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dissecting aortic aneurysm; aortic dissection (acute aortic syndrome)

Includes acute aortic syndromes: 1) acute aortic dissection 2) aortic intramural hematoma 3) penetrating atherosclerotic ulcer Classification: 1) proximal (type A): those that involve the ascending aorta 2) distal (type B): a) involvement limited to the descending aorta* b) origin distal to the left suclavian artery 3) acute: < 2 weeks 4) chronic: > 2 weeks * rarely isolated to the infrarenal aorta Etiology: 1) cystic medial necrosis 2) hormonal state of pregnancy predisposes to dissection during labor 3) congenital disorders a) Marfan's syndrome b) Ehlers-Danlos syndrome c) Turner's syndrome d) coarctation of the aorta 4) hypertension 5) trauma including iatrogenic trauma 6) inflammatory conditions a) polychondritis b) temporal arteritis 7) cocaine increases risk Epidemiology: 1) may occur at any age 2) mean age is 59 years 3) male/female ratio is 3/1 Pathology: 1) intimal tear a) primary b) secondary to cystic medial necrosis with intramural hemorrhage c) penetration of blood from the lumen into the media with separation of the intimal & adventitial aortic layers 2) spontaneous aortic intramural hematoma a) formation within the vessel wall from diseased vaso vasorum b) splits aorta into 2 layers creating a false lumen c) no intimal tear 3) penetrating aortic ulcer a) gradual erosion of the internal elastic lamina by an expanding atheromatous plaque b) occurs in descending thoracic aorta c) generally does NOT propagate longitudinally 4) propagation may occur in the anterograde or retrograde direction (exception is penetrating aortic ulcer) 5) a secondary intimal tear may occur at the aortic/iliac bifurcation to produce a double-barrel aorta Clinical manifestations: 1) pain is the predominant symptom a) sudden, sharp, crushing substernal &/or back pain - chest pain, abdominal pain &/or back pain [3] b) may be described as ripping or tearing pain c) often migrates to the neck, jaw, flanks or legs d) onset is so catastrophic that patients may stagger or fall to the ground e) if onset is gradual, pain may be absent 2) generally blood pressure is maintained in contrast to MI a) hypertension at presentation is more common than hypotension b) patients with proximal dissection may present with hypotension; consider 1] pericardial tamponade 2] aortic rupture c) if subclavian artery is involved, blood pressure measurements in affected arm may be low 3) loss of peripheral pulse a) common with proximal dissection (50%) - may occur if subclavian artery is involved b) uncommon with distal dissection 4) neurologic manifestations are more common with proximal than distal aortic dissection (36% vs 6%) a) mental status changes may occur secondary to impaired cerebral perfusion or administration of narcotics for pain control b) syncope may occur secondary to pain or hypotension or may be the presenting symptom c) hemiplegia or paraplegia may be present d) peripheral ischemic neuropathy 5) dyspnea is generally present, but rarely the presenting symptom 6) aortic insufficiency a) occurs in 2/3 of patients with proximal dissection b) generally the cause of heart failure in patients with aortic dissection c) diastolic murmur e) elevated central venous pressure may be observed from right heart failure as a consequence of left heart failure 7) pericardial friction rub (rare) is often followed by pericardial tamponade - pulsus paradoxus 8) tracheal tug due to traction on the left main bronchus during systolic expansion of dissected aorta (rare) 9) clinical examination insufficiently sensitive to rule out aortic dissection [8] Laboratory: - D-dimer within first 24 hours is useful for ruling out aortic dissection [4] - with cutoff of 500 ng/mL: - negative likelihood ratio = 0.07 - positive likelihood ratio = 1.82 Special laboratory: - electrocardiogram: 1) sinus tachycardia 2) low voltage (LVH [8]) 3) ST segment depression is most mommon ECG abnormality [16] 4) generally does NOT show evidence of myocardial ischemia unless dissection occludes a coronary artery - ST segment dep Radiology: 1) chest X-ray may show widening of aorta - widened mediastinum especially with ascending aortic dissection [16] - calcific plaques on intima may be widely separated from outer border of aorta 2) CT angiography diagnostic test of choice [3] a) high sensitivity & specificity b) FAST 3) CT or MRI of thorax* - useful for chronic aortic dissection in stable patients - a dark band seen