EFFECT OF AN INELASTIC AORTIC SYNTHETIC VASCULAR GRAFT ON EXERCISE HEMODYNAMICS

This study compared aortic input impedance characteristics between pat ients with aortic interposition Dacron grafts placed for traumatic aor tic injury and normal age-matched control subjects. All subjects were examined at rest and after treadmill exercise. Magnetic resonance imag ing was conducted to rule out anatomic (stenosis) effects. Exercise in creased characteristic impedance (ie, reduced aortic distensibility) b y 29% and decreased total systemic arterial compliance by 21% in the p atient group, whereas the normal control group showed insignificant ch ange in these variables after exercise. Peripheral pressure wave refle ction was reduced substantially with exercise (27%) in the control gro up, with much less reduction observed in the patient group. These abno rmal vascular hemodynamics were associated with significantly high car diac energetic costs in the patient group. A plausible explanation for the observed differences lies in the exaggerated vascular impedance m ismatch between compliant aorta and inelastic graft, when cardiac outp ut increases dramatically.