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Slide 1 :
Aortic Dissection Dr. Henry K. Cheng Mackay Memorial Hospital Emergency Department
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Epidemiology 2-3X more in male majority between 50-70 years of age relatively rare before 40 y/o except in association with : Marfan’s syndrome, Ehlers-Danlos syndrome, congenital heart disease, familial incidence, pregnancy, coarctation of aorta, Turner’s syndrome and trauma history of systemic hypertension occur in more than 2/3 of patients
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Pathophysiology and pathoanatomy 3 layers of aortic wall : intima, media, and adventita medial degeneration: a process of degeneration characterized by loss of smooth muscle cells and elastic tissue that is accompanied by scarring, fibrosis, hyalin-like changes. cystic medial necrosis is no longer used mechanism: medial degeneration, repeated flexion of the aorta, and hydrodynamic stresses on the aortic intima, an aortic dissection occurs 2 important factors determine the continued dissection of aorta: degree of elevation of blood pressure and the steepness(slope) of the pulse wave(dP/dT)
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Classification DeBakey : Type I: involve the ascending aorta, aortic arch and the decending aorta Type II:confined to the ascending aorta Type III: confined to the descending aorta Type IIIA: above the diaphragm Type IIIB: below the diaphragm Stanford: Type A:involve the ascending aorta Type B: do not involve the ascending aorta Acute: less than 2 weeks Chronic: more than 2 weeks
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Clinical Findings(I) Diagnostic Findings Pain is by far the most common presenting complaint(90%) pain is decribed as “tearing, knifelike” usually the pain occurs quite abruptly and is most severe at onset neurologic deficit(20%) syncope(5%)
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Clinical Findings(II) Physical Examination pulse deficits and discrepancies in BP between limbs are key diagnostic clues pulse deficits (50%) aortic regurgitation(50%) neurologic findings(20%): altered sensorium, hemiplegia, hemianesthesia, gaze preference to the affected side
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Ancillary Evaluation Routine Lab. Tests: non-specific EKG: shows LVH reflecting long-standing hypertension the EKG is useful in excluding myocardial infarction
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Radiography (I) Chest X ray mediastinal widening(75%) “calcium sign” -uncommon but highly specific, >5mm double-density appearance of the aorta a localized bulge along a normally smooth aortic contour a disparity in the caliber between the descending and ascending aorta obliteration of the aortic knob displacement of the trachea or nasogastric tube to the right by the dissection pleural effusions(left)
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Radiography(II) Echocardiography transthoracic approach: M-mode & 2-D=low sensitivity and specificity transesophageal = more accuracy and very sensitive, can be done in ER (safer).
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Radiography (III) Computed Tomography dilatation of the aorta identification of an intimal flap differential rates of flow in true and false lumina the clear demonstration of both the true and false lumina
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Radiography(IV) limitations of CT scan: it dose not provide information about the presence of aortic regurgitation no information about the relationship of the dissection to the major arterial branches of the aorta time-consuming and requires the patient to be outside ER advantages over aortography: greater contrast resolution and detects small or delayed differences in the opacification of true and false channels may be able to detect a thrombosed false lumen despite nonopacification does not require arterial catheterization
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Radiology(V) Aortography filling of a false channel or channels with or without an intervening intimal flap distortion of the true lumen by either a patent or thrombosed false lumen thickening of the aortic wall by more than 5-6 mm caused by a thrombosed false lumen displaced intimal calcification
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Radiography(VI) disadvantages of aortography: most invasive, most expensive risks of intravenous contrast material inadequate detection of pleural leak advantages of aortography: accurate for determining the site of the initmal tear and extent of the dissection easily demonstrated aortic regurgitation the only procedure that demonstrates the extent and location of dissection into aortic side branches
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Radiography(VII) Magnetic Resonance Imaging shows the site of intimal tear, type and extent of dissection, presence of aortic insufficiency, and differential flow velocities in the true and false channels and in the aortic side branches advantages: no contrast material, no ionizing radiation, noninvasive
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Differential Diagnosis Chest pain is the most common symptom in AD Acute myocardial infarction pain is more typically pressurelike but may radiate to the arms or neck pain does not typically migrate over time CK-MB levels are elevated Pulmonary embolus pain is generally respirophasic hypoxemia secondary to ventilation/perfusion mismatch Pericarditis pain typically changes with position auscultation may reveal a pericardial friction rub EKG is common diagnostic(ST-segment elevation prominent in V5-6 and lead I)
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Treatment(I) Emergency Department Objective:maintaining systolic blood pressure between 100 and 120 mmHg Antihypertensive agents: Sodium nitroprusside: 50-100mg +D5W 500ml infused at a rate of 0.5~3 ug/min Beta-adrenergic blocker:reduce the heart rate to 60-80/m Propranolol: 1mg IV q 5 min, MAX initial dose < 0.15mg/kg Metoprolol Esmolol Trimethaphan camsylate: a ganglionic blocking agent 500mg +D5W 500ml infused at a rate of 1-2 mg/min Labetalol:both alpha and beta-blockade properties initial bolus 10-20 mg, then infuse of
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2 important factors determine the continued dissection of aorta: degree ofType I: involve the ascen
2 important factors determine the continued dissection of aorta: degree ofType I: involve the ascending aorta, aortic arch and the decending aorta ...