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Three Part Question

In [adult patients with suspected acute aortic dissection] is [bilateral blood pressure differential compared to a pulse deficit] a [reliable diagnostic sign]?

Clinical Scenario

A 71-year-old male with a history of tobacco abuse, sleep apnea, and obesity presents after awakening from sleep due to sudden onset, severe chest pain that radiates to the back between the shoulder blades. Exam reveals a diaphoretic and anxious appearing male. He is tachycardic and hypertensive with regular heart sounds. There is no pulse differential and no neurologic deficit. You suspect that the patient has an acute aortic dissection and you request that nursing perform bilateral upper extremity blood pressure (BP) readings. The right arm reads 191/92 mmHg and the left arm reads 168/90 mmHg. You wonder how reliable this finding is in determining whether the patient likely has an acute aortic dissection.

Search Strategy

Medline 1966-07/20 using PubMed, Cochrane Library (2020), and Embase
[(Exp thoracic aortic dissection OR exp aortic aneurysm OR exp dissecting aneurysm OR exp dissecting aortic aneurysm) AND (exp clinical features)] Limit to humans and English language

[(Exp thoracic aortic dissection OR exp aortic aneurysm OR exp dissecting aneurysm OR exp dissecting aortic aneurysm) AND (exp systolic pressure differential OR pressure differential OR exp blood pressure differentials)] Limit to humans and English language

Search Outcome

383 studies were identified: almost all combined systolic BP differential with pulse deficit in their analysis. There was only one study assessing the independent association of systolic BP differential with acute aortic dissection (AAD).

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Um SW, et al. Sept 2018 Canada	222 adults with a bilateral BP measurement and triage diagnosis of non-traumatic truncal pain and an absence of a clear diagnosis on basic investigation	Case-control study	Association of systolic BP differential and pulse deficit with AAD	A systolic BP differential >10 mm Hg was associated with AAD (diagnostic odds ratio 1.4); a systolic BP differential > 20 mm Hg was associated with AAD (OR 2.7).	Retrospective study; user variability in obtaining BP measurements; and partial verification bias. Controls may not exactly represent patients from whom clinicians would consider AAD in their differential.
				Combining pulse deficit with systolic BP differential > 20 mmHg increased the diagnostic accuracy (OR 4.2).
				Pulse deficit alone had an OR of 28.9

Comment(s)

Acute aortic dissection is an uncommon diagnosis; however, it carries a high mortality. Two clinical exam findings that may be seen are blood pressure differential and pulse deficit. A difference of >20 mmHg between the two systolic blood pressure readings from each arm is considered a blood pressure differential. A pulse deficit is described as a difference in palpable force between right and left upper extremities. A pulse deficit alone (OR 28.9) was more suggestive of AAD than either an isolated systolic BP differential of >20 mm Hg (OR 2.71) or a pulse deficit and systolic BP differential used in combination (OR 4.2). Though blood pressure differential carries a classic association with aortic dissection, it is not a specific finding. In several studies, up to 20% of ambulatory ED patients were found to have a systolic or a diastolic interarm blood pressure difference > 20 mmHg. Blood pressure measurements in general were also found to have interobserver variability and discrepancies in repeat measurements.

Clinical Bottom Line

Neither a blood pressure differential nor a pulse deficit can rule acute aortic dissection in or out, but a positive finding may heighten your suspicion in the right clinical context. Obtaining a pulse deficit has better diagnostic accuracy. It is useful to pursue bilateral blood pressure measurements once a diagnosis of acute aortic dissection is made; tailoring blood pressure control using the higher of the two values will optimize patient care until final disposition.

References

1. Um SW, Ohle R, Perry JJ. Bilateral blood pressure differential as a clinical marker for acute aortic dissection in the emergency department. Emerg Med J 2018 Sep;35(9):556-558