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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 e433 CLINICAL STATEMENTS AND GUIDELINES left ventricular function. The presence or absence of symptoms potentially referable to intermittent bradycardia will usually guide evaluation of the patient with fascicular or bundle branch block. 7.4 Evaluation of Conduction Disorders Recommendations for Evaluation of Conduction Disorders (With 1:1 Atrioventricular Conduction and Normal PR Interval) Referenced studies that support recommendations are summarized in Online Data Supplements 41 and 42. COR LOE Recommendations I B-NR 1. In patients with newly detected LBBB, a transthoracic echocardiogram to exclude structural heart disease is recommended.S7.4-1–S7.4-3 I C-LD 2. In symptomatic patients with conduction system disease, in whom atrioventricular block is suspected, ambulatory electrocardiographic monitoring is useful.S7.4-4–S7.4-11 IIa B-NR 3. In selected patients presenting with intraventricular conduction disorders other than LBBB, transthoracic echocardiography is reasonable if structural heart disease is suspected.S7.4-3,S7.4-12,S7.4-13 IIa B-NR 4. In patients with symptoms suggestive of intermittent bradycardia (eg, lightheadedness, syncope), with conduction system disease identified by ECG and no demonstrated atrioventricular block, an EPS is reasonable.S7.4-14 IIa C-LD 5. In selected patients with LBBB in whom structural heart disease is suspected and echocardiogram is unrevealing, advanced imaging (eg, cardiac MRI, computed tomography, or nuclear studies) is reasonable.S7.4-15 IIb C-LD 6. In selected asymptomatic patients with extensive conduction system disease (bifascicular or trifascicular block), ambulatory electrocardiographic recording may be considered to document suspected higher degree of atrioventricular block.S7.4- 4,S7.4-6 IIb C-LD 7. In selected asymptomatic patients with LBBB in whom ischemic heart disease is suspected, stress testing with imaging may be considered.S7.4-2 Synopsis Ambulatory electrocardiographic monitoring can help establish a symptom-rhythm correlation or document previously unknown pathologic atrioventricular block. Cohort studies have generally demonstrated an association between LBBB, but not RBBB, presence and the development of coronary disease and heart failure.S7.4-1–S7.4-3,S7.4-16 Nonspecific intraventricular conduction delay was a marker for poorer prognosis in 1 study but in another study was not found to be an independent predictor of mortality in the absence of coronary artery disease.S7.4-17,S7.4-18 Thus, the threshold for further imaging or functional study is lower in patients with LBBB and echocardiogram, cardiac MR, and stress testing may be potentially useful. An EPS has a low specificity and sensitivity overall but may be helpful in selected patients with demonstrated conduction abnormalities in whom other testing has been unrevealing. A proposed algorithm for evaluating patients with conduction disorders is shown in Figure 8. Recommendation-Specific Supportive Text 1. In patients in whom structural heart disease is suspected, an echocardiogram may uncover treatable disease, or impact management decisions such as cardiac resynchronization device placement. The presence of LBBB on ECG markedly increases the likelihood that left ventricular systolic dysfunction will be diagnosed by echocardiogram.S7.4-3 2. Electrocardiography is the primary method of diagnosing potential conduction disorders. Recording duration may vary from a 10-second ECG through continuous ambulatory recordings of various (24-, 48-, 72-hour) durations to event monitors or implantable loop recorders, aiming to uncover a symptom-rhythm correlation for patients with fatigue, dizziness, or syncope suspected of having atrioventricular block or SND in addition to their manifest conduction system disease.S7.4-19 Such devices are also often capable of automated detection and storage of bradycardic or tachycardic events, although these detections are influenced by recording quality (artifacts). In addition to prescribed medical devices, direct-to-consumer devices are becoming increasingly available, particularly in association with personal electronics. 3. Patients with RBBB or intraventricular conduction delay on ECG also have increased risk of left ventricular systolic dysfunction compared with those with completely normal ECGs, yet the yield is lower than those patients with LBBB.S7.4-12 Echocardiography can identify various structural cardiac abnormalities underlying conduction disturbance, including cardiomyopathy, valvular heart disease, congenital anomalies, tumors, infections, infiltrative processes, immunologically mediated conditions, and diseases of the great vessels and pericardium.S7.4-13 4. An EPS may provide acute diagnostic information, avoiding the potential risks of delayed diagnosis with outpatient monitoring strategies, but has variable sensitivity depending on the presentation and does impart a small procedural risk. In patients with fascicular or bundle branch block, Downloaded from http://ahajournals.org by on October 7, 2026