Radiological approach to aortic aneurysm and acute diseases

Disease of aorta and aneurysm by Dr. Crystal KC

1. RADIOLOGICAL APPROACH TO AORTIC ANEURYSM AND ACUTE DISEASES Dr. Crystal K C Resident MD Radiodiagnosis NAMS, BIR Hospital

2. Anatomy Aorta begins in the aortic root as ascending aorta. The aortic arch begins at the innominate artery and ends at the ligamentum arteriosum. Its most distal aspect, which is often slightly narrowed, is termed the “aortic isthmus .” In some cases small diverticulum called ductus diverticulum . The descending aorta begins at the ligamentum. Its proximal portion may appear slightly dilated and has been termed the “aortic spindle.”

3. Fig: Normal angiographic anatomy: Arch(DSA) shows normal branches

4. Branches of Aorta Descending thoracic aorta • Visceral branches: Pericardial branches, Bronchial arteries (one on the right and two on the left side), Mediastinal branches, Phrenic branches. • Parietal branches: Intercostal arteries, subcostal arteries Abdominal aorta Ventral : Unpaired- coeliac axis, superior mesenteric, inferior mesenteric Lateral : Paired-inferior phrenic , Middle suprarenal, Renal, Testicular or ovarian Dorsal : Lumbar (5-Paired), Median sacral (Unpaired) Terminal : Common iliac (Paired).

5. Variant Anatomy This normal branching pattern is seen in about 70% of individuals . Left CCA and Brachiocephalic trunk have common origin -20–30 % of individuals, most common => Bovine arch. In about 5% of cases, the left vertebral artery arises as a separate branch directly from the aorta, between the left common carotid artery and the left subclavian artery . Common origin of both CCA. Paired brachiocephalic trunk.

6. Variant anatomy – Abdominal Aorta left hepatic artery originating from the left gastric artery (25%). The “replaced origin” of the right hepatic artery from the superior mesenteric artery (SMA) in 10% of the The common hepatic artery may take origin directly from the SMA or the aorta The celiac axis and SMA may have a common origin.

7. Aneurysm A localized abnormal dilatation of an artery, vein, or the heart. Aortic aneurysm thoracic abdominal thoracoabdominal

8. Aortic root 3.6 cm AA 1 cm proximal to arch 3.5 cm Proximal des aorta 2.6 cm Middle des aorta 2.5 cm Distal des aorta 2.4 cm Abdominal aorta 2.0 cm Normal diameter

9. Maximal Normal Aortic Diameter Segment Size (cm) Ascending 4 Descending thoracic 3 Abdominal 2

10. CLASSIFICATION TRUE VS FALSE True aneurysm all layers False aneurysm- contained by adventitia or perivascular connective tissue and organized hematoma FUSIFORM VS SACCULAR Fusiform aneurysm Circumferential involvement Saccular aneurysm Portion of a wall

11. Causes of aortic aneurysms Atherosclerosis(70-90%) Traumatic ( 15-20%) Congenital (2%)- aortic sinus, postcoarctation, ductus diverticulum. Syphilis Mycotic Cystic media necrosis( Marfan, Ehlers- Danlos syndrome, annuloaortic ectasia) Inflammation of media+ adventitia- Takayasu arteritis, Giant cell arteritis, Rheumatic fever, Rheumatoid arthritis, Ankylosing spondylitis, Reiter syndrome, etc.

12. Atherosclerotic aneurysm Cause - Atherosclerosis of the aorta In elderly Location Descending aorta distal to Left SCA. Infrarenal aorta Thoracoabdominal Fusiform- 80%, saccular-20%

13. Mycotic aneurysm I nfectious break in the wall of an artery with formation of a blind , saccular outpouching that is contiguous with the arterial lumen. Predisposing factors IV drug abuse Bacterial endocarditis (12%) Immunocompromise (malignancy, steroids, chemo, DM, etc.) Infected prosthetic valves or sternal wires

14. Organisms S. aureus (53%) Salmonella (33-50%) Streptococcus Mycobacterium ( contiguous spread from spine/lymph node) The most common cause of an infected aneurysm is direct deposition of circulating bacteria in a diseased, atherosclerotic, or traumatized aortic intima , after which organisms penetrate the aortic wall through breeches in intimal integrity to cause microbial arteritis .

15. Site Ascending aorta > visceral artery > intracranial artery > upper/lower extremity artery. Poor prognosis due to quick expansion- rupture.

