THE INFLUENCE OF ANGIOGRAPHIC END-POINTS ON THE OUTCOME OF LIPID INTERVENTION STUDIES - A PROPOSAL FOR STANDARDIZATION

The aims of this study were to evaluate the influence of different cor onary angiographic endpoints on the outcome of lipid intervention stud ies and to formulate a proposal for angiographic endpoint standardizat ion. In recent angiographic intervention studies a confusing diversity in angiographic endpoints has been used to determine the outcome. In addition, differences in study populations (eg, bypass patients includ ed or not) could influence results. This makes comparisons between stu dies cumbersome and raises the question to what extent the results of various studies may be subject to the selection of angiographic endpoi nts. The investigators compared three frequently used endpoints (mean segment diameter, minimum obstruction diameter, and % stenosis) in a g roup of 505 patients who had just finished a trial designed to assess the effect of cholesterol lowering by pravastatin. To exclude a potent ial bias this analysis was carried out at the time that the study was still blinded. They found poor intercorrelation coefficients for mean segment diameter calculated in different ways, ranging from 0.55 to 0. 95, dependent on inclusion or exclusion of segments influenced by coro nary angioplasty or bypass grafting and on whether or not a value of 0 was assumed for occluded segments and segments distal to occlusions. The correlation between mean segment diameter and minimum obstruction diameter was 0.79; between minimum obstruction diameter and % stenosis , 0.85; and between mean segment diameter and % stenosis, only 0.64. D ifferent endpoints sometimes correlate poorly. This may lead to differ ences in results of angiographic intervention trials. The authors prop ose standardization by (1) using both mean segment diameter and minimu m obstruction diameter as endpoints and (2) excluding from the primary analysis segments influenced by mechanical interventions.