The presence of at least 3 serial imaging studies showing a con- sistent decline in LVEF ensures that the changes seen are not simply attributable to recording, measurement, or physiological variability.8 11 Hemodynamic progression eventually leading to symptom onset occurs in nearly all asymptom- atic patients with AS. The survival rate during the asymptomatic phase is similar to age-matched controls, with a low risk of sudden death (<1% per year) when patients are followed prospec- tively and when patients promptly report symp- tom onset. The rate of symptom onset is strongly dependent on the severity of AS, with an event- free survival rate of about 75% to 80% at 2 years in those with a jet velocity <3.0 m/s, compared with only 30% to 50% in those with a jet veloc- ity 4.0 m/s. Patients with asymptomatic AS require periodic monitoring for development of symptoms and progressive disease (Section 3.1). In patients with moderate calcific AS undergoing cardiac surgery for other indications, the risk of progressive VHD is balanced against the risk of repeat surgery or TAVI (Sections 4.3.3 and 10). This decision must be individualized on the basis of the specific operative risk in each patient, clini- cal factors such as age and comorbid conditions, valve durability, and patient preferences.13,49,62 64 3.2.4. Choice of Intervention 3.2.4.1. Choice of Mechanical Versus Bioprosthetic AVR Recommendations for Choice of Mechanical Versus Bioprosthetic AVR Referenced studies that support the recommendations are summarized in Online Data Supplements 11 and 12. 