Experimental model for comparative evaluation of pharmacologically induced vasodilation of arterial wall mechanical properties.

Arterial wall compliance (C) and distensibility coefficient (DC) are key factors of pathologic physiology, especially in arteries less than 2 mm in diameter. The aim of this study was to design an experimental model allowing comparative measurement of C and DC during pharmacologically induced vasodilation on small-diameter arteries. Both femoral arteries were exposed in eight New Zealand White rabbits. Diameter (d) and systolic/diastolic diameter changes (deltad) were measured simultaneously, and C and DC were calculated before and after topical application of 1 mL of 4% papaverine on the right side and topical application of 1 mL of 1% lidocaine on the left side. Diameter measurements were performed by echo tracking with 20-MHz implanted microprobes. After papaverine and lidocaine application, respectively, d increased from 1.36 mm to 2.23 mm (P < 0.0001) and from 1.45 mm to 2.4 mm (P < 0.0001), deltad increased from 0.0568 mm to 0.0571 mm (P = 0.34) and from 0.064 mm to 0.077 mm (P < 0.01), C increased from 5.7 x 10(-3) mm/mm Hg to 6 x 10(-3) mm/mm Hg (P < 0.02) and from 6.23 x 10(-3) mm/mm Hg to 8.49 x 10(-3) mm/mm Hg (P < 0.01), and DC decreased from 4.22 x 10(-3) mm Hg(-1) to 2.61 x 10(-3) mm Hg(-1) (P < 0.0004) and from 4.36 x 10(-3) mm/mm Hg to 3.46 x 10(-3) mm/mm Hg (P < 0.005). Papaverine- and lidocaine-induced changes were significantly different for deltad, C, and DC (P < 0.01). These results suggest that, unlike that with papaverine, lidocaine-induced vasodilation leads the artery up to the nonlinear part of its pressure/diameter relationship, with decreased distensibility contrasting with increased diameter and compliance. Our experimental model may be useful to compare the effects of different vasoactive drugs at different concentrations on the mechanical properties of the arterial wall.