Arterial Disease 2 Flashcards
Aneurysms - Definitions
An aneurysm is a >150% dilation of its original diameter but remember it is an ongoing process.
- True aneurysms are abnormal dilations of arteries that involve all layers of the vessel wall.
- False aneurysms (pseudo-aneurysms) are organised haematomas around a vessel wall – occur when there is a hole in an artery e.g. after trauma and procedures - sticking needles into arteries for angiography.
- Dissecting aneurysm – vessel dilation is caused by blood tracking between layers of the vessel wall.
- Shapes - aneurysms may be fusiform e.g. AAA or sac like e.g. berry aneurysm.
Aneurysms - Causes
Atheroma, trauma, infection (e.g. mycotic aneurysm in endocarditis or tertiary syphilis), connective tissue disorders (e.g. Marfan’s or Ehlers-Danlos) or inflammatory (e.g. Takayasu’s).
Aneurysms - Sites and Complications
- Common sites – aorta (most commonly at infrarenal position), iliac, femoral and popliteal arteries.
- Complications – rupture, thrombosis, embolism, fistula or pressure on surrounding structures.
Ruptured AAA - Death and Mortality Rates
- Death rates per year from ruptured abdominal aortic aneurysms rise with age – 125 per million in 55-59 year olds and 2728 per million in >85 year olds.
- Mortality rates – 41% if treated (this is improving all the time) but 100% if left untreated.
Ruptured AAA - Clinical Features
Intermittent or continuous abdominal pain that radiates to the back, iliac fossa or groins (don’t dismiss this as renal colic), collapse, expansile abdominal mass (it expands and contracts) and shock. If in any doubt assume a ruptured aortic aneurysm.
Ruptured AAA - Emergency Management
Inform a vascular surgeon, an anaesthetist and inform the theatre manager. Take bloods for FBC, U+Es, clotting, LFTs and crossmatch (may need 10-40 units).
Insert 2 large bore cannulas and treat shock with ORh negative blood (if desperate) but keep systolic BP <100mmHg.
Give analgesia, antibiotics e.g. 1.5g cefuroxime and 500mg metronidazole IV and take the patient straight to theatre.
Ruptured AAA - Surgery and Complications
Clamp the aorta above the leak and insert a Dacron tube graft. If there is a significant iliac aneurysm also insert a ‘trouser graft’ – each leg of the graft is attached to an iliac artery.
- Complications of surgery – haemorrhage, renal failure, embolism, aorto-duodenal fistula, graft infection, myocardial infarction or multi-organ failure (due to prolonged aortic clamping).
Unruptured AAA - Incidence and Causes
Prevalence is 3% in over 50’s, men to women ratio is 3:1 and less common in DM.
- Cause – degeneration of elastic lamellae, smooth muscle loss and a genetic component.
Unruptured AAA - Symptoms and Complications
- Symptoms – often none but may cause abdominal or back pain often discovered incidentally.
- Complications of AAA – rupture (rates are 9% if <4.5cm, 35% if 4.5-7cm and 75% if >7cm), thrombosis, embolisation (blue toe syndrome), erosion of vertebrae or fistulisation
Unruptured AAA - Monitoring and Risk Factors
- Monitoring – the UK small aneurysm trial suggested aneurysms <5.5cm might be safely monitored by regular examination and ultrasound or CT although repair may be better. Risk of rupture below this size is <1% per year compared to 25% per year for aneurysms >6cm across.
- Risk factors – rupture is more likely if there is hypertension, smoking, female or strong family history.
Unruptured AAA - Surgery and Stenting
- Elective surgery – reserve for aneurysms >5cm or expanding at >1cm per year or symptomatic. Operative mortality is 5% - complications include spinal or mesenteric ischaemia and distal trash from dislodged thrombus debris. Studies show age >80 is not a reason to decline surgery.
- Stenting – big operations can be avoided by inserting an endovascular stent via the femoral artery. Failure of the stent to totally exclude blood flow to the aneurysm may occur resulting in ‘endoleak’ – aneurysm can grow so monitoring is required. When successfully positioned such stents can lead to a short hospital stay and fewer transfusions than with conventional surgery.
Thoracic Artery Dissection - Definition and Symptoms
Blood splits the aortic media with a sudden tearing chest pain ± radiation to the back. As the dissection unfolds branches of the aorta occlude sequentially leading to hemiplegia (carotid artery), unequal arm pulses and blood pressure or acute limb ischaemia, paraplegia (anterior spinal artery) and anuria (renal arteries). Inferior MI may occur if the dissection moves proximally.
Thoracic Artery Dissection - Types and Causes
- Type A (70%) – dissections involving the ascending aorta (irrespective of the site of the tear) and all should be considered for surgery.
- Type B (30%) – the ascending aorta is not involved – surgery reserved for distal dissections that are leaking, ruptured or compromising vital organs.
- Causes - congenital in Marfan’s disease or Ehlers-Danlos syndrome or acquired in hypertension or arteriosclerosis (age and hypertension related changes in the blood vessels).
Thoracic Artery Dissection - Management
Crossmatch 10 units of blood, ECG, chest x-ray (for expanded mediastinum) and CT, MRI or trans-oesophageal echocardiography.
Transfer to ITU and give antihypertensive to maintain the blood pressure at around 100-110 mmHg e.g. IVI of labetalol or esmolol.
Popliteal Aneurysm
50% of patients with a popliteal aneurysm will have a co-existent aortic aneurysm. A popliteal aneurysm should be suspected when the pulse is unusually prominent or easily palpated.
They rarely rupture and the most common complication is acute thrombosis of the aneurysm causing acute ischaemia – this will require emergency femoro-popliteal bypass grafting.
If a popliteal aneurysm is identified before thrombosis has occurred an elective bypass should be performed.
