Flashcards in 17 - Peripheral Arterial Disease Deck (58)
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?
What are other causes of PAD?
- Fibromuscular dysplasia
- Cystic adventitial disease
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
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
You NEED to get them to quit smoking
What are the non-modifiable risk factors for atherosclerosis?
- 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...
Chronic metabolic changes lead to...
- 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%)
- 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%
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
What will you see in addition to this in more severe disease?
More severe disease…
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.