Wide Blood Pressure Variation Between Arms

Question

The patient is a 70-year-old female with a history of left carotid endarterectomy who presented for an unrelated complaint of posterior neck pain, most likely musculoskeletal. The blood pressure taken in her left arm was 124/74, but 226/74 when taken using the right arm (repeated exams and confirmed by Doppler). These differences persisted in the sitting and supine positions. A chart review revealed that she has always previously been normotensive, but pressures were most likely taken in the left arm. Please discuss this finding, including differential diagnoses and recommended evaluation.

Sheldon J. Elfenbein, DO

Response from Bruce M. Gardner, MD

Blood pressure readings should be roughly the same in both arms, as noted below. Standard measurement technique must include measuring the blood pressure with an appropriate-sized cuff at the level of the right atrium, with the patient rested for 5 minutes, and with her back supported.^[1]

Several studies^[2,3,4] have established that blood pressure measurements taken from either arm will give consistent results. However, some researchers have reported surprising variation in arm-to-arm blood pressure differences. Fotherby^[2] noted an interarm difference of 10 mm/Hg or greater in 10% of his elderly patients; Lane found 20% with this degree of variation.^[3] Cassidy and colleagues^[4] discovered that 40% of their ambulatory patients demonstrated this 10-mm/Hg gradient. Another interesting investigation randomized which arm was checked first, in an attempt to determine if there was a relaxation effect.^[5] The results showed no effect, and the researchers concluded that "Age was the only significant predictor of clinically significant variations in inter-arm blood pressures."

However, your patient shows a much higher gradient, and an underlying condition should be sought. Congenital conditions in the differential diagnosis include aortic coarctation and thinning of 1 of the subclavian, axillary, or brachial arteries. Acquired arterial conditions include aortic dissection, atheroma, thrombus, embolus, and extrinsic compression (as might be seen in association with a mass in the upper chest).

Interarm blood pressure difference is a key finding in dissection of the aorta, a life-threatening emergency. However, when considered in light of the characteristics of the general population previously described and the relative rarity of aortic dissection, the presence of interarm blood pressure differences has no significant positive predictive value in this condition.^[6]

Your patient should have a contrast-enhanced CT of the chest to effectively delineate among the possibilities mentioned above. A vascular ultrasound would be helpful as well, but the CT would better show an extrinsic compression.

Cite this: Bruce M Gardner. Wide Blood Pressure Variation Between Arms - Medscape - Jun 20, 2002.

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