Emergency diagnosis and treatment of aortic dissection

EMERGENCY DIAGNOSIS AND TREATMENT OF AORTIC DISSECTION

• Alan C. Braverman, M.D.

• Washington University School of Medicine

• Richard Devereux, M.D.

• New York Hospital/Cornell Medical Center

• Reed Pyeritz, M.D., Ph.D.

• University of Pennsylvania School of Medicine

• Joseph Coselli, M.D.

• Baylor College and Methodist Hospital

HISTORY

• 1761: Morgagni. Described dissecting aneurysm.

• 1804: Scarpa. Dissection related to “corrosion and rupture of the proper coats of the aorta.” Hematoma resulting from blood dissecting through the arterial wall.

• 1826: Laennec. Introduced term “dissecting aneurysm.”

• 1855: First antemortem diagnosis of dissection

• 1843-1863:

• Thomas Peacock. Cadaver experiments.

• 1. Ruptured intima (“lacerable”)

• 2. Blood penetrating the media

• 3. Distal reentry (“imperfect natural cure”)

HISTORY cont’d.

• 1864: von Recklinghausen. Attributed dissection to molecular changes in elastic tissue

• 1910: Babes, Mironescu. Aortic dissection could occur secondary to hemorrhage in vasa vasorum “dissecting mesarteritis.”

• 1910: Moriani. Microscopic changes in elastic tissue and connective tissue of media

• 1929: Erdheim. Cystic medial necrosis as underlying cause.

• 1934: Shennan. “Dissecting aneurysms”

• - degeneration of media frequent

• - neither atheroma nor lues were important

HISTORY cont’d.

• 1943: Oppenheimer and Taussig. First described ascending aortic aneurysm in the Marfan syndrome

• Etter and Glover. First described ascending aortic dissection in the Marfan syndrome

• 1955: McKusick. Documented that aortic dissection is a common cause of death in the Marfan syndrome

• 1958: Hirst. Review of 505 cases.

• Atherosclerosis not a related factor.

• 1973: Gore and Hirst. Rupture of vasa vasorum initiating event.

PATHOGENESIS

• 1. Intimal Tear as Primary Event

• Propagation of dissecting hematoma within media.

• Intramural hemorrhage due to rupture

• of vasa vasorum in a defective media

• - Intimal tear is a secondary event.

• - Propagation of cleavage plane by

• pulsatile force of blood.

RISK FACTORS

• ROLE OF ABNORMAL AORTIC MEDIA

• Cystic medial necrosis (Erdheim)

• - Not always present in dissecting aorta

• - Also present in patients without dissection

• Aortic dissection associated with connective tissue diseases

• - The Marfan syndrome, Ehlers-Danlos

• - Aortic dilation (thoracic or abdominal, often familial)

• Aortic dissection associated with

• - Bicuspid aortic valve

• - Aortic coarctation

• - Turner syndrome

RISK FACTORS cont’d.

• Marfan syndrome

• (Present in 5-10% of ascending aortic dissections, .02% of adults)

• Aortic dilatation

• Bicuspid aortic valve, coarctation

• Turner, Ehlers-Danlos (type IV), Noonan syndrome

• Family history of…

• Marfan syndrome, aortic dissection, aortic disease

• Hypertension

• (Present in 70-90% of dissections, but 20-40% of adults)

MARFAN SYNDROME

• FEATURES

• Very long arms, fingers, toes

• Pigeon breast or severe pectus carinatum

• Moderate or severe scoliosis

• Dislocated lenses

• Family history of the Marfan syndrome

1995 GHENT NOSOLOGY

• INDEX CASE: Major criteria in two systems and involvement of a third system

• FAMILY MEMBER: One major criterion in an organ system and involvement of a second organ system

CARDIOVASCULAR SYSTEM

• MAJOR CRITERIA

• dilation of ascending aorta

• aortic dissection

• MINOR CRITERIA

• mitral valve prolapse

• dilation of a main pulmonary artery

• premature mitral anular calcification (<40yrs.)

• descending thoracic or abdominal aortic aneurysm (< 50 yrs.)

• Cardiovascular involvement: one minor criterion

OCULAR SYSTEM

• MAJOR CRITERION

• Ectopia lentis

SKELETAL SYSTEM

• MAJOR CRITERIA

• Presence of at least four of the following:

• pectus carinatum

• pectus excavatum requiring surgery

• reduced upper to lower segment ratio or arm span to height ratio > 1.05

• wrist and thumb signs

• scoliosis > 20° or spondylolisthesis

• reduced extension at the elbows (<170°)

• medial displacement of the medial malleolus causing pes planus

• protusio acetabulae of any degree

PROLONGING LIFE

• Correct Diagnosis
• Medical Management
• Surgical Repair

DIAGNOSIS

• Clinical Evaluation

• Complete physical examination, including a careful musculoskeletal and skin examination

• Detailed medical and family history

• Electrocardiogram (EKG) and echocardiogram, looking for cardiovascualr involvement

• Eye examination by an ophthalmologist, who dilates the pupil and uses a slit lamp to assess for lens dislocation

MANAGEMENT

• UNDERLYING PRINCIPAL:

• Weak connective tissue cannot withstand normal tension on aorta.

