**Core Concept**
The treatment of hypothyroidism in patients with ischemic heart disease requires careful consideration of the potential risks and benefits of thyroid hormone replacement therapy. This is because thyroid hormone can increase myocardial oxygen demand, potentially worsening angina or precipitating myocardial infarction.

**Why the Correct Answer is Right**
In patients with ischemic heart disease, the initial recommended dose of levothyroxine (T4) is often lower than the standard replacement dose, typically starting at 25-50 mcg daily. This is because the goal is to avoid excessive increases in cardiac workload and oxygen demand. As the patient's cardiac function is monitored and stabilized, the dose can be gradually increased to achieve a euthyroid state. This approach is essential to prevent adverse cardiovascular events.

**Why Each Wrong Option is Incorrect**
* **Option A:** Starting with a high dose of levothyroxine in patients with ischemic heart disease can lead to an excessive increase in cardiac workload, potentially resulting in angina or myocardial infarction.
* **Option B:** There is no evidence to suggest that triiodothyronine (T3) is the preferred initial treatment for hypothyroidism in patients with ischemic heart disease. In fact, T3 can have more pronounced effects on cardiac workload and oxygen demand compared to T4.
* **Option D:** Combination therapy with both T4 and T3 is not typically recommended as initial treatment for hypothyroidism in patients with ischemic heart disease, as it can increase the risk of adverse cardiovascular events.

**Clinical Pearl / High-Yield Fact**
When initiating thyroid hormone replacement therapy in patients with ischemic heart disease, it is essential to start with a low dose and gradually increase as tolerated, while closely monitoring cardiac function and adjusting the dose accordingly.

**Correct Answer: C.**