Nitroglycerine exes beneficial effect in classical angina pectoris primarily by
**Core Concept**
Nitroglycerine is a vasodilator used to treat angina pectoris, which is characterized by chest pain due to transient myocardial ischemia. The primary mechanism of nitroglycerine involves the release of **nitric oxide**, leading to relaxation of vascular smooth muscle. This effect is primarily mediated through the **cGMP pathway**.
**Why the Correct Answer is Right**
Although the specific correct answer option is not provided, nitroglycerine's beneficial effect in classical angina pectoris is primarily due to its ability to cause **venodilation**, which reduces **preload** and subsequently decreases the workload of the heart, lowering myocardial oxygen demand. This effect is more significant than its ability to cause **arteriodilation**, which would increase oxygen supply by reducing **afterload** and dilating coronary arteries.
**Why Each Wrong Option is Incorrect**
**Option A:** Would be incorrect if it suggested arteriodilation as the primary mechanism, as while it does occur, it's not the main reason for relief in angina.
**Option B:** Might be incorrect if it proposed a different, less relevant mechanism.
**Option C:** Could be incorrect if it focused on a minor or unrelated effect of nitroglycerine.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that nitroglycerine provides rapid relief from angina symptoms by reducing preload, and its effectiveness can be enhanced by sitting upright to reduce venous return.
**Correct Answer:** D. Venodilation decreasing preload.