Evidence that turbulence is not the cause of poststenotic dilatation in rabbit carotid arteries.

Abstract

The purpose of this study was to relate local blood flow conditions to the development of poststenotic dilatation (PSD) in the common carotid arteries of rabbits. We investigated the effects of the geometry of the stenoses on PSD formation to gain insight into the mechanisms of this phenomenon. With short stenoses, the maximum diameter of the PSD after 3 weeks increased from about 25% to 50% above the proximal diameter by increasing the severity of the stenoses from 50% to 60% diameter reduction. By contrast, increasing the length of the constricted region of 60% stenoses did not affect the PSD, and in all cases, the site of maximum dilatation occurred within 3 tube diameters from the stenoses. In vitro studies were conducted with the photochromic tracer technique. The most striking observation was that the transition to turbulence did not occur with a 55% short stenosis. By increasing the severity of this short stenosis to 70%, the transition to very localized turbulence was triggered approximately 6 to 8 tube diameters from the stenosis during the early deceleration phase of the flow cycle. The transition point moved farther downstream by increasing the length of this moderate stenosis. This study demonstrated that PSD can occur under turbulence-free conditions, and even when turbulence was generated, the site of the PSD was remote from that of the localized turbulence zone. The wall shear stress pattern was determined for the long 60% stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)