Arterial Vascular Disease Flashcards
What are the steps in atherosclerosis?
- Endothelial injury occurs
A. Smoking, ↑ LDL, HTN effect, immune mechanisms - Monocytes & platelets adhere to injured endothelium & cells ∆
- Transformed cells (macrophages) oxidize & ingest LDL → foam cells
- Foam cells stimulate inflammatory response → endothelial dysfunction
- Streaky plaques form between intima & media → lumen narrows
- Arterial walls weaken due to plaques
- Unstable plaque ruptures & thrombus forms at rupture site→ thrombus or embolus causes ischemic event
What percent of artery stenosis can cause ischemic sxs?
In general, asymptomatic until plaque stenosis exceeds 70-80% of luminal diameter which leads to in blood flow to vital tissues (ischemia)
Define peripheral artery disease
any pathologic process causing obstruction to blood flow in the arteries, exclusive of the coronary and cerebral vascular beds
What is the most common artery occluded by atherosclerosis?
Superficial femoral artery
What can chronic decreased blood flow to the skin on the lower leg cause?
- Atrophy
- Hair loss
- Thinning of skin and SQ tissue
- Pale and/or cool skin
- Ulcers w/ worsening ischemia –> necrosis, infection, cellulitis
What are the risk factors for PAD?
- Cigarette smoking
- Diabetes
- Hyperlipidemia
- HTN
- Hyperhomocystinemia
- Chronic renal insufficiency
What groups are at risk for lower extremity PAD?
- ≥70 yrs
- 50 - 69 yrs w/ Hx of smoking or DM
- 40 - 49 yrs w/ DM + 1 other risk factor for atherosclerosis
- Leg symptoms suggestive of claudication w/exertion or ischemic pain at rest
- Abnormal lower extremity pulse exam
- Known atherosclerosis at other sites (coronary, carotid, renal artery disease)
What are the sxs of PAD?
- Dependent Rubor
2. Claudication
Define Dependent rubor
- foot below heart level turns dusky red
a. Elevation of foot causes pallor
b. Foot pain when supine or leg eleved, relieved when dependent
- foot below heart level turns dusky red
Define claudication
- severe, cramping pain in calf or thigh while walking
A. Pain relieved at rest
B. Blood flow (O2 supply) can’t keep up w/ demand of exercise
What group is tibial and pedal artery occlusion most often seen in? What may be the first sxs?
Seen primarily w/ DM
Foot pain at rest or ulceration may be 1st sign of arterial insufficiency
How is tibial/pedal artery occlusion differentiated from diabetic neuropathy?
If foot pain relieved by dangling over edge of bed, then the pain is d/t ischemia
Define cellulitis. What are common causative agents?
- Skin and soft tissue infection
- Erythema, warmth, pain, edema
- Most common pathogens
Strep pyogenes, Staph aureus
How is atherosclerosis assessed in heart and lung PE?
Auscultate for carotid, clavicle bruits
How is atherosclerosis assessed in abdominal PE?
- Auscultate for aorta, renal, iliac, femoral bruits
A. R/O pulsatile mass (aortic aneurysm)
How is atherosclerosis assessed in lower extremity PE?
- Shoes and socks removed
- Peripheral pulses
- Hair loss
- Skin color
- Skin changes, sensations
What are the non-invasive tests for PAD?
- ABI- ankle-brachial index
- TBI – toe brachial index
- VWF – velocity wave form (Doppler USN)
- PVR – pulse volume recording
What is the best initial screening test to perform in a patient with suspected PAD?
Ankle Brachial Index (ABI)
Define Ankle Brachial Index (ABI). How is it performed?
- The ratio of the highest systolic ankle BP to the highest arm BP
- Obtained with a hand-held Doppler instrument and a BP cuff
What is an abnormal ABI ratio?
- A ratio of < 0.90 mmHg
When do you suspect an inaccurate ABI? What groups are susceptible?
- ABI may be inaccurate in individuals with noncompressible arteries due to medial calcification (suspect when ABI > 1.3mmHg
- DM, elderly, end stage renal Dz on dialysis
What is the rationale behind Pulse volume recordings?
