The business of risk.

Predictions about the future feature prominently in all aspects of human endeavour from weather to economics to politics and, increasingly, to medicine. In cardiovascular disease where scientists often deal with strategies of care, the design of clinical trials is greatly influenced by consideration of risk in the patients to be treated; in this case, issues of patient population, baseline demographics and predicted event rates are used to design sample size and power calculations. For patients, risk prediction is less ethereal, instead being very concrete and of the utmost importance because the potential endpoints to be predicted are often hard ones and once they occur they cannot be taken back, such as stroke, myocardial infarction or mortality. In the field of structural heart disease, transcatheter aortic valve replacement (TAVR) occupies a positon of great importance by virtue of treating what had been an unmet clinical need, the number of patients who have actually been treated, the fact that there are alternative treatments available, namely surgical aortic valve replacement (SAVR), the potential for further expansion of the instructions for use (IFU), and the fact that associated patient comorbidities greatly increase risk so that hard points, such as mortality and stroke, are of significant concern and more than rare. In this issue of EuroIntervention, Arsalan et al1 provide important information for the field by using their unique data set of 946 consecutive patients undergoing TAVR to validate the recently developed STS/ACC TAVI risk score for in-hospital TAVR mortality and compare its ability to predict 30-day mortality with that of four other established risk models, including EuroSCORE I2, EuroSCORE II3, STS-PROM4, and the German AV Score5.