Aortic dysfunction Flashcards
What is normal diameter of aorta
2cm
increases with age
Define aneurysm
Permanent dilation of the artery to TWICE the normal diameter
Difference between a true aneurysm and false aneurysm
True - abnormal dilatation that involve all layers of arterial wall
False (pseudoaneurysm) - involves the collection of blood in the OUTER LAYER ONLY (ADVENTITIA) which communicates with the lumen e.g. after trauma from a femoral artery puncture
What arteries are generally involved in a True Aneurysm
Abdominal aorta (most common)
Iliac, popliteal and femoral arteries
Thoracic aorta
(abdominal aneurysms are classified as abdominal or thoracic)
Do abdominal aortic aneurysms (AAA) most commonly occur above or below the renal arteries
Below
AAA: epidemiology
Incidence increases with age
Present in 5% of population >60
More common in men
Abdominal aneurysms are classified as an aortic diameter exceeding what?
3cm
Causes/Risk factors of AAAs
Often no specific identifiable causes • Severe atherosclerotic damage • Family history • Tobacco smoking • Male • Increasing age • Hypertension • COPD • Trauma • Hyperlipidaemia
AAA: Pathophysiology
Degradation of the elastic lamellae resulting in leukocyte infiltrate causing
enhanced proteolysis and smooth muscle cell loss.
The dilatation affects ALL THREE LAYERS of the vascular tunic (if it doesnt then it’s a pseudoaneurysm).
Unruptured AAA clinical presentation
- Often asymptomatic and only picked up via a routing abdominal examination or plain X-ray
- Pain in abdomen, back, loin or groin
- Pulsatile abdominal swelling (less pronounced)
Ruptured AAA: clinical presentation
- Intermittent or continuous abdominal pain (radiates to the back, iliac fossa’s or groin)
- Pulsatile abdominal swelling (more pronounced)
- Collapse
- Hypotension
- Tachycardia
- Profound anaemia
- Sudden death
What increases chance of rupturing an AAA
Increased BP
Female
Smoker
Strong family history
AAA Differential diagnosis
- GI bleed
- Ischaemic bowel
- MSK pain
- Perforated GI ulcer
- Pyelonephritis
- Appendicitis
AAA Diagnosis
Abdominal ultrasound - can assess aorta to degree of 3mm
CT and/or MRI angiography scans
AAA Treatment
Small aneurysms below 5.5cm are generally just monitored
Treat underlying causes
Modify risk factors e.g. smoking and diet
Vigorous BP control
Lowering of lipid in blood
Surgery
What surgery could be done for a symptomatic AAA patient
Open surgical repair
Endovascular repair - stent inserted via femoral or iliac arteries
What is normal size of mid-descending thoracic aorta?
26-28mm
What patients are more prone to ascending thoracic aorta aneurysm
Marfan syndrome
Hypertension
What patients are more prone to descending or arch thoracic aorta aneurysms
Secondary to atherosclerosis
sometimes Syphilis
Causes of Thoracic Aorta Aneurysm
STRONG GENETIC LINK - in some families it appears to be an autosomal dominant trait
Connective tissue disorders e.g. Marfan’s syndrome
Weight lifting, cocaine and amphetamine use - perhaps due to the large rise in BP when undertaking these activities
Aortic dissection
Risk factors of Thoracic Aorta Aneurysm
- Hypertension
- Increasing age
- Smoking
- Bicuspid or unicuspid aortic valves
- Atherosclerosis
- COPD
- Renal failure
- Previous aortic aneurysm repair
Pathophysiology of Thoracic Aorta Aneurysm
Inflammation, proteolysis and reduced survival of the smooth muscle cells in the aortic wall.
Once the aorta reaches a crucial diameter (around 6cm in the ascending and
7cm in the descending) it loses all distensibility so that a rise in BP to around
200mmHg can exceed the arterial wall strength and may trigger dissection
or rupture.
