Acute Aortic Syndrome

ACUTE AORTIC SYNDROME

AAMIR SUHAIL MD DALHOUSIE UNIVERSITY

ACUTE AORTIC SYNDROME

• Heterogeneous group of patients with a similar clinical profile . • Non-traumatic life threatening injuries of the thoracic aorta. • Aortic Dissection • Intramural Hematoma (IMH) • Penetrating Atherosclerotic Ulcer (PAU) • Overall incidence is 2.6 – 3.5 cases / 100,000 person years. • Approx 65% of patients are men • Average at of presentation is 65

Abbas, A., I. Brown W., C. Peebles R., S. Harden P., and J. Shambrook S. "The Role of Multidetector-row CT in the Diagnosis, Classification and Management of Acute Aortic Syndrome." The British Journal of Radiology BJR 87.1042 (2014): 20140354. Web. RISK FACTORS

• Hypertension (~72%) • Genetic • Marfan’s Sx (70%), Loeys-Dietz sx (32%), Ehlers-Danlos sx, Turner • Bicuspid Aortic Valve (2-9% of Type A, 3% of Type b) • HAS. • Mutations that affect structural proteins at the interface between ECM and smooth muscle cells • Influence aortic response to mechanical stimuli • Inflammatory Vascular Disease • Syphillis, Behcet’s, Takayasu arteritis, GCA • Iatrogenic • Aortic catheterization, Cardiac valve or Aortic Surgery

• Severe tearing chest pain • 84-90% of cases • Maximal intensity at the time of onset • Acute Coronary Syndrome (ACS) – gradual increase in intensity. • Radiating to the neck, jaw or throat • Involvement of ascending aorta • Referred pain to the back or abdomen • Descending aorta • Other • Pulse deficits, regurgitant aortic murmur • Syncope • Heralds rupture or cerebrovascular occlusion

• Aortic Root: aortic annulus to sinotubular junction. • Sinuses of valsalva • Tubular ascending: STJ to Brachiocephalic trunk • ~3cm of aA is within pericardium • Coronary arteries

Mokrane, F.z., P. Revel-Mouroz, B. Lebes Saint, and H. Rousseau. "Traumatic Injuries of the Thoracic Aorta: The Role of Imaging in Diagnosis and Treatment." Diagnostic and Interventional Imaging 96.7-8 (2015): 693-706. Web. AORTIC ARCH

• BCT to Lt Subclav. • Aortic Isthmus: • Lt. Subclav to Lig. Arteriosum.

• Multiple branches • Bronchial • Intercostal • Spinal • Sup phrenic • Small mediastinal branches

• Ductus diverticulum • Focal bulge along the inner aspect of the isthmus • Remnant of ductus arteriousus. • Challenging to distinguish from traumatic aortic dissection. • Smooth margins with with obtuse angles relative to adjacent aorta. • Transection: irregular margins with acute angles.

• Pseudocoarctation • Normal variant secondary to incomplete fusion of the third to seventh embryonic dorsal segments. • High proximal arch and “pseudokinking” of redundant aorta at the site of tethering to lig. Arteriosum. • No hemodynamically significant luminal narrowing.

ECHOCARDIOGRAPHY

• Readily available, can be performed quickly and allows bedside imaging and interpretation. • Transthoracic (TTE) and Transesophageal (TEE) • TTE • Aortic valve dysfunction • Pericardial tamponade • Wall motion abnormalities. • Allows screening of proximal 4 – 8 mm of the ascending aorta to just above the sinotubular junction. • Short segment of descending aorta. • Distal ascending and arch NOT well-visualized.

