A clinical appraisal of different Z-score equations for aortic root assessment in the diagnostic evaluation of Marfan syndrome.

Abstract

Aortic sinus diameter dilatation expressed as a Z-score >2.0 is diagnostic in Marfan syndrome. In addition to the classic equation (Z1) for calculating Z-scores, two new equations were recently introduced (Z2 and Z3). We studied the effects of obesity, age, and the absolute cut point of 40 mm on these three equations in 2,674 echocardiographic measurements of 260 patients with Marfan syndrome. Diameters ≥40 mm were associated with Z1 scores <2.0 in 109 measurements (11.0%; 35 patients), Z2 scores <2.0 in 37 measurements (3.8%; 13 patients), and Z3 scores <2.0 in 24 measurements (2.4%; 11 patients). Mean diameters increased after the 40th birthday: 42.0 (37.3-44.8 mm interquartile range) to 42.5 (39.0-45.0 mm interquartile range; P = not significant) and mean Z1 scores decreased from 3.60 to 2.17 (P < 0.01), whereas Z2 and Z3 scores tended to increase (Z2: 3.04-3.27; Z3: 3.39-3.55; P = not significant for both). Comparing Z-scores between patients with body mass index <25 kg/m² (group A) and those with body mass index ≥25 kg/m² (group B), median Z1 scores differed between groups (Z1 = 3.00 in group A, Z1 = 1.78 in group B; P = 0.012), whereas Z2 (Z2 = 2.82 in group A, Z2 = 2.47 in group B; P = 0.52) and Z3 scores (Z3 = 2.72 in group A, Z2 = 3.12 in group B; P = 0.32) did not. Z1 scores are inferior to Z2 and Z3 scores in Marfan syndrome. In particular, the Z3 score, correcting aortic sinus diameter for body height, seems excellent.