Peripheral Vascular System: Comprehensive Study Notes

Anatomy of the Arterial Wall

• Three concentric layers

  • Intima
  • Single layer of endothelial cells with extensive metabolic activity
  • Internal elastic membrane forms its outer border
  • Site where atherosclerosis begins
  • Media
  • Smooth-muscle layer with elastic properties (internal & external elastic laminae)
  • Receives blood via the vasa vasorum
  • Adventitia
  • Outer connective-tissue layer containing nerve fibers & vasa vasorum

• Atherosclerosis (Box 17-1, Fig 17-2)

  • Endothelial injury (e.g.
  • Smoking, hypertension) → LDLs enter intima → oxidation → inflammatory response
  • Monocytes → macrophages → foam cells → fatty streaks → fibrous cap over necrotic lipid core
  • Plaque rupture/erosion exposes thrombogenic core → thrombus →
  • Coronary arteries → acute MI
  • Carotids → embolic stroke
  • Key concept: plaque activation (not just luminal stenosis) precipitates ischemia/infarction

Arterial Tree, Diameters & Functional Sub-classes

• Elastic (conducting) arteries: aorta, common carotid, iliac
• Muscular (distributing) arteries: coronary, renal
• Small arteries: <2\,\text{mm}
• Arterioles: 20\text{–}100\,\mu\text{m} – principal “resistance vessels” (major determinant of systemic vascular resistance & BP)
• Capillaries: 7\text{–}8\,\mu\text{m} (≈1 RBC width); endothelium only → rapid gas exchange
• Collateral circulation: chronic obstruction → enlargement of anastomoses

Major Palpable Arterial Pulses

• Upper limb (Fig 17-3)
  • Brachial: medial to biceps tendon in antecubital fossa
  • Radial: lateral flexor wrist
  • Ulnar: medial flexor wrist (often obscured)
  • Two palmar arches protect hand/finger perfusion
• Abdomen (Fig 17-4)
  • Aortic pulsation in epigastrium
  • Branches (non-palpable):
  • Celiac trunk → foregut organs
  • Superior mesenteric → midgut
  • Inferior mesenteric → hindgut
• Lower limb (Fig 17-5)
  • Femoral: below inguinal ligament (midway ASIS ↔︎ symphysis)
  • Popliteal: deep behind knee
  • Posterior tibial (PT): behind medial malleolus
  • Dorsalis pedis (DP): dorsum foot, lateral to extensor tendon of great toe

Venous System

• Thin-walled, highly distensible; accommodate ≈\tfrac23 circulating blood
• Intima: non-thrombogenic endothelium; valves ensure unidirectional flow
• Media: elastic tissue + smooth muscle; caliber changes with small pressure variations
• Deep vs Superficial leg veins (Fig 17-6 & 17-7)
  • Deep: ≈90\% of venous return, well supported
  • Superficial: subcutaneous, poor support
  • Great saphenous → femoral vein
  • Small saphenous → popliteal vein
  • Perforators bridge systems; calf-muscle pump propels blood ↑
• Leg veins prone to dilatation, compression, ulceration, tumor invasion

Lymphatic System

• Capillaries → thin channels → collecting ducts → venous angles
  • Right lymphatic duct: right head/neck, thorax, upper limb
  • Thoracic duct: remainder of body
• Lymph nodes: filter lymph & mount immune response
  • Palpable superficial groups: cervical, axillary, epitrochlear (≈3\,\text{cm} above medial epicondyle), inguinal
  • Inguinal nodes (Fig 17-9)
  • Horizontal chain: drains lower abdomen, buttock, external genitalia (not testes), anal canal, lower vagina
  • Vertical group: along upper great saphenous; drains leg
• Clinical terms
  • Lymphedema: obstructed lymph drainage → non-pitting, brawny swelling
  • Lymphadenopathy: enlarged nodes (>1\text{–}2\,\text{cm} inguinal; smaller elsewhere)

