Aim of this study is to evaluate whether microsurgical repair or replacement of the aortic valve is a treatment option for a subgroup of patients suffering from aortic Stenosis.

Stenosis of the aortic valve leads to a narrowing of the valve, consequently to low blood flow from the heart into the Aorta, and is associated with symptoms like fatigue, breathlessness, dizziness, fainting, and chest pain. For many of the patients suffering from severe aortic stenosis surgical or catheter-assisted repair or replacement of the damaged aortic valve has been proven to be a safe and effective treatment option.

Probably about 20-30% of patients suffering from severe aortic stenosis display a deviation from the usually observed disease pattern: These patients do not show the typical high pressure difference between the left ventricle (heart chamber) and the aorta (transvalvular gradient; "paradoxical" low flow/low gradient aortic stenosis). For these patients it is not yet clear, if microsurgical repair of the aortic valve (transcatheter aortic valve repair - TAVR) should be a treatment option as well.

REBOOT-PARADOX evaluates whether TAVR is advantageous compared to optimal medical Treatment alone for patients suffering from paradoxical aortic stenosis. Two thirds of the participating patients will be treated by TAVR, one third will receive medical Treatment alone.

Inclusion Criteria:

• I1. Patients with symptomatic native aortic valve stenosis and age ≥18 years
• I2. Aortic valve area (AVA) ≤ 1 cm2 or indexed AVA ≤ 0.6 cm2/m2, mean aortic gradient < 40 mmHg and stroke volume index (SVI) < 35ml/m2
• I3. Left ventricular ejection fraction ≥ 50%
• I4. MDCT aortic valve calcium score men > 2000AU, women > 1200AU OR the likelihood criteria are fulfilled (symptoms without other explanation and LV hypertrophy; age < 70 yrs., AVS < 0.8 cm2; SVI < 35ml/m2 confirmed by 3D TOE, MRI or invasive; reduced LV longitudinal function without other reason)
• I5. Heart team agrees on eligibility for TAVR
• I6. Written informed consent
• I7. Negative pregnancy test in women with childbearing potential

Exclusion Criteria:

• E1. Hemodynamic instability
• E2. Cardiogenic shock
• E3. Pre-existing mechanical or bio-prosthetic valve in any position
• E4. Concomitant severe valvular heart disease
• E5. Pre-existing or active endocarditis
• E6. Need for heart surgery due to other conditions
• E7. Aortic valve is congenital unicuspid or congenital bicuspid
• E8. Hypertrophic cardiomyopathy with or without obstruction
• E9. Echocardiographic evidence of intracardiac mass, thrombus or vegetation
• E10. Acute myocardial infarction within 1 month before intended AS-treatment
• E11. Renal replacement therapy
• E12. Estimated life expectancy < 24 months (730 days) due to carcinomas end stage liver disease or renal disease
• E13. Currently participating in an investigational drug or another device study. Note: Trials requiring extended follow-up for products that were investigational, but have since become commercially available, are not considered investigational trials.
• E14. Patient refuses aortic valve repair