**Core Concept**
Sublingual nitroglycerin is a vasodilator used in the treatment of acute chest pain, particularly in angina pectoris. It works by releasing nitric oxide, which activates guanylyl cyclase and increases cyclic guanosine monophosphate (cGMP) levels, leading to smooth muscle relaxation in blood vessels.

**Why the Correct Answer is Right**
Sublingual nitroglycerin causes reflex tachycardia due to the activation of baroreceptors in the carotid sinus and aortic arch. The decrease in blood pressure triggers a reflex increase in heart rate to maintain cardiac output. This reflex tachycardia is a common side effect of nitroglycerin therapy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** While nitroglycerin can cause hypotension, it is not the most direct consequence of its use in acute chest pain.
**Option C:** Although nitroglycerin can cause headache, it is not the primary concern in the treatment of acute chest pain.

**Clinical Pearl / High-Yield Fact**
When administering sublingual nitroglycerin, it's essential to monitor the patient's blood pressure and heart rate closely, as reflex tachycardia can occur.

**Correct Answer:** B. Hypotension.