Baliga, Ragavendra R., Christoph Nienaber A., Eduardo Bossone, Jae Oh K., Eric Isselbacher M., Udo Sechtem, Rossella Fattori, Subha Raman V., and Kim Eagle A. "The Role of Imaging in Aortic Dissection and Related Syndromes." JACC: Cardiovascular Imaging 7.4 (2014): 406-24. Web. ECHOCARDIOGRAPHY

• Overall SN only 59 – 83% , SP 63 – 93% • Type A dissection: SN 78-100% • Type B dissection: SN 31-55%

• TEE • Highly accurate as a result of close proximity of the esophagus to thoracic aorta. • Can visualize both ascending and descending aorta and parts of the arch with high spatial resolution in real time. • ~7.5 MHz transducer mounted to the end of a gastroscopic probe. • TEE can reach SN 99% , SP 89% • 100% SN in detecting aortic regurgitation the complicates dissection.

• Requires esophageal intubation, but bedside evaluation w/in 15 min.

• Limitations • Requires esophageal intubation, conscious sedation. • Limited visualization of the distal ascending aorta and proximal arch because of interposition of air-filled trachea and main bronchus. • Reverberation artefacts may mimic dissection flap.

• Modality of choice • SN 100%, SP 98-99% • Rapid acquisition, universal emergency access. • >64 detector row MDCT can provide isovolumetric imaging with image reconstruction in any desired plane. • Cross-sectional reconstructions perpendicular to long axis of aortic lumen. • Can assess branch vessel involvement. • Provides detailed map of entire aorta and its branches • Serial measurements, easily identifiable landmarks

Husainy, Mohammad Ali, Farhina Sayyed, and Sapna Puppala. "Acute Aortic Syndrome—pitfalls on Gated and Non-gated CT Scan." Emerg Radiol Emergency Radiology 23.4 (2016): 397-403. Web. MDCT

• Significantly reduces cardiac motion artefacts that can often mimic AD. • Aortic root, Ascending aorta. • Enables more accurate assessment of the proximal coronary arteries. • Not routinely performed at all institutions. • Can lead to inappropriate transfer of patients to tertiary care centers (or negative open surgery) for patients with atypical cardiac motion artefact mimicking acute dissection flaps on non-gated MDCT. • ECG-gated pre-contrast imaging is critical • Pre-medication with B-Blockers and Nitroglycerin is not required and should be avoided.

Husainy, Mohammad Ali, Farhina Sayyed, and Sapna Puppala. "Acute Aortic Syndrome—pitfalls on Gated and Non-gated CT Scan." Emerg Radiol Emergency Radiology 23.4 (2016): 397-403. Web. MDCT

• Pre-contrast imaging is critical • Allows evaluation for presence of Intramural Hematoma • Localized rupture into the pleura or pericardium.

• Followed by CTA • Bolus-tracked using 120 ml of [370 mgl/ml] iodinated contrast delivered at a rate of 4-5 cc/s via power injector • Target opacification of aorta of >250 HU • Contrast volume should be reduced to 80-100 ml in elderly patients (reduced cardiac output).

• Ensure right arm IV access • Avoids streak artefact from contrast in the left brachiocephalic vein.

• Further artefact minimization in IVC • 20 ml saline flush should immediately follow contrast medium injection

Husainy, Mohammad Ali, Farhina Sayyed, and Sapna Puppala. "Acute Aortic Syndrome—pitfalls on Gated and Non-gated CT Scan." Emerg Radiol Emergency Radiology 23.4 (2016): 397-403. Web.

INSTITUTIONAL PROTOCOL

• DISSECTION PROTOCOL • Unenhanced phase followed by CE arterial acquisition.

• FLASH scanner (256 MDCT) • ECG-triggered. • Acquisition in mid-diastole. • Low kvp • Pitch 3.4

• 100 mg Isovue 370 @ 4cc/sec via dual head injector using a 40 cc saline chaser over 35 seconds (25+10)

• Bolus-tracking method triggers off ascending aorta at HU attenuation of 120

• Scan range from thoracic inlet to femoral head • Allows evaluation of supraaortic branches and iliac vessels

MRI

• Role in acute evaluation is limited given a relatively long examination (20-30 min) • Not readily compatible with life support and monitoring equipment required for critically ill patients. • Mainly used for serial follow-up of chronic Aortic Dissection. • Avoids radiation exposure and the use of contrast material. • IV gadolinium-enhanced imaging of the Aorta • Black-blood T1-weighted and T2-weighted images used to assess • Luminal calibre • Aortic wall thickness • Aortic wall signal • Dynamic steady-state free precession images sequences for aortic valve function and aortic root calibre.

