The initial cost of an ICD device is similar regardless of the clinical indication, so variations in ICD cost-ef- fectiveness are driven primarily by potential differences in clinical effectiveness in extending survival in differ- ent patient populations. The effect of the years of life added by an ICD on its incremental cost-effectiveness ratio is illustrated in Figure 17: the cost-effectiveness ratio becomes rapidly unfavorable as the extension in survival time falls below 1 year, particularly below 0.5 year. This inverse relation strongly suggests that the value provided by an ICD will be highest when the risk of arrhythmic death due to VT/VF is relatively high and the risk of nonarrhythmic death (either cardiac or noncardiac) is relatively low, such that a meaning- ful increase in survival can be expected from the ICD. Thus, appropriate patient selection is fundamental to high value care in using the ICD to prevent SCD. It should also be recognized that cost-effectiveness is also influenced by the costs for the ICD and implanta- tion procedure, which are likely to change significantly over time. The empirical evidence suggests that ICDs are not effective for primary prevention of SCD when im- planted early after CABGS16-15 or an acute myocardial An analysis of individual patient lev- el data from 3 secondary prevention trialsS16-18 showed a significant variation (P=0.011) in the clinical effec- tiveness of ICDs between patients with an LVEF 35% (hazard ratio: 0.66) and an LVEF >35% (hazard ratio: 1.2). 