Angiography

Summary

  • The emergence of multiple alternative noninvasive studies (CT, MRI and U/S) as well as a stronger reliance on clinical exam in certain injuries (penetrating neck and extremity trauma) has led to a decrease in the use of emergent angiography.
  • On the other hand, angiography remains the gold-standard for many vascular emergencies, and the improvement in technology (nonionic contrast, safer microcatheters) and technique has considerably lowered the risk of complications. All contraindications are relative and most can be overcome either with nonionic contrast and antiallergic retreatment, and correction of coagulopathy.
  • The indications for angiography can be divided into four groups:

  1. first-line diagnostic test;
  2. first-line diagnostic test and therapeutic modality;
  3. therapeutic modality;
  4. not first-line diagnostic test.

  • First-line diagnostic test: Penetrating extremity trauma—due to the high sensitivity of physical exam, the self-limited nature of most vascular injuries discovered on angiography, and the good outcome of delayed repair, angiography is no longer commonly used for patients without hard signs of vascular injury.
  • Penetrating neck trauma—the high sensitivity of color-flow doppler and clinical observation has reduced the use of angiography for zone 1 and 3 injuries.
  • Pulmonary embolus—patients with nondiagnostic V/Q scans and negative CT scans are appropriate candidates for angiography, unless pretest clinical suspicion is not high and the patient has negative serial lower extremity duplex scans.
  • Any patient with strongly suspected mesenteric ischemia requires emergent angiography to confirm the disease and guide the vascular surgeon’s approach.
  • Nontraumatic limb ischemia—Although angiography is the gold-standard for evaluating peripheral vascular disease, the diagnosis of acute limb ischemia is usually made reliably by clinical exam.
  • First-line diagnostic test and therapeutic modality: Subarachnoid hemorrhage—emergency cerebral angiography is required for all acute SAH patients to prepare surgical approach or embolectomy before rebleeding occurs.
  • Upper GI bleeding requires emergency angiography and embolization or vasopressin infusion to control massive bleeding in patients who do not respond to endoscopic treatment.
  • Heavy lower GI bleeding (>3 units/day) may require angiography to localize and control bleeding and will sometimes precede colonoscopy.

Therapeutic modality:

Emergency Medicine

  • Pelvic fracture hemorrhage—although there is little evidence determining whether angiography improves outcome, this is the preferred therapy for pelvic fracture patients with persistent hypotension after other causes for hypotension are excluded and after application of an external fixator.
  • No longer first-line diagnostic test: Aortic dissection—although angiography is still used by many vascular surgeons preoperatively, MRI and TEE are both considered more accurate tests without the associated risks, while CT has equivalent accuracy with much greater convenience.
  • Blunt aortic injury—angiography is the gold standard but CT is recommended as the initial test with angio reserved for indeterminate cases.
  • Abdominal aortic aneurysm—angiography has been replaced by CT, ultrasound (U/S) and MRI.
  • Renal trauma—CT is first-line with angiography used for indeterminate vascular injuries.

Indications

Extremity Trauma

  • Angiography remains the gold standard for evaluating potential arterial injuries in penetrating extremity trauma (PET), but the indications for its use have narrowed over the last ten years.
  • Most arterial injuries will present with classic “hard” signs: pulsatile hemorrhage, pulsatile hematoma, overt distal ischemia, audible bruit, palpable thrill.
  • These signs require immediate operative management, and generally angiography will only be performed intraoperatively if at all. Soft signs such as small hematoma, transient hypotension, absence of hemorrhage, fracture, and nerve injury are no longer treated differently than an absence of hard signs because studies show they have no clinical correlation with vascular injury. The management of injuries in proximity to a vascular structure is more controversial but a trend toward noninvasive studies (duplex or doppler ABIs), observation, or discharge home has replaced surgical exploration and angiograms.
  • Angiography not only has a 2.6-5% complication rate), but it has a 1.9% false positive rate, prompting unnecessary surgical exploration. Using physical exam with the hard signs listed above reduces the false positive rate to 0%.

Duplex U/S

  • Many centers use duplex U/S to assess vascular injury, but there are no studies with long-term follow-up to confirm its safety. At least one study has demonstrated its lack of reliability.
  • Even if U/S had comparable sensitivity to angiography, since several studies show that there is no morbidity when patients are only repaired if they manifest hard signs, the U/S result (either positive or negative) may not change management.
  • Indications for arteriography in extremity trauma include:
    • Hemodynamic instability
    • Blunt trauma with signs of vascular injury
    • Intraoperative or postoperative evaluation
    • Delayed diagnosis with hard signs
    • Follow-up of nonoperatively managed arterial injuries
    • Penetratring trauma with hard signs plus:
    • Multiple potential sites of injury (i.e., shotguns)
    • Missile parallels vessel over long distance
    • Chronic vascular disease
    • Extensive bone or soft-tissue injury

Special Imaging Studies for the Emergency Department

  • Blunt trauma to right common iliac with small defect to left internal iliac.
  • Although most patients with PET who present with hard signs of vascular injury will undergo immediate operative management, a few situations will prompt initial

Arteriography.

