A nurse is caring for a 45-year-old female client with suspected thoracic aortic aneurysm who presents to the emergency department with sudden onset of severe chest pain radiating to her back, blood pressure of 180/100 mmHg in the right arm and 140/80 mmHg in the left arm, anxiety, and a report of feeling like something is "tearing" inside her chest. Which assessment finding should be the nurse's immediate priority?

Blood pressure differences between arms is a critical sign of aortic dissection requiring immediate intervention. Other findings are important but less urgent in this emergency context.

Clinical Priority in Suspected Thoracic Aortic Aneurysm

The client’s presentation—sudden, severe chest pain radiating to the back with a “tearing” sensation, extreme anxiety, and a markedly asymmetric blood pressure reading (180/100 mmHg right arm vs. 140/80 mmHg left arm)—is a classic clinical picture for an acute aortic syndrome, such as a dissecting thoracic aortic aneurysm. In this high-stakes scenario, the nurse’s immediate priority is to further quantify and document the finding that most directly supports the suspected vascular catastrophe and guides emergency intervention.

Why Assessing Blood Pressure Differences Between Arms Is the Priority

A significant interarm blood pressure difference is a critical, readily obtainable bedside cue that can signal involvement of the aortic arch and its major branches in the pathological process. In a dissection, a propagating hematoma within the aortic media can compress or shear off the origin of a subclavian artery, leading to a unilateral pressure drop. The provided evidence underscores this principle: a case of an occluded aberrant left subclavian artery was first suspected due to the coincidental finding of an interarm blood pressure difference ^[1]. While that specific case involved a congenital arch anomaly and an asymptomatic chronic occlusion, the underlying physiological mechanism—unilateral subclavian flow obstruction causing a pressure differential—is identical to what can occur acutely in a thoracic aortic dissection. Confirming and precisely documenting the magnitude of this asymmetry in both arms (and ideally in a lower extremity) provides immediate, objective data that can confirm the suspicion of arch vessel involvement, stratify the urgency of the situation, and directly inform the medical team’s decision to proceed with emergent blood pressure control and definitive imaging, such as a CT angiogram. The other options represent important, but secondary, assessments. Monitoring peripheral pulses and evaluating for a new aortic regurgitation murmur or jugular venous distension (a late sign of tamponade) are all part of the comprehensive examination for a dissection, but they do not take precedence over the immediate, focused clarification of the interarm blood pressure differential, which is the most direct and rapidly interpretable sign of the suspected pathology at the bedside.