- Based on concept that arterial inflow into the lower extremities is pulsatile leading to measurable changes in the lower-limb volume with each cardiac cycle
- Sequential decrease signifies the presence of a flow-limiting lesion in the more proximal arterial segment
How is the doppler US used for pts w/ suspected PVR? When is stenosis suspected?
- Used in conjunction with the PVR to obtain segmental velocity waveforms & SBP measurements along the UE or LE
- ↓ Pulsatility index between the adjacent proximal and the distal arterial segments = significant stenosis
When may a false positive be present on a doppler US?
Superficial femoral artery Dz w/out aortoiliac disease → false (+)
How does a duplex US help dx PAD?
Provides both vascular imaging and flow velocity info
> 90% accuracy to Dx the location & severity of LE PAD
What are the benefits of CT angiogram to dx PAD?
- Allows fast imaging of the entire lower extremity and abdomen
- Better evaluation (than angiography) of stenoses and visualization of all collateral vessels & surrounding tissues
- Safe in patients with pacemakers and defibrillators
What are the drawbacks of using CT angiogram to dx PAD?
Contrast has risk of nephrotoxicity
What are the drawbacks of using MRA to dx PAD?
- Cannot scan pt’s with pacemakers, defibrillators, metal stents, or clips
- Gadolinium associated with rare occasions of renal toxicity
What are the benefits of using MRA to dx PAD?
High accuracy (90-100%) similar to that of intraoperative catheter angiography
What is the gold standard for diagnosing PAD?
Contrast angiography
Provides detailed information about the arterial anatomy and is recommended as the “gold standard”
What are the drawbacks of using Contrast angiography to dx PAD?
- Invasive procedure
- Risk of contrast induced nephropathy in renal dysfunction, DM, low cardiac output, dehydration, advanced age, multiple myeloma
How can the kidney damage from contrast angiography be mitigated?
- Vigorous IV hydration
- Use low-osmolar contrast agents
- Minimizing the overall amount of contrast
- Pretreatment with N-acetylcysteine (Mucomyst)
How is PAD managed?
- Risk factor modification: smoking cessation
- Exercise program
- Pharmacologic treatment
- If warranted for symptomatic relief, endovascular or surgical revascularization
What are the sequlae of PAD?
Cellulitis Osteomyelitis Gangrene Limb amputation Sepsis Cardiovascular events - major cause of death in patients with PAD
What meds are used for PAD?
1. Cholesterol lowering LDL < 70-100 mg/dL A. Statin (HMG-CoA reductase inhibitor) 2. HTN Tx BP < 140/90 3. DM management HbA1c < 7.0% 4. Cilostazol (Pletal) 5. Pentoxifylline (Trental) 6. ACE inhibitors
What is the class, moa and contraindications for Cilostazol (Pletal)?
Phosphodiesterase inhibitor
Inhibits platelet aggregation
Contraindicated in CHF
What is the moa of Pentoxifylline (Trental)?
Inconclusive data on benefit
Lowers blood viscosity RBC flex
What effect do ACEi have on pts with PAD?
ACE inhibitors (ramipril/Altace) reduce the risk of MI, stroke or vascular death by 25% in patients with PAD
What drug should be considered in all pts with symptomatic PAD w/o contraindications?
Ramipril
a. has shown improvement in walking distance in stable claudication pts
What are the indications for surgery in pts with PAD?
Failed medical management
Limb-threatening ischemia
What are the surgical options for pts w/ PAD? What are the indications for each?
- Percutaneous revascularization/angioplasty
A. Less morbidity/mortality. Used for short segments - Surgical revascularization
A. Indicated for long length occlusion and distal to origin of iliac arteries (i.e. femoropopliteal bypass)
What are PAD emergencies?
- Acute limb ischemia
2. Thrombus In-Situ
Define acute limb ischemia
Sudden occlusion due to 1. Arterial Embolism (30%)
A. Typically from heart
B. Most commonly seen with MI, CHF, A. fib
C. Sudden onset of sx’s w/out pre-existing claudication