Which gradient threshold is considered acceptable for inter-arm comparison in pre-op arterial evaluation?

• A. Less Than 10 mmHg
• B. Less Than 15 mmHg
• C. Less Than 20 mmHg
• D. Less Than 30 mmHg

Answer: (C)

In pre-op arterial evaluation, comparing systolic pressures between arms helps detect significant proximal disease that could affect access or perfusion. A small inter-arm gradient suggests both arms have similar proximal arterial status and is acceptable for proceeding with planned procedures. The commonly used cutoff is a gradient under 20 mmHg; differences at or below this level are considered acceptable because they are unlikely to reflect clinically meaningful stenosis. If the gradient is larger than this, it raises concern for subclavian or axillary stenosis or occlusion in the arm with the lower pressure, prompting further imaging and possible adjustment of the planned approach. In short, a difference under 20 mmHg is the threshold that supports continuing with the current pre-op evaluation.