Basic Science Peripheral Vascular Disease

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

28. Diagnostic algorithm

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. 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

31. 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

32. Peripheral Arterial Occlusive Disease Acute Thromboembolic Disease

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. 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

35. 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%

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

37. 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

38. 6 Ps • Pain • Pallor • Pulselessness • Paresthesia • Paraparesis • Poikilothermia

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

40. 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

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. 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

43. 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

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

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

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

49. 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

50. 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