In normal patients, we typically observe a greater systolic arterial pressure (SAP) in peripheral arteries than in the aorta, while the mean arterial pressure (MAP) is the same in peripheral arteries and in the aorta.¹ Nevertheless, after cardiopulmonary bypass (CPB), this relationship is completely altered, and the radial artery SAP becomes significantly lower compared with the central aortic pressure. Several other investigators from the USA,^2,3 Chile,⁴ Australia,⁵ Israel,⁶ Belgium,⁷ and Canada^8,9,10 have reported similar observations. Those observations have led several cardiac centres to abandon radial artery pressure monitoring in cardiac surgery or to combine radial monitoring with more central arterial access such as the brachial³ or the femoral artery.¹¹ An alternative approach would be selective monitoring of central blood pressures if known risk factors for an attenuated radial blood pressure post-CPB were present in a particular patient. The question then becomes: what are these risk factors?