A combined test of acetylcholine-mediated vasodilation of both the forearm resistance vessels and the radial artery.

OBJECTIVE

To evaluate a new combined test of endothelium-dependent vasodilation (EDV) in the forearm resistance vessel and the radial artery.

METHODS

Acetylcholine (ACh) and sodium nitroprusside (SNP) infusion in the brachial artery were used to simultaneous evaluate EDV and endothelium-independent vasodilation (EIDV) in forearm resistance vessels (plethysmography) and in the radial artery (ultrasound) in 76 healthy subjects. Brachial artery ultrasound was used to assess flow-mediated vasodilation (FMD).

RESULTS

Acetylcholine induced a 4·5% (median value, P = 0·0010) increase in the radial artery diameter, while SNP induced a 31·2% increase in diameter (P<0·0001). While no increase in radial artery blood flow was induced by ACh (P = 0·69), an increase by 181% in radial blood flow was induced by SNP (P<0·0001). When relating the radial artery diameter data to FMD, the change in radial artery diameter induced by ACh was significantly correlated with FMD (r = 0·35, P = 0·013). No such relationship was seen for the diameter change induced by SNP (r = -0·03, P = 0·81). When relating the radial artery blood flow data to EDV and EIDV, the change in radial artery blood flow induced by ACh was significantly correlated with EDV in an inverse fashion (r = -0·42, P = 0·0032). No such relationship was seen for the blood flow change induced by SNP when related to EIDV (r = -0·07, P = 0·63).

CONCLUSION

Simultaneous measurements of blood flow in forearm vessels by plethysmography and in the radial artery by ultrasound during ACh infusion is a new way to assess EDV in both resistance and conduit arteries during one investigation.