17 - Peripheral Arterial Disease Flashcards
Define peripheral artery disease
- Clinical disorder which consists of stenosis of the aorta or arteries in the limbs
What is the leading cause of PAD in patients over 40?
Atherosclerosis ***
KNOW THIS
What are other causes of PAD?
- Thrombosis
- Embolism
- Vasculitis
- Fibromuscular dysplasia
- Entrapment
- Cystic adventitial disease
- Trauma
How do we diagnose PAD for epidemiology?
Ankle-brachial index (ABI)
What is the prevalence of PAD?
- 6% in persons 40 years and older
- 5% to 20% in those 65 years and older.
- Highest prevalence in 60s and 70s
- Highest prevalence with diabetes, smoking, hyperlipidemia, hypertension and renal insufficiency
What percent of PAD is symptomatic
Only 10-30%
What are the modifiable risk factors for atherosclerosis?
- Diabetes – endothelial cell dysfunction, inflammation
- Hypertension – increased shear stress = ↓NO, ↑ inflammation, endothelial remodeling
- ***Tobacco exposure – vasoconstriction, pro-inflammatory substances
- Obesity – pro-inflammatory state
- Hyperlipidemia – High LDL, low HDL, small dense LDL particles, hypertriglyceridemia
- CKD
You NEED to get them to quit smoking
What are the non-modifiable risk factors for atherosclerosis?
- Male
- Age
- Race (African American)
- Family history of vascular disease
Pathophysiology of PAD
- Disease of inflammation
- Leukocytes, C-reactive protein and monocytes correlate with PAD
- Serum bilirubin (endogenous antioxidant) associated with reduced PAD prevalence
- Balance of circulatory supply and demand of oxygen & nutrient to skeletal muscle
Describe the importance of balancing circulatory supply and demand of oxygen
- Intermittent claudication - oxygen demand of skeletal muscle during effort exceeds the blood’s oxygen supply
- Activation of local sensory receptors by accumulation of lactate or other metabolites.
Describe the major factor regulating blood flow through an artery
Flow through an artery is directly related to perfusion pressure and inversely related to vascular resistance
Describe what happens as a stenotic lesion increases
- As the severity of a stenotic lesion increases, flow becomes progressively reduced.
- BP gradient exists at rest if the stenosis reduces the diameter of the lumen by more than 50% because as distorted flow develops, kinetic energy is lost.
- As flow through a stenosis increases, distal perfusion pressure drops
- Adenosine, nitric oxide, potassium, and hydrogen ion accumulate and vasodilation of peripheral vessels occur
- IM pressure rise during exercise and may exceed arterial pressure distal to occlusion and halt blood flow
- Collateral blood vessels usually suffice at rest but not during exercise
- Abnormalities in microcirculation also contribute
The hallmark of nearly all diabetic complications is…
ENDOTHELIAL DYSFUNCTION
Chronic metabolic changes lead to…
- Vasoconstriction
- Chronic inflammation
- Tendency towards thrombosis
Describe vasoconstriction in diabetic vascular disease
- Autonomic dysfunction
- Decreased vasodilatory (NO, prostacyclin) and increased vasoconstrictive (prostanoids) cytokines
Describe chronic inflammation in diabetic vascular disease
- Free radicals, oxidative stress
- Increased expression of leukocyte adhesion molecules
Describe tendency towards thrombosis in diabetic vascular disease
- Increased coagulation factor production
- Increased platelet aggregation (elevated GP IIb/IIIa)
Describe the risk of vascular disease in patients with chornic kidney disease
- Patients with CKD at increased risk for PAD
- Essentially ossification of arteries will occur
- May have significant stenosis without evidence of plaque on angiography
- Harder to treat ossification
What is the cardinal symptom of PAD?
- Claudication (10-30%)
Describe claudication
- Pain, ache, sense of fatigue, or discomfort occurs with exercise and resolves with rest.
- Location of symptoms is related to the site of most proximal stenosis
Describe the location of stenosis with the location of claudication pain
Site of pain: atery stenosed
- Buttock/hip/thigh: Aorta/iliac
- Calf: femoral/popliteal (consumes more oxygen during walking than other muscles —> most frequent symptoms)
- Ankle/foot: tibial/peroneal
- Shoulder: subclavian
- Biceps: axillary
- Forearm: brachial
What is another clinical feature of PAD?
Critical limb ischemia
Describe critical limb ischemia
Critical limb ischemia
- Pain or paresthesias in foot or toes
- Worsens with leg elevation and improves with dependency
- Skin is very sensitive (weight of bedclothes/sheets elicits pain)
- Dangle legs on edge of bed to alleviate discomfort
- Diabetic neuropathy: little or no pain
What are the other clinical features?
Asymptomatic – 20-50% Atypical leg pain – 40-50% Critical limb ischemia – 1-2% Walking impairment Ischemic rest pain Non-healing ischemic ulcers
What are the physical findings of PAD?
Decreased or absent pulses distal to obstruction
Bruits over narrowed artery
Muscle atrophy
What will you see in addition to this in more severe disease?
More severe disease… Hair loss Thickened nails Smooth and shiny skin Reduced skin temperature Pallor or cyanosis
What is a risk of critical limb ischemia?
Ulcers or gangrene
How do you non-invasively test for PAD?
- Usually H&P are sufficient to establish diagnosis
- Segmental Pressure Measurement
- Ankel brachial index
- Treadmill exercise protocol
- Pulse volume recording
- Continuse pulse with wave doppler
How do you do a segmental pressure measurement?
Measure SBP at different upper and lower extremities segments
In iliac and femoral arteries a 70-90% decrease in cross-sectional area will cause a resting pressure gradient sufficient to decrease SBP distal to the stenosis.