Trans-Capillary Fluid Exchange & Edema Pathogenesis

• Forces: venous hydrostatic pressure, plasma oncotic pressure, capillary permeability, lymphatic clearance
• Mechanisms → edema
  • \uparrow Plasma volume (Na⁺ retention)
  • Altered Starling forces with net filtration
  • Lymphatic or venous obstruction
  • \uparrow Capillary permeability (e.g.
    sepsis)
• Pitting vs non-pitting
  • Pitting → low protein fluid (HF, nephrotic syndrome, cirrhosis, dependency)
  • Non-pitting → lymphatic etiology or myxedema

Health History & Symptom Assessment

• Key aims: differentiate vascular vs neuro/musculoskeletal causes; assess perfusion
• Common/Concerning Sx
  • Pain, cramping, throbbing, coldness, numbness, pallor, hair loss, ulcers, swelling
  • Intermittent claudication (relieved within \le10 min rest)
  • Rest pain (critical limb ischemia)
  • Abdominal/flank/back pain (consider AAA, mesenteric ischemia)
• Peripheral Arterial Disease (PAD)
  • Atherosclerotic dz distal to aortic bifurcation
  • Triples risk of MI & stroke
  • Classic claudication in only \approx10\%; many have atypical leg pain or are asymptomatic
  • Risk factors = CAD risks: age ≥50, smoking, diabetes, HTN, hyperlipidemia, African American ethnicity, family Hx AAA
  • PAD warning signs (Box 17-2)
  • Fatigue, aching, numbness, pain limiting walking/exertion
  • Erectile dysfunction (aorto-iliac)
  • Non-healing wounds
  • Rest pain changing with position
  • Post-prandial abd pain + weight loss (mesenteric ischemia)
• Symptom location → likely arterial level
  • Buttock/hip → aorto-iliac
  • Thigh → common femoral
  • Upper calf → superficial femoral
  • Lower calf → popliteal
  • Foot → tibial/peroneal
• AAA clues: sudden flank/back pain, pulsatile abd mass; food fear, early satiety, urinary sx
• Venous thromboembolism (VTE)
  • DVT ~2,000,000 cases/yr US; \approx20\% → PE
  • Upper-extremity DVT \approx10\% (catheters, pacers)
  • Unilateral swelling, pain, discoloration
  • Use Wells or Geneva scores; individual findings unreliable

Physical Examination Strategy (Top ↘ Bottom)

1. Carotids → Upper extremities → Abdomen → Lower extremities
2. Compare bilaterally:
   • Pulse quality & amplitude
   • Vessel size
   • Skin temp & color
   • Hair distribution
   • Edema presence
3. Palpate abdominal aorta for width & pulsatile mass (AAA)

Pulse Grading (ACC/AHA 0–3 scale, Box 17-3)

• 3+ = bounding
• 2+ = brisk/normal
• 1+ = diminished
• 0 = absent

Upper Extremity Exam

• Inspection: size, symmetry, color, venous pattern
• Palpation
  • Radial pulse (Fig 17-11)
  • Brachial pulse (Fig 17-13)
  • Epitrochlear nodes (Fig 17-14)
• Raynaud disease: normal wrist pulses but episodic digital pallor (Fig 17-12)

Abdominal Exam Highlights

• Auscultate: aortic, renal, femoral bruits
• Palpate: aortic diameter (<3\,\text{cm} normal); detect pulsatile masses
• Palpate superficial inguinal nodes (Fig 17-15) – normal ≤2\,\text{cm}, nontender

Lower Extremity Exam

• Inspection (supine & standing)
  • Size (measure calf ≈10\,\text{cm} below tibial tuberosity; ⊿>3\,\text{cm} → LR>2 for DVT)
  • Edema pattern (uni vs bilateral)
  • Venous pattern/varicosities (Fig 17-16) – fill when standing
  • Skin: color, texture, ulceration (Tables 17-3 & 17-4)
  • Hair loss, nail dystrophy
• Palpation – Arteries
  • Femoral (Fig 17-19) – absent pulse LR >6 for PAD; widened → aneurysm
  • Popliteal (Fig 17-20 & 17-21) – deeper, diffuse; widened → aneurysm (men ≥50)
  • DP (Fig 17-22) – congenitally absent ≈8\%; absent with preserved proximal pulses LR >14 for PAD
  • PT (Fig 17-23) – behind medial malleolus
  • Temperature: asymmetric coolness LR >6 for PAD (poikilothermia)
• Palpation – Veins & Edema
  • Pitting: press dorsum foot, behind medial malleolus, shin (Fig 17-24)
  • Grading 1+ to 4+ (Fig 17-25 shows 3+)
  • Tenderness/cords: calf & groin (iliofemoral DVT → painful, pale, swollen leg)
  • Homan sign is obsolete

