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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 e435 CLINICAL STATEMENTS AND GUIDELINES

IIb C-LD 4.  In patients with Anderson-Fabry disease and QRS prolongation greater than 110 ms, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, may be considered.S7.5-6,S7.5-7

IIb C-LD 5.  In patients with heart failure, a mildly to moderately reduced LVEF (36%-50%), and LBBB (QRS ≥150 ms), CRT may be considered.S7.5-8,S7.5-9

III: Harm B-NR 6.  In asymptomatic patients with isolated conduction disease and 1:1 atrioventricular conduction, permanent pacing is not indicated (in the absence of other indications for pacing).S7.5-10–S7.5-15

Synopsis

Management of conduction disorders with 1:1 atrioventricular conduction with a normal PR interval requires a patient-centered approach with assessment of any known underlying heart disease, symptomatology and the baseline ECG (bundle branch block, nonspecific intraventricular delay, fascicular block in isolation or in combination) (Figure 9). Pacing therapy can be considered in the presence or absence of symptoms if an underlying disorder associated with progressive disease is present such as Emery-Dreifuss muscular dystrophy or Kearns-Sayre syndrome. True alternating bundle branch block (QRS complexes with alternating LBBB and RBBB morphologies) is evidence for significant infranodal disease and a high likelihood for developing sudden onset of complete heart block with a slow or absent ventricular escape rate.

Recommendation-Specific Supportive Text

1.	 In a patient with syncope, the presence of bundle branch block on ECG is a predictor for abnormal conduction properties identified at EPS.S7.5-16 However, for patients with bundle branch block, the underlying cause for syncope may be related to vasodepressor mechanisms rather than heart block mediated bradycardia. An EPS can be used to evaluate atrioventricular conduction and identify the presence and extent of infranodal disease. Permanent pacing has been recommended for patients with syncope and HV intervals ≥70 ms or frank infranodal block.S7.5-17 2.	 Alternating bundle branch block (QRS complexes with alternating LBBB and RBBB morphologies) implies unstable conduction disease in both conduction bundles, and patients with this electrocardiographic pattern should receive a pacemaker because of high risk of developing complete atrioventricular block.S7.5-3

3.	 In Kearns-Sayre syndrome, a mitochondrial genetic disorder with progressive external ophthalmoplegia and myopathy, there is a high incidence of atrioventricular block and sudden cardiac death.S7.5-4,S7.5-5 In a series of 35 patients with Kearns-Sayre syndrome, 66% had conduction delays, and 4 patients had sudden cardiac death.S7.5-4 4.	 Anderson Fabry disease is an X-linked lysosomal storage disorder. In 1 cohort study of 189 patients 6.3% of patients had permanent pacing for bradycardia attributable to atrioventricular block or SND and an additional 2.6% of patients underwent ICD implantation.S7.5-6,S7.5-7 A QRS duration of >110 ms was an independent predictor for requiring pacing therapy (HR: 1.05; 95% CI: 1.02–1.09; P=0.001; c=0.726). Myocardial scarring and sudden death have been reported in patients with Anderson Fabry disease.S7.5-18,S7.5-19 5.	 In 1 retrospective study of 1 436 patients with and LVEF of 36% to 50% and LBBB who were matched to a group of patients without conduction disease, LBBB was associated with

Recommendations for Management of Conduction Disorders (With 1:1 Atrioventricular Conduction and Normal PR Intervals) (Continued)

COR LOE Recommendations

Figure 9. Management of conduction disorders algorithm. Colors correspond to Class of Recommendation in Table 2. *For severe firstdegree atrioventricular block or first-degree atrioventricular block with an accompanying neuromuscular disease, also refer to Section 6.4., Figure 7, the atrioventricular block algorithm. †See Section 4.3.2., Figure 3. AV indicates atrioventricular; BBB, bundle branch block; HF, heart failure; LBBB, left bundle branch block; and LVEF, left ventricular ejection fraction.

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