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Kusumoto et al 2018 Bradycardia Clinical Practice Guidelines

August 20, 2019 Circulation. 2019;140:e382–e482. DOI: 10.1161/CIR.0000000000000628 e434

CLINICAL STATEMENTS AND GUIDELINES

a prolonged HV interval at EPS predicts a higher risk for complete heart block.S7.4-14 In another study, first-degree atrioventricular block or bundle branch block were markers for abnormal EPS findings in patients with syncope.S7.4-20 5.	 Cardiac MRI may be considered in selected patients with LBBB and normal left ventricular function by echocardiography where sarcoidosis, connective tissue disease, myocarditis, or other dilated cardiomyopathies are suspected on clinical grounds. In 1 study, cardiac MRI detected subclinical cardiomyopathy in one-third of patients with asymptomatic LBBB and a normal echocardiogram.S7.4-15 In another study of patients with connective tissue disease, new onset LBBB, and normal transthoracic echocardiograms, cardiac MRI identified significant abnormalities in 42% of patients.S7.4-21

6.	 Ambulatory electrocardiographic monitoring can be used to document clinically significant arrhythmias in asymptomatic patients as well. Most current monitoring systems will automatically store clinically abnormal rhythms in addition to patient-triggered recordings. Selected patients with conduction system disease may benefit from such screening, even in the absence of significant symptoms such as syncope.S7.4-4,S7.4-6 However, progression of LBBB and bifascicular block to atrioventricular block and bradycardia is low, approximately 1% per year, with approximately half of the patients presenting with syncope and the other half with a constellation of symptoms including fatigue, chest pain, or dyspnea.S7.4-14 Most studies have reported that LBBB is associated with higher mortality than other forms of conduction disorders.S7.4-2,S7.4-22 7.	 The threshold to consider stress testing is lower in patients with LBBB and concern for ischemia as well, given the higher probability of associated cardiac disease.S7.4-23–S7.4-27 If LBBB is present, ischemic electrocardiographic changes are more difficult to interpret, and an imaging component is necessary.S7.4-2 Rate related LBBB has also been reported as a possible cause of nonischemic chest pain.S7.4-28 Exercise induced LBBB, but not exercise induced RBBB, has been associated with increased risk of death and cardiac events.S7.4-29,S7.4-30

7.5 Management of Conduction

Disorders (With 1:1 Atrioventricular Conduction)

Recommendations for Management of Conduction Disorders (With 1:1 Atrioventricular Conduction and Normal PR Intervals) Referenced studies that support recommendations are summarized in Online Data Supplements 41, 42, and 43.

COR LOE Recommendations

I C-LD 1.  In patients with syncope and bundle branch block who are found to have an HV interval 70 ms or greater or evidence of infranodal block at EPS, permanent pacing is recommended.S7.5-1,S7.5-2

I C-LD 2.  In patients with alternating bundle branch block, permanent pacing is recommended.S7.5-3

IIa C-LD 3.  In patients with Kearns-Sayre syndrome and conduction disorders, permanent pacing is reasonable, with additional defibrillator capability if appropriate and meaningful survival of greater than 1 year is expected.S7.5-4,S7.5-5

Figure 8. Evaluation of conduction disorders algorithm. Colors correspond to Class of Recommendation in Table 2. See Section 7.4. for discussion. *Refer to Section 7.5., Figure 9. †Advanced imaging could include magnetic resonance imaging, computed tomography, or transesophageal echocardiography. ‡Monitor choice based on the frequency of symptoms. §Extensive conduction disease (eg, first-degree atrioventricular block combined with LBBB). ACHD indicates adult congenital heart disease; CM, cardiomyopathy; ECG, electrocardiogram/electrocardiographic; LBBB, left bundle branch block; and RBBB, right bundle branch block.

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