10.3 Participant Enrollment and Follow-Up 2750 enrollees, will be followed up to 5 years. 10.4 Analysis Plan Because the anticipated event rate is small (4-5%), and the number of potential predictive risk factors is large (20+), an exploratory, tree classification analysis will be used to identify the strongest predictors and eliminate any that are judged to have little or no predictive power. Based on the risk factors identified in the exploratory analysis, a regression prediction model will be developed from which a summary risk score for HCM can be calculated and easily used in clinical settings.