Hydraulic input impedance measurements in physical models of the arterial wall

The influence of intraarterial prostaglandin E(1) on vascular hydraulic impedance and infrainguinal graft patency

OBJECTIVES

To evaluate the influence of intraoperative arterial prostaglandin E(1)(alprostadil) infusion on hydraulic impedance in relation to graft patency.

METHODS

Hydraulic impedance was measured in 115 infrainguinal bypasses by means of the extracorporeal-bypass-flow method (EBF). Fifty-eight femoro-popliteal and 57 femoro-crural polytetrafluoroethylene (PTFE) grafts were included. 10 microg of alprostadil were administered into a temporary bypass and the haemodynamic changes were recorded. The reactions of input (Z(x)) and characteristic (Z(0)) impedances as well as phase relations were derived and related to graft outcome after three years.

RESULTS

Significant changes after administration of prostaglandin were observed for overall pressure (74 vs. 84 mmHg, p<0.01), flow rate (194 vs 160 ml/min, p<0.01), input impedance (0.55 vs. 0.75 PRU, p<0.01) and the phase angle of the first harmonic (-18 degrees vs -26 degrees, p<0.01). An increase of at least one degree of the first harmonic phase angle following alprostadil injection in the crural bypass group was associated with a significant better graft prognosis of crural (p<0.01) but not popliteal grafts. Primary and secondary patency rates after three years for crural grafts with an increase of at least one degree were 62% and 63% (n=45) and for non-responders 18% and 0% (n=12, p(prim)<0.01, p(sec)<0.001). All crural bypasses with poor prostaglandin reaction occluded within 9 months (n=12) after the operation.

CONCLUSIONS

The EBF method allows a combined assessment of peripheral resistance and impedance parameters. The response of the first harmonic phase angle provides important predictive information regarding femoro-crural grafts.