Cause of Intermittent Claudication
Intermittent claudication is caused by atherosclerotic occlusive disease of the lower extremity arteries, resulting in inadequate blood supply to the leg muscles during exercise. 1
Underlying Pathophysiology
Peripheral arterial disease (PAD) refers to atherosclerotic occlusive disease of the arterial system distal to the aortic bifurcation, which is the fundamental cause of intermittent claudication in the Western world. 1 The disease process involves:
- Atherosclerotic plaque formation that progressively narrows the arterial lumen, reducing blood flow to the lower extremities 1, 2
- Exercise-induced ischemia occurs when oxygen demand of working leg muscles exceeds the supply available through stenotic arteries, producing the characteristic pain, cramping, and fatigue 2, 3
- Rest relieves symptoms because oxygen demand decreases when exercise stops, allowing the limited blood supply to meet baseline metabolic needs 1, 2
In patients with diabetes, the disease more frequently affects arteries below the knee, making the condition more challenging to treat. 1
Major Risk Factors
The development of atherosclerotic PAD causing claudication is driven by specific risk factors:
- Cigarette smoking is the most powerful risk factor, increasing PAD risk 2- to 6-fold and claudication risk 3- to 10-fold, with over 80% of PAD patients being current or former smokers 1
- Diabetes mellitus increases PAD risk 2- to 4-fold, with diabetic patients being 7- to 15-fold more likely to undergo major amputation 1
- Hypercholesterolemia and lipid abnormalities (elevated LDL, decreased HDL, hypertriglyceridemia) contribute to atherosclerotic plaque formation 1
- Hypertension is associated with PAD, though the relationship is weaker than with coronary disease 1
- Older age dramatically increases prevalence, with 3-5% affected at age 60 and over 25% between ages 80-90 4
Clinical Significance
PAD causing claudication is an extremely important marker of systemic atherosclerosis. 3 The arterial obstruction between the aortic arch and feet that produces claudication symptoms reflects widespread atherosclerotic disease:
- Up to 60% of patients with intermittent claudication have significant underlying coronary and/or carotid disease 3
- 40% of all patients with claudication die or suffer a stroke within 5 years of presentation 3
- The severity of claudication symptoms correlates poorly with ankle-brachial index (ABI), but cardiovascular outcomes worsen as ABI decreases 4
Common Pitfall
Not all exertional leg pain is vascular claudication. Pseudoclaudication from spinal stenosis, nerve root compression, hip arthritis, and venous claudication can mimic PAD symptoms but have different underlying causes. 1, 5 True vascular claudication is distinguished by consistent onset with activity, relief within 10 minutes of rest, and association with diminished pulses or abnormal ABI. 5