Invasive Assessment of the Human Arterial Palmar Arch and Forearm Collateral Function During Transradial Access

Background: The present study aimed to quantitatively measure the pressure-derived function of the palmar arch and forearm arterial collateral circulation during transradial access. Methods and Results: Palmar arch and forearm collateral function was determined using radial artery pressure signals in the nonobstructed vessel and during brief manual occlusions of the more proximal radial artery and of the radial plus ulnar arteries. Collateral flow index (CFI), the ratio of mean occlusive divided by mean nonocclusive arterial blood pressure, both subtracted by central venous pressure, was determined for CFI during radial artery occlusion (CFIrad ) and CFI during radial plus ulnar artery occlusion. Before invasive CFI measurements, arterial palmar arch and forearm function was tested noninvasively by the modified Allen test (MAT). Two hundred fifty patients undergoing transradial access coronary angiography were included in the study. CFIrad was equal to 0.802±0.150 (95% CI, 0.783–0.820). CFI during radial plus ulnar artery occlusion was equal to 0.424±0.188 (95% CI, 0.400–0.447). There was an inverse linear relation between CFIrad and MAT in seconds (s): MAT=64−63×CFIrad (r 2 =0.229;P 15 seconds) MAT. The group with normal MAT had a CFIrad of 0.830±0.111, and patients with abnormal MAT had a CFIrad of 0.648±0.224 (P <0.0001).Conclusions: Direct invasive hemodynamic assessment of the palmar arch and forearm arterial function reveals collateral supply to the briefly occluded in comparison to the patent radial artery of 0.802. During external occlusion of both radial and ulnar artery, CFI amounts to an unexpectedly high value of 0.424.