Acute Peripheral Artery Occlusion And PAD Flashcards
Beyond just acute arterial thromboembolism and acute thrombotic occlusion what are some other causes of acute peripheral arterial occlusion? (6 answers)
- Atheroembolism due to atherosclerotic plaque particles: “MICROEMBOLI”. Cause blue toe syndrome and livedo reticularis, with pulses intact (because it isn’t cause a large vessel occlusion)
- Infectious emboli from bacterial endocarditis
- Malignant emboli from melanoma or lung cancer
- Foriegn body emboli (bullet fragment)
- Raynauds
- Vasculitis
6 P’s of limb ischemia/acute arterial occlusion
Of these which is usually the first symptom and which are usually the last most ominous/concerning symptoms/signs?
Pain - usually the first symptom (later on, when it ischemia is more severe, pain may decrease due to sensory loss)
Pallor - often early on
Poikilothermia (inability to regulate temperature) - usually seen with pallor
Paresthesias - numbness is usually the first neuro manifestation, sensory loss is a later finding
Pulselessness
Paralysis (loss of sensation and loss of motor function are ominous signs)
What is the name of the classification scheme that allows for classification of acute limb ischemia? (Know so you can look it up when needed)
For each class (4 of them) what is the urgency in evaluation/intervention?
Rutherford Classification Scheme
Ranges from Class I —> Class III (with IIa and IIb in between)
Class I = viable - needs evaluation within 24 hours, with possible intervention
Class IIa = marginally threatened (urgent revascularization - within 24 hours)
Class IIb = immediately threatened (emergent revascularization)
Class III = non-viable - amputation, but does not necessarily need to be immediate
How do you measure ABI?
Take the systolic BP of the ankle (higher of posteriolateral tibial and dorsal pedal) divided by systolic BP at the brachial artery
What physical exam findings should you look for in every patient with suspicion for acute limb ischemia?
Pulses! Duh (get a Doppler!)
Cap refill
Skin color, warmth vs cool
Ulcers present? (Toes = PAD) - signs of gangrene?
Sensation - just numb? Or complete loss?
Motor function
Describe the differences between acute arterial occlusion caused by thromboembolism vs. acute thrombotic occlusion (aka thrombosis in situ). Include which type is more common.
Acute thromboembolism:
- Less common (10-15%)
- Usually a more severe presentation (because there is less collateral circulation): sudden onset, more dramatic symptoms
- Treated with: Heparin + Fogarty catheter embolectomy
Thrombotic occlusion:
- Most common (85%)
- Usually have some chronic PAD causing collateral circulation and thus less dramatic symptoms when there is an acute thrombus that forms.
- Treated with: Heparin + embolectomy + bypass grafting
How is acute limb ischemia defined, vs. chronic limb ischemia?
Acute limb ischemia: symptoms present <2 weeks causing a sudden decrease in perfusion to tissues —> cell death and necrosis
Chronic limb ischemia: symptoms present >2 weeks. A sustained state of inadequate tissue perfusion which can occur with exertion (Claudication) or at rest (rest pain). Leads to development of collateral circulation.
What are some clues that can help you distinguish between acute arterial occlusion being caused by embolism vs. acute thrombosis? (History, physical, etc). Why is this important to know?
Embolism caused:
- Hx A. Fib; recent MI (b/c LV mural thrombus formation); Hx cardiac valve dz; NO history of peripheral atherosclerosis.
- Sudden dramatic presentation
Thrombosis caused:
- Hx of peripheral atherosclerosis, claudication, and/or neuropathy (b/c PAD)
- PEx findings suggestive of PAD: hair loss, shiny skin, thick nails, muscle atrophy, chronic ulcers
Important to know because the treatment is slightly different between the two causes
Treatment of acute peripheral arterial occlusion (be sure to differentiate between the causes)
All: HEPARIN: 80 units/kg IV bolus followed by 18 units/kg/hr infusion
Vascular surgery consult. But be able to have an intelligent conversation and use the Rutherford Acute Limb Ischemia Classification Scheme.
Embolism caused: Heparin + Fogarty catheter embolectomy
Thrombosis caused with limb-threatening ischemia: Heparin + embolectomy + Bypass grafting
Thrombosis caused without limb-threatening ischemia: Heparin +/- Thrombolysis (talk to vascular)
ALSO! IV fluids - patients with acute limb ischemia often have concomitant volume depletion that requires prompt treatment.
Obviously there is more to it than this, this is just a general idea - the vascular surgeon will ultimately decide on definitive therapy.
How many hours can skeletal muscle tolerate ischemia when there is a peripheral artery occlusion causing limb ischemia?
4-6 hours - the longer the ischemia the higher likelihood of irreversibility damage.
What subset of patients with limb ischemia can potentially be discharged home?
Patients with chronic limb ischemia only (>2 weeks of symptoms) without superimposed acute limb ischemia. —> Make sure to talk to vascular first and ensure close outpatient f/u!
Possibly Rutherford class I patients only if they have prompt f/u with vascular set up. Obviously discuss with vascular first.
Everyone else —> admit!
Most common cause of embolic acute arterial occlusion?
If you can name a few other possible sources of embolism.
Thrombus formation due to A. Fib (2/3rds of cases)
Next most common is mural thrombus from LV after recent MI
Other sources:
- Cardiac tumor (atrial myxomatosis)
- Endocarditis debris
- Aneurysm - aortic, iliac, femoral
- Popliteal aneurysms - rare but cause acute ischemia in 46%! HIGH rate of amputation because compromised tibial and pedal arteries.
- Aortic or iliac plaques
- PFO patient with DVT
What compartment of the leg is most susceptible to ischemia? How does this translate into signs/symptoms?
Anterior compartment.
Loss of sensation of the dorsal foot can be the first sign of acute vascular insufficiency
This is a late and poor prognostic sign of acute peripheral arterial occlusion
Paralysis
Describe an abnormal ABI. What ABI is diagnostic for PAD? What ABI warrants starting heparin immediately?
Abnormal ABI: <0.9
ABI <0.6 virtually diagnostic for PAD
ABI <0.4 —> Acute emergency —> start Heparin before imaging and consult vascular!
