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Basic Science Peripheral Vascular Disease

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  1. Basic Science Peripheral Vascular Disease

  2. Peripheral Arterial Occlusive Disease Basic Considerations

  3. Atherosclerosis - Risk factors • Hypercholesterolemia • Diabetes • Hypertension • Smoking • Relative factors - advanced age, male gender, hypertriglyceridemia, hyperhomocysteinemia, sedentary lifestyle, family history

  4. Pathophysiology of Atherosclerosis • Atheroma – porridge; Sclerosis – hardening • Response to endothelial injury hypothesis • Loss of barrier function, antiadhesive properties and antiproliferative influence on underlying SMCs • Migration and proliferation of SMCs  production of ECM • Oxidized lipid accumulation in vessel walls • Recruitment of macrophages and lymphocytes • Adherence of platelets to dysfunctional endothelium, exposed matrix, and macrophages

  5. Critical Diameter Adaptive arterial enlargement preserves luminal caliber until a critical plaque mass is reached

  6. Diagnostic Modalities • Non-invasive • ABIs • Segmental limb pressures • Limb plethysmography • Exercise testing • Doppler & duplex ultrasound • MR angiography • Invasive • Contrast arteriography • CT angiography

  7. Ankle-Brachial Index • Comparison of ankle pressure to brachial SBP • Reproducible, useful for long term surveillance • Normal 0.85-1.2 • Claudicants 0.5-0.7 • Critical ischemia < 0.4 • May be falsely elevated in calcified vessels (DM)

  8. ABI algorithm

  9. PVR • Calibrated air plethysmographic wave form recording system • Helps localize site of obstruction • Placement of cuffs at levels of proximal and distal thigh, calf and ankle

  10. Medical Therapy • Risk factor management • Lipid-lowering therapy • Smoking cessation • Exercise regimen • Antiplatelet therapy - ASA, ticlodipine, clopidogrel • Vasoactive - Cilostazol (Pletal), pentoxyfilline (Trental)

  11. Surgical Interventions

  12. Peripheral Arterial Occlusive Disease Carotid Stenosis

  13. Question A patient with symptomatic 85% carotid stenosis is found to have asymptomatic 50% stenosis on the contralateral side. Appropriate initial treatment includes: A. Simultaneous bilateral CEA B. Staged bilateral CEA with 1 week interval between stages C. CEA on symptomatic side only D. CEA on side of greatest stenosis regardless of symptoms

  14. Question A patient with symptomatic 85% carotid stenosis is found to have asymptomatic 50% stenosis on the contralateral side. Appropriate initial treatment includes: A. Simultaneous bilateral CEA B. Staged bilateral CEA with 1 week interval between stages C. CEA on symptomatic side only D. CEA on side of greatest stenosis regardless of symptoms

  15. Stroke • Third leading cause of death • Major modifiable risk factors • HTN • Smoking • Carotid stenosis • Cardiac diseases - a-fib, endocarditis, MS, recent MI • Atherosclerosis = leading cause of ischemic stroke • Artery-to-artery emboli • Thrombotic occlusion • Hypoperfusion from advanced stenosis

  16. CarotidStenosis • Causes of atherosclerosis at bifurcation • Low wall shear stress • Flow separation • Complex flow reversal along posterior wall of sinus • Sequence of events • b. Establishment of plaque • c. Soft, central necrotic core with overlying fibrous cap • d. Disruption of cap - necrotic cellular debris and lipid material become atherogenic emboli • e. Empty necrotic core becomes a deep ulcer = thrombogenic  thromboembolism

  17. Presentation • Asymptomatic bruit • Amaurosis fugax – transient monocular visual disturbance • Lateralizing TIA • Crescendo TIA • Stroke-in-evolution • CVA

  18. Diagnostic Algorithm

  19. Duplex Scanning • B-mode scan – Anatomic information • Doppler – Flow velocities • Plague  Increased peak and range of velocities

  20. Indications for CEA • Symptomatic – TIA, AF, small stroke • Proven – Stenosis > 70% • Acceptable – Stenosis 50-69% • Lesser symptoms, failed medical therapy • Asymptomatic • Proven – Stenosis > 60%, good risk • Uncertain • High risk patient • Surgeon morbidity-mortality >3% • Combined carotid coronary operation • Non-stenotic ulcerative lesions • Presence of ulceration or contralateral occlusion may lower threshhold for surgery

  21. Peripheral Arterial Occlusive Disease Chronic Occlusive Disease of the Lower Extremities

  22. Question Which of the following is an indication for bypass? A. Claudication within ½ block B. ABI of 0.5 C. Rest pain D. Occlusion of the superficial femoral and anterior tibial arteries

  23. Question Which of the following is an indication for bypass? A. Claudication within ½ block B. ABI of 0.5 C. Rest pain D. Occlusion of the superficial femoral and anterior tibial arteries

  24. Prevalence and survival • 2-3% population >50y, 10% > 70y • Lower extremity ischemia associated with decreased 5-yr survival • 97.4 % intermittent claudication • 80% claudication requiring surgery • 48% limb-threatening ischemia • 12% re-op for limb-threatening ischemia

  25. Signs and symptoms • Claudication • Extremity pain, discomfort or weakness • Consistently produced by the same amount of activity • Relieved with rest • Rest pain • Localized to metatarsal heads and toes • Worse with elevation or recumbent position • Improved with foot dependency

  26. Temperature • Hair loss • Pallor • Nail hypertrophy • Ulcer • Gangrene • Dry - non infected black eschar • Wet - tissue maceration and purulence

