A 45 year old woman with a history of hypertension presented to the emergency room with loss of consciousness, chest pain, and diaphoresis. On examination, she was grossly unstable, and the bilateral pulses were unequal. ECG showed nonspecific ST-T changes. What is the next best investigation?

Correct Answer: D. Transoesophageal echocardiography

This clinical presentation—hypertensive woman with acute loss of consciousness, chest pain, diaphoresis, haemodynamic instability, and unequal bilateral pulses—is pathognomonic for acute aortic dissection. The unequal pulses are the discriminating sign: dissection of the ascending aorta can compromise branch vessels (subclavian, carotid) asymmetrically, causing pulse differentials. ECG showing only nonspecific ST-T changes (not diagnostic STEMI pattern) further supports dissection over MI. In acute aortic dissection, the next best investigation is transoesophageal echocardiography (TEE), which offers superior sensitivity (95–98%) for detecting the intimal flap, true/false lumens, and aortic regurgitation in the acute setting. TEE is rapid, bedside-capable, does not require patient transport (critical in unstable patients), and provides real-time haemodynamic assessment. It is the gold standard for emergency diagnosis when CT angiography is unavailable or contraindicated. In Indian emergency settings where CT angiography may have limited availability, TEE remains the fastest confirmatory tool before emergency surgical intervention. The sensitivity of TEE for detecting dissection is superior to transthoracic echo (which may miss ascending aortic pathology due to acoustic windows), making it the investigation of choice in this unstable, high-risk scenario.

Why the other options are wrong

A. MRI — MRI is the gold standard for aortic dissection diagnosis in stable, elective settings due to excellent spatial resolution and tissue characterization. However, it is contraindicated in acutely unstable patients (this woman is unconscious and haemodynamically unstable). MRI requires prolonged scanning time, patient cooperation, and is incompatible with monitoring equipment. In emergency dissection, MRI is impractical and delays life-saving intervention. B. X-ray — Chest X-ray may show nonspecific findings (widened mediastinum, pleural effusion) in dissection but has low sensitivity (~60%) and cannot visualize the intimal flap or confirm the diagnosis. It is a screening tool only and delays definitive diagnosis. In an unstable patient with clinical signs of dissection, X-ray alone is insufficient and wastes critical time before surgical intervention. C. Cardiac enzymes — Cardiac enzymes (troponin, CK-MB) are used to diagnose acute myocardial infarction, not aortic dissection. While troponin may be mildly elevated in dissection if the dissection involves coronary ostia, enzymes do not visualize the aorta or confirm dissection. This is an NBE trap: the chest pain and ECG changes may tempt students to order enzymes first, but the unequal pulses and haemodynamic instability point to dissection, not MI.

High-Yield Facts

Mnemonics

DISSECTION RED FLAGS Diaphoresis + Instability, Sudden onset, Syncope, Equal pulses ABSENT (unequal), Chest pain, Tear of intima (dissection), Imaging TEE, Outcome: surgery, Need speed. ACUTE DISSECTION = TEE FIRST Transoesophageal = Emergency, Excellent sensitivity. Unstable patient → no MRI, no CT transport. Bedside TEE shows intimal flap in minutes.

NBE Trap

NBE pairs acute chest pain + ECG changes with cardiac enzymes/troponin to lure students into diagnosing MI. The unequal pulses are the discriminating clue that this is dissection, not MI—students who miss this sign may incorrectly order enzymes or stress testing, delaying life-saving imaging.

Clinical Pearl

In Indian emergency departments, where CT angiography may be unavailable or require patient transport, bedside TEE is the lifesaving investigation for suspected dissection. A 45-year-old hypertensive woman with unequal pulses is a surgical emergency—TEE confirmation takes minutes and guides immediate cardiothoracic intervention, whereas delays in imaging increase mortality.

_Reference: Harrison Ch. 242 (Aortic Dissection); Robbins Ch. 10 (Cardiovascular Pathology); KD Tripathi Ch. 8 (Cardiovascular Pharmacology—antihypertensive management in dissection)_