COMPARATIVE REACTIVITY AND MECHANICAL-PROPERTIES OF HUMAN ISOLATED INTERNAL MAMMARY AND RADIAL ARTERIES

Objective: The aim of this study was to analyse the arterial wall mech anics and the vasoreactive properties of the radial artery in comparis on with those of the internal mammary artery and to discuss their impl ications for coronary bypass grafts. Methods: Measurements of pressure and diameter were obtained from cylindrical segments, whereas measure ments of reactivity were obtained from ring segments from the same art eries. We used an echo-tracking technique of high resolution enabling to investigate, in vitro, the diameter and the wall thickness of arter ial cylindrical segments. Furthermore, the compliance, distensibility and incremental elastic modulus of the radial and of the mammary arter ies were determined for a wide range of transmural pressure (0-200 mmH g) in presence and absence of norepinephrine (NE). Results: Our result s show that NE caused vasoconstriction of the two arteries. Strain was found significantly higher for the radial artery than for the interna l mammary artery at any given value of stress both in the presence and in the absence of NE. In presence of NE, compliance for radial artery , in the overall transmural pressure range, did not change, whereas, d istensibility was significantly increased and the elastic modulus was significantly decreased. Under the same conditions, the distensibility of the mammary artery tended to decrease and its elastic modulus to i ncrease. In parallel, the vasoreactive properties of the two arteries confirmed the previous results showing that radial artery developed a significant higher tension to vasoconstricting agents (KCI, NE and phe nylephrine (PHE)) and higher relaxation to isradipine than internal ma mmary artery. Moreover, radial artery displayed a lesser sensivity to sodium nitroprusside than internal mammary artery. Furthermore, sensit ivity to NE was found to be 7-fold higher for radial artery than for i nternal mammary artery. Conclusion: Taken together, data on the mechan ical and reactive properties of radial and internal mammary arteries s how why the radial artery displayed a higher potential for spasm than the internal mammary artery and why the use of Ca2+ channel blocker ca n decrease the incidence of occlusion and spasm. (C) 1998 Elsevier Sci ence B.V.