Impact of two formulas to calculate percentage diameter stenosis of coronary lesions: from stenosis models (phantom lesion model) to actual clinical lesions.

Percentage diameter stenosis (%DS) by angiography is still commonly used to determine luminal obstruction of coronary artery disease (CAD) lesions. While visual estimation of %DS is widespread, because of high inter-operator variability, quantitative coronary arteriography (QCA) analysis is the gold standard. There are two %DS formulas: %DS1 averages the proximal and distal reference vessel diameter (RVD); %DS2 interpolates the RVD. This study aims to evaluate the difference between %DS assessed by QCA in two datasets, phantom lesion models and CAD patients. Ten phantom lesion models (PLMs) and 354 CAD lesions from the FIRST trial were assessed by QCA. In the latter, two scenarios were assessed: Scenario A (worst view), the most common approach in the clinical setting; and Scenario B (average of two complementary views), the standard core-laboratory analysis. In the PLMs, %DS1 and %DS2 mean ± standard deviation (median) was 58.5 ± 21.7 (61.6) and 58.7 ± 21.6 (61.8), respectively, with a signed difference of - 0.2% ± 0.3% (- 0.1%). In Scenario A, the mean %DS1 was 43.8 ± 9.1 (43.3) and 44.0 ± 9.1 (42 .9) in %DS2. In Scenario B, the mean %DS1 was 45.3 ± 8.8 (45.1) and 45.5 ± 9.0 (45.1) in %DS2. The signed difference was - 0.2% ± 2.4% (0.0%) and - 0.2% ± 2.1% (0.0%) in Scenario A and B, respectively. These differences between formulas ranged from - 1.2 to 0.5% for the phantom cases compared to - 17.7% to 7.7% in Scenario A and to - 15.5% to 7.1% in Scenario B. Although the overall means of the formulas provide similar results, significant lesion-level differences are observed. The use of the worst view versus the average of two views provided similar results.