**Core Concept**
The patient's presentation of sudden onset central chest pain radiating to the back, ST segment elevation in multiple leads on ECG, and a widened mediastinum on chest X-ray is indicative of an acute myocardial infarction (MI) with potential for cardiac rupture or other complications. This scenario highlights the importance of recognizing acute coronary syndromes and their complications.

**Why the Correct Answer is Right**
The patient's symptoms and ECG findings are consistent with an ST-elevation myocardial infarction (STEMI). The presence of ST segment elevation in leads V1-V6, I, and aVL suggests an anterior wall MI. The widened mediastinum on chest X-ray is a red flag for cardiac tamponade or rupture, which can occur as a complication of MI. The anterior wall MI can cause damage to the interventricular septum, leading to cardiac rupture.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the patient's presentation of acute chest pain and ECG changes.
**Option B:** While aortic dissection can present with sudden onset chest pain, the ECG findings and widened mediastinum are not typical for this condition.
**Option C:** Pulmonary embolism can cause sudden onset chest pain, but the ECG findings and widened mediastinum are not characteristic of this condition.

**Clinical Pearl / High-Yield Fact**
A widened mediastinum on chest X-ray in the setting of acute chest pain and ECG changes should raise suspicion for cardiac tamponade or rupture, and prompt further investigation and management.

**Correct Answer:** C. Acute myocardial infarction.