How do you determine if stenosis is present?
Stenosis is present if:
BP gradient >20 mmHg between cuffs in LE
BP gradient of >10 mmHg in UE
How can you invasively test for PAD?
Contrast Angiography
- Gold standard for diagnosis
- Catheter is placed into a selected artery in both legs
- Contrast is injected into vessels under fluoroscopy
- Contrast injected form iliacs to tibials
What are the advantages of contrast angiography?
- Allows identification & quantification of lesions and assessment of inflow and outflow
- Endovascular therapy and stenting can occur at the same time as the diagnostic exam
What are the disadvantages of contrast angiography?
- Invasive, higher complication rate than non-invasive
- $$$, time-consuming, requires sedation/recovery
Describe magnetic resonance angiography
- Gadolinium enhanced
- Sensitivity 94.7%
- Specificity 95.6%
- Utility: symptomatic patients to assist in decision making before endovascular and surgical intervention or in patients at risk for renal, allergic, or other complications during conventional angiography.
Describe computed tomographic angiography
- Sensitivity 95%
- Specificity 96%
- Can be used in patients with stents, metal clips, and pacemakers
- Requires radiocontrast material and ionizing radiation.
What are the goals of treatment for PAD?
- Reduce cardiovascular morbidity and mortality
- Improve quality of life
- Decreasing symptoms claudication
- Eliminating rest pain
- Preserving limb viability
- Reduce risk for adverse cardiovascular events: MI, stroke, death
How ca you reduce risk factors in the treatment of PAD?
- QUIT SMOKING ***
- Control blood sugar
- Lose weight
- Control HTN
- Control hyperlipidemia
- Rehab (supervised_ exercise training
How do you treat intermittent claudication?
Supportive measures
- Foot care: clean, moisturized, well fitting and protective shoes
- Elastic support hose should be avoided
- In critical limb ischemia: shock block under the HOB with a canopy over feet
- Exercise regularly and at progressively more strenuous levels
- Beneficial effect of supervised exercise training on walking performance in patients with claudication often is similar to or greater than that realized after a revascularization procedure.
What type of patients with PAD should be on antiplatelet medication?
- All patients with symptomatic PAD
- All patients with intermittent claudication + risk factors
- All patients with previous revascularization
- May be useful for asymptomatic patients with ABI
What is recommended for aspirin use for antiplatelet therapy?
ASA – 75mg-325mg daily dosing
Recommended to reduce risk of MI, CVA, and vascular death in individuals with symptomatic PAD
What is recommended for clopidogrel for antiplatelet therapy?
Clopidogrel
- Safe and effective alternative to ASA
- May be used in addition to ASA in patients with severe PAD or those with progression despite ASA therapy
What is recommended for anti-claudication medication?
- Cilostazol
- Pentoxifylline
Describe cilostazol
Cilostazol 100mg PO BID
- Phosphodiesterase (PDE) inhibitor – non-homogenous vasodilation (femoral beds»others)
- Reversibly inhibits platelet aggregation
- Improves symptoms and walking distance (40-60%)
Describe pentoxifyline
Pentoxifylline 400mg PO TID
- Similar mechanism, though less well-defined
- Second-line alternative to cilostazol
Which therapies are ineffective in treating PAD?
Documented lack of efficacy:
- Oral prostaglandins – beraprost, iloprost
- Vitamin E
- Chelation therapy
Marginal or insufficient evidence
- L-arginine supplementation
- L-carnitine supplementation
- Gingko biloba
What are the three surgical interventions for PAD?
Endovascular
Open bypass
Amputation
What is the indication for percutaneous transluminal angioplasty (PTA) and stenting?
Indications:
- Lifestyle-limiting disability due to claudication AND
- Inadequate response to medical therapy AND
- Reasonable likelihood of improvement with therapy
When is PTA preferred?
- Preferred first line therapy for iliac to fem/pop lesions
90–95% of iliac PTAs are initially successful - 3-year patency >75%
When is stent placement preferred?
- Primary therapy in iliac stenosis/occlusion
- Increased potency than PTA
- Femoral-popliteal PTA and stenting 80% initially successful
- 60% 3-year patency rates
What is acute limb ischemia?
Sudden decrease in limb perfusion that causes a potential threat to limb viability
What are the 6 Ps of acute limb ischemia?
- Paresthesia
- Pain
- Pallor
- Pulselessness
- Poikilothermia – inability to regulate temperature
- Paralysis – later stage – a very bad sign (limb usually not viable)
How do you manage acute limb ischemia?
Requires prompt intervention with:
- Catheter directed thrombolysis (ALI
How common is amputation?
- 10% of patients with claudication progress to critical limb ischemia within 5 years
- 20-30% of patients with critical limb ischemia go on to require major amputation
What are the indications for amputation?
Indications
- Extensive skin and tissue loss (especially on weight-bearing surfaces)
- Major infection (sepsis)
- Rest pain not controlled with all other measures
- Uncorrectable flexion contracture
- Paresis of the extremity
- Poor life expectancy without intervention
What is the overall mortality in post-amputation patients?
Overall mortality in post-amputation patients
- Post-op – 5-20%
- 2 year – 25-30%
- 5 year – 50-75%
What are the morbidities that occur with amputation?
Pain
Disability
Need for further surgery, amputation
Describe the progression of complications and morbitidies
Complications/morbidity - above-knee»_space; below-knee»_space; below-ankle
What are the key points of emphasis?
- Atherosclerosis is a SYSTEMIC disease with REGIONAL preference
- Atherosclerosis is in all the arteries
- Peripheral arterial disease presents in a variety of ways from asymptomatic to acute life threatening events
- Treatment of PAD involves lifestyle changes, medical therapy, and surgical intervention
