Chapter Title: Management of Sinus Bradycardia with Conduction Abnormalities

Diagnosis and Evaluation

The American College of Cardiology recommends assessing patients with sinus bradycardia for symptoms associated with bradycardia, such as dizziness, syncope, and fatigue, and evaluating vital signs, including blood pressure 1
Sinus bradycardia with marked sinus arrhythmia is characterized by a heart rate < 50 bpm with variable R-R intervals, and may be benign or pathological depending on symptoms, according to the American College of Cardiology 1
The American Heart Association notes that right ventricular conduction delay, as indicated by a rightward axis and RSR' pattern in V1, is consistent with RBBB or incomplete RBBB, and may be associated with structural heart disease or may be an isolated finding 2
The European Society of Cardiology states that ST & T wave abnormality suggesting anterior ischemia requires urgent evaluation for acute coronary syndrome, and may represent acute myocardial infarction requiring immediate intervention 3

Echocardiography is a Class I recommendation for assessing left atrial size, evaluating for structural heart disease, valvular abnormalities, and wall motion abnormalities, and assessing left ventricular function, according to the American College of Cardiology and the American Heart Association 1, 2
The European Society of Cardiology recommends obtaining troponin levels to evaluate for myocardial injury, and serial measurements may be necessary 3
Cardiac biomarkers, such as troponin levels, should be obtained to evaluate for myocardial injury, with serial measurements as needed, as suggested by the American College of Cardiology 1

The American College of Cardiology recommends considering urgent coronary angiography if ST-T wave changes suggest acute ischemia, especially with positive cardiac biomarkers 3
The American Heart Association suggests that extended cardiac monitoring, such as 24-48 hour Holter monitoring or event recorder, may be necessary to assess for intermittent conduction abnormalities or arrhythmias 2
The European Society of Cardiology states that if hemodynamically unstable, atropine 0.5 mg IV should be administered, and transcutaneous pacing pads should be applied, with consideration for temporary transvenous pacing if no response to atropine 3
The American College of Cardiology recommends that if hemodynamically stable but symptomatic, patients should be monitored closely, and medications that may exacerbate bradycardia should be discontinued, with consideration for permanent pacemaker if symptomatic bradycardia persists 1

The American Heart Association notes that regular ECG monitoring is necessary to assess for progression of conduction disease, and echocardiographic follow-up is necessary to monitor left atrial size and ventricular function 2
The European Society of Cardiology recommends risk factor modification for underlying cardiovascular disease, and consideration for electrophysiology consultation if complex conduction abnormalities persist 3

The American College of Cardiology states that combined conduction abnormalities, such as RBBB with other conduction abnormalities, increase the risk of developing complete heart block, and prophylactic temporary pacing should be considered in acute settings, especially with anterior ischemia 1
The American Heart Association suggests that left atrial enlargement may be an early sign of hypertensive heart disease, and is associated with increased risk of atrial fibrillation and thromboembolic events 2