Fig. 1

Flow chart. FR-APG femoral-to-radial arterial pressure gradient; NIBR-APG non-invasive brachial-to-radial arterial pressure gradient. The index test is the average NIBR-APG mean arterial pressure (MAP) measured three times (T1, T2, T3) with non-invasive cuff at the two arms at the brachial level and with an invasive radial artery cannulae. The “final diagnostic or reference standard” is defined as FR-APG of more than 10 mmHg of MAP measured with invasive femoral and radial cannulae