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Kusumoto et al 2018 Bradycardia Clinical Practice Guidelines

Circulation. 2019;140:e382–e482. DOI: 10.1161/CIR.0000000000000628 August 20, 2019 e445 CLINICAL STATEMENTS AND GUIDELINES

cally significant stenosis or baffle leak before placing endocardial leads. This detail is beyond the scope of these broad guideline statements, and for such specialized care, these patients should be referred to dedicated centers with multimodality experience in managing this type of patient.

Recommendation-Specific Supportive Text

1.	 Permanent pacing can alleviate symptoms from SND in adults with ACHD. In adults with ACHD, SND is associated with higher mortality and a higher rate of atrial flutter although there is no randomized trial evaluating whether permanent pacing prevents these sequelae.S8.2-1–S8.2-6 Given the younger median age of presentation of sinus node disease in this group of patients, they remain at higher risk for multiple transvenous leads over their lifetime. Single-lead atrial-based pacing is an established strategy for this type of patient and pathophysiology and is recommended for patients with isolated sinus nodal disease and preserved atrioventricular conduction. Single lead atrial-based pacing aims to limit the number of leads and potentially preserve vascular patency.S8.2-19–S8.2-23 2.	 Atrioventricular block at any level is associated with a higher mortality in the ACHD patient, yet no randomized studies exist to compare treatment strategies for the asymptomatic patient. The degree of atrioventricular block from first-degree to complete atrioventricular block is relevant as far as reliability of an escape rhythm or unexpected syncope is concerned, yet patients may develop symptoms, regardless of the level block. As an example, patients with significant prolongation of atrioventricular conduction (without block) can develop atrioventricular dyssynchrony to such a degree that pacemaker syndrome can develop. Certain congenital anomalies (eg, ccTGA and the endocardial cushion defects) are inherently associated with a more fragile atrioventricular conduction system, and more rigorous scrutiny of these patient groups is necessary.S8.2-7–S8.2-9 3.	 Certain clinical features have been identified as high-risk markers for adverse outcomes including death in patients with congenital complete heart block.S8.2-10,S8.2-11,S8.2-24 These reflect a deterioration or unreliability of the escape rate and an increased propensity to develop bradycardiarelated ventricular arrhythmias including torsades de pointes.S8.2-10,S8.2-11,S8.2-24 4.	 The incidence and natural history of postoperative heart block in adults with ACHD varies by underlying anatomy, surgery performed, and genetic effects.S8.2-25 The optimal duration the clinician should wait before permanent pacing is not well defined given the multiple mechanisms at play including direct traumatic injury, ischemia, infarction, autonomic tone, stunned myocardium and differences in reperfusion that all influence recovery of conduction. Recent investigations suggest that waiting 7 to 9 days is likely unnecessary, but the clinician is urged to carefully consider and generally avoid early implantation <72 hours, so as to avoid unnecessary implantation of pacemakers.S8.2-12,S8.2-13 One study has shown that patients are at high risk for permanent heart block if conduction has not resumed within 72 hours postoperatively.S8.2-13

5.	 Patients with congenital complete heart block have a high incidence of late sudden death at any age, and although the supporting literature is somewhat conflicting, there is sufficient concern for unpredictability of disease progression that the clinician can consider permanent pacing in the asymptomatic individual.S8.2-7–S8.2-11 6.	 The reentrant nature of the most common atrial arrhythmias in adults with ACHD will potentially allow for effective and reliable pace termination. This is distinctly different from managing the most common atrial arrhythmia in normal hearts and those with acquired disease, where AF predominates and cannot be consistently pace-terminated.S8.2-14,S8.2-15 7.	 Long-term longitudinal observational studies have consistently demonstrated that endocardial leads retain better longevity and are less likely to fail. This is likely related to epicardial fibrosis in patients who have undergone prior pericardiotomy.S8.2-26,S8.2-27 However, given the low-risk in placing epicardial leads at the time of cardiac surgery, it is recommended that this opportunity be used for lead placement—before the development of more epicardial fibrosis/ adhesions in this patient group who are likely to undergo repeat operation and are at significant risk of sinus and atrioventricular node disease. In patients with single-ventricle anatomy who have undergone orthoterminal correction by some version of a Fontan procedure, there is likely not to be transcutaneous access for atrial pacing, because the atria have been excluded from the systemic venous pathway. These patients will require epicardial atrial electrodes to atrial pacing, and in general, will need both atrial and ventricular permanent epicardial leads. Although traditionally considered a contraindication, it may be that MRI can be performed safely in selected patients with abandoned leads using specialized protocols.S8.2-28–S8.2-30

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