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Background: The Gorlin equation is the reference method for the assessment of aortic valve area in aortic stenosis and is calculated using a constant, called the coefficient of contraction, which is empirically assumed to be 1. This coefficient is the ratio of effective aortic area to anatomic aortic area, and a value of 1 indicates that both are the same. The purpose of this study was to estimate the actual coefficient of contraction in patients with aortic stenosis and to evaluate its impact on aortic area as calculated by the Gorlin equation. Methods: We studied 17 patients with moderate to severe aortic stenosis. Effective aortic area was calculated using the continuity equation. Anatomic aortic area was obtained by planimetry with transesophageal echocardiography. Aortic valve area by the Gorlin equation was calculated from echocardiography data. The coefficient of contraction was derived as above. Results: The coefficient of contraction was inversely related to the pressure recovery. Effective area was correlated with anatomic area (r = 0.86, P < 0.01) but there was a high mean difference (0.22 ± 0.14 cm 2 ). Aortic area by the Gorlin equation was not correlated with anatomic area, but the correlation became significant when the Gorlin equation was corrected for coefficient of contraction and pressure recovery. Conclusions: Using a coefficient of contraction of 1 in the Gorlin equation gives a poor correlation with anatomic area. Using the calculated coefficient of contraction for each patient and the mean gradient for pressure recovery improves the correlation with anatomic area. These facts could be taken in account when Gorlin equation is considered as the reference method.

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Background Studies of ejection dynamics in severe aortic stenosis and prosthetic valve obstruction had demonstrated a delay in aortic valve opening. Purpose The aim of this study was to compare and evaluate ejection dynamics and valve kinetics in patients with severe aortic stenosis with preserved ejection fraction with normal and low flow. Methods 83 patients (age average 68±11 years) with severe aortic stenosis (aortic valve area &lt;1cm2) and preserved ejection fraction (≥50%) were studied with Doppler echocardiography and included prospectively. The ratio of aortic valve area measured at mid-deceleration and mid-acceleration (Md/Ma) were calculated using velocity of left ventricular outflow tract and aortic transvalvular velocity in continuity equation as an index of valvular kinetics. A ratio of Md/Ma &gt;1 indicate delay in opening of aortic valve. Assessment of ejection dynamics was evaluated with acceleration time (AT), ejection time (ET) and the ratio AT/ET estimated from aortic Doppler velocities profiles. Aortic flow was calculated as stroke volume/ET. According to stroke volume index and mean gradient patients were classified in 3 groups: normal-flow, low-gradient (NFLG) 25 patients, low-flow, low-gradient (LFLG) 28 patients and normal-flow, high-gradient (HG) 30 patients. Analysis of the variance and coefficient of correlation “r” were used for statistical evaluation. A p value &lt;0.05 was considered significant. Results There was no significant difference among the 3 groups with regard to ratio Md/Ma: NFLG 1.29±0.38, LFLG 1.22±0.26 and HG 1.23±0.45, NS. No difference was found in AT in the 3 groups, but ET was shorter in LFLG (310±30 ms) in comparison with NFLG (345±32 ms) and HG (361±31 ms), p&lt;0.01. Ratio AT/ET occurred in early systole in NFLG (0.27±0.07) compared with LFLG (0.32±0.07) and HG (0.39±0.07), p&lt;0.01. As expected, flow was decreased in LFLG (163±20 ml/s, p&lt;0.001) compared with NFLG (217±13 ml/s) and HG (233±44 ml/s). There was no correlation among AT/ET and aortic flow or stroke volume index. Conclusions There were not differences among the groups with regard to kinetic of the valve evaluated by mean of ratio Md/Ma. According to ratio AT/ET, aortic valve takes less time to open in NFLG compared with LFLG and HG independent of aortic flow suggesting a different ejection dynamics pattern in this group. Funding Acknowledgement Type of funding source: None

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