Brachial artery differential characteristic impedance: Contributions from changes in young's modulus and diameter

Abstract

This examination of brachial artery (BA) differential characteristic impedance, ΔZc, illustrates that changes in Zc can occur from changes in either BA wall stiffness (Young's modulus, E) and/or its diameter, D. Furthermore, we assessed how changes in both E and D combine in either an isolated, synergistic, or antagonistic manner to yield the net change in BA Zc. The basis of this analysis is a partial differential equation which approximates ΔZc as a total differential. The effects on BA ΔZc of acetylcholine, atenolol, fenoldapine, nitroglycerin, hydrochlorothiazide and other medications are examined using data from previously published studies. Clinical situations which alter BA Zc, such as congestive heart failure, hypertension, and hyperemia, are also analyzed. Results illustrate the usefulness of the present approach in differentiating how medications, hyperemia, and pathological conditions affect BA ΔZc by causing independent changes to E and/or D. © Springer Science+Business Media, LLC 2009.