Primary Prevention of CVD: The Role of Imaging Trials.

The optimal approach for screening for cardiovascular disease remains controversial. A new standard of "therapeutic efficacy" requires that screening tests which involve cardiac imaging not only predict events but also improve clinical outcomes compared with usual care. To date, 5 prospective randomized trials have been conducted to compare outcomes based on imaging-guided screening and prevention versus assignment to usual care in screening populations. One trial involved cardiac stress imaging, 3 involved coronary artery calcium scanning, and 1 involved coronary computed tomography angiography. Due to the current very low event risk in asymptomatic populations, these trials have been substantially underpowered to assess the impact of imaging-guided prevention on hard cardiac events. This review derives lessons learned from these trials relative to the future design of imaging-based screening trials, including analysis regarding the optimal methods for screening, and what are the relevant clinical outcomes to assess the efficacy of imaging-based screening for prevention.