What could cause sudden heaviness in the left leg, considering factors such as age, medical history, smoking status, and family history of vascular disease?

Sudden Heaviness in Left Leg: Differential Diagnosis and Evaluation

Sudden heaviness in the left leg is most concerning for acute limb ischemia (ALI) from arterial thrombosis or embolism, which requires urgent evaluation within hours to prevent limb loss, though other causes including deep vein thrombosis, neurological conditions, and chronic peripheral artery disease must also be considered based on the clinical presentation. 1

Immediate Life- and Limb-Threatening Causes

Acute Limb Ischemia (ALI)

• ALI presents with sudden onset (<2 weeks) of the "6 Ps": pain, pallor, pulselessness, poikilothermia (coolness), paresthesias, and paralysis. 1
• The severity depends on whether the occlusion is embolic (more severe, sudden) versus thrombotic (may be less severe if collaterals exist). 1
• Embolic sources include atrial fibrillation, dilated cardiomyopathy, left ventricular aneurysm, or proximal arterial aneurysms. 1
• Thrombotic ALI typically occurs on pre-existing atherosclerotic disease and may have preceding claudication symptoms. 1

Critical Classification (Rutherford): 1

• Class I (Viable): No sensory/motor loss, audible Doppler signals—not immediately threatened
• Class IIa (Marginally threatened): Mild sensory loss limited to toes, no motor loss, often inaudible arterial Doppler—salvageable if promptly treated
• Class IIb (Immediately threatened): Sensory loss beyond toes, mild-moderate motor weakness, inaudible arterial Doppler—requires urgent revascularization
• Class III (Irreversible): Complete sensory loss, paralysis, inaudible arterial and venous Doppler—major tissue loss inevitable

Deep Vein Thrombosis

• Presents with unilateral leg swelling, heaviness, pain, warmth, and possible palpable cord. 2
• Risk factors include immobilization, malignancy, hypercoagulable states, recent surgery, or trauma. 2

Chronic Vascular Causes

Peripheral Artery Disease (PAD)

• Smoking is the single most important modifiable risk factor for PAD, with heavy smokers having substantially elevated risk. 3
• Patients ≥50 years old with smoking history or diabetes should undergo ankle-brachial index (ABI) testing, which is 95% sensitive and specific when <0.90. 3, 1
• Critical pitfall: Normal pulses do NOT reliably rule out PAD—never rely on palpable pulses alone to exclude disease. 3, 1
• Typical claudication presents as exertional leg muscle pain that resolves within 10 minutes of rest, but atypical presentations include heaviness, fatigue, or tingling. 1

Isolated Internal Iliac Artery Stenosis

• Presents with bilateral buttock, hip, and thigh claudication during exercise that resolves with rest, and may have normal femoral pulses and normal ABI, which can mislead clinicians. 4
• The ACC/AHA guidelines note that arterial imaging (CTA or MRA) should be considered even with normal post-exercise ABI when isolated internal iliac artery disease is suspected. 4

Chronic Venous Insufficiency

• Most common localized cause in older patients, characterized by peripheral edema with hyperpigmentation, trophic skin changes, and lipodermatosclerosis. 2
• Edema typically worsens in the evening and improves with leg elevation. 2
• Never apply compression therapy without first checking ABI to exclude PAD. 2

Neurological Causes

Diabetic Peripheral Neuropathy

• Presents with tingling, numbness, burning, throbbing, or shooting sensations rather than true heaviness. 1
• Diagnosis requires one or more abnormal tests: 10-g monofilament, vibration (128-Hz tuning fork), pinprick sensation, ankle reflexes, or vibration perception threshold. 1
• All adults with diabetes should undergo comprehensive foot examination at least annually. 1

Lumbar Radiculopathy or Spinal Stenosis

• Presents with unilateral leg heaviness, weakness, or numbness in dermatomal distribution. 1
• Neurogenic claudication worsens with standing/walking and improves with sitting or forward flexion (unlike vascular claudication). 1