• Since T~P x R

• Avoid strenuous exercise that increases BP.

• Use medicine to lower BP and dP/dT.

• ß-blockers
• Verapamil
• Other calcium blockers or ACE inhibitors that lower BP

• Replace aortic root/valve when aortic diameter > 6.0 cm without AR or > 5.0 cm with 3+ - 4+ AR.

ETIOLOGIC MECHANISM

• Intimal tear with secondary extension into media

• Hemorrhage into media precipitating secondary intimal tear

• Intramural hematoma

• Penetrating atherosclerotic ulcer

CLASSIFICATION

• DEBAKEY

• Type I

• Ascending aorta extending beyond arch

• Type II

• Ascending aorta only

• Type III

• Desending aorta

• Type IIIb

• Descending aorta extending below diaphragm

CLASSIFICATION cont’d.

• ASCENDING

• DISSECTIONS

• 65-75% of dissections

• Entry tear within a few centimeters of aortic valve

• 50% extend to iliac bifurcation

COMPLICATIONS

• 1. Rupture through outer wall of false channel

• *typically directly across from entry tear

• - pericardial tamponade

• - mediastinal or pleural rupture

• - exsanguination

• 2. Acute Aortic Regurgitation

• *50% of ascending dissections

• - medial split undermines support of aortic valve

• - may lead to severe CHF

COMPLICATIONS cont’d.

• 3. Branch Vessel Compromise

• - extension of dissection into a branch vessel

• - compression of orifice by intimal flap

• Clinical Scenarios

• - stroke

• - paraplegia

• - HTN-renal failure

• - visceral ischemia

• - MI

• 4. Aneurysmal Dilation and Subsequent Rupture

CLINICAL FEATURES

• Incidence uncertain.

• Available information: 5,000 – 10,000 cases/year in U.S.

• Number may be higher (not reportable condition, few autopsies now)

• Autopsy series – 0.2% autopsies

• Males 2-5 times more frequent than females

• Ascending dissections: 50-55 years old

• (<40 years: Marfan, pregnancy, AV disease)

• 5. Descending dissections: 60-70 years old

CLINICAL FEATURES cont’d.

• Most important factor

• leading to a correct diagnosis is

• a high clinical suspicion!

CLINICAL FEATURES cont’d.

• Sudden Onset Severe Pain

• May or may not be catastrophic
• Ripping, tearing
• Migratory
• Never experienced before
• Restless, sense of doom

• Look for underlying connective tissue disorder

• 3. Hypertension (especially moderate or severe)

• or known aortic aneurysm

PAIN CHARACTERISTICS

• SEVERE PAIN (90%)

• Most Severe at Onset

• Anterior Pain: Proximal Dissection

• Posterior Pain: Distal Dissection

• Migratory Pain

• Pain in these locations usually due to other more common disorders (MI, pneumonia, pleurisy, pulmonary embolism, pneumothorax, ulcer, cholecystitis, pancreatitis)

• Must consider aortic dissection in cases without other confirmed cause of pain.

CLINICAL FEATURES

PHYSICAL EXAMINATION

• Acutely ill

• Hypertension (catecholamines, renal ischemia)

• Hypotension (20%): acute complications

• Aortic insufficiency: (50-60% ascending dissections)

• Pulse deficits: (60% ascending dissections)

• May change over time
• Be wary the pt with acute (L) leg ischemia and negative embolectomy

• Other

• Sternoclavicular joint pulsation, high JVP, bruits, abdominal mass

NATURAL HISTORY

• Autopsy Series: >50% of people with untreated aortic dissections are dead within 48 hours.

• 1934 Shennan: >300 cases reviewed.

• 40% acute ascending dissections died suddenly.
• None lived > 5 weeks

• Anagnostopoulos et al. Am J Card 1972

• 973 pts with untreated proximal and distal dissections
• 50% died with 48 hours
• 84% died within 1 month

• 1% per hour risk of death in first 48 hours

Acute 0-14 days

• Acute 0-14 days

• Chronic 14+ days

DIAGNOSTIC EVALUATION

• Chest radiograph

• Transthoracic echocardiogram

• Transesophageal echocardiogram*

• Computed tomography*

• Magnetic resonance imaging*

• Aortography

• *Choose based on rapid availability and quality of performance

CHEST X-RAY

• Signs of dissection are indirect

• Abnormal aortic knob, widened mediastinum, pleural effusion

• Insensitive with variable inter-observer agreement

• Look for changes compared with old films

• Displaced intimal calcification (>5 mm) – useful in older patients

• Normal in 18%

• A Normal CXR Should Not Deter Further Evaluation.

