Comparison of quantitative coronary angiography to visual estimates of lesion severity pre and post PTCA.

Quantitative coronary angiographic measurements and visual estimates of coronary lesion severity were compared prospectively before, immediately following, and 6 months following percutaneous transluminal coronary angioplasty. Mean percent diameter stenosis before angioplasty was 87.9 +/- 9.9% by visual analysis and 64.6 +/- 9.2% by quantitative coronary angiography (p = 0.0001). Differences between these two techniques were also found immediately post-angioplasty (visual analysis 29.5 +/- 11.8%, quantitative coronary angiography 22.8 +/- 11.8%, p = 0.0002) and at 6 months (visual analysis 46.5 +/- 27.4%, quantitative coronary angiography 30.2 +/- 20.4%, p = 0.0001). These differences significantly affected the determination of restenosis by three definitions. (1) Lesion recurrence with greater than or equal to 50% stenosis at follow-up: 38 of 92 (41%) by visual analysis versus 20 of 92 (22%) by quantitative coronary angiography (p less than 0.01). (2) Increase of greater than or equal to 30% stenosis: 34 of 92 (37%) by visual analysis versus 20 of 92 (22%) by quantitative coronary angiography (p less than 0.01). (3) Loss of 50% of previous improvement: 31 of 92 (34%) by visual analysis versus 24 of 92 (26%) by quantitative coronary angiography (p = 0.08). In addition, determination of success or failure of percutaneous transluminal coronary angioplasty was affected by the interpretative technique, but these differences were not statistically significant. We conclude that visual estimates of lesion severity are consistently and significantly higher than quantitative measurements. Consequently, restenosis rates, using currently applied definitions, differ considerably depending on the method of analyzing lesion severity.