16. Findings in mycotic aneurysm Unusual location (non infrarenal) Saccular aneurysm Irregular contour Lack of calcification Rapid enlargement Signs of infection Perianeurysmal air Perianeurysmal fluid collection with enhancing wall Enlarged perianeursymal lymph nodes Osteomyelitis of adjacent vertebra

17. Images obtained in a 73-year-old man with infected i nfrarenal aortic aneurysm associated with osteomyelitis and psoas muscle abscess. (a) Transverse contrast-enhanced CT scan shows an infrarenal aortic aneurysm ( * ) measuring 11 x 6 cm in diameter associated with a left psoas muscle abscess (arrowhead ) and vertebral body destruction (arrow ). (b) Sagittal T1-weighted MR image shows abnormal signal intensity (arrow) in the bone marrow of the vertebral body.

18. Abdominal aortic aneurysm Abdominal aortic aneurysms (AAAs) are segmental dilatations of the aortic wall that cause the vessel to be larger than 1.5 times its normal diameter or that cause the distal aorta to exceed 3 cm. Prevalence: Increases with age Greater with atherosclerotic disease Male predominance Whites: Blacks = 3:1

19. Risk factors: male age >75 years white race prior vascular disease hypertension cigarette smoking family history hypercholesterolemia

20. Associated with: occlusion of inferior mesenteric artery (80%) occlusion of lumbar arteries (78%) stenosis of renal artery (22-30%) stenosis / occlusion of celiac trunk / SMA (22%) isolated iliac + femoral artery aneurysm (16%) common iliac (89%), internal iliac (10%), external iliac (1%) visceral + renal artery aneurysm (2%)

21. Clinical abdominal pain (37%) asymptomatic (30%) abdominal mass (26%)

22. Anatomical classification In relation to the renal arteries. Suprarenal Juxtarenal (within 1.5 cm of renal artery origin) Pararenal (involving one or both renal arteries) Infrarenal ~90-95% of AAAs -infrarenal Extension above renal arteries rare Extension to common iliac arteries fairly common (66-70%).

23. Progression of AAA Over time, ~80% enlarge . Most enlarge slowly. Larger- faster. smaller-slower >=5cm 4-8mm/year 4-5cm 3-7mm/year <4cm 2-5mm/year

24. Imaging modalities Plain X -ray: mural calcification (75-86%) US initial screening If the aneurysm is approaching 5 cm or more or if rapid enlargement is seen on serial US images CT and CTA/ MR and MRA Angiography

25. Curvilinear calcification (arrowheads) is consistent with a significant size calcified abdominal aortic aneurysm. The lateral view clearly shows calcification of both walls. Abdominal aortic aneurysm can be diagnosed with certainty- egg shell calcification.

26. USG >98% accuracy in size measurement screening examination of choice as a result of its relative availability, speed, low cost and no radiation. Problems with obese pt distended bowel with gas proximal iliac arteries

27. US findings:- Focal dilatation beyond normal. Any increase in the size as the aorta travels distally is abnormal

28. US findings of rupture Partially encapsulated hematomas - a hypoechoic or anechoic paraaortic space-occupying lesion. Color Doppler-site of leak or extravasation

29. CT-non-contrast perianeurysmal fibrosis (10%) "crescent sign" = peripheral high-attenuating crescent in aneurysm wall (= acute intramural hematoma) = sign of impending rupture

30. CT-contrast-enhanced Accurately demonstrates dilation of the aorta Extent of aneurysm Degree of calcification, presence of mural thrombus Major branch vessels proximally and distally-- helps in determining the appropriate intervention (surgical or endovascular repair). Assessment of other abdominal organs possible. CTA -multiplanar assessment of the aneurysm and associated relevant vessels (visceral arteries, iliac and femoral arteries). Complications

31. MRI MRI and MRA good alternatives in impaired renal function and allergy to ICM

32. Angiography Often ordered for preoperative evaluation in patients with manifestations of atherosclerotic vascular disease such as renal artery stenosis or peripheral vascular disease. The role of angiography is in planning surgical or endovascular repair. Largely replaced by CTA or MRA .

33. Angiography findings focally widened aortic lumen >3 cm mural clot (80%) apparent normal size of lumen secondary to mural thrombus (11%) slow antegrade flow of contrast medium

34. Lateral aortogram in a patient with severe mid back pain and lumbar spine images which demonstrated anterior erosion of the lower thoracic vertebral bodies . The angiogram demonstrates that this has been caused by a pulsatile thoracoabdominal aortic aneurysm.

