## **Core Concept**
The clinical presentation described suggests an acute aortic dissection, particularly given the combination of sudden onset unrelenting chest pain, loss of peripheral pulses, and differential blood pressure readings between the two arms. Aortic dissection occurs when there is a tear in the intimal layer of the aorta, allowing blood to enter the wall of the aorta and potentially leading to aortic rupture or compromise of branch vessels.

## **Why the Correct Answer is Right**
The correct answer, **Aortic dissection**, is supported by the patient's symptoms and signs. The sudden onset of severe, tearing chest pain is classic for aortic dissection. The loss of peripheral pulses can occur due to the dissection extending into and occluding branch vessels that supply the limbs. Differential blood pressure readings between the two arms can also be seen if the dissection compromises the blood flow to one of the arms, for example, by involving the origin of the subclavian artery. This condition is a medical emergency requiring immediate diagnosis and treatment.

## **Why Each Wrong Option is Incorrect**
- **Option B: Myocardial Infarction** - While myocardial infarction can present with chest pain, it does not typically cause differential blood pressures between arms or loss of peripheral pulses as primary manifestations.
- **Option C: Pulmonary Embolism** - Pulmonary embolism can cause sudden onset chest pain and potentially lead to hemodynamic instability but does not usually present with differential arm blood pressures or limb pulses loss.
- **Option D: Gastroesophageal Reflux Disease (GERD)** - GERD can cause chest pain but is not associated with loss of peripheral pulses or differential blood pressures between arms.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is to consider aortic dissection in the differential diagnosis of acute chest pain, especially when accompanied by signs of limb ischemia (e.g., loss of pulses) or differential blood pressures. The classic triad of chest pain, loss of pulses, and differential blood pressures, though not always present, should heighten suspicion for this life-threatening condition.

## **Correct Answer: A. Aortic dissection**