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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 e429 CLINICAL STATEMENTS AND GUIDELINES

referred for biopsy proven AL cardiac amyloidosis had evidence of conduction disease on the baseline ECG and almost all had a prolonged HV interval (>55 ms) despite a narrow QRS.S6.4.4-26,S6.4.4-28 6.	 Patients with mutations in the lamin A/C gene can present with atrioventricular block, atrial arrhythmias, and ventricular arrhythmias.S6.4.4-

31,S6.4.4-33,S6.4.4-40–S6.4.4-45 Lamin A/C genetic defects have been linked to dilated cardiomyopathy, limb girdle muscular dystrophy, and an autosomal dominant variant of Emery-Dreifuss.S6.4.4-31 Case series in patients with lamin A/C cardiomyopathy have found some form of atrioventricular block in approximately 50% of patients and may be attributable to intramyocardial fibrosis that can be seen on cardiac MRI with gadolinium enhancement.S6.4.4-32,S6.4.4-40 Lamin A/C affected patients with evidence of atrioventricular block, with or without symptoms, are at an increased risk of sudden death.S6.4.4-46 One study showed that a first-degree atrioventricular block may be predictive of future ventricular arrhythmiasS6.4.4-33 Because of the high risk of ventricular arrhythmias and sudden cardiac death in these patients, devices with pacing as well as defibrillator capabilities are typically implanted.S6.4.4-42,S6.4.4-47–S6.4.4-49 7.	 First-degree atrioventricular block and seconddegree Mobitz type I (Wenckebach) atrioventricular block, when above or at the level of the atrioventricular node, are not concerning for progression to a higher degree atrioventricular block. They are also typically asymptomatic. However, in some patients, severe first-degree atrioventricular block can cause symptoms similar to pacemaker syndrome, as well as heart failure, and exertional intolerance.S6.4.4-34,S6.4.4-37 If the PR interval is very long, atrial contraction occurs when the atrioventricular valves are closed which can lead to an increase in wedge pressure and a decrease in cardiac output.S6.4.4-50 This phenomenon has been referred to as “pseudo-pacemaker syndrome” and has also been reported in patients with dual pathway physiology of the atrioventricular node.S6.4.4-51,S6.4.4-52 In patients with second-degree atrioventricular block Mobitz type I, frequently dropped QRS complexes can lead to symptoms attributable to loss of atrioventricular synchrony even in the absence of bradycardia.S6.4.4-52 8.	 In patients with neuromuscular diseases that can affect the cardiac conduction system, such as myotonic dystrophy 1, the degree of the conduction abnormality can vary from mild first-degree atrioventricular block to complete heart block and it often progresses over a variable period of time.S6.4.4-10,S6.4.4-53–S6.4.4-55 Serial ambulatory electrocardiographic monitoring and EPSs have been done to determine whether paroxysmal atrioventricular block is present or for identifying a prolonged HV interval (ie, >70 ms).S6.4.4-9 In a single center study of 211 myotonic dystrophy type 1 patients, 45 patients were categorized as having a severe electrocardiographic abnormality (PR interval >240 ms, QRS >120 ms, seconddegree or third-degree atrioventricular block, or a nonsinus rhythm) and 29 (65%) underwent pacemaker or ICD implantation.S6.4.4-12 Over 90% of the patients were asymptomatic at initial implant and at 5-year follow-up 13% of patients were pacemaker dependent.S6.4.4-12 In a multicenter prospective registry of patients with type 1 diabetes mellitus, this definition for severe electrocardiographic abnormalities had a sensitivity of 74% and a negative predictive value of 97.1% for predicting sudden death (rhythm at death unknown).S6.4.4-11 In this study, sudden death accounted for 33% of deaths while 40% of deaths were attributable to progressive neuromuscular respiratory failure, emphasizing that use of a CIED and type of CIED chosen should be based on arrhythmia risk profile, patient preference, and overall prognosis.S6.4.4-11 Data for other types of less common neuromuscular disorders (without lamin A/C involvement) is limited to case reports. Although neuromuscular disorders are a heterogeneous group with different cardiac effects, in the presence of severe conduction disorders the recommendations are similar, while acknowledging the limited evidence base.

6.4.4.1. Permanent Pacing Techniques and Methods for Chronic Therapy/Management of Bradycardia Attributable to Atrioventricular Block

Recommendations for Permanent Pacing Techniques and Methods for Chronic Therapy/Management of Bradycardia Attributable to Atrioventricular Block Referenced studies that support recommendations are summarized in Online Data Supplements 39 and 40 and the Systematic Review.

COR LOE Recommendations

I A 1.  In patients with SND and atrioventricular block who require permanent pacing, dual chamber pacing is recommended over single chamber ventricular pacing.S6.4.4.1-1–S6.4.4.1-7

I A 2.  In select patients with atrioventricular block who require permanent pacing in whom frequent ventricular pacing is not expected, or who have significant comorbidities that are likely to determine clinical outcomes and that may limit the benefit of dual chamber pacing, single chamber ventricular pacing is effective.S6.4.4.1-1–S6.4.4.1-6,S6.4.4.1-8–S6.4.4.1-10

I B-R 3.  For patients in sinus rhythm with a single chamber ventricular pacemaker who develop pacemaker syndrome, revising to a dual chamber pacemaker is recommended.S6.4.4.1-1,

S6.4.4.1-2,S6.4.4.1-5,S6.4.4.1-8–S6.4.4.1-10

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