuries resulting from fractures and dislocations are uncommon. Clinical evaluation is often difficult as the hematoma from a fracture may be quite large and indistinguishable from one associated with a vascular injury. Crush wounds, angulation deformities, and fracture hematomas may cause a pulse deficit by kinking, entrapping the vessel, or inducing spasm without an intrinsic vascular injury. A laceration into muscle may result in external blood loss without major vascular injury. Finally, a compartment syndrome may result in tissue ischemia without loss of pulses.
Almost all peripheral vascular injuries can be reached using a 5 French catheter from femoral access provided a long enough catheter is available. Angiography should be done in multiple projections with opaque marking of the entry and exit wounds demonstrating that the entire course of the wounding agent is within the field of view. Iso-osmolar nonionic contrast medium is the optimal agent for visualization. Multiple images in the arterial, capillary, and venous phases are necessary.
The imaging signs of vascular injury include luminal narrowing, arterial extravasation, bulge of the wall, intraluminal filling defects, occlusions, and arteriovenous fistulas. The imaging signs are in some cases quite nonspecific. Luminal narrowing can result from spasm, mural thrombus, intramural hematoma, and extrinsic compression, while dilatation can result from a traumatic true aneurysm, traumatic false aneurysm (“pseudoaneurysm”), or arteriovenous fistula. Finally, occlusion can be caused by thrombosis or vasospasm.
The natural history of many injuries cannot be predicted by the angiographic appearance. Therefore, observation of some injuries is warranted. Equivocal findings such as luminal narrowing can be assessed by repeating angiography after infusion of an intra-arterial vasodilator, on a subsequent day. Small irregularities and intimal tears that are not flow restricting may be treated by antiplatelet therapy and will heal (Fig. 15-49A–D).
“Minimal injury” of the popliteal artery. Pedestrian who was struck by a motor vehicle sustained comminuted tibial plateau fracture of the left knee. Pulses were diminished and angiography was sought after incomplete reduction. (A and B) Initial popliteal arteriogram showed numerous filling defects consistent with intimal tears (white arrows). Patient was treated with aspirin. (C and D) Arteriogram 1 week later showed healing of the intimal tears.
Treatment of angiographically diagnosed vascular injuries is based on the criticality of the bleeding vessel, its size, location, and accessibility, the hemodynamic condition of the patient, and the type of lesion. Small vessels that are not essential for tissue perfusion can be treated by small particle embolization, using surgical gelatin pledgets or more permanent smaller agents. Permanent agents have no advantage, but in some instances are more easily administered through microcatheters than surgical gelatin. These agents are delivered by flow direction toward the path of least resistance, which is usually toward the bleeding site. Microcoils can be utilized for injury to a small vessel provided they can be delivered near enough to the injury site to avoid collateral recruitment that permits continued bleeding. Examples of vessels that can be treated by embolization of small particles include hemorrhage from a pelvic fracture, multifocal hepatic arterial hemorrhage, and injuries to small muscular branches in the extremities.
Injury to larger vessels such as those greater than 3 mm in diameter requires two techniques, one for essential vessels and one for expendable vessels. The treatment of essential vessels requires repair of the bleeding site while allowing continued blood flow. Thus, stent grafts can be deployed to cover the injured segment while allowing prograde flow (Fig. 15-50).
Thrombosis of popliteal artery with endovascular repair. A 46-year-old morbidly obese woman sustained comminuted tibial plateau fractures after a fall from curb. Pulses were absent. (A) Popliteal arteriogram shows complete occlusion of the mid-popliteal artery. (B) The catheter was quickly advanced to a location just above the occlusion and a guidewire advanced easily into the posterior tibial artery. An ePTFE reinforced stent graft was deployed between proximal and distal extent of the occlusion. (C) Follow-up popliteal arteriogram showed restoration of direct line flow. The entire procedure took less than 1.5 hours.
Nonessential conduits, such as branches of the profunda femoris artery or the brachial artery, or one of the arteries in the shank, can be safely embolized. Particulate embolization will flow past the injury and penetrate deep into the vascular bed. When conduits are injured, this insult to the vascular bed is unnecessary. Therefore, large vessel agents are used to occlude the damaged segment of the conduit while the vascular bed is perfused through collaterals (Fig. 15-51).
Example of vascular isolation by proximal and distal coil occlusion. A 22-year-old male sustained a single stab wound of the upper left chest resulting in very large hemothorax. (A) Subclavian arteriogram shows that there is active arterial hemorrhage from a lacerated fourth anterior intercostal branch of the left internal mammary artery. (B) Because there was continuity between anterior and posterior intercostals, it was necessary to advance a 2.8-French microcatheter across the laceration into the distal segment to deliver a coil distally before withdrawing the catheter and delivering a coil proximally.
Coils in various sizes, some containing threads or fibers to accelerate thrombosis, are the most common devices used to occlude a large vessel. A coil is sized to have a diameter large enough to prevent distal migration, but not too large to end up recoiling into a parent, nontarget vessel.
The technique of conduit isolation attempts to occlude both the proximal and distal vessels around the area of injury by coiling (Fig. 15-51). The goal is to exclude the vascular defect and prevent rebleeding through collateral vessels. This is highly desirable in most circumstances, but mandatory when treating arteriovenous fistulas. The guidewire is carefully maneuvered distal to the injured segment, but proximal to any branches, and coils are delivered. The catheter is then withdrawn, and coils are placed in the proximal segment.