AORTIC DISSECTION

• Disruption of the aortic intima and inner layer of the media. • Formation of double channel aorta divided by a dissection flap. • True and False lumen. • Intimomedial flap. • Entrance tear most commonly at sites of greatest hydraulic stress • Right lateral wall of the ascending aorta • Proximal segment of the descending aorta. • Re-entrance tear and several fenestrations between the True and False lumen are common.

• Cardiac motion and streak artefacts may mimic a dissection flap. • Streak artefacts • Typically demonstrate inconsistent orientation on contiguous slices • Characteristically radiate away from a high-density focus • Cardiac motion • Characteristically in the right posterior and left anterior positions of the proximal aorta.

• False Lumen • Typically slower flow and usually larger (not always reliable) • Cobweb sign: low attenuation thin strands which represent residual threads of incompletely dissected media tissue. • Specific but uncommon • Beak sign: acute angle formed by the intimomedial flap with the outer wall of the false lumen. • Most consistently identified • Absence of outer wall calcification can help distinguish false lumen from a wall adherent thrombus of aortic aneurysm. • Intraluminal thrombus more frequently identified in false lumen (46%) than true lumen (6%)

• MORTALITY– usually the result of major branch vessel occlusion, pericardial tamponade, acute aortic regurgitation or aortic rupture. • Aortic rupture • Pericardium • Left pleural cavity • Mediastinum • Presence of hyperattentuating fluid collections. • Cardiac tamponade – compression of the free wall of the right ventricle. • Aortic valve insufficiency/rupture – distance from valve.

• End-organ ischemia • Dynamic occlusion • Dissection flap protruding across the branch vessel origin. • Static obstruction • Direct extension of the dissection flap into the wall of the branch vessel. • ECG-gating • Careful assessment of coronary artery involvement, branch vessel extension. • Aberrant origin of the left subclavian artery • Important for endovascular therapy. • Assessment of abdominal vessels and iliac axis.

INTRAMURAL HEMATOMA

• Hemorrhage localized to the aortic media • Absence of a visible intimal tear • May progress to dissection and rupture • Considered equivalent to dissection re prognostic and therapeutic implications. • Accounts for 8-15% of patients with AAS. • Traditionally thought to be caused by rupture of the vasa vasorum without intimal disruption. • Growing appreciation of microscopic intimal tears suggesting less pathologic distinction from AD. • Intimal tear with complete thrombosis of the false lumen.

Gunn, Martin L. D., Bruce Lehnert E., Rachel Lungren S., Chitti Narparla Babu, Lee Mitsumori, Joel Gross A., and Benjamin Starnes. "Minimal Aortic Injury of the Thoracic Aorta: Imaging Appearances and Outcome." Emerg Radiol Emergency Radiology 21.3 (2014): 227-33. Web. INTRAMURAL HEMATOMA

• Crescent-shaped area of high attenuation thickening in the aortic wall. • Typical attenuation of >45 HU. • Remains unenhanced after contrast injection • No dissection flap is seen. • MPRs can help distinguish true IMH from hemorrhagic fluid within the superior pericardial recess. • Can be confused with atheromatous mural thrombus.

Chiu, Keith W.h., Raghuram Lakshminarayan, and Duncan Ettles F. "Re: Acute Aortic Syndrome: CT Findings." Clinical Radiology 69.1 (2014): n. pag. Web.

INTRAMURAL HEMATOMA

• Unpredictable clinical course. • Higher risk patients • Involvement of the ascending aorta. • Maximum aortic diameter >5.0 cm. • Presence of large, hemorrhagic or enlarging pleural or pericardial effusions.

• Can develop ulcer-like projections (ULPs) • Localized contrast filled pouch that communicates with the TL. • Can develop intramural blood pool • Very narrow intimal orifice • Typically in descending aorta in patients with IMH > 10 mm thickness • Typically communicates with a lumbar or intercostal artery and does not communicate with true lumen • Associated with benign clinical course (unlike ULP).

