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September 25, 2018 Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 e302

CLINICAL STATEMENTS AND GUIDELINES

Recommendation-Specific Supportive Text

1.	In the AVID trial,S7.1.1-1 the ICD improved overall survival compared with antiarrhythmic medication therapy (primarily amiodarone) in patients who survived SCD or with hemodynamically unstable VT, with a 2-year relative risk reduction in mortality of 27% and an absolute risk reduction of 7%. CIDS (Canadian Implantable Defibrillator Study),S7.1.1-2 which was stopped early after the results of the AVID trial were released, showed a similar, but not statistically significant, benefit of the ICD over antiarrhythmic medication therapy. A subsequent meta-analysis using data from 3 RCTs showed a statistically significant reduction in both arrhythmic and all-cause mortality with secondary prevention ICDs.S7.1.1-3

In survivors of life-threatening VA that may be due to transient or reversible factors, such as AMI, proarrhythmic medication effects, or electrolyte disturbances, an ICD is not implanted if the cause may be correctable. This is a population of patients that still requires thorough evaluation, treatment, and close follow-up and, as in the AVID registry, mortality was still high in the population that may have had a reversible cause for their arrest.S7.1.1-8 Small increases in troponin present a challenge in selecting patients for an ICD, as it often cannot be determined whether troponin elevation is due to ischemia from VT/VF and resuscitation, in which case an ICD is likely warranted, or an indication that ischemia caused the arrhythmia, in which case prevention of ischemia would be the therapeutic focus.

ICDs may improve the outcomes of patients with hemodynamically tolerated sustained VT and structural heart diseaseS7.1.1-5; however, this has not proved in any RCT. VT ablation has been used as an alternative in selected patients with well-tolerated VT and appears to reduce recurrences, but the impact on long-term mortality is unknown; there is not yet sufficient evidence to recommend this approach as an alternative to ICD implantation.S7.1.1-9,S7.1.1-10 2.	 Economic outcomes of ICD implantation for secondary prevention of SCD were assessed in the AVID and CIDS trials,S7.1.1-11,S7.1.1-12 as well as in a simulation modelS7.1.1-13 and an observational study of Medicare beneficiaries.S7.1.1-14 All studies compared ICD recipients with non-ICD recipients, and all found that ICD recipients had longer overall survival and higher lifetime costs of medical care. All studies reported incremental cost-effectiveness ratios between $64 000 and $100 000 per year of life added by an ICD,S7.1.1-11–S7.1.1-14 which is in the range of intermediate value by the benchmarks applied in the ACC/ AHA cost/value statement.S7.1.1-15 3.	 VAs are an important cause of syncope or near syncope in patients with ischemic heart disease, particularly those with prior infarction. A study of 70 patients with unexplained syncope who underwent an electrophysiological study identified positive findings in 37 patients; 31 with VT. During 3 years of follow-up, patients with a positive electrophysiological study had higher rates of SCD and 3-year total mortality (61% versus 15%, respectively) than those with a negative electrophysiological study.S7.1.1-7 An ICD is warranted for patients with syncope and inducible sustained monomorphic VT even if they do not otherwise meet criteria for primary prevention (Figure 4). 7.1.1.1. Coronary Artery Spasm

Recommendations for Patients With Coronary Artery Spasm References that support the recommendations are summarized in Online Data Supplement 20.

COR LOE Recommendations

I B-NR 1. In patients with VA due to coronary artery spasm, treatment with maximally tolerated doses of a calcium channel blocker and smoking cessation are indicated to reduce recurrent ischemia and VA.S7.1.1.1-1,S7.1.1.1-2

IIa B-NR 2. In patients resuscitated from SCA due to coronary artery spasm in whom medical therapy is ineffective or not tolerated, an ICD is reasonable if meaningful survival of greater than 1 year is expected.S7.1.1.1-3–S7.1.1.1-6

IIb B-NR 3. In patients resuscitated from SCA due to coronary artery spasm, an ICD in addition to medical therapy may be reasonable if meaningful survival of greater than 1 year is expected.S7.1.1.1-3–S7.1.1.1-6

Figure 3. Secondary prevention patients with ischemic heart disease. Colors correspond to Class of Recommendation in Table 1. See Sections 4.3.1 and 7.1.1 for discussion. *Exclude reversible causes. †History consistent with an arrhythmic etiology for syncope. ‡ICD candidacy as determined by functional status, life expectancy, or patient preference. EP indicates electrophysiological; GDMT, guideline-directed management and therapy; ICD, implantable cardioverter-defibrillator; IHD, ischemic heart disease; LVEF, left ventricular ejection fraction; pts, patients; SCA, sudden cardiac arrest; SCD, sudden cardiac death; and VT, ventricular tachycardia.

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