Orthostatic stress echocardiography as a useful test to measure variability of transvalvular pressure gradients in aortic stenosis

The aim of the study was to assess the influence of the orthostatic stress test on changes in aortic pressure gradients in patients with aortic stenosis (AS). METHODS: The orthostatic stress test was performed in 56 AS patients. The maximum aortic gradient was compared between the supine and the upright position (using Doppler echocardiography from the apical window). The left hand of each patient was kept on top of their head for both readings. 21 patients were excluded from the study for three reasons: 1) atrial fibrillation (significant beat-to-beat variability of measured gradient), 2) suboptimal Doppler signal during the orthostatic test, and 3) aortic gradient significantly higher in suprasternal or right parasternal windows than in apical window (different direction of stenosed blood jets) in the supine examination. The last limitation (#3) is methodologically important because during the orthostatic examination, only the transapical measurement was used. We were able to analyze 35 AS patients (20 males, 15 females, mean age 74.8 ± 9.2 years). RESULTS: The wide range of severity of AS was examined (maximal aortic gradient in the supine position from 30 to 146 mmHg). With regard to statistical trends, the mean value of the maximum aortic gradient significantly decreased after orthostatic stress (from 87.5 ± 28.6 to 75.8 ± 23.7 mmHg), p > 0.01). In 7 patients (increasing responders) the peak aortic gradient slightly increased during the stress test. Five of the seven only increased by a few percent. The other two patients increased by nearly 10%. In contrast, the remaining 28 AS patients’ gradient decreased by as much as 40% (decreasing responders). CONCLUSIONS: The orthostatic position test frequently generated a decrease of “theoretically fixed at rest” valvular gradient in AS. The combination of the stiffened stenotic valve apparatus and a reduced LV preload may be responsible for this decreasing response.