Chiu, Keith W.h., Raghuram Lakshminarayan, and Duncan Ettles F. "Re: Acute Aortic Syndrome: CT Findings." Clinical Radiology 69.1 (2014): n. pag. Web.

INTRAMURAL HEMATOMA ULCER-LIKE PROJECTION INTRAMURAL BLOOD POOL

Eggebrecht, H., B. Plicht, P. Kahlert, and R. Erbel. "Intramural Hematoma and Penetrating Ulcers: Indications to Endovascular Treatment." European Journal of Vascular and Endovascular Surgery38.6 (2009): 659-65. Web. PENETRATING ATHEROSCLEROTIC ULCER

• Arise from atherosclerotic lesions that ulcerate and penetrate the internal elastic intima into the media. • Predominantly elderly patients with severe atherosclerosis (7.6% of AAS). • Commonly within middle or distal thirds of the descending aorta. • Differ from simple ulcerated plaque by presence of intimal disruption with subsequent extension of blood into media. • Location of intimal calcification can be a helpful marker.

Chou, Alan S., Bulat Ziganshin A., Paris Charilaou, Maryann Tranquilli, John Rizzo A., and John Elefteriades A. "Long-term Behavior of Aortic Intramural Hematomas and Penetrating Ulcers." The Journal of Thoracic and Cardiovascular Surgery 151.2 (2016): n. pag. Web. PENETRATING ATHEROSCLEROTIC ULCER PENETRATING ATHEROSCLEROTIC ULCER

• Focal contrast filled out pouching of the aortic wall with jagged edges • Usually in the presence of extensive aortic atheroma. • Deep ulcers often associated with an IMH. • Up to 45% in recent literature. • Concomitant aneurysms of thoracic aorta common. • Generally portends worse prognosis than IMH.

• CT features can be similar or identical to that of saccular psuedoaneurysm. • Given preponderance in elderly population, usually treated conservatively unless accompanied by signs of impending rupture.

Piffaretti, Gabriele, Mario Galli, Chiara Lomazzi, Marco Franchin, Patrizio Castelli, Giovanni Mariscalco, and Santi Trimarchi. "Endograft Repair for Pseudoaneurysms and Penetrating Ulcers of the Ascending Aorta." The Journal of Thoracic and Cardiovascular Surgery 151.6 (2016): 1606-614. Web PENETRATING ATHEROSCLEROTIC ULCER

• Differs from ulcer-like projection (ULP) • ULP is a lesion that appears days or weeks after acute IMH. • PAU is diagnosed on the first diagnostic study in AAS. • PAU presents with irregularities in the intimal layer with calcification of the ulcer edges, typical of atheromatous plaque, and may be accompanied by localized hematoma. • ULP detected during the course of an IMH and frequently appears as an image of intimal rupture with a small intimal flap.

AUCTE AORTIC SYNDROME

Chiu, Keith W.h., Raghuram Lakshminarayan, and Duncan Ettles F. "Re: Acute Aortic Syndrome: CT Findings. A Reply." Clinical Radiology 69.1 (2014): n. pag. Web.

CLASSIFICATION

• Classified anatomically based on extent of involvement of the thoracic aorta.

• DeBakey and colleagues (1965) • Origin of the intimal tear • Purely for aortic dissection.

• Stanford system (1970) • Applies to all entities of AAS • Dichotomous based on involvement of the ascending aorta.

CLASSIFICATION

• Stanford Type A • 75% of all aortic dissections. • Non-operative treatment associated with 24% mortality w/in 24 h and 49% by Day 14. • Type A IMH also associated with high risk of progression to dissection and rupture if left untreated • Early mortality rate of 8% with surgical repair vs 55% with medical therapy (Western populations). • Limited data regarding Type A/Type B PAU, but current consensus is to management based on Stanford classification.