bisecting the aorta into two unequal parts [16] (CT image) - a dissection flap in the aorta is seen in another view [16] (CT image) 4) transesophageal echocardiogram (TEE)* a) visualization of true & false lumens based on presence or absence of blood flow [16] b) intimal flap c) associated aortic insufficiency d) involvement of proximal coronary arteries 5) aortic angiography a) previously gold standard b) extent of dissection c) degree of branch vessel involvement including coronary arteries d) associated aortic regurgitation * CT, MRI & TEE with equally reliable diagnostic value [5] Differential diagnosis: 1) myocardial infarction a) 1-2% of proximal aortic dissections extend to proximal coronary arteries & cause MI b) an ECG consistent with myocardial ischemia or infarction does not rule out concurrent aortic dissection 2) aortic insufficiency without aortic dissection 3) non-dissected aortic aneurysm 4) pericarditis 5) musculoskeletal chest pain 6) mediastinal tumors 7) pulmonary embolism 8) esophageal disorders 9) pleurisy Complications: 1) proximal progression of dissection a) distortion aortic valve to cause aortic regurgitation b) occlusion of coronary ostia resulting in MI c) hemopericardium - pericardial friction rub - cardiac tamponade d) swelling at the base of the aorta - pulsating sternoclavicular joint 2) distal progression of dissection a) occlusion of arterial branches - carotid artery - vertebral arteries - renal arteries - others b) loss of arterial pulses c) focal neurologic deficits d) patency of false lumen & maximum aortic diameter > 4 cm is associated with greater risk of progression to organ damage from perfusion insufficiency, aortic rupture & death 3) late aneurysm formation a) region of dissection b) aortic site remote from dissection c) cause of mortality in up to 30% of patients 4) thromboembolism: stroke, myocardial infarction [3] 5) cardiac tamponade [3] 6) hemothorax [16] Management: 1) pharmacologic therapy a) administration of thrombolytic agents is CONTRAINDICATED with aortic dissection b) beta blocker prior to vasodilator [7] - target pulse rate < 65/min [3] - systolic blood pressure < 120 mm Hg in 1st hour [3,7] - propranolol: 5 mg IV push, then 1 mg IV every 5 min up to 10 mg - labetalol: 5-10 mg IV every 2 min, then 40-120 mg/hour - metoprolol: 5 mg IV every 2 min up to 15 mg, then 50 mg PO every 6 hours - esmolol: 30 mg IV bolus, then 3-12 mg IV - verapamil or diltiazem if beta-blocker is contraindicated [7] c) vasodilators - nitroprusside (must use with beta-blocker) - begin 25 ug/min IV until systolic BP is 100-120 mm Hg - 20-800 ug/min IV - nifedipine (sustained-release) - 10 mg PO, then 10-40 mg PO every 8 hours - enalaprilat - 0.625 mg IV, then 0.625-5.0 mg IV every 6 hours - MKSAP19 nixes enalaprilat [3] - do not use hydralazine; increases shear stress [3] d) analgesia - morphine sulfate 3-5 mg IV every 10 min PRN to reduce systolic shear forces 2) surgery a) emergent surgery for proximal aortic dissection (type A)* or proximal aortic intramural hematoma - open surgical repair is standard of care (2022) [3] - resection of the most severely damaged aortic segment - decompression of the false channel - resuspension or replacement of the aortic valve may be indicated b) patients with distal aortic dissection (type B) - indications for emergent surgery - Marfan's syndrome - occlusion of a major aortic branch with visceral or limb ischemia - renal arteries involved* - progressive dilation or extension despite appropriate medical therapy - persistent pain - persistent severe hypertension - contained (aortic enlargement) or threatened aortic rupture - penetrating atherosclerotic ulcers > 20 mm in diameter & > 10 mm in depth - penetrating atherosclerotic ulcers associated with hematoma - uncontrolled pain - fenestration of dissecting membrane may be an option for emergent surgery - otherwise, elective surgery is an option - percutaneous placement of endovascular stent(s) - may be treated medically if no complications c) uncomplicated penetrating aortic ulcer may be treated medically 3) follow-up a) continued risk of re-dissection b) long blood pressure control even after surgical correction - beta blockers - verapamil c) chest X-ray & non-invasive imaging quarterly for 1st year & biannually thereafter * emergency surgery also indicated for Type A intramural hematoma [3] * type B aortic dissection extending through the level of the of the origins of the renal arteries are not necessarily canditates for urgent surgery

