## Core Concept
Ranolazine is a medication used in the management of chronic angina. It works by improving blood flow to help the heart work more efficiently. The primary mechanism of action involves the inhibition of the late sodium current (I_Na) in cardiac cells.

## Why the Correct Answer is Right
Ranolazine is known for its anti-anginal effects without significantly affecting heart rate or blood pressure. By inhibiting the late sodium current, it reduces sodium and calcium overload in ischemic cardiac cells, thereby decreasing wall tension and improving diastolic function. This action does not significantly alter heart rate or contractility.

## Why Each Wrong Option is Incorrect
- **Option A:** Not provided, so we cannot assess its accuracy directly.
- **Option B:** Not provided, so we cannot assess its accuracy directly.
- **Option D:** Not provided, so we cannot assess its accuracy directly.

## Clinical Pearl / High-Yield Fact
A key point to remember about ranolazine is that it can prolong the QT interval, which may increase the risk of arrhythmias. Therefore, it's contraindicated in patients with long QT syndrome. Also, ranolazine is often used as an add-on therapy for patients with chronic angina who have not achieved adequate control with other anti-anginal medications.

## Correct Answer: D.