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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 e427 CLINICAL STATEMENTS AND GUIDELINES help identify the presence of His bundle extrasystoles as a cause of bradycardia that presents as atrioventricular block on ECG. 4. Carotid sinus massage and medication challenges can be used to identify the presence of paroxysmal atrioventricular block or determine the level of block in patients with second-degree block where the level of block is uncertain by electrocardiographic analysis alone (eg, 2:1 atrioventricular block or Mobitz type I atrioventricular block in the setting of a wide QRS complex). One study showed that in patients with bifascicular block on ECG, a 15-ms increase in the His-ventricular (HV) interval or induced infranodal atrioventricular block with procainamide challenge was considered abnormal and possibly indicative of underlying infra-Hisian block.S6.4.3-11 The sensitivity of a procainamide challenge for distal conduction disease is low. However, it could be potentially useful in cases where the HV interval is borderline or atrioventricular block cannot be induced.S6.4.3- 11,S6.4.3-17 Atropine shortens the refractoriness of the atrioventricular node but has little effect on infranodal conduction tissues.S6.4.3-10 Atropine will improve or have no change in atrioventricular conduction block if the block is at the level of the atrioventricular node but will worsen atrioventricular conduction block in the presence of intra-His or distal conduction disease.S6.4.3-8,S6.4.3-18 Isoproterenol can also be used to unmask underlying pathologic His-Purkinje disease by enhancing atrioventricular nodal and sinus conduction and precipitating heart block with faster heart rates.S6.4.3-12,S6.4.3-19 Similar to atropine, worsening atrioventricular block with isoproterenol infusion would be suggestive of infranodal block. Conversely, improvement of atrioventricular conduction with carotid sinus massage may be observed in patients with infranodal atrioventricular block.S6.4.3-10 All provocative testing should be done with careful monitoring, particularly when using a drug, because the pharmacologic effects can be prolonged. 6.4.4 Permanent Pacing Recommendations for Permanent Pacing for Chronic Therapy/ Management of Bradycardia Attributable to Atrioventricular Block Referenced studies that support recommendations are summarized in Online Data Supplements 34, 39, and 40. COR LOE Recommendations I B-NR 1. In patients with acquired second-degree Mobitz type II atrioventricular block, highgrade atrioventricular block, or third-degree atrioventricular block not attributable to reversible or physiologic causes, permanent pacing is recommended regardless of symptoms.S6.4.4-1–S6.4.4-7 I B-NR 2. In patients with neuromuscular diseases associated with conduction disorders, including muscular dystrophy (eg, myotonic dystrophy type 1) or Kearns-Sayre syndrome, who have evidence of seconddegree atrioventricular block, third-degree atrioventricular block, or an HV interval of 70 ms or greater, regardless of symptoms, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, is recommended.S6.4.4-8–S6.4.4-15 I C-LD 3. In patients with permanent AF and symptomatic bradycardia, permanent pacing is recommended.S6.4.4-2,S6.4.4-16,S6.4.4-17 I C-LD 4. In patients who develop symptomatic atrioventricular block as a consequence of guideline-directed management and therapy for which there is no alternative treatment and continued treatment is clinically necessary, permanent pacing is recommended to increase heart rate and improve symptoms.S6.4.4-18–S6.4.4-24 IIa B-NR 5. In patients with an infiltrative cardiomyopathy, such as cardiac sarcoidosis or amyloidosis, and seconddegree Mobitz type II atrioventricular block, high-grade atrioventricular block, or thirddegree atrioventricular block, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, is reasonable.S6.4.4-25–S6.4.4-30 IIa B-NR 6. In patients with lamin A/C gene mutations, including limb-girdle and Emery-Dreifuss muscular dystrophies, with a PR interval greater than 240 ms and LBBB, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, is reasonable.S6.4.4-31–S6.4.4-33 IIa C-LD 7. In patients with marked first-degree or second-degree Mobitz type I (Wenckebach) atrioventricular block with symptoms that are clearly attributable to the atrioventricular block, permanent pacing is reasonable.S6.4.4-34–S6.4.4-37 IIb C-LD 8. In patients with neuromuscular diseases, such as myotonic dystrophy type 1, with a PR interval greater than 240 ms, a QRS duration greater than 120 ms, or fascicular block, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, may be considered.S6.4.4-9–S6.4.4-13,S6.4.4-15 Synopsis Similar to SND, symptoms are an important factor when determining whether permanent pacing is indicated. If the patient is symptomatic, regardless of the level of atrioventricular block and the likelihood of future progression of atrioventricular block, permanent pacing is Recommendations for Permanent Pacing for Chronic Therapy/ Management of Bradycardia Attributable to Atrioventricular Block (Continued) COR LOE Recommendations Downloaded from http://ahajournals.org by on October 7, 2026