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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 e393 CLINICAL STATEMENTS AND GUIDELINES

confirm the rhythm and rate, the nature and extent of conduction disturbance, and to document other abnormalities suggestive of structural heart or systemic disease (eg, left ventricular hypertrophy, diagnostic Q waves, prolonged corrected QT interval, findings suggestive of hyperkalemia).

Recommendation-Specific Supportive Text

1.	Unless a patient with suspected bradycardia or conduction disorder is symptomatic or bradycardic at the time of the recording, the 12-lead ECG will not provide a rhythm correlation with symptoms. In patients presenting with syncope, the initial ECG provides a diagnosis in only approximately 5%S4.2.1-2,S4.2.1-4 and in those with less well-defined clinical presentations and nonspecific symptoms, the diagnostic yield is probably lower. However, an abnormal initial ECG is predictive of adverse outcomes in patients presenting with syncope and near syncope, in large part as an indicator of underlying structural heart disease or the presence of systemic disease. A multicenter, prospective observational study of syncope evaluated in the emergency department concluded that a broad range of electrocardiographic abnormalities was associated with increased all-cause mortality at 1 year.S4.2.1-1 The prognostic value of an abnormal initial ECG in those with syncope and near syncope is reflected in its inclusion in most published multivariate risk scores used to predict adverse outcomes in this population.S4.2.1-5 This risk does not necessarily correlate with pathological bradycardia as the mechanism of syncope, as only approximately 10% of syncope can be attributed to bradycardia or a conduction disorder at the time of initial presentation. An additional 18% can be attributed to neurally mediated syncope which frequently is manifest by both bradycardia and hypotension.S4.2.1-2

Figure 1. Evaluation of bradycardia and conduction disease algorithm. Colors correspond to Class of Recommendation in Table 2. See Section 4 for discussion. Dashed lines indicate possible optional strategies based on the specific clinical situation. *Sinus bradycardia, ectopic atrial rhythm, junctional rhythm, sinus pause. †Refer to Section 4.3.2., Figure 2. ‡Refer to Section 4.3.2., Figure 3. § Refer to Section 7.4., Figure 8. ‖ Monitor choice based on the frequency of symptoms. AV indicates atrioventricular; and ECG, electrocardiogram/ electrocardiographic.

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