## Core Concept
The Anrep effect refers to the increase in contractility of the heart in response to an increase in afterload. This phenomenon is an intrinsic property of the heart, demonstrating how the heart muscle adapts to changes in the pressure it must pump against.

## Why the Correct Answer is Right
The Anrep effect is a physiological response where an increase in afterload (the pressure against which the heart must work to eject blood) leads to an increase in the contractile force of the heart. This effect is mediated through an increase in intracellular calcium concentration in cardiac myocytes, which enhances the interaction between actin and myosin filaments, thereby increasing contractility. The Anrep effect is an important mechanism by which the heart adapts to changes in blood pressure.

## Why Each Wrong Option is Incorrect
- **Option A:** This option does not accurately describe the Anrep effect. Without specific details on what option A states, we can infer based on the definition of the Anrep effect that any option not describing an increase in contractility in response to increased afterload is incorrect.
- **Option B:** Similarly, if option B does not relate to the heart's response to increased afterload by increasing contractility, it is incorrect.
- **Option C:** If option C describes a different physiological response not related to the Anrep effect, it is incorrect.

## Clinical Pearl / High-Yield Fact
A key clinical pearl related to the Anrep effect is that it helps explain why patients with hypertension (high blood pressure) often have left ventricular hypertrophy (LVH) as a compensatory mechanism. The heart works harder to pump against the increased pressure (increased afterload), leading to muscle thickening. Understanding this effect is crucial for managing patients with cardiovascular diseases.

## Correct Answer Line
**Correct Answer: D.**