35. Complications: Rupture (25%) Peripheral embolization Infection Spontaneous occlusion of aorta Pseudoaneurysm Compression of adjacent structures Anterior vertebral scalloping

36. Rupture Sites into retroperitoneum: commonly on left into GI tract: massive GI hemorrhage into IVC: rapid cardiac decompensation Symptoms of rupture sudden severe abdominal pain ± radiating into back fainting, syncope, hypotension Prognosis:64-94% die before reaching hospital

37. High risk for rupture of AAA >5cm Rapid growth ( >5mm per 6 months) or a diameter of 7cm Mycotic aneurysm Signs of AAA rupture Primary signs Periaortic stranding Retroperitoneal hematoma Extravasation of IV contrast Secondary signs High attenuating crescent sign Focal discontinuity of intimal calcification Tangential calcium sign Draped aorta sign Thrombus fissuration

38. Foccal discontinuity of intimal calcification Tangential calcium sign: Intimal calcification points away from the aneurysm and there is retroperitoneal leakage.

39. LEFT: Subtle periaortic stranding, MIDDLE: Hemorrhage into posterior pararenal and perirenal compartment, RIGHT: Extravasation of iv. contrast

40. CECT-draped aorta sign: Posterior wall of the aneurysm is not seen and the aneurysm extends around the vertebral body and on left paravertebral region An important imaging feature that may be seen in a contained rupture of an abdominal aortic aneurysm is the draped aorta sign . This sign is considered present when the posterior wall of the aorta either is not identifiable as distinct from adjacent structures or when it closely follows the contour of adjacent vertebral bodies.

41. Aortic aneurysm with high-attenuation crescents

42. Ruptured aneurysm anterior displacement of kidney extravasation of contrast material fluid collection / hematoma within posterior pararenal + perirenal spaces free intraperitoneal fluid

43. False positive CT dx of aneurysm rupture Asymmetric aneurysm thrombus Partial volume averaging of periaortic tissue at the level of the aneurysm neck. Perianeurysmal fibrosis( in NECT) Unopacified 3 rd and 4 th portion of Duodenum. Retroperitoneal lymphadenopathy.

44. Pre-op assessment of AAA We should assess : Maximum diameter of the aneurysm Proximal and distal extent of aneurysm Assessment of iliac and renal arteries Perianeurysmal fibrosis Congenital variations: Accessory renal arteries Retroaortic course of left renal vein CT/CTA or MR/MRA is required for pre-op assessment. USG is not enough because: Perianeurysmal soft tissue can not be assessed Relation with renal arteries & congenital variations are difficult to assess

45. Intervention Open surgery Endovascular repair

46. Open surgery- indications (1) Any patient with a documented rupture or suspected rupture ; (2) symptomatic or rapidly expanding aneurysm , regardless of its size; (3) aneurysms larger than 5 cm in diameter; (4) complicated aneurysms with embolism, thrombosis, or symptomatic occlusive disease; and (5) atypical aneurysms ( eg , dissecting , mycotic , saccular ).

47. Endovascular aortic aneurysm repair (EVAR) EVAR has been shown to reduce blood loss, operative time, length of hospital stay, mortality, and morbidity compared with open surgical repair of infrarenal abdominal aortic aneurysms (AAAs). 

48. Endovascular repair such as stent-graft placement

49. Endoleaks. Persistent flow in an excluded aneurysmal sac after endovascular treatment with stent graft. Type I: leak at graft attachment site Ia : proximal, Ib : distal and Ic : iliac occluder Type II: aneurysm sac filling branch vessel {M/C} IIa : single vessel, IIb : 2 or more vessels Type III: leaks through defect in graft IIIa junctional separation of modular component, IIIb fracture or holes Type IV: leak through the graft fabric as result of graft porosity Type V : continued expansion of aneursymal sac without demonstrable leak on imaging (ENDOTENSION)

50. Close follow-up is required CT scans performed at one, six, and 12 months, and then yearly

51. Thoracic aortic aneurysm Aneurysmal dilatation of ascending, arch, or descending thoracic aorta. Aneurysm - localized or diffuse dilatation of more than 50% normal diameter of the aorta.

52. Anatomical classification Type Cause 1.Aneurysm of sinus of Valsalva 2 . Ascending aorta 3. Arch of aorta 4. Descending aorta 5. Aortic isthmus 1.Congenital, Syphilis 2. Atherosclerosis, Marfan syndrome, Ehlers- Danlos syndrome, syphilis, mycotic aneurysm 3. Atherosclerotic 4. Atherosclerotic 5. Post traumatic aneurysm

53. Descending aorta > ascending aorta > Arch of Aorta aneurysms Descending aortic thoracic aneurysms may extend distally to involve the abdominal aorta and create a thoracoabdominal aortic aneurysm. Mean age 65 years M:F 3:1 Clinical features Substernal/back/shoulder pain SVC syndrome ( venous compression) Dysphagia (esophageal compression) Stridor, dyspnea ( tracheobronchial ) Hoarseness (recurrent laryngeal nerve com)

54. Imaging of thoracic aneurysms: Modalities: CXR CT/CTA MR/MRA TEE Aortography

55. CXR Many readily visible on CXR. Findings (1) widening of the mediastinal silhouette, (2) enlargement of the aortic knob (3) displacement of the trachea/esophagus from the midline.

