Measuring progression and regression of coronary atherosclerosis in clinical trials: problems and progress.

Interventions that may influence the evolution of coronary atherosclerosis can be evaluated more rapidly and efficiently in clinical trials with angiographic endpoints as opposed to using coronary events as endpoints. Quantitative coronary arteriography provides precise and reproducible measurements of coronary artery dimensions for this purpose. The variability of 2 quantitative systems was assessed in 54 lesions under 4 different conditions: same film, same frame; same film, same view; different frame; same view from different films obtained within one month; and same view from different films obtained one to 6 months apart. With the Cardiovascular Angiographic Analysis System (CAAS), variability of repeat measurement of minimum diameter, expressed as 1 standard deviation of the mean, increased from 0.088 mm (same frame) to 0.197 mm (films 1 to 6 months apart) as conditions decreased from optimal to those encountered in clinical studies. With the Cardiovascular Measurement System (CMS), 1 standard deviation for repeat measurements of minimum diameter increased from 0.087 mm (same frame to 0.240 mm (films one to 6 months apart). The differences between the two systems for measurements of minimum diameter were not statistically significant and CMS tracked the arterial edge more meticulously than did CAAS. A change in minimum diameter greater than or equal to 0.4 mm for CAAS or greater than or equal to 0.48 mm for CMS is more than 2 standard deviations of the mid-term variability and therefore represents a true change, either progression or regression, with greater than 95% probability. Quantitative coronary arteriography is an essential tool in clinical trials to assess the effect of an intervention upon the evolution of coronary atherosclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)