Blunt Thoracic Aortic Injury

Transcription

1 September 2004 Blunt Thoracic Aortic Injury Richelle Williams, Harvard Medical School, Year III

2 Blunt Aortic Injury ~8000 deaths/year in the U.S. Most common cause of sudden death following: - high-speed MVA - fall from a great height Rapid deceleration results in shear forces along the aortic arch and aortic rupture 2

3 Mechanism of Injury 2 main proposed mechanisms (Marcura et al): Differential deceleration ascending and descending aorta mobile aortic arch relatively fixed by brachiocephalic vessels maximal stress at attachment points, aortic isthmus, and aortic root Osseous pinch theory aorta pinched between spine and anterior bony thorax From Gray, Henry. Anatomy of the Human Body 3

4 Traumatic Aortic Injury Spectrum of injury: Intima + media + adventitia transection Intima + media pseudoaneurysm Intima dissection Complete transection Dissection Partial transection Pseudoaneurysm 4

5 Epidemiology 75-90% of patients die at accident scene Complete rupture (all three layers of aorta) with rapid exsanguination Survivors form a pseudoaneurysm Without treatment, 50% die within a week (includes deaths due to comorbid injuries) With treatment, mortality decreases to <20% Sites most commonly affected: Aortic Isthmus (distal to left subclavian) ~ 95% Ascending aorta ~ 5% Diaphragmatic hiatus ~ 1 to 3% ~5% 95% ~1% 5

6 Clinical Presentation Symptoms variable and nonspecific Include chest or midscapular pain, dyspnea, hoarseness, dysphagia PE often noncontributory 5% of patients have decreased L arm pressure 50% have no external signs of chest trauma Diagnosis based on radiographic studies 6

7 Imaging Modalities CXR CT Angiography Transesophageal echocardiography (TEE) *MRI not currently in clinical use 7

8 Diagnostic Algorithm CXR used initially to screen for aortic injury Main factor determining subsequent studies is patient s s hemodynamic stability 8

9 Findings on CXR Widened superior mediastinum (mediastinal/chest ratio greater than 1:4 at aortic knob) Apical cap Abnormal contour of the aortic knob Tracheal/NG tube deviation to right of the T4 spinous process Depression of the left mainstream bronchus greater than 40º from horizontal or greater than 140º from the tracheal axis Left hemothorax without rib fracture Fracture of the first and second ribs, indicative of a high velocity injury 9

10 Funny-looking Mediastinum Differential diagnosis: Hemorrhage or hematoma sternal or vertebral fractures, venous and arterial tears, ruptured aneurysm Hiatal hernia (large) Lymphadenopathy TB, sarcoidosis,, lymphoma, histoplasmosis Mediastinal cyst or tumor Pneumomediastinum spontaneous, traumatic Vascular abnormality aneurysm, dissection or coarctation of the aorta; dilated SVC Normal CXR has 98% negative predictive value Technical consideration 40% of widened mediastinums normalize when patient is upright 10

11 Patient M.G. 17-year year-old female restrained back seat passenger involved in high-speed T-bone accident on 8/28/04 Lost consciousness at the scene of the accident, prolonged time to extraction Hypotensive,, low O2 saturation with decreased BS on right Transferred to BIDMC ED hemodynamically stable upon arrival with SBP in the 90s and HR of 103 In ED, awake and able to move all 4 extremities but no response to painful stimuli 11

12 What next? What injuries are we concerned about? Aortic Injury Brain and/or spinal cord injury Pneumothorax Fractures Hemorrhage What test should we order first? CXR 12

13 Chest Radiograph Patient MG Portable AP view No identifiable pneumothorax or rib fractures Widened upper mediastinum Indistinct aortic knob with opacification of aorto- pulmonary window Tracheal deviation to the right of T4 spinous process From PACS, BIDMC 13

14 CT Patient MG High density material in mediastinum consistent with hemorrhage Dependent atelectasis in both lungs From PACS, BIDMC 14