General

aortic aneurysm dissecting aneurysm

References

  1. DeGowin & DeGowin's Diagnostic Examination, 6th edition, RL DeGowin (ed), McGraw Hill, NY 1994, pg 243-45
  2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 262-264
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 16, 17, 18, 19. American College of Physicians, Philadelphia 1998, 2006, 2012, 2015, 2018, 2021. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  4. Suzuki T et al. for the IRAD-Bio Investigators. Diagnosis of acute aortic dissection by D-dimer: The International Registry of Acute Aortic Dissection Substudy on Biomarkers (IRAD-Bio) experience. Circulation 2009 May 26; 119:2702 PMID: 19433758
  5. Shiga T, Wajima Z, Apfel CC, Inoue T, Ohe Y. Diagnostic accuracy of transesophageal echocardiography, helical computed tomography, and magnetic resonance imaging for suspected thoracic aortic dissection: systematic review and meta-analysis. Arch Intern Med. 2006 Jul 10;166(13):1350-6. PMID: 16831999
  6. Nienaber CA, Rousseau H, Eggebrecht H et al Randomized comparison of strategies for type B aortic dissection: the INvestigation of STEnt Grafts in Aortic Dissection (INSTEAD) trial. Circulation. 2009 Dec 22;120(25):2519-28 PMID: 19996018
  7. Hiratzka LF et al 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with Thoracic Aortic Disease: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, American Association for Thoracic Surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of Thoracic Surgeons, and Society for Vascular Medicine. Circulation. 2010 Jul 27;122(4):e410. PMID: 20233780 (corresponding NGC guideline withdrawn Nov 2015)
  8. The NNT: Aortic Dissection Diagnostics and Likelihood Ratios, Explained http://www.thennt.com/lr/aortic-dissection/ - Klompas M Does this patient have an acute thoracic aortic dissection? JAMA. 2002 May 1;287(17):2262-72. PMID: 11980527
  9. Braverman AC Aortic dissection: prompt diagnosis and emergency treatment are critical. Cleve Clin J Med. 2011 Oct;78(10):685-96 PMID: 21968475 - Braverman AC Acute aortic dissection: clinician update. Circulation. 2010 Jul 13;122(2):184-8 PMID: 20625143
  10. Nienaber CA, Kische S, Rousseau H et al Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial. Circ Cardiovasc Interv. 2013 Aug;6(4):407-16 PMID: 23922146
  11. Nienaber CA, Clough RE. Management of acute aortic dissection. Lancet. 2015 Feb 28;385(9970):800-11. Review. PMID: 25662791
  12. Lederle FA, Powell JT, Nienaber CA. Does intensive medical treatment improve outcomes in aortic dissection? BMJ. 2014 Sep 9;349:g5288. Review. PMID: 25205491
  13. Lo BM. An evidence-based approach to acute aortic syndromes. Emerg Med Pract. 2013 Dec;15(12):1-23; quiz 23-4. Review. PMID: 24804329
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  15. Mussa FF, Horton JD, Moridzadeh R et al Acute Aortic Dissection and Intramural Hematoma: A Systematic Review. JAMA. 2016 Aug 16;316(7):754-63. Review. PMID: 27533160 Free Article
  16. Grimm L Aortic Dissection: A Double-Barreled Threat. Medscape. Oct 3, 2022 https://reference.medscape.com/slideshow/aortic-dissection-6009191
  17. Hameed I, Cifu AS, Vallabhajosyula P Management of Thoracic Aortic Dissection. JAMA. Published online February 16, 2023. PMID: 36795378 https://jamanetwork.com/journals/jama/fullarticle/2801761