1.6 Vascular Diseases (Aortic Aneurysm, PAD, DVT)

Vascular Diseases (Aortic Aneurysm, PAD, DVT)

PANCE High-Yield Focus: Vascular diseases encompass high-acuity surgical emergencies and common chronic conditions. Memorize the USPSTF screening guidelines for Abdominal Aortic Aneurysm (AAA) and surgical size thresholds, the Stanford classification of aortic dissection and its immediate pharmacological management, the clinical interpretation of the Ankle-Brachial Index (ABI) for Peripheral Arterial Disease (PAD), and the diagnostic workup for Deep Vein Thrombosis (DVT).

Abdominal Aortic Aneurysm (AAA)

An abdominal aortic aneurysm is defined as a permanent, localized dilation of the abdominal aorta resulting in a diameter >=3.0 cm, typically occurring infrarenally.

• Pathophysiology: Driven by chronic transmural inflammation, matrix metalloproteinase-mediated degradation of elastin and collagen, and smooth muscle cell depletion. These processes lead to progressive thinning and weakening of the medial layer of the aortic wall.
• Risk Factors: Cigarette smoking is the strongest modifiable risk factor. Other risk factors include male sex, advanced age (>=65 years), white race, hypertension, and a positive family history.
• Screening Guidelines: The USPSTF recommends a one-time screening for AAA using abdominal ultrasound in men aged 65 to 75 who have ever smoked (defined as >=100 cigarettes in their lifetime). Screening is not recommended for women or men who have never smoked.
• Clinical Presentation: Most AAAs are asymptomatic and found incidentally. A ruptured AAA is a catastrophic event presenting with the classic triad of:
  1. Severe, acute-onset abdominal, back, or flank pain.
  2. Hypotension or hemodynamic collapse.
  3. A pulsatile abdominal mass.
• Diagnostic Workup: Abdominal ultrasound is the initial diagnostic test of choice for screening and monitoring. CT angiography of the abdomen and pelvis is the gold standard for defining anatomical details prior to surgical planning.
• Management & Surgical Thresholds:
  • Surgical Repair: Indicated for aneurysms >=5.5 cm in diameter, those that grow rapidly (>0.5 cm in 6 months or >1.0 cm in 1 year), or if the patient becomes symptomatic (pain, tenderness), regardless of size. Repair can be performed via open laparotomy or Endovascular Aneurysm Repair (EVAR).
  • Monitoring Intervals:
    • 3.0 to 3.9 cm: Ultrasound every 3 years.
    • 4.0 to 4.9 cm: Ultrasound every 12 months.
    • 5.0 to 5.4 cm: Ultrasound every 6 months.

Aortic Dissection

Aortic dissection is a life-threatening emergency characterized by an intimal tear that allows blood to enter the media, creating a false lumen that propagates along the vessel.

• Pathophysiology: Associated with cystic medial necrosis. The primary driver is chronic hypertension, which increases shear stress on the aortic wall. Other risk factors include cocaine use, bicuspid aortic valve, and connective tissue disorders (Marfan and Ehlers-Danlos syndromes).
• Clinical Presentation: Sudden-onset, excruciating, "tearing" or "ripping" chest pain that radiates to the back between the scapulae. Physical exam findings include asymmetric blood pressures between the arms (difference >20 mmHg), diminished distal pulses, a new murmur of aortic regurgitation (indicating proximal extension), or focal neurological deficits.
• Classification:
  • Stanford Classification:
    • Type A: Involves the ascending aorta (proximal to the brachiocephalic artery). This is a surgical emergency.
    • Type B: Involves only the descending aorta (distal to the left subclavian artery). This is initially managed medically.
  • DeBakey Classification: Type I (ascending and descending), Type II (ascending only), Type III (descending only).
• Diagnostic Workup: CT angiography of the chest and abdomen is the initial test of choice in stable patients. Transesophageal echocardiography (TEE) is the test of choice in hemodynamically unstable patients or those with severe renal impairment (to avoid contrast).
• Management:
  • Stanford Type A: Emergent surgical repair.
  • Stanford Type B: Medical management to control heart rate and blood pressure.
    • Pharmacotherapy: First-line therapy is intravenous short-acting beta-blockers (e.g., Esmolol, Labetalol) to target a heart rate <60 bpm and systolic blood pressure of 100–120 mmHg. Lowering the heart rate first minimizes the rate of pressure rise (dp/dt) and prevents dissection propagation. Vasodilators (like nitroprusside) may be added only after beta-blockade is established, to prevent reflex tachycardia and increased wall shear stress.

