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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 e419 CLINICAL STATEMENTS AND GUIDELINES

6.2 Clinical Presentation

Symptoms related to atrioventricular block vary and depend largely on the degree of atrioventricular block, the ventricular rate, and the frequency of its occurrence.S6.2-1 Profound first-degree atrioventricular block can lead to symptoms of fatigue or exertional intolerance if the PR interval is long enough to allow for loss of atrioventricular synchrony that results in a decrease in cardiac output and an increase pulmonary capillary wedge pressure (often called “pseudo pacemaker syndrome” and may occur with PR interval >300 ms).S6.2-2–S6.2-4 Second-degree atrioventricular block type I (Wenckebach) is often asymptomatic and seen in active, healthy patients with no history of heart disease. However, if occurring frequently or during exercise, it can cause symptoms of exertional intolerance or dizziness. Patients who present with complaints of syncope and have a negative initial workup such as a negative physical examination, ECG, and echocardiogram are sometimes found to have intermittent episodes of atrioventricular block with long-term monitoring.S6.2-5–S6.2-7 Intermittent complete atrioventricular block causing syncope or presyncope is more typically seen in patients with underlying heart disease or an underlying bundle branch block at baseline but can also be seen in patients with no baseline heart disease or evident conduction abnormalities. One study found that 8% of syncope patients with a normal ECG and echocardiogram had paroxysmal idiopathic atrioventricular block with no identifiable underlying cause.S6.2-5 Other studies evaluating patients with syncope and underlying bundle branch block or bifascicular block found that 61% had significant, clinically relevant His Purkinje conduction abnormalities identified at EPS.S6.2-8,S6.2-9 Patients with atrioventricular block that conducts in a 2:1 pattern can also have symptoms of fatigue and dizziness particularly if it persists during exertion.

6.3 Acute Management

6.3.1 Acute Management of Reversible Causes of Bradycardia Attributable to Atrioventricular Block

Recommendations for Acute Management of Reversible Causes of Bradycardia Attributable to Atrioventricular Block Referenced studies that support recommendations are summarized in Online Data Supplement 26.

COR LOE Recommendations

I B-NR 1.  Patients with transient or reversible causes of atrioventricular block, such as Lyme carditis or drug toxicity, should have medical therapy and supportive care, including temporary transvenous pacing if necessary, before determination of need for permanent pacing.S6.3.1-1–S6.3.1-5

IIa B-NR 2.  In selected patients with symptomatic second-degree or third-degree atrioventricular block who are on chronic stable doses of medically necessary antiarrhythmic or betablocker therapy, it is reasonable to proceed to permanent pacing without further observation for drug washout or reversibility.S6.3.1-6–S6.3.1-9 IIa B-NR 3.  In patients with second-degree or thirddegree atrioventricular block associated with cardiac sarcoidosis, permanent pacing, with additional defibrillator capability if needed and meaningful survival of greater than 1 year is expected, without further observation for reversibility is reasonable.S6.3.1-10,S6.3.1-11

IIb C-LD 4.  In patients with symptomatic seconddegree or third-degree atrioventricular block associated with thyroid function abnormalities but without clinical myxedema, permanent pacing without further observation for reversibility may be considered.S6.3.1-12

Synopsis

In patients presenting with new atrioventricular block, medical evaluation may disclose transient or reversible causes, the treatment or resolution of which may make permanent pacing unnecessary. Lyme carditis is one of the more common reversible causes of atrioventricular block in endemic areas and should be sought in appropriate patients, as atrioventricular block in such cases is almost always reversible.S6.3.1-13,S6.3.1-14 Digoxin toxicity, although increasingly uncommon, is another cause of atrioventricular block that may be reversed with drug washout or neutralizing antibody fragment therapy.S6.3.1-1,S6.3.1-3 Although overdoses of other antiarrhythmic drugs, beta blockers, and calcium channel blockers may cause reversible atrioventricular block, several studies have shown that therapeutic doses of these drugs are not commonly responsible for presentation with new atrioventricular block, and most patients in this scenario ultimately require permanent pacing.S6.3.1-6–S6.3.1-9 Similarly, treatment of hypothyroidism suggested by laboratory testing and cardiac sarcoidosis associated with new atrioventricular block usually does not make permanent pacing unnecessary when otherwise indicated.S6.3.1-10–S6.3.1-12

Recommendation-Specific Supportive Text

1.	 Lyme disease is caused by the spirochete Borrelia burgdorferi and is transmitted by the Ixodes deer tick.S6.3.1-13 The most common manifestation of Lyme carditis is atrioventricular block, usually at the atrioventricular nodal level.S6.3.1-14 Approximately 40% of patients who are identified clinically require temporary pacing, but permanent atrioventricular block after antibiotic therapy is rare. In 1 review of published cases, median time to resolution of atrioventricular block was 6 days, with a range out to 42 days.S6.3.1-2,S6.3.1-4,S6.3.1-5 Despite the use of lower

Recommendations for Acute Management of Reversible Causes of Bradycardia Attributable to Atrioventricular Block (Continued)

COR LOE Recommendations

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