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September 25, 2018 Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 e308

CLINICAL STATEMENTS AND GUIDELINES ischemic heart disease and VF, polymorphic VT, or exercise-induced arrhythmias associated with ischemia.S7.1.3-25

7.2 Nonischemic Cardiomyopathy

Recommendations for Patients With NICM References that support the recommendations are summarized in Online Data Supplement 24.

COR LOE Recommendations

I B-NR 1. In patients with suspected NICM from myocardial infiltrative processes, cardiac MRI with late gadolinium enhancement is useful for diagnosis.S7.2-1–S7.2-3

IIa B-NR 2. In patients with suspected NICM, cardiac MRI with late gadolinium enhancement can be useful for assessing risk of SCA/SCD.S7.2-1–S7.2-3

IIa C-EO 3. In patients with NICM who develop conduction disease or LV dysfunction at less than 40 years of age, or who have a family history of NICM or SCD in a first-degree relative (<50 years of age), genetic counseling and genetic testing are reasonable to detect a heritable disease that may clarify prognosis and facilitate cascade screening of relatives.S7.2-4,S7.2-5

Recommendation-Specific Supportive Text

1.	 Cardiac MRI allows for evaluation of structural heart disease and assessment of LV and RV function including quantification of LVEF, LV mass and volume, and valvular structure. Cardiac MRI can help in the evaluation for myocardial infiltrative processes and evidence of scar, indicated by delayed hyperenhancement, associated with VA.S7.2-1–S7.2-4,S7.2-6 2.	 The presence of delayed hyperenhancement has been associated with worse outcomes, including SCD.S7.2-1–S7.2-3 3.	 It is important to consider genetic etiologies for NICM. Goals of genetic testing for NICM are to identify at-risk relatives who host a diseasecausing mutation and to help clarify prognosis. Lamin A/C and NKX 2.5 mutationsS7.2-7–S7.2-12 are associated with a particularly high risk of early conduction disease, arrhythmias, and SCD, and their identification often prompts consideration of early use of an ICD. It is unknown, however, whether early pharmacological treatment of mutation-positive, asymptomatic subjects can prevent or delay manifestation of the disease or whether genetic testing ultimately improves survival. 7.2.1 Secondary Prevention of SCD in Patients With NICM

Recommendations for Secondary Prevention of SCD in Patients With NICM References that support the recommendations are summarized in Online Data Supplements 25 and 26.

COR LOE Recommendations

I B-R

1. In patients with NICM who either survive SCA due to VT/VF or experience hemodynamically unstable VT (LOE: B-R) S7.2.1-1–S7.2.1-4 or stable sustained VT (LOE: B-NR) S7.2.1-5 not due to reversible causes, an ICD is recommended if meaningful survival greater than 1 year is expected. B-NR

IIa B-NR 2. In patients with NICM who experience syncope presumed to be due to VA and who do not meet indications for a primary prevention ICD, an ICD or an electrophysiological study for risk stratification for SCD can be beneficial if meaningful survival greater than 1 year is expected.S7.2.1-6–S7.2.1-11

IIb B-R 3. In patients with NICM who survive a cardiac arrest, have sustained VT, or have symptomatic VA who are ineligible for an ICD (due to a limited life-expectancy and/ or functional status or lack of access to an ICD), amiodarone may be considered for prevention of SCD.S7.2.1-12,S7.2.1-13

Recommendation-Specific Supportive Text

1.	 Three prospective RCTs compared the ICD with pharmacological therapy in patients resuscitated from SCA due to VT/VF or hemodynamically significant VT.S7.2.1-1,S7.2.1-2,S7.2.1-4 The antiarrhythmic medications most commonly used were amiodarone, a beta blocker, or both, although in the CASH (Cardiac Arrest Study Hamburg) trial,S7.2.1-4 there was also a propafenone arm that was terminated early due to increased mortality. The 3 trials enrolled 1963 patients, but only 292 (14.8%) had NICM. A meta-analysis in which data from AVID and CIDS were pooled found a nonsignificant 31% reduction in all-cause mortality relative to medical therapy in patients with NICM.S7.2.1-3 Although this analysis was underpowered, the observed mortality reduction was consistent with the observed benefit in the entire study population. In the AVID trial,S7.2.1-1 patients who were ineligible for the RCT were included in a registry, and sustained VT without serious symptoms or hemodynamic compromise was associated with a mortality rate similar to that of patients with unstable VT who were assigned to medical therapy. Therefore, stable VT is likely a marker for a substrate capable of producing subsequent lethal arrhythmias.S7.2.1-5

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