  • Patients with multiple potential sites of injury, a missile that parallels the vessel over a long distance, extensive bony or soft-tissue injury, and thoracic outlet injuries will usually require arteriography even with hard signs because the surgical approach will vary depending on the location of arterial injury.
  • Right popliteal artery dividing into the posterior tibial artery and peroneal artery.

Emergency Medicine

Aortic Dissection

  • Retrograde aortography was long considered the study of choice for evaluating suspected thoracic aortic dissection simply because it was the only way to accurately diagnose dissection antemortem.
  • The introduction of CT, MRI and transesophageal echocardiography (TEE) have all proven to be safer studies for aortic dissection while demonstrating that aortography was probably not as sensitive as previously thought.
  • The sensitivity of aortography is commonly listed as 80-90% with a specificity of 90-95%. False-negative angiograms may occur in cases of thrombosis of the false lumen, faint opacification of the false lumen, or opacification of both true and false lumens so that an intimal flap is not visualized.
  • Plain radiography will miss 10-20% of aortic dissections so if there is a suspicion of aortic dissection another study is necessary. Based on their prospective blinded comparison of MR, TEE and CT, Nienaber et al recommend MR for the evaluation of aortic dissection in stable patients and TEE for unstable patients.

Penetrating Trauma to the Neck

  • Angiography is the gold standard to evaluate penetrating vascular injuries to the neck. Preiviously angiography was routinely performed for all penetrating injuries to zone 1 (clavicles to cricoid cartilage) and zone 3 (above the angle of the mandible) of the neck regardless of exam or symptoms, with surgical exploration or angiography for zone 2 injuries.
  • Although mandatory angiography or surgical exploration is considered the safest way to avoid missing vascular injuries, there is a growing body of evidence to support the conservative approach of ultrasonography and/or 24 h clinical observation
  • Like penetrating extremity trauma, the majority of penetrating neck injuries without hard signs will not have vascular injuries, and those that do will rarely require surgery. Ultimately the majority of these patients will be admitted to a surgeon, and the decision for angiography will be made in consultation with that surgeon.

Special Imaging Studies for the Emergency Department

  • Innominate artery—right arrow shows an angio catheter in the innominate artery with distal stenosis and contrast extravasation.

Pelvic Fracture Hemorrhage

  • The mortality rates in patients with pelvic fractures range from 9%-20% but are reportedly as high as 50% in patients who present with pelvic fractures and hemodynamic instability.
  • Angiography’s primary role in pelvic fracture hemorrhage is a therapeutic one because of the potential for embolectomy of the injured small arteries.
  • Large vessel injuries (aorta, iliacs, femorals) in pelvic fractures are fairly rare (1%) and are not amenable to embolization so these injuries, if discovered on angiogram, are an indication for surgical repair.
  • 90% of bleeding in pelvic fractures comes from low pressure venous plexus and fractured cancellous bone surfaces which is not amenable to venous embolectomy because of the extensive anastamoses and valveless collateral flow.
  • Only 10% of pelvic fracture hemorrhage is due to arterial bleeding (branches of the internal iliac) and this is seen most commonly with anterior-posterior injuries—APC II (symphisis widening) and APC III (symphisis and SI disruption).
  • Arterial embolectomy will help control venous hemorrhage by slowing the arterial supply.
  • Embolectomy is achieved using various embolic agents including hemostatic absorbable gelfoam cakes, autologous clots, muscle, detachable balloons, polystyrene spheres, and wire coils which are injected from the angiography catheter.
  • Because the majority of bleeding in pelvic fractures can be controlled by tamponade, angiography is deferred at many trauma centers until the external fixator is applied.

