The purpose of this study is to determine whether spironolactone reduces aortic stiffness, measured by carotid-femoral pulse wave velocity (cfPWV), compared with placebo, in patients with degenerative thoracic aortic aneurysms.

Inclusion Criteria

1. Adults ≥ 18 years old with dTAA of the aortic root and/or ascending aorta exceeding the upper limit of normal for age, sex, and body surface area (≥ 4.0 cm as an example of a common threshold; but age, sex and body size-specific thresholds have been established for the aortic root24 and ascending aorta25);
2. no antihypertensive use or stable antihypertensive regimen ≥ 4 weeks;
3. eGFR ≥ 50 mL/min/1.73 m²;
4. serum potassium ≤ 5.1 mmol/L;
5. ability to provide informed consent.

Exclusion Criteria

1. Heritable aortopathies (Marfan, Loeys-Dietz, vascular Ehlers-Danlos, Turner syndromes; familial TAA, genetically-proven TAA);
2. bicuspid aortic valve;
3. inflammatory aortitis,
4. prior aortic surgery, endovascular repair, or acute aortic syndrome;
5. permanent atrial fibrillation/flutter;
6. major peripheral artery disease affecting the carotids, iliacs and/or external femoral arteries precluding cfPWV measurement;
7. current use of spironolactone, eplerenone or finererone;
8. pregnancy or lactation.