Arterial Disease Flashcards
Stage 1 - asymptomatic ischaemia
Haemodynamically significant lower limb ischaemia is defined as an ankle:brachial pressure index of <0.8 at rest.
Most of these patients are asymptomatic either because they choose not to walk very far or because their exercise tolerance is limited by other pathology.
They have as high a risk for vascular complications as those with symptoms and should be assessed and treated as if they have intermittant claudication.
Stage 2 - intermittant claudication
Pain in the legs on walking due to arterial insufficiency is the most common symptoms of PVD. The pain typically occurs in the calf and the patient describes a tightness and cramp like pain which develops after a relatively constant distance (shorter if walking uphill). The pain disappears completely within a few minutes of rest but reoccurs. The claudication distance is how far patient can walk before pain (patients may underestimate).
Neurogenic claudication – leg pain on walking due to neurological or musculoskeletal disorder of the lumbar spine.
Venous claudication – pain in the leg due to venous outflow obstruction for the leg following extensive deep vein thrombosis (the last 2 causes are must less common).
Stage 3 - night or rest pain
The patient is woken by severe pain in the foot, usually in the instep. This occurs because the beneficial effects of gravity on lower limb perfusion are lost when lying. Sleep is also associated with a decrease in heart rate, blood pressure and cardiac output. It can usually be relieved by hanging the leg over the side of the bed or walking around but symptoms soon return on lying. Rest pain indicates severe, multi-level arterial disease.
In diabetic patients it can be difficult to differentiate between an arterial cause and diabetic neurpathy – this is normally associated with burning, tingling or numbness and is not relieved by dependancy.
Stage 4 - tissue loss
Ulceration ± gangrene – in patients with critical limb ischaemia, trivial injuries do not heal allowing bacteria to enter, leading to gangrene and/or ulceration. Without revascularisation the ischaemia rapidly progresses leading to amputation and eventually death.
Raynaud’s phenomenon
Digital ischaemia induced by cold and emotion causing reflex vasospasm of normal arterioloes.
It has 3 phases – pallor (due to digital artery spasm and obstruction), cyanosis (due to deoxygenation of static venous blood) and redness (due to reactive hyperaemia).
Assume that patients **>40 years **presenting with unilateral Raynaud’s have underlying PAD unless proven otherwise.
Raynaud’s - definitions
Raynaud’s phenomenon may be primary (Raynaud’s disease) and due to idiopathic digital artery spasm or scondary (Raynaud’s syndrome) which has many causes e.g. connective tissue syndrome (systemic sclerosis, CREST or SLE), athersclerosis or embolism from a proximal source, drug related e.g. nicotine or β-blockers, malignancy or hyperviscosity.
Raynaud’s - investigation and management
Investigations – needed to diagnose other causes – FBC, TFT, LFTs, ANA or rheumatoid factor.
Management:
- Conservative – remove cause, heated gloves or socks, avoid cold and stop smoking.
- Medical – calcium antagonists e.g. nifedipine or 5-HT antagonists can be given.
- Surgical – in some cases a sympathectomy may be required but symptoms re-occur.
Vascular history - arterial disease
- Risk factors – for atheroma - smoking, hypercholesterolaemia, hypertension, diabetes mellitus and a family history of premature arterial disease.
- The impact of claudication – a postman who can only walk 400 metres has a serious problem but an elderly person who only needs to cross the road to go to the shop may cope well.
- Ask practical questions – can you walk to the clinic from the car or bus without stopping, can you do your own shopping or what can’t you do because of the pain.
- Past medical history – the patient may be equally limited by osteoarthritis, angina or severe breathlessness. Male patients with buttick claudication may not be able to achieve or maintain erection – ask about sexual activity.
Limb Ischaemia - definition
Acute limb ischaemia surgical emergency – requires revascularisation within 4-6 hours to save the limb. Mortality rate is 22% and amputation rate is 16%.
- Can be classified as acute (occurred within 14 days), chronic or acute on chronic limb ischaemia
- Can be sub-classified as incomplete (collateral supply), complete (6 hour window) or irreversible.
Limb ischaemia - causes
- Thrombosis (in 40%) – usually occurs in a previously stenosed vessel – risk factors include dehydration, malignancy, hypotension, hyperviscosity, thrombophilia or an unusual posture.
- Emboli (in 38%) – a fluid or solid particle that travels in the vascular system and lodges at a site where the diameter of the embolus is greater than that of the vessel it is within. 80% are from the left atrium in atrial fibrillation. Others are from an atheroma, tumour, mycotic (in SBE), air, nitrogen (Caeson’s disease), cholesterol (in long bone fractures), foreign body or paradoxical (a DVT thrombus passes into arterial circulation through a septum defect – very rare).
- Others – trauma, vasospastic disorders, iatrogenic, aortic dissection or aneurysm e.g. popliteal.
Limb ischaemia - symptoms and signs
The 6 P’s – the ischaemic limb is pale, pulseless, painful, paralysed, paraesthetic and perishingly cold.
Paralysis and paraesthesia are the 2 most worrying features and suggest severe ischaemia threatening loss of the limb. The onset of fixed mottling implies irreversibility.
In some cases the limb can be red (when dependant) and lead to a disastrous misdiagnoses of cellulitis or gout.
Limb ischaemia - initial management
This is an emergency – all patients require analgesia, rehydration, to be kept nil by mouth, antibiotics, heparinisation (rule out aortic dissection first) and angiogram if incomplete ischaemia as it will guide any distal bypass (however if complete it causes unacceptable delay).
Limb ischaemia - emboli management
The options are surgical embolectomy (femoral arteriotomy and removal of the thromboembolus with a Fogarty catheter) or local thrombolysis e.g. with tissue plasminogen activator. The decision involves balancing the risks of surgery against the haemorrhagic complications of thrombolysis.
If the embolus is removed it should be sent for histology and culture to exclude rare causes – atrial myxoma or infected thrombus from SBE.
Patients should be given heparin whilst investigations to identify the cause continue – e.g. with an echo, ultrasound of the aorta, femoral and popliteal arteries.
Limb ischaemia - thrombosis management
The patient should have an arteriogram (a catheter is passed through the femoral artery into the aorta and contrast is injected) or a digital subtraction angiography before surgery as an embolectomy may not be sufficient.
Depending on the findings the leg may require thrombolysis, angioplasty, stent, or reconstruction to restore blood flow.
Limb ischaemia - post-operatively
All patients should be given a heparin pump for 48 hours and will need long term anticoagulation with warfarin. Risk factors for further events should be minimised as much as possible.
Be aware of the possibility of post-operative reperfusion injury caused by release of free radicals e.g. acidosis, hyperkalaemia, kidney failure due to myoglobin leaking out from damaged muscles (myoglobinuria) or toxic shock. Compartment syndrome can also occur – (some surgeons may divide the deep fascia of the calf (fasciotomy) routinely after surgery in order to avoid this).
