1. Subjects who are considered to be operable and high risk for surgical valve replacement: 8 ≤ STS Score ≤ 15 or 15 ≤ Logistic EuroSCORE ≤ 40. If STS score is below 8 and/or Logistic EuroSCORE is below 15, patients should have other clinical or anatomical risk factors that would be considered high risk for surgery and documented by the heart team.