the best valves currently in use. A linearized rate is calculated as the number of events divided by total patientyears, which is then multiplied by 100 to convert the rate to units of “events per 100 years” or “percent per year.” For mechanical valves, the OPC (percent/year) is estimated at 0.8 for valve thrombosis and 3.0 for thromboembolism. For biologic valves, the OPC (percent/year) is est...