Laplace's law applied to ventricular wall stress states: Wall stress = (Pressure × Radius) / (2 × Wall thickness). In a dilated cardiomyopathy patient with an LV end-diastolic radius of 4 cm and wall thickness of 0.8 cm compared to a normal LV with radius 2.5 cm and wall thickness 1.1 cm, systolic wall stress is markedly elevated because:

• A Increased chamber pressure directly raises wall stress without geometric influence
• B Increased radius and thinned wall both amplify wall stress; this is the mechanism of eccentric hypertrophy compensation ✓
• C Thinned wall alone accounts for increased stress; radius does not affect wall stress
• D Increased heart rate raises wall stress by shortening diastolic filling time

Explanation

Laplace's law shows that wall stress increases proportionally with cavity radius and inversely with wall thickness. In dilated cardiomyopathy, both the numerator (larger radius) and denominator (thinner wall) worsen simultaneously, dramatically raising systolic wall stress (afterload). Eccentric hypertrophy adds sarcomeres in series to increase cavity volume. Concentric hypertrophy increases wall thickness to normalise wall stress in pressure overload states.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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