**Core Concept**
The management of established coronary artery disease (CAD) post-myocardial infarction (MI) involves the use of various pharmacological agents to improve survival and reduce the risk of future cardiovascular events. The primary goal is to prevent further ischemic damage and minimize the progression of atherosclerosis.

**Why the Correct Answer is Right**
The correct answer involves understanding the role of various pharmacological agents in the management of CAD post-MI. **Beta-blockers** (e.g., metoprolol) are commonly used to reduce myocardial oxygen demand by decreasing heart rate and contractility. They also have a proven benefit in reducing mortality and morbidity in patients with CAD post-MI. However, **nitrates** (e.g., nitroglycerin) are primarily used to alleviate angina symptoms by dilating coronary arteries and reducing preload. While they may provide symptomatic relief, they do not have a significant impact on long-term survival.

**Why Each Wrong Option is Incorrect**
**Option B:** This option is incorrect as **calcium channel blockers** (e.g., amlodipine) are effective in reducing blood pressure and myocardial oxygen demand, thereby improving survival in patients with CAD post-MI.
**Option C:** This option is incorrect as **ACE inhibitors** (e.g., lisinopril) have been shown to reduce mortality and morbidity in patients with CAD post-MI by reducing afterload and preventing progressive left ventricular dysfunction.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the benefits of pharmacological therapy in CAD post-MI are time-dependent, and early initiation of therapy is crucial to improve outcomes.

**Correct Answer: D. Nitrates**