Cardiovascular Dynamics Lab Practice Test

An increased preload is equivalent to, or causes, a(n) _______.

Increased EDV Decreased EDV Increased heart rate Decreased contractility

Correct Answer:

Increased EDV

Explanation:

Preload is the initial stretch of the ventricular myocardium just before it contracts, driven by venous return. That stretch corresponds to the end-diastolic volume inside the ventricle. So when preload increases, the ventricle fills more, raising the end-diastolic volume. This is exactly why an increased preload is equivalent to an increased EDV. This relationship is the basis of the Frank-Starling mechanism: more EDV stretches the muscle to a more favorable length, increasing the force of contraction (and thus stroke volume) up to a limit. Preload itself doesn’t directly dictate heart rate or contractility, which is why those options don’t fit.

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