To determine the optimal treat- ment for a patient with VHD, ancillary testing may be required, such as transesophageal echocardiography (TEE), computed tomography (CT), cardiac magnetic resonance (CMR) imaging, stress testing, Holter moni- toring, diagnostic hemodynamic cardiac catheteriza- tion, or positron emission tomography (PET) combined with CT imaging. If intervention is contemplated, surgi- cal or procedural risk should be estimated and other factors also considered, including comorbidities, frailty, and patient preferences and values (Table 3). 2.2. Definitions of Severity of Valve Disease Classification of valve disease severity is based on multiple criteria, including symptoms, valve anatomy, valve hemo- dynamics and the effects of valve dysfunction on ven- tricular and vascular function (eg, end-organ damage). Surgical and transcatheter interventions are performed primarily on patients with severe VHD, but diagnosis, pa- tient education, periodic monitoring, and medical thera- py are essential elements in the management of patients at risk of VHD and with mild to moderate valve dysfunc- tion. This document provides a classification of the pro- gression of VHD, with 4 stages (A to D). Indications for intervention and periodic monitoring are dependent on 1) the presence or absence of symptoms, 2) the severity of VHD, 3) the response of the LV and/or RV to volume or pressure overload caused by VHD, and 4) the effects on the pulmonary or systemic circulation (Table 4). The purpose of valvular intervention is to improve symptoms, prolong survival, and minimize the risk of VHD-related complications, such as irreversible ventricular dysfunction, pulmonary hypertension, stroke, and atrial fibrillation (AF). Thus, the criteria for severe VHD are based on predictors of clinical outcome from observational studies, registry data, and randomized clinical trials (RCTs) of pa- tients with VHD. 