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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e347 CLINICAL STATEMENTS AND GUIDELINES cardioverter-defibrillator implantation may be an appropriate option for some patients.S10.8-42,S10.8-53 11. Adult patients with complex adult congenital heart disease typically have hypertrophy and ventricular dysfunction of varying degrees, increasing their risk for worsening ventricular function with antiarrhythmic medications. In the only large study of antiarrhythmic medications for congenital heart disease, the use of flecainide was associated with proarrhythmia in 5.8% of patients and SCA in 3.9% of patients.S10.8-30 The use of amiodarone is generally reserved for refractory symptomatic VA or asymptomatic VA that can aggravate ventricular dysfunction, due to the high risk of adverse effects including thyroid dysfunction, particularly among females and patients with univentricular physiology.S10.8-31,S10.8-32 11 DEFIBRILLATORS OTHER THAN TRANSVENOUS ICDS 11.1 Subcutaneous Implantable Cardioverter-Defibrillator Recommendations for Subcutaneous Implantable Cardioverter- Defibrillator References that support the recommendations are summarized in Online Data Supplement 55. COR LOE Recommendations I B-NR 1. In patients who meet criteria for an ICD who have inadequate vascular access or are at high risk for infection, and in whom pacing for bradycardia or VT termination or as part of CRT is neither needed nor anticipated, a subcutaneous implantable cardioverter-defibrillator is recommended.S11.1-1–S11.1-5 IIa B-NR 2. In patients who meet indication for an ICD, implantation of a subcutaneous implantable cardioverter-defibrillator is reasonable if pacing for bradycardia or VT termination or as part of CRT is neither needed nor anticipated.S11.1-1–S11.1-4 III: Harm B-NR 3. In patients with an indication for bradycardia pacing or CRT, or for whom antitachycardia pacing for VT termination is required, a subcutaneous implantable cardioverter-defibrillator should not be implanted.S11.1-1–S11.1-4,S11.1-6–S11.1-8 Synopsis In patients being considered for a subcutaneous implantable cardioverter-defibrillator, a preimplant ECG to establish QRS-T wave morphology is needed to reduce the risk of under sensing of VT/VF and the risk of inappropriate shocks.S11.1-9–S11.1-11 The subcutaneous implantable cardioverter-defibrillator is implanted using primarily anatomical landmarks, thereby minimizing the need for fluoroscopy. The subcutaneous implantable cardioverter-defibrillator consists of a pulse generator that is placed at the midaxillary line between the fifth and sixth intercostal spaces and a lead with 2 sensing electrodes and a shocking coil, positioned subcutaneously adjacent to the sternum. As with the transvenous ICD, the pulse generator housing serves as an electrode for defibrillation but, in addition, it can also serve as an optional electrode for sensing. The subcutaneous implantable cardioverter-defibrillator cannot achieve adequate arrhythmia sensing for all patients, and electrocardiographic screening to assess sensing is required prior to implantation.S11.1-10,S11.1-11 Some advocate exercise testing after device implantation to ensure proper sensing with exercise. Both transvenous and subcutaneous implantable cardioverter-defibrillators have SVT-VT discriminators that can be programmed to facilitate discrimination of SVT from VT; however, these discriminators do not always work. If sustained VT is confirmed, therapy to terminate the arrhythmia is delivered. All ICDs provide shocks to terminate VT or VF, but shocks in an awake patient are painful and associated with decreased QoL. Transvenous ICDs are capable of bradycardia pacing as well as antitachycardia pacing that can terminate many VTs painlessly. Subcutaneous implantable cardioverterdefibrillators provide limited postshock bradycardia pacing but do not provide either bradycardia or antitachycardia pacing. The subcutaneous implantable cardioverter-defibrillator recommendations supplant, but do not nullify, the need for waiting periods and other requirements to be satisfied for ICD/CRT implantation specified in other parts of this document. Recommendation-Specific Supportive Text 1. The subcutaneous implantable cardioverterdefibrillator was designed to avoid the need for venous access and some of the complications of inserting transvenous lead(s)S11.1-1–S11.1-4 that include pneumothorax, hemothorax, and cardiac tamponade.S11.1-12 Difficulties in achieving venous access can prolong the implantation procedure and occasionally result in failed ICD implantation. These difficulties are more likely to be encountered in patients with limited venous access such as patients with ESRD. In a study of 27 patients with ESRD, the subcutaneous implantable cardioverter-defibrillator was not associated with an increased risk of procedural complications or inappropriate shocks.S11.1-5 The risk of infection appears to be lower with subcutaneous implantable cardioverter-defibrillators than with transvenous ICDs.S11.1-1–S11.1-4 Therefore, a subcutaneous Downloaded from http://ahajournals.org by on October 7, 2026