Clinical presentation of Thoracic Aorta Aneurysm
-Generally asymptomatic
-May be diagnosed incidentally e.g. on routing CXR or cardiological
investigation or if complicated by dissection, rupture or other complications
- Pain in chest, neck, upper back, mid-back or epigastrium
- Aortic regurgitation
- Fever (if infective cause)
- Symptoms due to compression of local structures
- Acute pain
- Collapse, shock and sudden death
- Cardiac tamponade
- Haemoptysis
Differential diagnosis of Thoracic Aorta Aneurysm
- Thoracic back pain
- Arterial ischaemia
- Collapse
- MI
Diagnosis of Thoracic Aorta Aneurysm
- CT or MRI used for assessment of TAA
- Aortography (helpful for assessing the position of the key branches in relation to the aneurysm)
- Transoesophageal echocardiography (useful for identifying aortic
dissection) - Ultrasound
Treatment of Thoracic Aorta Aneurysm
Ruptured TAA requires urgent immediate surgery
Symptomatic TAA’s = surgery regardless of size
Regular monitoring by CT or MRI every 6 months
Rigorous BP control using Beta-blockers e.g. Bisoprolol
Smoking cessation
Treat underlying cause
Process of aortic dissection
Begins with a tear in the intima (inner wall)
Blood then penetrates the diseased medial layer and flows between the layers of aorta
Forces layers apart = results in dissection
Medical emergency that can lead to death
What is the most common medical emergency affecting the aorta
Aortic dissection
What people are more at risk of aortic dissection
Men more at risk
Most common between ages of 50-70 (<40 is rare)
How can aortic dissection be classified
According to the timing of diagnosis from the origin of symptoms:
• Acute - less than 2 weeks
• Subacute - 2-8 weeks
• Chronic - more than 8 weeks
Causes of aortic dissection
- Inherited
- Degenerative
- Atherosclerotic
- Inflammatory
- Trauma e.g. shearing stresses in a road traffic accident (RTA)
Pathophysiology of aortic dissection
Begins with a tear in the intimal lining of the aorta
Tear allows a column of blood under prssure to enter the aortic wall, forming a haemotoma that separates the intima and adventitia to create a false lumen.
False lumen extends for a variable distance in either direction.
Pathophysiology of aortic dissection: In what directions can the false lumen extend
Anterograde - towards bifurcations
Retrograde - towards the aortic root
Pathophysiology of aortic dissection: What are the most common sites for intimal tears
Within 2-3cm of aortic valve
Distal to left subclavian artery in the descending aorta
Pathophysiology of aortic dissection: Between which layers of the artery does false lumen form
Intima and adventitia
Clinical presentation of aortic dissection
Sudden onset of central chest pain that radiates to the back and down arms (mimics MI)
Hypertension
Pain is maximal from the onset (but in MI pain gains intensity)
Shock and neurological symptoms secondary to loss of blood supply to spinal cord.
Aortic regurgitation, coronary ischaemia and cardiac tamponade may develop.
Peripheral pulses may be absent.
Acute kidney failure, acute lower limb ischaemia or visceral ischaemia
What symptom of MI is mimiced by aortic dissection
Sudden onset of sever and central chest pain that radiates to the back and down the arms.
But in MI pain increses from onset, but in aortic dissection the level of pain does not change.
Differential diagnosis of aortic dissection
Acute coronary syndrome, MI, Aortic regurgitation without dissection, MSK
pain, pericarditis, cholecystitis, atherosclerotic embolism
Diagnosis of aortic dissection
CXR - widened mediastinum
Urgant CT scan, Transoesophageal echocardiography
or MRI will confirm the diagnosis
Treatment of aortic dissection
- At least 50% are hypertensive and may require urgent antihypertensive medication to reduce blood pressure to less than 120mmHg - give IV betablockers e.g. IV metoprolol or vasodilators e.g. IV GTN
- Adequate analgesia e.g. morphine
- Surgery to replace aortic arch
- Endovascular intervention with stents
- Patients require long term follow-up with CT or MRI
