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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 e420

CLINICAL STATEMENTS AND GUIDELINES chronic doses and widespread availability of testing for serum levels, digoxin toxicity as a cause of reversible atrioventricular block still occurs.S6.3.1-14a Most cases of atrioventricular block attributable to digoxin toxicity will respond to observation and supportive care; severe cases may respond to antidigoxin Fab antibody therapy.S6.3.1-1,S6.3.1-3

2.	 Medications that slow or block atrioventricular conduction are commonly used in the treatment of hypertension, arrhythmias, heart failure, and other cardiac disease. Common examples are beta blockers, nondihydropyridine calcium channel blockers, and class I and III antiarrhythmic medications. Therefore, patients may commonly present with atrioventricular block while taking ≥1 of these medications. Moreover, these medications are sometimes part of an essential pharmacologic regimen that should not be interrupted. Although these scenarios may occasionally represent a reversible cause of atrioventricular block, several case series suggest that it is unusual for atrioventricular block to reverse with cessation of medications when used at therapeutic doses and even when reversal of atrioventricular block is observed acutely, later implant of a PPM is often necessary.S6.3.1-6–S6.3.1-9 The decision for whether to proceed with permanent pacing must account for the potentially deleterious effect of high amounts of right ventricular pacing and whether alternate medications without atrioventricular slowing could be used. 3.	 Cardiac sarcoidosis is an infiltrative/inflammatory cardiomyopathy that is often associated with atrioventricular block and ventricular arrhythmias.S6.3.1-15 Limited, small, nonrandomized studies of patients with cardiac sarcoidosis and atrioventricular block treated with corticosteroids found that only a few patients (13%–47%) had any reversibility of atrioventricular block.S6.3.1-

10,S6.3.1-11 Moreover, cardiac sarcoidosis may have a waxing and waning or progressive course and initial improvement in atrioventricular conduction may later reverse. Given the known risks of delay in implantation of PPMs in patients with atrioventricular block, it is often reasonable to proceed to implantation without further delay in this clinical scenario.S6.3.1-16 Because of the risk of ventricular arrhythmias in patients with cardiac sarcoidosis, a CIED with defibrillator capability is often considered in patients who require permanent pacing.S6.3.1-17 4.	 Severe thyroid disease, such as myxedema, rarely may be associated with reversible atrioventricular block.S6.3.1-18 However, there is little evidence to suggest reversibility of atrioventricular block presenting in the context of less severe thyroid function abnormalities commonly seen in clinical practice. One series of 50 patients with atrioventricular block presenting in the context of hyperthyroidism or hypothyroidism found that only about 20% of patients had resolution of atrioventricular block with restoration of euthyroid state.S6.3.1-12

6.3.2 Acute Medical Therapy for Bradycardia Attributable to Atrioventricular Block

Recommendations for Acute Medical Therapy for Bradycardia Attributable to Atrioventricular Block Referenced studies that support recommendations are summarized in Online Data Supplements 27 and 28.

COR LOE Recommendations

IIa C-LD 1.  For patients with second-degree or thirddegree atrioventricular block believed to be at the atrioventricular nodal level associated with symptoms or hemodynamic compromise, atropine is reasonable to improve atrioventricular conduction, increase ventricular rate, and improve symptoms.S6.3.2-1–S6.3.2-3

IIb B-NR 2.  For patients with second-degree or thirddegree atrioventricular block associated with symptoms or hemodynamic compromise and who have low likelihood for coronary ischemia, beta-adrenergic agonists, such as isoproterenol, dopamine, dobutamine, or epinephrine, may be considered to improve atrioventricular conduction, increase ventricular rate, and improve symptoms.S6.3.2-3–S6.3.2-7

IIb C-LD 3.  For patients with second-degree or thirddegree atrioventricular block associated with symptoms or hemodynamic compromise in the setting of acute inferior MI, intravenous aminophylline may be considered to improve atrioventricular conduction, increase ventricular rate, and improve symptoms.S6.3.2-8–S6.3.2-11

Synopsis

The acute treatment of bradycardia attributable to atrioventricular block will often begin with timely identification and removal of potential causative factors as well as medical therapy. Atropine has a long track record of use for this indication because of ease of administration and relatively low risk of adverse reactions. It is more likely to be useful for atrioventricular block at the atrioventricular nodal level and for bradycardia attributable to excess vagal tone. Because of its short duration of action, it is generally used as a bridge to longer-lasting therapy, such as infusion of a beta-adrenergic drug or temporary pacing. Aminophylline and glucagon have a possible role in treatment of atrioventricular block in the setting of acute MI and beta-blocker toxicity, respectively, but data are sparse.

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