Reliability of mechanical and phased-array designs for serial intravascular ultrasound examinations - Animal and clinical studies in stented and non-stented coronary arteries

Background: Both mechanical and multi-element intravascular ultrasound desi gns have potential advantages and limitations that may impact on their valu e for clinical and research purposes. Determination of the reproducibility of measurements is critical before a given system can be used in studies su ch as regression of atherosclerosis trials. Methods: We performed serial in travascular ultrasound imaging with catheters using mechanical and phased-a rray designs in stented and non-stented coronary arteries in dogs and in pa tients. Results: Both systems correlated well for areas (r greater than or equal to 0.90, p < 0.0001) and diameters (r greater than or equal to 0.84, p < 0.0001) in dogs and in patients. There was a slight difference between multi-element and mechanical designs for measurements of area (mean differe nce in dogs and in patients: -0.24 and 0.96 mm(2), p < 0.055) and diameter (-0.08 and 0.16 mm, p < 0.0001). The reproducibility of the multi-element s ystem for reanalysis of the same frames and for analysis of serial pullback s was similar to the same measurements with the mechanical system (r greate r than or equal to 0.96 for all measurements). The differences in absolute and relative variability between the mechanical and phased-array designs, b oth for reanalysis of same frames and serial pullbacks, were very small. Co nclusions: Although multi-element and mechanical intravascular ultrasound d esigns are not strictly interchangeable, their similar reproducibility and the small differences in measurements demonstrate that both designs are acc eptable alternatives for trials of regression of atherosclerosis. Determina tion of the variability for serial pullbacks of both designs was also impor tant to assess the statistical power of such trials.