Special Tests

• Ankle–Brachial Index (ABI)
  • Procedure (Fig 17-26 & 17-27)
  1. Supine ≥10 min
  2. Measure bilateral brachial systolic BP with Doppler (avg of 2)
  3. Measure ankle systolic BP (DP & PT both legs)
  • Calculation
    {\displaystyle \text{ABI} = \frac{\text{higher ankle SBP}}{\text{higher brachial SBP}}}
  • Interpretation
  • Normal 0.90\text{–}1.40
  • >1.40 → non-compressible (calcified) artery
  • <0.90 → PAD; <0.50 → severe PAD
  • Caveat: diabetes/elderly calcification → falsely high readings
• Allen Test (Fig 17-29 – 31)
  • Occlude radial & ulnar; patient opens hand → release one artery
  • Flush in 3\text{–}5\,\text{s} = patent
  • Persisting pallor (Fig 17-32) → occlusion
  • Barbeau test: oximeter-based alternative

Documentation Example

"Extremities warm, no edema or varicosities. Calves supple, nontender. No bruits. Brachial, radial, femoral, popliteal, DP, PT pulses 2+ & symmetric."

Health Promotion & Screening

• PAD Screening
  • Prevalence: 200\,\text{M} worldwide; 8\% (65-75 y) → 18\% (>75 y)
  • ABI
  • USPSTF: evidence insufficient (I); ACC/AHA: reasonable in high-risk patients
• AAA Screening
  • Definition: infrarenal aorta ≥3\,\text{cm}; rupture risk ↑ markedly >5.5\,\text{cm}
  • Prevalence: 3.9-7.2 % men, 1.0-1.3 % women >50 y
  • Strongest risks: male, age, smoking, family Hx (15-28 %)
  • Modality: abdominal US (Sn 94\text{–}100\%, Sp 98\text{–}100\%)
  • USPSTF: one-time US men 65-75 y with ≥100 lifetime cigarettes (grade B); selective for nonsmokers (C); against routine in women nonsmokers (D)

Edema Types (Table 17-1)

• Pitting (low protein): HF, nephrotic, cirrhosis, dependency, meds
• Chronic Venous Insufficiency: soft pitting ± brawny skin, pigmentation, ulceration
• Lymphedema: initially pitting → indurated, non-pitting; thick skin; usually bilateral; no pigmentation

Chronic Insufficiency of Arteries vs Veins (Table 17-3)

Common Ulcers (Table 17-4)

• Venous: medial/lateral malleolus; irregular shallow; edema + pigmentation; pain in 75 %
• Arterial: toes/feet; punched-out; severe pain unless neuropathic; gangrene common
• Neuropathic: pressure points in insensate foot; surrounding callus; painless; no gangrene unless infected

Practical/Philosophical Points

• Vascular assessment integrates anatomy (palpable pulses), physiology (ABI), & pathology (plaque biology)
• Atherosclerosis is systemic—finding PAD should prompt CV risk reduction (statins, antiplatelets, lifestyle)
• Venous & lymphatic disorders impact quality of life (pain, ulceration, disfigurement); early recognition prevents morbidity
• Ethical duty: screen those who benefit (AAA in male smokers) but avoid over-screening low-yield populations
• Remember “diligent comparison” – asymmetry is a powerful diagnostic clue

Key Numbers & Formulas

• Arteriole diameter: 20\text{–}100\,\mu\text{m}
• Capillary diameter: 7\text{–}8\,\mu\text{m}
• ABI formula: \text{ABI}=\dfrac{\text{ankle SBP}}{\text{brachial SBP}}
• ABI normals: 0.90\text{–}1.40; severe PAD <0.50
• AAA: diameter \ge3\,\text{cm}; rupture risk high >5.5\,\text{cm}
• Calf ⊿ >3\,\text{cm} → consider DVT
• Leg veins carry \approx90\% of return via deep system
• Portal vein supplies \approx75\% of hepatic blood flow