**Core Concept**
Beta-blockers are a class of medications that slow the heart rate and reduce the force of contraction, thereby decreasing the workload on the heart. After an acute myocardial infarction (AMI), beta-blockers are often prescribed to reduce the risk of further cardiac complications.

**Why the Correct Answer is Right**
The use of beta-blockers after AMI is contraindicated in certain conditions due to the risk of unopposed alpha-receptor stimulation, leading to increased peripheral vascular resistance and potentially catastrophic consequences. One such condition is **Option C: Prinzmetal's angina**. Prinzmetal's angina is caused by coronary artery vasospasm, and beta-blockers can worsen this condition by blocking the beta-2 receptors that normally help to dilate the coronary arteries. This can lead to increased myocardial ischemia and infarction.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hypertension is not a contraindication for beta-blockers after AMI, as these medications are often used to manage hypertension and reduce cardiac workload.
* **Option B:** Heart failure with reduced ejection fraction is a common indication for beta-blockers, as these medications can help to improve cardiac function and reduce mortality.
* **Option D:** Asthma is not a contraindication for beta-blockers after AMI, as the benefits of these medications in reducing cardiac complications often outweigh the risks associated with asthma exacerbation.

**Clinical Pearl / High-Yield Fact**
Beta-blockers can be used in patients with asthma, but it's essential to use non-selective beta-blockers with caution and to have a rescue plan in place for potential asthma exacerbation.

**Correct Answer: C. Prinzmetal's angina**