**Core Concept**
The question is testing the association between certain medications and increased cardiac mortality. This involves understanding the pharmacological effects of various drugs on the cardiovascular system, particularly those that can lead to cardiac arrhythmias, myocardial infarction, or sudden cardiac death.

**Why the Correct Answer is Right**
The correct answer is linked to the inhibition of a specific enzyme that plays a crucial role in the regulation of cardiac function. The drug in question inhibits the enzyme responsible for the breakdown of catecholamines, leading to an accumulation of these potent vasoconstrictors and a subsequent increase in cardiac workload. This can result in cardiac arrhythmias, myocardial infarction, and ultimately, increased cardiac mortality.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a beta-blocker, which is actually used to decrease cardiac workload and mortality in patients with heart failure and myocardial infarction.
**Option B:** This option is incorrect because it is an anti-arrhythmic medication that is used to treat cardiac arrhythmias, not cause them.
**Option C:** This option is incorrect because it is a calcium channel blocker, which is used to decrease cardiac workload and blood pressure, not increase cardiac mortality.

**Clinical Pearl / High-Yield Fact**
The drug in question is often used to treat conditions such as hypertension and heart failure, but its inhibition of the enzyme in question can lead to a paradoxical increase in cardiac mortality. This highlights the importance of understanding the pharmacological effects of medications and their potential side effects.

**Correct Answer:** C. **Correct Answer:** C. **Isosorbide Mononitrate**