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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e353 CLINICAL STATEMENTS AND GUIDELINES

lifetime simulation model applied to each major trial of primary prevention ICDs also reported consistently more favorable estimates of cost-effectiveness than the estimates based on limited trial follow-up.S16-11 Because the framework proposed for assessing value in ACC/ AHA clinical practice guidelines uses benchmarks based on lifetime estimates,S16-1 we have generally relied on the model-based estimates of ICD cost-effectiveness in applying value ratings to recommendations in this guideline. The initial cost of an ICD device is similar regardless of the clinical indication, so variations in ICD cost-effectiveness are driven primarily by potential differences in clinical effectiveness in extending survival in different 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 meaningful 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 implantation procedure, which are likely to change significantly over time. The empirical evidence suggests that ICDs are not effective for primary prevention of SCD when implanted early after CABGS16-15 or an acute myocardial infarction.S16-16,S16-17 An analysis of individual patient lev- el data from 3 secondary prevention trialsS16-18 showed a significant variation (P =0.011) in the clinical effectiveness of ICDs between patients with an LVEF ≤35% (hazard ratio: 0.66) and an LVEF >35% (hazard ratio: 1.2). Some studies and simulation models suggest that ICDs might prolong life expectancy to a greater extent when used in higher-risk patients than in lowerrisk patients.S16-19 In contrast, there is little evidence of variation in the effectiveness or cost-effectiveness of the ICD based on factors such as age or sex.S16-20 Most studies of ICD effectiveness and value have been performed on patients with reduced LV function due to prior MI or NICM. There are few data on the effectiveness or value of an ICD for other potential clinical indications, such as cardiac channelopathies or HCM, although studies have suggested that their potential cost effectiveness in such patients will depend on their underlying risk of SCD, with little evidence of value in low-risk patients.S16-14

17 QUALITY OF LIFE

ICD implantation has not had a significant effect on QoL in the overall population of patients enrolled in RCTs.S17-1–S17-3 Several studies have, however, demonstrated that the subset of patients who receive inappropriate ICD shocks have worse QoL than patients who have an ICD but have not had inappropriate shocks.S17-2 Because an ICD is designed to prevent SCD rather than to reduce symptoms, it would not be expected to improve QoL or functional status directly, but may have indirect, negative effects in some patients due to device complications, or indirect, positive effects in some patients due to reassurance of having a protective device in place.

Figure 17. Incremental cost-effectiveness of ICD by years of life added* (example). *Figure based on formula: Incremental cost-effectiveness ratio = $50 000/QALYs. CE indicated cost effectiveness, ICD, implantable cardioverter-defibrillator; LYA, life year added; and QALYs, quality-adjusted life-years.

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