**Core Concept**
Bupivacaine is a local anesthetic known for its high lipid solubility, which contributes to its cardiotoxic potential. The cardiotoxic effects of local anesthetics are primarily due to their ability to block sodium channels in cardiac cells, leading to depolarization and potentially fatal arrhythmias.

**Why the Correct Answer is Right**
Bupivacaine's high lipid solubility allows it to easily penetrate the myocardial cell membrane, leading to rapid sodium channel blockade. This results in a significant increase in the duration of the action potential, which can lead to re-entry arrhythmias, such as ventricular fibrillation. The cardiotoxic effects of bupivacaine are more pronounced due to its ability to bind to cardiac sodium channels with high affinity.

**Why Each Wrong Option is Incorrect**
**Option A:** Lidocaine is actually used to treat local anesthetic systemic toxicity, including cardiotoxicity, due to its ability to block sodium channels and stabilize cardiac membranes.
**Option B:** Mepivacaine has a lower lipid solubility compared to bupivacaine, making it less cardiotoxic.
**Option C:** Procaine has a very low lipid solubility and is not typically associated with significant cardiotoxicity.

**Clinical Pearl / High-Yield Fact**
Bupivacaine's cardiotoxic effects can be treated with intravenous lipid emulsion therapy, a technique that has been shown to be effective in stabilizing cardiac membranes and improving survival in cases of bupivacaine overdose.

**Correct Answer: C. Bupivacaine**