Effect of catheter positioning on the variability of measured gradient in aortic stenosis

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Abstract
The purpose of this study was to quantify the variation in measured aortic valve gradient and calculated aortic valve area when different techniques of cardiac catheterization were utilized. Hemodynamic assessment of aortic stenosis severity requires an accurately determined pressure gradient. In aortic stenosis, the presence of intraventricular pressure gradients and downstream pressure recovery within the aorta means that a range of aortic valve gradients could be measured in a given patient depending upon catheter position and measurement technique. To quantify the degree of variation in measured gradient and calculated aortic valve area, we generated transvalvular gradients by nine different techniques in 15 patients (11 men, 4 women; 29‐86 years old). Patients were divided into those with severe aortic stenosis (aortic valve area ≤ 0.6 cm2, n = 6) and those with moderately severe aortic stenosis (aortic valve area 0.61‐0.90 cm2, n = 9). Considerable variation in measured gradient and calculated aortic valve area was observed. The maximum variation in gradient was similar in severe and moderately severe aortic stenosis groups (33 mm Hg. vs. 32 mm Hg., p = NS). However, the variation in gradient as a percent of maximum gradient was greater (P < 0.05) in the moderately severe aortic stenosis group. The maximum variation in calculated aortic valve area was 0.1 cm2 in the severe group and 0.3 cm2 in the moderately severe group (P < 0.01). An intraventricular gradient, present in 13 of 15 (87%) patients, was partially responsible for the variation in pressure gradient measurement and calculated aortic valve area.We conclude that in patients with valvular aortic stenosis, catheterization technique has an important impact on the hemodynamic assessment of aortic stenosis severity. This is particularly true in patients with moderately severe aortic stenosis where any variation tends to represent a larger percentage of the total gradient. © 1993 Wlley‐Liss, Inc