Stroke or Transient Ischemic Attack

• Sudden onset unilateral leg weakness or heaviness with possible associated arm weakness, facial droop, or speech changes. 5

Systematic Diagnostic Approach

Step 1: Assess Urgency (Rule Out ALI)

Examine for the "6 Ps" immediately: 1

• Pain (sudden onset or worsening)
• Pallor (pale or mottled skin)
• Pulselessness (absent pedal pulses)
• Poikilothermia (cold to touch)
• Paresthesias (numbness, tingling)
• Paralysis (inability to move toes/foot)

If any Class IIb or III findings present, this is a surgical emergency requiring immediate vascular surgery consultation. 1

Step 2: Obtain Focused History

• Timing: Sudden (<2 weeks) versus gradual onset 1
• Smoking history: Automatic trigger for PAD evaluation if ≥50 years old 3
• Cardiovascular risk factors: Diabetes, hypertension, hyperlipidemia, age >50 years 1, 3
• Cardiac history: Atrial fibrillation, recent MI, cardiomyopathy (embolic sources) 1
• Previous vascular disease: Prior claudication, ulceration, amputation, revascularization 1
• Exertional pattern: Does heaviness occur with walking and resolve with rest? 1
• Associated symptoms: Swelling, skin changes, neurological symptoms 1, 2

Step 3: Perform Comprehensive Vascular Examination

Inspection: 1

• Skin color (pallor, rubor, cyanosis)
• Temperature (cool versus warm)
• Skin integrity (ulcers, gangrene, fissures)
• Trophic changes (hair loss, shiny skin, nail changes)
• Edema pattern (unilateral versus bilateral, pitting versus non-pitting)

Palpation: 1

• Femoral, popliteal, dorsalis pedis, and posterior tibial pulses bilaterally
• Grade pulse intensity (0 = absent, 1+ = diminished, 2+ = normal, 3+ = bounding)

Functional assessment: 1

• Capillary refill time (normal <3 seconds)
• Rubor on dependency
• Pallor on elevation
• Venous filling time

Step 4: Obtain Ankle-Brachial Index (ABI)

Perform bilateral resting ABI regardless of pulse examination findings. 3, 1

• ABI <0.90: Confirms PAD diagnosis 3, 1
• ABI 0.91-1.40: Normal range 1
• ABI >1.40: Obtain toe-brachial index due to noncompressible vessels (common in diabetes) 3, 1

If clinical suspicion for PAD exists despite normal ABI (especially with proximal symptoms), obtain exercise ABI or proceed to imaging. 4, 1

Step 5: Advanced Imaging When Indicated

• CTA or MRA of pelvis with lower extremity runoff: For suspected internal iliac stenosis with normal ABI 4
• Duplex ultrasound: For suspected DVT or chronic venous insufficiency 2
• Contrast arteriography: For definitive localization before revascularization 6
• MRI lumbar spine: For suspected neurological causes 1

High-Risk Populations Requiring Lower Threshold for Evaluation

Patients with diabetes, hypertension, or hyperlipidemia have 2-4 fold increased risk of PAD. 2

• Diabetes increases critical limb ischemia and amputation risk 7-15 fold. 2
• Hypertension increases PAD risk 2.5-4 fold. 2, 7
• Patients with PAD have 25-35% risk of MI or stroke over 5 years, with additional 25% mortality rate. 3

Critical Pitfalls to Avoid

1. Never rely on palpable pulses alone to exclude PAD—pulses can be normal even with significant disease. 3, 1
2. Don't underestimate smoking as a risk factor—it's the most potent modifiable risk factor for PAD. 3, 5
3. Don't assume bilateral symptoms exclude unilateral vascular pathology—internal iliac stenosis can present bilaterally with normal distal pulses. 4
4. Never apply compression therapy for presumed venous insufficiency without first checking ABI to exclude PAD. 2
5. Don't delay vascular surgery consultation for suspected ALI—time to revascularization directly impacts limb salvage. 1