QUALITY OF LIFE ICD implantation has not had a significant effect on QoL in the overall population of patients enrolled in Several studies have, however, demon- strated that the subset of patients who receive inap- propriate ICD shocks have worse QoL than patients who have an ICD but have not had inappropriate Because an ICD is designed to prevent SCD rather than to reduce symptoms, it would not be ex- pected to improve QoL or functional status directly, but may have indirect, negative effects in some pa- tients 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 = $50000/QALYs. CE indicated cost effectiveness, ICD, implantable cardioverter-defibrillator; LYA, life year added; and QALYs, quality-adjusted life-years. CLINICAL STATEMENTS AND GUIDELINES 18. EVIDENCE GAPS AND FUTURE RESEARCH NEEDS Despite the numerous advances in risk stratification for SCD and prevention and treatment of SCD and VA, many gaps in knowledge remain. These gaps include: Identification of patients who are most likely to benefit from an ICD among all ICD-eligible patients. The role of novel markers (including genetic and imaging markers) and combinations of markers should be studied. Characterizing the role of the ICD in patient sub- groups not well-represented in the pivotal ICD trials. Such subgroups include patients 80 years of age and those with kidney disease, espe- cially patients with ESRD on dialysis, or multiple comorbidities. Methods to identify and treat patients at high indi- vidual risk for SCD who are not identified by cur- rent ICD eligibility criteria, including those who are within 40 days of an MI. 