56. TEE can be quickly performed at bedside under sedation without radiation or the injection of contrast material. excellent at detecting pericardial effusion and aortic regurgitation 90% accuracy in imaging intimal membranes for signs of aortic dissection Disadvantage - poorly depicts aneurysms below the diaphragm and in the transverse aortic arch . Atherosclerotic and enlarged descending aorta with eccentric thickening of the wall.

57. CT/CTA primary diagnostic test of choice in most institutions reliable test for diagnosing aneurysm and dissection effective to define maximum diameter To monitor diameter over time. Findings: increase in aortic diameter outward displacement of calcium of the aortic wall.

58. MR/MRA Alternative of CT/CTA specially in pt with impaired renal function and allergy to ICM Velocity-encoded cine MRI measurement of the differential flow velocity in the true and false channels to quantify the volume of concomitant aortic regurgitation in patients with aortoannular abnormalities.

59. Aortography The criterion standard until late But rarely used with the advent of helical CT/MRI/MRA/TEE Still a modality for pre-op evaluation of thoracic aortic aneurysms for precise definition of the anatomy of the aneurysm and great vessels Ascending aortogram showing ascending aortic aneurysm.

60. Thoraco- Abdominal Aneurysms Type I and Type II TAAAs involve the entire thoracic aorta extending distally to or beyond the renal arteries, respectively. Type III TAAAs start below the T6 level and extend beyond the renal arteries. Type IV TAAAs are the simplest form, starting at the level of the celiac axis and extending distal into the infrarenal aorta or iliac arteries . Type VI: start below the T6 level and extend upto the renal arteries.

61. Aortic Dissection Separation of the aortic intima with tear in it communicating with the true lumen. True lumen-inside the intima False lumen-outside the intima Most dissections arise either just distal to the aortic valve or the aortic isthmus

62. Pathophysiology The essential feature of aortic dissection is a tear in the intimal layer , followed by formation and propagation of a subintimal hematoma. The dissecting hematoma commonly occupies about half and occasionally the entire circumference of the aorta. This produces a false lumen or double-barreled aorta, which can reduce blood flow to the major arteries arising from the aorta. Aortic dissection often occurs along the right lateral wall of ascending aorta and descending thoracic aorta just below the ligamentum arteriosum. The dissection usually propagates distally down the descending aorta and into its major branches, but it also may propagate proximally.

63. New Theory

64. C/F:- Predisposing factors Starts in fusiform aneurysms in 28 % cases Hypertension (60-90%) Marfan syndrome Ehlers- Danlos syndrome Trauma Catheterization Aortitis Sudden onset of sharp, tearing, intractable chest pain, may radiate to back, esp. interscapular region Previously hypertensive, now possible shock (Signs of peripheral organ blood flow hypoperfusion, including decreased urine output, ischemia bowel, ischemia pain of lower extremities, etc.) Asymmetric peripheral pulse Diastolic murmur or bruit of aortic regurgitation Pulmonary edema Signs result from compression of adjacent tissues

65. Imaging Findings   Chest X-ray:   Mediastinal widening Displacement of intimal calcifications Apical pleural cap Left pleural effusion Displacement of endotracheal tube or nasogastric tube

66. CT Intimal flap Displacement of intimal calcification Differential contrast enhancement of true versus false lumen  MRI Intimal flap Slow flow or clot in false lumen TEE Intimal flap Angiography Intimal flap Double lumen Compression of true lumen by false channel Obstruction of branch vessels 

67. True versus false channel

68. TEE view of the descending thoracic aorta in the horizontal plane. An aortic dissection is manifested by the presence of a true lumen (TL), a false lumen (FL), and a free-floating intimal flap (F). LA left atrium

69. Axial double-inversion-recovery MR images (TR/TE, 1875/18; inversion time, 150 msec) of 37-year-old man with Marfan syndrome . Image shows classic aortic dissection with double-channel aorta. True lumen ( straight arrow ) is smaller than false lumen ( curved arrow ). High-velocity flow in true lumen causes signal void. Slower flow with higher signal can be seen in false lumen.

70. 61-year-old man with chest pain and acute type A aortic dissection. Axial enhanced CT scan of ascending aorta shows type A aortic dissection with intimomedial tear ( arrows ) entering false lumen (F) from true lumen (T). DA = descending thoracic aorta, PA = pulmonary artery.

