Correct Answer: A. Acute aortic dissection
Acute aortic dissection presents with the classic triad of sudden-onset tearing chest pain radiating to the interscapular region, widened mediastinum on CXR, and blood pressure differential between limbs. The key discriminator here is the blood pressure differential (110/90 mmHg right arm vs 160/100 mmHg left arm), which occurs when the dissection flap compromises the origin of the right subclavian artery, reducing perfusion pressure distally. This is pathognomonic for Type A aortic dissection (involving ascending aorta). The widened mediastinum reflects mediastinal hemorrhage from the dissecting hematoma. Aortic dissection is a surgical emergency requiring immediate CT angiography (CTA) chest with IV contrast for confirmation and assessment of extent (Stanford Type A vs B classification). In Indian practice, mortality without surgical intervention approaches 1–2% per hour in the first 48 hours. The sudden, tearing quality of pain (not gradual angina) and the interscapular radiation are cardinal features that distinguish dissection from ACS. Management involves immediate blood pressure control (target SBP 100–120 mmHg) with IV beta-blockers (esmolol/labetalol) followed by vasodilators, and urgent cardiothoracic surgery consultation for Type A cases.
Why the other options are wrong
B. Esophageal rupture — Esophageal rupture (Boerhaave syndrome) does present with sudden chest pain and widened mediastinum, but it typically follows forceful vomiting or instrumentation. The clinical clue here—blood pressure differential between limbs—is absent in esophageal rupture. Rupture causes mediastinitis and subcutaneous emphysema, not vascular compromise. NBE may pair widened mediastinum with rupture to trap students who don't recognize the BP differential as the discriminator. C. Acute coronary syndrome — ACS presents with chest pain but typically has a gradual onset (minutes to hours), not sudden tearing pain. The pain is usually substernal and crushing, not shooting to the interscapular region. Critically, ACS does not cause blood pressure differential between limbs or widened mediastinum. The sudden, tearing quality and interscapular radiation are red flags that point away from ACS toward dissection. D. Acute pulmonary embolism — PE presents with acute chest pain and may show widened mediastinum if massive, but it does not produce blood pressure differential between upper limbs. PE typically causes pleuritic chest pain, dyspnea, and tachycardia, not tearing interscapular pain. The absence of risk factors (immobility, surgery, malignancy) and the specific BP differential make dissection far more likely.
High-Yield Facts
- Blood pressure differential >20 mmHg between limbs is pathognomonic for aortic dissection involving subclavian artery origin.
- Widened mediastinum on CXR (>8 cm at level of aortic knob) is present in ~60% of Type A dissections; CTA chest is gold standard for diagnosis.
- Sudden tearing/ripping chest pain radiating to interscapular region is the cardinal presenting symptom; gradual onset favors ACS.
- Type A dissection (ascending aorta involved) requires emergency surgery; Type B (descending aorta) is usually managed medically with BP control.
- Initial management: IV beta-blocker first (target HR <60 bpm), then vasodilator (nitroprusside/hydralazine); target SBP 100–120 mmHg to reduce aortic shear stress.
Mnemonics
TEAR for Aortic Dissection Tearing pain, Evidence of BP differential, Acute onset, Radiation to back. Use this at bedside to rapidly rule in dissection before imaging. Type A = Anterior (Surgery); Type B = Below (Medical) Type A involves ascending aorta → anterior → requires surgery. Type B is below the left subclavian → managed medically. Helps recall management urgency.
NBE Trap
NBE pairs widened mediastinum with esophageal rupture to distract from the true discriminator—blood pressure differential between limbs—which is specific to aortic dissection with subclavian involvement. Students who fixate on mediastinal widening alone may incorrectly choose rupture.
Clinical Pearl
In Indian emergency departments, aortic dissection is often missed because hypertensive patients with sudden chest pain are reflexively worked up for ACS. The interscapular radiation and BP differential should immediately trigger dissection suspicion and CTA, not troponin. Early recognition and BP control within the first hour dramatically improve outcomes in Type A cases.
_Reference: Bailey & Love Ch. 61 (Aortic Dissection); Harrison Ch. 242 (Aortic Diseases)_