CLASSIFICATION

• Type A ruptures can: • Cause coronary artery occlusion • Rupture into the pericardium (tamponade) • Dissect into the aortic valve (aortic insufficiency)

• Type B dissections treated medically unless: • Recurrent pain • Aortic expansion • Dissection progression • End-organ malperfusion

• Aortic arch dissection • Dissection flap or IMH with extension into the transverse arch between to the innominate and left subclavian artery • May be confined to the arch OR extend caudally into the descending aorta. • Relative protection from localized dissecting process • flexing of the ascending aorta above the aortic annulus and immediately distal to the Lt. Subclav a. • Vulnerable points at the meeting of fixed and mobile structures • Studied 121 cases of thoracic dissection • 7.4% involved the arch as the most proximal extent. • 11% of Type B dissections. • 30.6% involving ascending aorta with or without arch. • 62% involving the descending aorta.

Lempel, Jason K., Aletta Frazier Ann, Jean Jeudy, Seth Kligerman J., Randall Schultz, Hammed Ninalowo A., Elliott Gozansky K., Bartley Griffith, and Charles White S. "Aortic Arch Dissection: A Controversy of Classification." Radiology 271.3 (2014): 848-55. Web.

CLASSIFICATION

Arch dissections do not clearly fit into the Stanford or DeBakey scheme

Classification system based on the presence or absence of ascending aortic involvement.

Regardless of the primary site of intimal tear.

Whether the tear is confined to the ascending aorta, or a result of proximal extension of a distal tear.

Most studies have categorized arch dissections in Type B category.

CLASSIFICATION

• Long-standing discrepancy between surgeons and radiologists as to the classification of arch involvement. • Type A dissection • Proximal to Lt subclav? • Proximal to Innominate origin? • Current surgical consensus • Aortic arch dissections viewed as a variant of a Type B dissection. • Current radiologic consensus • Type A as involvement proximal to Lt. Subclav artery.

Maddu, Kiran K., Waqas Shuaib, Juan Telleria, Jamlik-Omari Johnson, and Faisal Khosa. "Nontraumatic Acute Aortic Emergencies: Part 1, Acute Aortic Syndrome." American Journal of Roentgenology 202.3 (2014): 656- 65. Web. MANAGEMENT

• Aimed at preventing aortic rupture or progression to classic dissection. • Considerable controversy regarding natural hx. • Surgery is usually indicated for Type A IMH/PAU • A conservative approach to uncomplicated Type B IMH is preferred • Antihypertensive treatment. • Watchful monitoring. • General approach to treat these entities like aortic dissection. • As PAU is usually a segmental localized wall lesion, it is an ideal candidate for endovascular stent graft.

MANAGEMENT

• Aortic replacement is the mainstay of therapy in Stanford Type A dissection. • TEVAR is an emerging therapeutic option for Type B dissection. • Uncontrollable hypertension • Intractable pain or shock suggesting impending rupture • Aimed at the complete exclusion of the false lumen by sealing the entry tear site with a stent graft. • Requires adequate landing zone • i.e. proximal neck > 5mm distal to Lt. Subclavian artery. • Adequate vascular access.

• Acute dissection involving the ascending aorta needs swift open surgical repair. • Uncomplicated dissection of the descending thoracic aorta can be managed medically. • Distinction between complicated and uncomplicated dissection is becoming blurred as understanding of the nature of dissection improves • Preemptive TEVAR is emerging as a way to prevent late complications. • Highest mortality from aortic dissection occurs in the first 48 h  immediate diagnosis is lifesaving. THANK YOU REFERENCES

