Appraisal of key trials in aortic and mitral fields. 
Aortic stenosis and mitral regurgitation are increasingly treated by percutaneous interventions including transcatheter aortic valve implantation (TAVI) and several mitral valve repair techniques, changing the landscape of valvular therapies in which surgery was predominant.  Several randomised studies on TAVI have led to the use of this procedure in patients at intermediate or higher operative risk and have set strong foundations for future trials aiming to expand indications or to overcome several residual issues with TAVI.  On the other hand, randomised evidence for percutaneous mitral valve repair (PMVR) techniques is still limited, supporting restricted indications to patients with high surgical risk when medical therapy fails.  However, in the mitral field, several ongoing trials comparing PMVR with medical therapy or surgery will help to define optimal mitral regurgitation management in this era of evolving catheter-based treatment options.  The present review will summarise randomised trials comparing TAVI or PMVR with medical therapy or surgery across the risk spectrum which have set the basis for guideline recommendations and for clinical use of transcatheter interventions.  Characteristics, results, implications, unresolved issues and cost-effectiveness analysis of those trials, grouped according to the surgical risk of enrolled patients, will be appraised.