15 CT Patient MG (2) Pseudoaneurysm of descending aorta note the unusual contour R lung contusion R lung hemothorax with chest tube From PACS, BIDMC 15

16 CT Reformations Patient MG Excellent visualization of pseudoaneurysm Watch out for aortic ductus diverticulum fakeout Pseudoaneurysm From PACS, BIDMC 16

17 Angiogram Patient MG Gold standard in assessing aortic injuries for many years Advantage: Wonderful visualization of other great vessels and their branches Disadvantage: Invasive and time- consuming with 1-10% 1 10% complication rate From PACS, BIDMC 17

18 TEE Small arrow indicates pseudoaneurysm Similar blood flow velocities seen on either side of medial flap. Mosaic of colors represents turbulent flow at site of tear. Advantages: Portable Study can be performed on unstable patients Disadvantages: Operator-dependent Requires patient sedation Difficult to visualize distal ascending aorta and proximal arch Interpretation confounded by presence of atherosclerosis Images from Lang and Vignon,

19 Treatment Two options for aortic repair: 1. Open surgical repair 2. Endovascular stent-graft Surgery risks include early mortality (15-29%), paraplegia (25%) & recurrent laryngeal nerve injury (~8%). Fewer short term complications with endovascular repair but long term risks unknown. Small pseudoaneurysms may be managed medically but risk of delayed rupture Comorbid injuries increase mortality and morbidity risk both pre and post- operatively From Fujikawa, T, et al. J of Trauma Feb. 2001; 50(2)

20 Patient MG Endovascular stent graft repair of pseudoaneurysm on 8/30/04 without complication IVC filter placement and open reduction-internal internal fixation of pelvic fracture on 9/2/04 Patient is now ambulatory but will require weeks of PT From Fujikawa, T, et al. J of Trauma Feb. 2001; 50(2)

21 Key Points Rapid deceleration event - high index of suspicion for thoracic aortic rupture Diagnostic algorithm imaging modality determined by patient stability Rapid treatment imperative given high mortality risk (Don t t forget comorbid injuries!) 21

22 References Brohi K. Chest Trauma Traumatic Aortic Injury. 4 April September Fujikawa T, Yukioka T, Ishimaru S, Kanai M, Muraoka A, Sasaki H, Honma H, Koike S, Kawaguchi S. Endovascular Stent Grafting for the Treatment of Blunt Thoracic Aortic Injury. J. Trauma February 2001; 50(2): Gray H. Anatomy of the Human Body. Philadelphia: Lea & Febiger,, 1918; Bartleby.com,, < > 20 September Marcura KJ, Corl FM, Fishman EK, Bluemke DA. Pathogenesis in Acute Aortic Syndromes: Aortic Aneurysm Leak and Rupture and Traumatic Aortic Transection. Am. J. Roentgenol. 2003; 181: Mechem CC. Intensive Care Unit Management of Trauma Patient. 20 April < > 15 September Mendez DR. Thoracic Trauma in Children. 2 February < > 19 September Ott MC, Stewart TC, Lawlor DK, Gray DK, Forbes TL. Management of Blunt Thoracic Aortic Injuries: Endovascular Stents versus Open Repair. J. Trauma March 2004; 56(3): Prêtre R, Chilcott M. Blunt Trauma to the Heart and GreatVessels. N Engl J Med 1997; 336(9): Reeder MM. Reeder and Felson s Gamuts in Radiology: Comprehensive List of Roentgen Differential Diagnosis. 4th ed. New York: Springer, Smith MD, Cassidy JM, Souther S, Morris EJ, Sapin PM, Johnson SB, Kearney PA. Transesophageal Echocardiography in the Diagnosis of Traumatic Rupture of the Aorta. N Engl J Med 1995; 332(6): Vignon P, Lang RM. Transesophageal Echocardiography in Traumatic Rupture of Aortic Isthmus. April < > 15 September

23 Acknowledgements Erik Stien,, MD Pamela Lepkowski Larry Barbaras our Webmaster 23