In stable angina –
**Core Concept**
In stable angina, the underlying pharmacological principle being tested involves the regulation of myocardial oxygen demand and supply. This is achieved through the use of medications that either reduce myocardial oxygen demand or increase oxygen supply to the heart.
**Why the Correct Answer is Right**
In stable angina, the primary goal of treatment is to reduce myocardial oxygen demand by decreasing heart rate, contractility, and blood pressure. This is typically achieved through the use of beta-blockers, which act on the beta-1 receptors in the heart to reduce heart rate and contractility. Beta-blockers also reduce the force of contraction, which further decreases myocardial oxygen demand. By reducing myocardial oxygen demand, beta-blockers help to prevent ischemia and angina attacks.
**Why Each Wrong Option is Incorrect**
**Option A:** Nitrates do not reduce myocardial oxygen demand; instead, they dilate blood vessels to increase oxygen supply to the heart. While nitrates are an effective treatment for angina, they do not address the root cause of reduced oxygen supply.
**Option B:** Calcium channel blockers may reduce myocardial oxygen demand by decreasing heart rate and contractility, but they are not the primary choice for treatment of stable angina.
**Option C:** ACE inhibitors do not have a direct effect on reducing myocardial oxygen demand in stable angina.
**Clinical Pearl / High-Yield Fact**
In stable angina, beta-blockers are a first-line treatment because they reduce myocardial oxygen demand and decrease the risk of ischemia and angina attacks.
**Correct Answer: A. Beta-blockers are used to reduce myocardial oxygen demand in stable angina.**