Blunt Aortic Injury

  • Blunt aortic injury is the second most common cause of death in blunt trauma patients with only 13-15% of patients arriving at the hospital with signs of life.
  • The most commonly noted signs are pseudocoarctation (kinking of aorta at the ligamentum arteriosum with decreased blood pressure in the lower extremities) and an intrascapular murmur.
    Blunt deceleration injury to descending aorta with aneurysmal dilatation.
  • Chest radiograph is the initial screening test and will detect at least one of the following abnormalities in most aortic injuries: widened mediastinum, indistinct aortic knob, depression of the left mainstem bronchus, deviation of the NG tube, opacification of the AP window, widened paratracheal and paraspinous stripes, and apical capping.
  • Angiography is the gold standard but contrast-enhanced helical or spiral CT has recently been shown to have excellent sensitivity with 100% negative predictive value.

Pulmonary Angiography

  • Pulmonary angiography (PA) is rarely indicated as an emergent diagnostic test from the emergency department.
  • Use of pulmonary angiography to diagnose pulmonary embolism is generally reserved for patients with conflicting pretest and scan probabilities (i.e., high pretest probability and low probability VQ scans or vice versa).
  • Angiography is now rarely ordered before spiral CT because a positive CT (either for PE or an alternative diagnosis) negates the need for angiogram.
  • Although spiral CT has acceptably high specificity to confidently rule-in PE, three metaanalyses published in 2000 demonstrated that CT’s sensitivity is too low to safely exclude PE so patients with negative CT need further tests (i.e., duplex, V/Q, or angiogram) to exclude it.

Upper Gastrointestinal Bleeding

  • Although endoscopy is the primary diagnostic modality to evaluate, localize and treat upper GI bleeding, approximately 10-20% of patients with massive hemorrhage (hemodynamic instability, requiring 4-6 units of blood in 24 h) will require angiography to control bleeding.
  • Endoscopy is always performed before angiography which will often negate the need for angiography or at the very least help guide which artery to cannulate first at angiography (celiac, superior mesenteric, left gastric, gastroduodenal, pancreaticoduodenal, and splenic). Therapeutic angiography is most strongly indicated in poor surgical candidates (elderly, severely ill patients) but is increasingly offered to all acute GI bleeders who continue to bleed after endoscopy.
    Pulmonary embolus demonstrated by abrupt cutoff in mid lower left lung zone with paucity of vessels distal to cutoff.
  • Selective intra-arterial vasopressin (usually 12-24 h infusion) is the standard angiographic therapy although embolotherapy is increasingly popular because of new microtherapy which reduces the chance of large vessel occlusion and consequent bowel infarction.

Lower Gastrointestinal Bleeding

  • Because colonoscopy of an unprepared colon is more difficult than upper endoscopy and lesions may be missed in a dirty colon because of poor preparation or active bleeding, the evaluation of lower GI bleeding is less straightforward.
  • The three diagnostic modalities employed emergently for evaluation of acute lower GI bleeding are colonoscopy/sigmoidoscopy, technetium bleeding scans and angiography.
  • As with upper GI bleeding, angiography is typically reserved for heavy bleeding (>1 ml/min), and has two advantages as a precedent to surgery—it may stabilize a patient through vasopressin and embolization to avoid surgery or allow for elective surgery, and angiography can localize the bleeding site to reduce the extent of bowel resection.

Subarachnoid Hemorrhage

  • The gold standard for the diagnosis of intracranial aneurysms remains angiography.
  • Emergent angiography is recommended in patients who have a positive CT scan, a negative CT scan but positive lumbar puncture, or in those with a very suggestive history despite negative studies.
  • The study should be done urgently, certainly within 24 h of presentation (ideally within 6-8 h), unless the patient is of poor Hunt-Hess grade

Abdominal Aortic Aneurysm

  • Although angiography is helpful in depicting the anatomy of the aorta, CT, MRI, and U/S are generally preferred for AAA because angiography is invasive, costly, fraught with complications, and not entirely reliable.
  • In some hospitals, an arteriogram is necessary for surgery.

Nontraumatic Limb Ischemia

  • Although angiography is the gold standard for evaluating peripheral vascular disease, the diagnosis of acute limb ischemia is usually made reliably by clinical exam.

Table: Grading system for SAH
0 = Asymptomatic; unruptured aneurysm
1 = Mild symptoms (headache)
2 = Severe headache with nuchal rigidity =/- Cranial nerve deficit
3 = Confusion/AMS +/- decerebrate rigidity
4 = AMS with moderate to severe hemiparesis +/- decerebrate rigidity
5 = Comatose with posturing or flaccidity

  • The emergency physician will consult a vascular surgeon as soon as acute peripheral ischemia is suspected.
  • The vascular surgeon may order angiography in three scenarios: (1) the diagnosis of acute arterial occlusion is uncertain, (2) consideration of emergency vascular bypass grafting, (3) characterization of the vascularabnormality before emergency surgical correction.
       
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