Distinguish dilated from hypertrophic cardiomyopathy in terms of structure and typical clinical presentation.

• A. Dilated: enlarged LV with reduced EF; HCM: thickened LV wall with preserved or increased EF, dynamic LV outflow tract obstruction
• B. Dilated: thin LV wall; HCM: dilated LV cavity
• C. Both have preserved EF
• D. HCM always causes LV dilation

Answer: (A)

Distinguishing these conditions comes down to how the left ventricle remodels and how this affects function. In dilated cardiomyopathy the LV becomes enlarged and its walls often thin, and systolic performance is depressed, so the ejection fraction is reduced. In hypertrophic cardiomyopathy the LV wall is thickened, often asymmetrically, making the ventricle stiff and impairing filling, while systolic function is usually preserved or even increased early on; there can also be dynamic obstruction of the LV outflow tract due to septal hypertrophy and systolic anterior motion of the mitral valve.

Clinically, that pairing shows up as heart failure symptoms from poor systolic function in the dilated form—exertional dyspnea, fatigue, edema—whereas hypertrophic cardiomyopathy tends to present with exertional symptoms like dyspnea and chest pain, possible syncope, and a murmur that reflects LVOT obstruction and changes with maneuvers affecting preload.