Measurement of Myocardial Stiffness Using Elastometry in Patients With Aortic Stenosis

Inclusion Criteria: * Group I (aortic stenosis): 1\. Patient undergoing planned surgical aortic valve replacement (SAVR) for aortic stenosis (aortic valve area \<1cm² or an aortic valve area index \<0.6 cm² / m²); * Group II: coronary bypass 2. Patient undergoing planned myocardial revascularization surgery (coronary bypass); * Groups I and II 3. Patient over 18 years of age; 4. Patient having read and understood the information letter and having signed the consent form; 5. Patient affiliated or benefiting from a health insurance scheme Exclusion Criteria: * Group II: coronary bypass 1. Ratio in TM mode of the wall thickness over the radius of the left ventricle (h / r \[0.45\]) confirmed by the TTE; 2. Scar of myocardial infarction defined by an ECG anomaly and / or hypo-akinesia on TTE, and / or a late enhancement in MRI; 3. Acute coronary syndrome less than 3 months old; 4. Significant aortic stenosis (Vmax\> 1.5 m / s); 5. Anomaly of segmental kinetics; 6. Presence of left ventricular hypertrophy * Groups I and II 7. Mitral valve disease (\> 1/4 confirmed by TTE); 8. Aortic insufficiency (\> 1/4 confirmed by TTE); 9. Left ventricle ejection fraction (LVEF) \<50% confirmed by TTE; 10. Hospitalization for heart failure less than 3 months old; 11. Urgent surgery; 12. Infiltrative heart disease; 13. Hostile pericardium defined by a history of mediastinal radiotherapy, tamponade or complicated pericarditis; 14. Decompensated or severe arterial hypertension. 15. Functional inability to walk preventing the performance of the walk test; 16. Proven pregnant woman (positive urine pregnancy test) or breastfeeding or absence of effective contraception (as defined by the WHO) or postmenopausal woman without confirmation diagnosis obtained (amenorrhea not medically induced for at least 12 months before the initiation visit) ; 17. Person deprived of their liberty by an administrative or judicial decision or person placed under the protection of justice / guardianship or curatorship 18. History of illness or psychological or sensory abnormality likely to prevent the subject from fully understanding the conditions required for participating in the protocol or preventing him from giving his informed consent