What is the management of sinus rhythm with bundle branch block and first degree Atrioventricular (AV) block?

From the Guidelines

Management of sinus rhythm with bundle branch block and first-degree AV block typically requires no specific treatment if the patient is asymptomatic, as these are generally benign conduction abnormalities. According to the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1, first-degree AV block and bundle branch block often don't require intervention unless they cause symptoms or are part of progressive conduction disease.

Key Considerations

• The presence of left bundle branch block on electrocardiogram markedly increases the likelihood of underlying structural heart disease and of diagnosing left ventricular systolic dysfunction, as noted in the guideline 1.
• Echocardiography is usually the most appropriate initial screening test for structural heart disease, including left ventricular systolic dysfunction, as recommended in the guideline 1.
• For symptomatic patients, addressing underlying causes is essential, including discontinuing medications that slow AV conduction, correcting electrolyte abnormalities, treating ischemia, or managing structural heart disease.

Recommendations

• Regular cardiac monitoring is recommended to detect progression to higher-degree blocks.
• If the patient develops symptomatic bradycardia or progresses to second- or third-degree AV block, a permanent pacemaker may be indicated, as stated in the guideline 1.
• The presence of both conduction abnormalities warrants closer follow-up as it may indicate more extensive conduction system disease.
• Patients should undergo comprehensive cardiac evaluation including echocardiography to assess for structural heart disease and possible electrophysiology consultation if there are concerns about progression or if the patient has syncope, presyncope, or significant bradycardia.

Clinical Approach

• Establishing temporal correlation between symptoms and bradycardia is important when determining whether permanent pacing is needed, as emphasized in the guideline 1.
• Treatment decisions should be based on the best available evidence and on the patient’s goals of care and preferences, using the principles of shared decision-making and informed consent/refusal, as recommended in the guideline 1.

From the FDA Drug Label

The degree of lengthening of PR and QRS intervals does not predict either efficacy or the development of cardiac adverse effects. In clinical trials, it was unusual for PR intervals to increase to 0.3 seconds or more, or for QRS intervals to increase to 0. 18 seconds or more. Thus, caution should be used when such intervals occur, and dose reductions may be considered. If second- or third-degree AV block, or right bundle branch block associated with a left hemiblock occur, flecainide therapy should be discontinued unless a temporary or implanted ventricular pacemaker is in place to ensure an adequate ventricular rate

The management of sinus rhythm with bundle branch block and first degree Atrioventricular (AV) block is to use caution and consider dose reduction if the intervals increase significantly.

• Discontinue flecainide therapy if second- or third-degree AV block occurs, unless a temporary or implanted ventricular pacemaker is in place.
• Monitor patients carefully, especially if they have a history of CHF or myocardial dysfunction. 2

From the Research

Management of Sinus Rhythm with Bundle Branch Block and First Degree Atrioventricular (AV) Block

• The management of sinus rhythm with bundle branch block and first degree AV block involves careful monitoring and potentially pacemaker implantation, as seen in patients with Stokes-Adams syndrome 3.
• In patients with first degree AV block, insertable cardiac monitors can reveal progression to higher grade block or bradycardia requiring pacemaker implantation 4.
• Bundle branch reentrant tachycardia can be treated with catheter ablation of the right or left bundle branch, with electroanatomic mapping guiding the procedure 5.
• First degree AV block is not always a benign condition, as it can be associated with an increased risk for heart failure, pacemaker implantation, and death 4.
• The presence of bundle branch block, such as left bundle branch block, can affect the management of sinus rhythm and AV block, with ablation of the left bundle branch being a potential treatment option for bundle branch reentrant tachycardia 5.

Treatment Options

• Pacemaker implantation is often necessary for patients with Stokes-Adams syndrome or those with first degree AV block who progress to higher grade block or bradycardia 3, 4.
• Catheter ablation of the right or left bundle branch can be an effective treatment for bundle branch reentrant tachycardia 5.
• Insertable cardiac monitors can be used to monitor patients with first degree AV block and detect progression to higher grade block or bradycardia 4.
• Medical management, such as with atropine, can be used to treat bradyarrhythmias in patients with acute coronary syndrome 6.

Diagnostic Tools

• Electrocardiogram (ECG) monitoring is essential for diagnosing and managing sinus rhythm with bundle branch block and first degree AV block 6, 3.
• Insertable cardiac monitors can be used to detect progression to higher grade block or bradycardia in patients with first degree AV block 4.
• Electroanatomic mapping can guide catheter ablation procedures for bundle branch reentrant tachycardia 5.
• Holter monitoring can be used to establish the diagnosis of sick sinus syndrome or other arrhythmias 3.