Which statement describes the relationship between dilation and ejection fraction in dilated cardiomyopathy?

• A. Dilation occurs with preserved ejection fraction
• B. Dilation is associated with reduced ejection fraction
• C. Dilation improves ejection fraction
• D. EF remains normal with dilation

Answer: (B)

In dilated cardiomyopathy, the heart muscle becomes weakened and the ventricle enlarges (dilation) as part of adverse remodeling. This dilation is paired with systolic dysfunction, meaning the heart cannot pump effectively. Since ejection fraction is the fraction of blood pumped out of the ventricle with each beat (EF = stroke volume / end-diastolic volume), the enlarged ventricle often has a disproportionately reduced stroke volume for the much larger end-diastolic volume. So EF falls, which is why dilated cardiomyopathy is typically associated with a reduced ejection fraction and a systolic heart failure picture.

This differs from scenarios where dilation occurs but EF remains normal or preserved (diastolic dysfunction with HFpEF) or where dilation is accompanied by an improvement in EF. The key point is that the dysfunction of contraction in the setting of dilation leads to a lowered EF, not a normal or increased one.