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**Importance of LV Outflow Tract Area measured by Computed Tomography on Aortic Stenosis Survival**
**Marie-Annick Clavel**^{1}, Joseph Malouf^{1}, David Messika-Zeitoun^{2}, Phillip A. Araoz^{1}, Hector I. Michelena^{1}, Maurice Enriquez-Sarano^{1}.

^{1}Mayo Clinic, Rochester, MN, USA, ^{2}AP-HP, Bichat Hospital, Paris, France.
**OBJECTIVE:** LV outflow tract (LVOT) is not circular and 2D echocardiography measurement may underestimate LVOT area and thus aortic valve area (AVA) calculation. However, this underestimation of AVA on survival after aortic stenosis (AS) diagnosis has not been addressed. The objective of this study was to assess the incremental value of AVA calculated with the use of LVOT area measured by Multi-Detector Computed Tomography (MDCT) over standard Doppler AVA calculation in determining survival under medical management.

**METHODS:** 269 AS patients underwent transthoracic Doppler-echocardiography and MDCT within an interval of 3 months. Aortic valve area (AVA) was calculated by Doppler (continuity equation) (AVAEcho) and by MDCT using direct measurement of LVOT area in the continuity equation (AVACT).

**RESULTS:** The patients were 76±11 years old and 163 (61%) were men. The mean AVAEcho was 0.94±0.32 cm2, AVACT 1.13±0.44 cm2, mean gradient 44±18 mmHg and LV ejection fraction 58±15%. AVACT was larger than AVAEcho in 230 (86%) patients with a mean difference of 0.19±0.20 cm2. During follow-up under medical management of 1.4±2.0 years, there were 55 deaths. Two multivariate models were constructed, one with AVAEcho and one with AVACT and adjusted for age, gender, NYHA≥3, mean gradient and left ventricular ejection fraction. AVAEcho and AVACT were independent predictor of survival under medical treatment (HR: 1.181.05-1.34] per 0.10cm2 decrease; p=0.003 and HR: 1.141.05-1.24] per 0.10cm2 decrease; p=0.0008, respectively) with similar accuracy of 2 models (all p=0.11 by C statistics). However, the thresholds defining mortality were highly different: AVAEcho≤1.00cm2 (HR: 3.181.48-7.37]; p=0.002) and AVACT≤1.20cm2 (HR: 2.661.35-5.60]; p=0.004) were independently predictive of mortality under medical treatment.

**CONCLUSIONS:** AVA calculated using LVOT area measured by MDCT is larger than AVA by Doppler-echocardiography. However, the threshold predicting an excess mortality after AS diagnosis was also larger (1.20 vs. 1.00 cm2) and the accuracy for risk stratification is equivalent.

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