71. CT scan obtained at one-quarter distance along length of dissected portion of aorta shows descending aortic dissection flap ( arrows ) that is curved toward false lumen (F) . Beak sign ( arrowheads ) is present in false lumen. Note that false lumen area is larger than true lumen area

72. CLASSIFICATION SYSTEMS FOR AORTIC DISSECTION Site of dissection Classification system Crawford DeBakey Stanford Both ascending and descending aorta Proximal dissections Type I Type A Ascending aorta and arch only Proximal dissections Type II Type A Descending aorta only (distal to left subclavian artery) Distal dissections Type III IIIa—limited to thoracic aorta IIIb—extends to abdominal aorta Type B

73. Aortitis Causes: Takayasu arteritis Rheumatic fever Reiter’s syndrome Syphilis Begins above sinotubular ridge Giant cell arteritis Ankylosing spondylitis Crosses sinotubular ridge and dilates both root and ascending aorta Sinotubular Ridge- The sinotubular ridge is the portion of the ascending aorta just distal to the sinuses of Valsalva at the junction with the tubular segment of the ascending aorta. 

74. Takayasu arteritis Granulomatous vasculitis of unknown etiology Commonly affects the thoracic and abdominal aorta causes intimal fibroproliferation of the aorta, great vessels, pulmonary arteries, and renal arteries results in segmental stenosis, occlusion, dilatation, and aneurysm formation in these vessels. Takayasu arteritis is the only form of aortitis that causes stenosis and occlusion of the aorta.

75. Pathophysiology: Not fully elucidated to date. begins as a nonspecific, cell-mediated inflammatory process in the patient's first 2 decades of life and progresses to the formation of fibrotic stenoses of the aorta and its major branches.

76. Clinical Details: 15-40 years 8:1 females, Early and late phases. Presenting symptoms are Non-specific – F ever, A rthralgia and weight loss. In pulseless phase- s/s of ischemia of limb, renovascular hypertension. The early phase – inflammatory -prepulseless phase Present with constitutional sign and symptoms with positive lab findings (Increased ESR, positive C-reactive protein). Radiological findings show only thickened vessel wall on CT and MR. Angiography is usually negative . The late phase occlusive -pulseless phase. has thickening of media and adventitia. Angiographic findings show smooth long segment stenosis and occlusions of the proximal great vessels. A 5- to 20-year interval between two phases.

77. Four types of late-phase Takayasu arteritis On the basis of the sites of involvement Type I – aortic arch and its branches Type II – thoraco -abdominal aorta and its major branches Type III - Combination of type I and II Type IV – any portion of the aorta with its branches + pulmonary artery. {source: Grainger}

78. Preferred Examination Angiography - criterion-standard imaging CTA and MRA : Of late have become equally valuable tools.

79. Advantages of CTA and MRA over conventional angiography: large fields of view noninvasive nature intravenous rather than intra-arterial contrast material increasing resolution of MDCT. Particularly useful in pediatric groups who are poor candidates for conventional angiography. Advantages of MRI over CT Better soft-tissue contrast- valuable in differentiating active versus quiescent forms of Takayasu disease. No use of ICM

80. Imaging Findings Angiography: The angiographic features occur late in the course of the disease and include luminal irregularity vessel stenosis, occlusion, dilatation, or aneurysms in the aorta or its primary branches. CTA and MRA- thickened wall of aorta with crescents and indistinct outlines Associated aneurysms may be saccular or fusiform. USG/Doppler study in accessible vessels. Shows wall thickness and stenosis.

81. Aortogram of a 15-year-old girl with Takayasu arteritis. Note large aneurysms of descending aorta and dilatation of innominate artery

82. Coronal MRI of abdomen of 15-year-old girl with Takayasu arteritis. Note thickening and tortuosity of abdominal aorta proximal to kidneys.

83. Intervention Corticosteroid- acute phase Bypass graft surgery is the procedure with the best long-term patency rate Percutaneous angioplasty : C/I in acute phase. Best results with short-segment stenosis. Stents

84. THANKYOU

85. References Textbook of radiology and imaging-David Sutton CT and MRI of the whole body-John R. Haaga Fundamentals of diagnostic radiology-William E.Brant Https://Radiologykey.com//thoracicaortic-aneurysms Takayasu arteritis : imaging spectrum at multidetector CT angiography; F P ZHU et al.; British Journal of Radiology; 2012. Acute Traumatic Aortic Injury: Imaging Evaluation and Management; Scott D. Steenburg;RSNA ; 2008:248; 3.