Effect of distal stenosis of internal thoracic artery bypass grafts on longitudinal phasic blood flow velocity characteristics

Background Left internal thoracic artery (LITA) bypass conduits show gradua l longitudinal transition in their phasic flow velocity patterns from the p roximal to distal segments, but little is known about the influence of dist al stenosis, particularly early after surgery, on that characteristic. The purpose of this study was to evaluate the influence of distal stenosis on t hese flow velocity patterns. Methods We examined 24 LITAs within 1 month (7 to 30 days) after surgery wi th a Doppler-tipped guide wire at the proximal, mid, and distal segments. M aximum peak velocities (MPV), time averaged peak velocities (APV), and velo city-time integrals (VTI) were measured. Results In LITAs without stenosis (n = 14, group A), the APV, MPV, and VTI values at the diastole were significantly greater than those for distal ste nosis (minimal lumen diameter >75%, n = 10, group B). The values of the 3 i ndexes at the systole in each segment did not differ significantly between the 2 groups. Both groups showed gradual increases in the diastolic/systoli c ratios of the 3 indexes from the proximal to distal portions, the ratios in group A being significantly larger than that in group B (APV, P < .001; MPV, P < .01; TVI, P < .01, respectively). For these indexes, sensitivity a nd specificity for predicting stenosis of LITA was higher in the proximal a nd mid portion than in the distal. Conclusions Anastomotic stenosis decreases the diastolic flow component but not the systolic one. By using diastolic/systolic ratios of the 3 indexes, it is possible to predict distal stenosis of LITA from the resting phasic Flow velocity pattern.