  27. Diagnostic algorithm

  28. Question Late vein graft failure is due to: A. Atherosclerotic changes in the vein B. Vein thrombosis C. Fibrointimal hyperplasia D. Kinking of the vein graft

  29. Question Late vein graft failure is due to: A. Atherosclerotic changes in the vein B. Vein thrombosis C. Fibrointimal hyperplasia D. Kinking of the vein graft

  30. Graft • Autologous Vein Graft - SV, arm vein • Synthetic - PTFE, Decron • Graft failure • 30 days - Technical error • 30 days to 2 years - Intimal hyperplasia • >2 years - Progression of atheresclerosis • Surveillance • Duplex 6 wks peri-op, 3 months/2 yrs, q 6 month

  31. Peripheral Arterial Occlusive Disease Acute Thromboembolic Disease

  32. Question 86 yo F with PMHx CAD, HTN, DM, A fib presents w/ sudden onset left lower extremity pain. Palpable femoral pulses. No palpable or doppler signals on left. Nl on right. Where is her obstruction? A. Common femoral artery B. Popliteal artery C. Iliac bifurcation D. Superficial femoral artery

  33. Question 86 yo F with PMHx CAD, HTN, DM, A fib presents w/ sudden onset left lower extremity pain. Palpable femoral pulses. No palpable or doppler signals on left. Nl on right. Where is her obstruction? A. Common femoral artery B. Popliteal artery C. Iliac bifurcation D. Superficial femoral artery

  34. Epidemiology • Incidence: 1.7 cases / 10,000 people / Yr. • Elderly • Male > female • Mortality 15%, Amputation 10-30% • Medical co-morbidities common • CVD 12%, CAD 45%, DM, 31%, HTN 60%, CHF 13%

  35. Sites of Embolization • Bifurcations • Femoral - 40% • Aortic - 10-15% • Iliac - 15% • Popliteal - 10% • Upper extremities - 10% • Cerebral - 10-15% • Mesenteric/visceral - 5%

  36. History • The onset and duration of symptoms • Pain • Sudden onset - embolic • Long-standing before acute event - thrombotic • Previous revascularization • Risk factors for atherosclerotic heart disease

  37. 6 Ps • Pain • Pallor • Pulselessness • Paresthesia • Paraparesis • Poikilothermia

  38. Palpable Pulses Location of Obstruction Femoral Popliteal Pedal - - - Aortoiliac segment + - - Femoral segment + + + - Distal popliteal ± tibials (Popliteal anerysm) + + - Distal popliteal ± tibials

  39. Management • Arteriography • Operative planning – target vessel • Therapeutic – thrombolysis, angioplasty • Should not delay revascularization & may be obtained intra-operatively • Rapid systemic anticoagulation • Heparin bolus/drip • Prevent propagation of thrombus, distal thrombosis, venous thrombosis • Surgery- Embolectomy • Percutaneous Thrombectomy

  40. Question 6 hours after a femoral-tibial artery bypass for advanced acute ischemia, the lower leg is swollen and painful with palpable pulse. The likely etiology is: A. DVT B. Reperfusion injury C. Thrombosis D. Arterial spasm

  41. Question 6 hours after a femoral-tibial artery bypass for advanced acute ischemia, the lower leg is swollen and painful with palpable pulse. The likely etiology is: A. DVT B. Reperfusion injury C. Thrombosis D. Arterial spasm

  42. Reperfusion injury • Local effects • Oxygen radicals accumulate • Compound cellular insult • Systemic effects • Acid, potassium, cytokines, cardiodepressants accumulate in ischemic limb • Sudden cardiac arrhythmias • Renal failure • Acute lung injury

  43. Prevention and management • Hydration • UO 100cc/hr • Alkalinization of urine • Prevent myoglobin precipitation in renal tubules • Mannitol • Antioxidant, osmotic diuretic • Insulin/glucose • Fasciotomy

  44. Question Regarding compartment syndrome, which of the following is correct? A. The leg is divided into two compartments--anterior and posterior B. The most commonly affected compartment is the posterior C. The earliest manifestation of acute compartment syndrome is pain D. Patients with compartment pressures greater than 15 mm Hg should undergo fasciotomy

  45. Question Regarding compartment syndrome, which of the following is correct? A. The leg is divided into two compartments--anterior and posterior B. The most commonly affected compartment is the posterior C. The earliest manifestation of acute compartment syndrome is pain D. Patients with compartment pressures greater than 15 mm Hg should undergo fasciotomy

  46. Anatomic Compartments of leg 4 compartments: Anterior Lateral (Peroneal) Deep Posterior Superficial Posterior

  47. Pathophysiology CELL INJURY CELL SWELLING TRANSUDATION OF FLUID  INTRACOMPARTMENT PRESSURE  CAPILLARY TRANSUDATE TISSUE PRES. = CAP. HYDR. PRES. VENULAR PRESSURE NO NUTRIENT FLOW ISCHEMIA

  48. Signs and symptoms • Pallor and pulselessness • Not always reliable • Distal pulses may be present • Paralysis - Late symptom • Pain - Severe and out of proportion, increased on passive motion • Paresthesia - Numbness, weak dorsiflexion, numbness in 1st dorsal web space • Tender, swollen, tense muscle compartments

  49. Indications for fasciotomy • Classically > 40-45 mm Hg at any point or > 30 mm Hg for 3-4 hrs • Arterial perfusion pressure is paramount • Mean arterial pressure - interstitial pressure < 30 mm Hg is critical • Diastolic pressure - compartment pressure < 20 mm Hg is critical