TRANSESOPHAGEAL ECHO

• Procedure of first choice for dissection, if readily available

• Portability of equipment facilities emergency management by cardiologist in ER or ICU

• High sensitivity and specificity

• Additional information: - aortic regurgitation

• - pericardial effusion

• - ostia of coronary arteries

• - LV function

COMPUTED TOMOGRAPHY

• Rapid IV bolus and sequential imaging

• 88-100% accuracy

• Limitations:

• no evaluation of aortic regurgitation
• Limited information on branch vessels
• “streak artefacts” may cause false (+)
• (Bone-air interface may simulate flap)
• False (-) from poor bolus of contrast

• Useful for follow-up of dissections

MRI

• Good alternative to TEE or CT, if readily available

• High sensitivity and specificity

• Can detect slow blood leaks

• Non-invasive; neither x-rays nor contrast needed

• 90-100% accuracy

• Limitation: requires patient to be in claustrophobic apparatus without standard ECG monitoring

• Useful for follow-up of dissections

AORTOGRAPHY

• Identify intimal flap, true and false lumen

• Thickened wall (thrombosed false lumen)

• Aortic insufficiency, branch vessel involvement

• Diagnostic accuracy 90-95%

• 5-10% false (-) rate

• thrombosed false lumen
• simultaneous opacification of both lumens
• misses intramural hematoma

• Risks of procedure (time delay in type A)

• Coronary angiography usually not necessary in acute ascending dissection (surgeon can inspect coronaries)

TREATMENT

• ICU admission in a tertiary center

• Immediate cardiothoracic surgical consultation

• Close observation of BP, urine output, neurologic status

• Prompt blood pressure control is critical

• Can reduce propagation of dissection
• Decrease BP and LV contractility to decrease dP/dt
• Sodium nitroprusside + b – blocker
• and - blocker, Calcium channel blocker
• (heart rate slowing)

INDICATIONS FOR SURGERY

• Consider operative treatment for all patients

• Hypotension: Emergency surgery

• Ascending Dissection: Emergency surgery

• Descending Dissection:

• Operation in acute phase no difference in survival compared to medical therapy 35-75% mortality
• Higher risk of surgery with renal failure, visceral ischemia, age > 70 years

• Risk of surgery inversely related to experience with dissection surgery

GOALS OF SURGERY

• Excise the intimal tear

• Obliterate entry into false lumen proximally and distally

• Reconstitute the aorta (Dacron graft)

GOALS OF SURGERY cont’d.

• If aortic regurgitation complicates ascending dissection:

• Surgical decompression of false lumen and resuspension AV leaflets
• Aortic valve replacement required if annular supports of leaflets damaged (composite graft or homograft)
• Aortic valve replacement required if aortic root >5 cm (likely to progress)

INDICATIONS FOR SURGICAL THERAPY

• Hemorrhage or rupture

• End-organ ischemia

• Continued pain

• Rapid expansion (>5mm in 6 months) of diameter of any segment >6 cm

• (less in some centers)

• Uncontrolled HTN

• Younger patients at relatively good operative risk

FOLLOW-UP

• Aneurysmal dilation and rupture are leading causes of late death

• 1982 DeBakey. 527 pts operated for aortic dissection: 30% of late deaths due to rupture of post-dissection aneurysms

• 1990 Crawford. Death from rupture occurred in 12/130 (9%) cases with a dilated but unrepaired residual aorta

• After extensive aortic dissection, many patients will eventually require surgical therapy (especially if on anticoagulants after composite graft repair)

FOLLOW-UP cont’d.

• Before hospital discharge: CT scan or MRI

• Initial evaluation after discharge: CT scan or MRI at 3, 6 and 12 months

• Reimage aorta every 6-12 months thereafter

• Meticulous control of blood pressure dP/dt (starting with b-blocker or heart rate slowing calcium channel blocker)

• Avoid isometric exercise.

SURGICAL THERAPY

• Early operations attempted to create reentry passage or restoration of circulation to ischemic branches. High failure rate.

• 1935 Gurin: Fenestrated dissecting membrane in iliac artery.

• 1948 Paullin and James: Wrapped chronic dissection of descending aorta with cellophane.

SURGICAL THERAPY cont’d.

• 1955 Michael DeBakey: Modern treatment of aortic dissection

• Collegues: Denton Cooley and O’ Creech

• 1st case: Descending thoracic dissection

• Excision of aneurysmal dilation
• Oversewed distal entry into the false channel
• End-to-end anastomosis of aorta

• Later: Dacron graft replacement of descending aorta

• 5. 1962 Spencer and Blake: First successful repair of chronic ascending dissection with resuspension of aortic valve commissures

SURGICAL THERAPY cont’d.

• 1960’s: Importance of sandwiching the friable aortic layers between strips of Teflon felt

• Bentall procedure

• Evolution of the composite graft approach

• Aortic homograft

• Aortic conduit with AV sparing

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