Peripheral Arterial Disease (PAD)

PAD results from systemic atherosclerosis causing progressive narrowing and occlusion of the lower extremity arteries.

• Clinical Presentation: The hallmark symptom is intermittent claudication, characterized by predictable calf, thigh, or buttock pain precipitated by physical exertion (walking) and relieved by rest. Advanced disease leads to critical limb ischemia, presenting as ischemic rest pain (typically worse at night when lying flat, relieved by dangling the leg over the bed) and non-healing arterial ulcers (typically on distal joints or toes, painful, with a "punched-out" appearance) or gangrene.
• Physical Exam Findings: Diminished or absent distal pulses (dorsalis pedis and posterior tibial), localized muscle atrophy, loss of hair, thin and shiny skin, cool extremities, pallor with leg elevation, and dependent rubor.
• Diagnostic Workup: The initial test of choice is the Ankle-Brachial Index (ABI), which compares the systolic blood pressure in the ankles to the arms.
  • ABI Interpretation:
    • 0.91 to 1.30: Normal.
    • 0.41 to 0.90: Mild-to-moderate PAD (claudication).
    • <=0.40: Severe PAD (critical limb ischemia).

    • 1.30: Non-compressible, calcified vessels (common in patients with diabetes or chronic kidney disease; requires toe-brachial index or duplex ultrasound).

• Management:
  1. Risk Factor Modification: Smoking cessation is critical. Initiate high-intensity statin therapy (Atorvastatin 80 mg) and control diabetes/hypertension.
  2. Exercise Therapy: A structured, supervised walking program improves walking distance.
  3. Antiplatelet Therapy: Aspirin or Clopidogrel to reduce cardiovascular mortality.
  4. Cilostazol: A phosphodiesterase-3 inhibitor that induces vasodilation and inhibits platelet aggregation, used for symptom relief in claudication.
     • PANCE Trap: Cilostazol is strictly contraindicated in patients with heart failure of any severity due to class-effect increased mortality.

Deep Vein Thrombosis (DVT) & Thrombophlebitis

DVT involves thrombus formation in the deep veins of the lower extremity (e.g., femoral, popliteal, iliac veins).

• Pathophysiology: Governed by Virchow's Triad:
  1. Venous Stasis: Prolonged immobility, hospitalization, long-distance travel.
  2. Hypercoagulability: Malignancy, pregnancy, oral contraceptives, genetic mutations (Factor V Leiden, Prothrombin G20210A, Antithrombin deficiency).
  3. Endothelial Injury: Surgery, trauma.
• Clinical Presentation: Unilateral calf or leg pain, swelling (difference in calf circumference >3 cm), warmth, and erythema. Homans' sign (pain in the calf upon ankle dorsiflexion) is unreliable.
• Diagnostic Workup: Guided by the Wells Criteria.
  • Low Probability: Perform a high-sensitivity D-dimer test. If negative, DVT is ruled out.
  • Moderate-to-High Probability: Perform compression venous duplex ultrasonography.
• Management: Anticoagulation for a minimum of 3 months. Options include Direct Oral Anticoagulants (DOACs like Apixaban or Rivaroxaban) or Low-Molecular-Weight Heparin (LMWH) bridged to Warfarin. An inferior vena cava (IVC) filter is indicated only if the patient has a documented proximal DVT and an absolute contraindication to anticoagulation.
• Superficial Thrombophlebitis: Presents with a painful, warm, erythematous, palpable cord-like vein. Typically managed with supportive care (NSAIDs, warm compresses, leg elevation). If the thrombus is within 5 cm of the saphenofemoral junction, anticoagulation is indicated to prevent propagation into the deep venous system.