1. Abbas, A., I. Brown W., C. Peebles R., S. Harden P., and J. Shambrook S. "The Role of Multidetector-row CT in the Diagnosis, Classification and Management of Acute Aortic Syndrome." The British Journal of Radiology BJR 87.1042 (2014): 20140354. Web. 2. Baliga, Ragavendra R., Christoph Nienaber A., Eduardo Bossone, Jae Oh K., Eric Isselbacher M., Udo Sechtem, Rossella Fattori, Subha Raman V., and Kim Eagle A. "The Role of Imaging in Aortic Dissection and Related Syndromes." JACC: Cardiovascular Imaging 7.4 (2014): 406-24. Web. 3. Chiu, Keith W.h., Raghuram Lakshminarayan, and Duncan Ettles F. "Re: Acute Aortic Syndrome: CT Findings. A Reply." Clinical Radiology 69.1 (2014): n. pag. Web. 4. Chou, Alan S., Bulat Ziganshin A., Paris Charilaou, Maryann Tranquilli, John Rizzo A., and John Elefteriades A. "Long-term Behavior of Aortic Intramural Hematomas and Penetrating Ulcers." The Journal of Thoracic and Cardiovascular Surgery 151.2 (2016): n. pag. Web. 5. Chung, Jonathan H., Brian Ghoshhajra B., Carlos Rojas A., Bhavika Dave R., and Suhny Abbara. "CT Angiography of the Thoracic Aorta." Radiologic Clinics of North America 48.2 (2010): 249-64. Web. 6. D'annoville, Thomas, Baris Ozdemir Ata, Pierre Alric, Charles Marty-Ané Henri, and Ludovic Canaud. "Thoracic Endovascular Aortic Repair for Penetrating Aortic Ulcer: Literature Review." The Annals of Thoracic Surgery 101.6 (2016): 2272-278. Web.

REFERENCES

7. Eggebrecht, H., B. Plicht, P. Kahlert, and R. Erbel. "Intramural Hematoma and Penetrating Ulcers: Indications to Endovascular Treatment." European Journal of Vascular and Endovascular Surgery38.6 (2009): 659-65. Web. 8. Evangelista, A., M. Czerny, C. Nienaber, M. Schepens, H. Rousseau, P. Cao, S. Moral, and R. Fattori. "Interdisciplinary Expert Consensus on Management of Type B Intramural Haematoma and Penetrating Aortic Ulcer." European Journal of Cardio-Thoracic Surgery 47.2 (2014): 209-17. Web. Gunn, Martin L. D., Bruce Lehnert E., Rachel Lungren S., Chitti Narparla Babu, Lee Mitsumori, Joel Gross A., and Benjamin Starnes. "Minimal Aortic Injury of the Thoracic Aorta: Imaging Appearances and Outcome." Emerg Radiol Emergency Radiology 21.3 (2014): 227-33. Web. 9. Husainy, Mohammad Ali, Farhina Sayyed, and Sapna Puppala. "Acute Aortic Syndrome— pitfalls on Gated and Non-gated CT Scan." Emerg Radiol Emergency Radiology 23.4 (2016): 397-403. Web. 10. Lempel, Jason K., Aletta Frazier Ann, Jean Jeudy, Seth Kligerman J., Randall Schultz, Hammed Ninalowo A., Elliott Gozansky K., Bartley Griffith, and Charles White S. "Aortic Arch Dissection: A Controversy of Classification." Radiology 271.3 (2014): 848-55. Web. 11. Maddu, Kiran K., Waqas Shuaib, Juan Telleria, Jamlik-Omari Johnson, and Faisal Khosa. "Nontraumatic Acute Aortic Emergencies: Part 1, Acute Aortic Syndrome." American Journal of Roentgenology 202.3 (2014): 656-65. Web. 12. Mokrane, F.z., P. Revel-Mouroz, B. Lebes Saint, and H. Rousseau. "Traumatic Injuries of the Thoracic Aorta: The Role of Imaging in Diagnosis and Treatment." Diagnostic and Interventional Imaging 96.7-8 (2015): 693-706. Web. 13. Piffaretti, Gabriele, Mario Galli, Chiara Lomazzi, Marco Franchin, Patrizio Castelli, Giovanni Mariscalco, and Santi Trimarchi. "Endograft Repair for Pseudoaneurysms and Penetrating Ulcers of the Ascending Aorta." The Journal of Thoracic and Cardiovascular Surgery 151.6 (2016): 1606-614. Web

THORACIC AORTA