A 62-year-old man is brought to the emergency department due to sudden-onset, severe chest… — USMLE Step 2 CK

A 62-year-old man is brought to the emergency department due to sudden-onset, severe chest pain that he describes as "tearing" and radiating to his upper back. He has a 20-year history of poorly controlled hypertension. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $215/115\text{ mm Hg}$ in the right arm and $178/92\text{ mm Hg}$ in the left arm, pulse is $112/\text{min}$ , and respirations are $22/\text{min}$ . Oxygen saturation is $97\%$ on room air. Physical examination reveals a bounding pulse and an early diastolic decrescendo murmur at the right upper sternal border. Electrocardiogram demonstrates sinus tachycardia and voltage criteria for left ventricular hypertrophy, but no acute ST-segment changes. A portable chest radiograph reveals a widened mediastinum. Arrange the following management steps in the most appropriate chronological order.

1Initiate intravenous beta-blocker therapy (e.g., esmolol)
2Initiate intravenous vasodilator therapy (e.g., nitroprusside)
3Perform computed tomography angiography (CTA) of the aorta
4Transfer to the operating room for emergent surgical repair

Answer

The correct sequence is to first stabilize the patient with an intravenous beta-blocker, followed by an intravenous vasodilator, then obtain a CTA to confirm the anatomy, and finally proceed with emergent surgical repair.

Acute aortic dissection requires immediate medical therapy to halt the progression of the intimal tear. The correct physiological sequence requires lowering the heart rate and contractility first with a beta-blocker (esmolol or labetalol), which safely allows for the subsequent use of a vasodilator (nitroprusside) to normalize blood pressure. Once the sheer stress on the aorta is controlled, anatomical mapping via CTA is safely performed to guide the cardiothoracic surgeon in the final step, which is emergent operative repair of the ascending aorta.

Step-by-Step Solution

Administer an intravenous beta-blocker.

Decreases heart rate (target

<60/\text{min}

) and left ventricular contractility (dP/dt).

This is the most crucial initial step to reduce the pulsatile shearing forces that drive the propagation of the aortic dissection. It also prevents the reflex tachycardia that would otherwise occur when vasodilators are introduced.

Administer an intravenous vasodilator.

Lowers systolic blood pressure to a target of

100-120\text{ mm Hg}

Further reduction in blood pressure is necessary to minimize mechanical stress on the aorta, but it must strictly follow beta-blockade to avoid reflex sympathetic stimulation.

Obtain computed tomography angiography (CTA).

Confirms the diagnosis and delineates the anatomical extent of the dissection.

For a hemodynamically stable patient, CTA is the gold standard diagnostic test to differentiate a Stanford Type A (ascending) from a Stanford Type B (descending) dissection, which is required for surgical planning.

Proceed to emergent surgical repair.

Provides definitive anatomical correction.

The clinical findings of right-arm hypertension and an early diastolic murmur (aortic regurgitation) indicate proximal aortic involvement (Type A). This carries a high mortality rate and requires immediate operative repair.

Key Concept

In the management of acute aortic dissection, medical stabilization must be prioritized before imaging or surgery, and specifically requires the administration of a beta-blocker prior to any vasodilator therapy to prevent reflex tachycardia and increased aortic shearing forces.

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