What is the treatment for first-degree atrioventricular (AV) block?

From the Guidelines

First-degree AV block typically does not require specific treatment as it is generally benign and asymptomatic, and observation with regular cardiac monitoring is the standard approach for most patients. The 2019 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1 provides a comprehensive approach to managing conduction disorders, including first-degree AV block. According to this guideline, the management of conduction disorders should be based on the presence of symptoms, the severity of the conduction delay, and the underlying cause of the conduction delay.

Key Considerations

• The PR interval is a critical factor in determining the need for treatment, with markedly prolonged PR intervals (>300 ms) potentially requiring further evaluation 1.
• Symptomatic patients, such as those with dizziness or exercise intolerance, may require a cardiac pacemaker, although this is uncommon.
• Underlying causes of the conduction delay, such as medications (e.g., beta-blockers, calcium channel blockers, digoxin, or certain antiarrhythmics) or electrolyte abnormalities, should be identified and addressed.
• Regular follow-up with a cardiologist is recommended to monitor for progression to higher-degree AV blocks, especially in patients with underlying structural heart disease.

Management Approach

• Observation and regular cardiac monitoring are the standard approach for most patients with first-degree AV block.
• Further evaluation may be warranted if the PR interval is markedly prolonged or if the patient is symptomatic.
• A cardiac pacemaker may be considered in rare cases where first-degree AV block is associated with symptoms like dizziness or exercise intolerance.
• The decision to implant a pacemaker should be based on the individual patient's symptoms, the severity of the conduction delay, and the underlying cause of the conduction delay, as outlined in the 2019 ACC/AHA/HRS guideline 1.

From the FDA Drug Label

Atropine also may lessen the degree of partial heart block when vagal activity is an etiologic factor The treatment of a first degree AV block may involve atropine if vagal activity is the cause, as it may lessen the degree of partial heart block. However, the use of atropine should be approached with caution and considered on a case-by-case basis, as the FDA label does not provide explicit guidance on the treatment of first degree AV block. 2

From the Research

Treatment of First-Degree AV Block

• The treatment of first-degree AV block is generally focused on managing symptoms and preventing progression to higher-grade block or bradycardia 3, 4.
• Permanent pacemaker implantation is considered reasonable for first-degree AV block with symptoms similar to those of pacemaker syndrome or with hemodynamic compromise 4.
• Conventional dual-chamber pacing may be effective in improving symptoms in patients with marked first-degree AV block (PR > 0.30 s) and normal left ventricular function 5.
• However, in patients with marked first-degree AV block and left ventricular systolic dysfunction, a biventricular DDD device may be a more suitable option to avoid the risks associated with right ventricular pacing 5.
• Patients with first-degree AV block may require closer monitoring and follow-up to detect any progression of the conduction disease or development of more severe bradycardia, which may warrant pacemaker implantation 3.

Indications for Pacing

• Symptoms similar to those of pacemaker syndrome, such as inadequate timing of atrial and ventricular contractions 4.
• Hemodynamic compromise 4.
• Marked first-degree AV block (PR > 0.30 s) with symptoms, especially during exercise 5.
• Left ventricular systolic dysfunction and heart failure, where a biventricular DDD device may be considered 5.

Pacemaker Management

• Proper programming of the pacemaker is crucial to avoid functional atrial undersensing and ensure optimal pacing 5.
• A relatively short postventricular atrial refractory period (PVARP) may be used to minimize the risk of endless loop tachycardia 5.
• Special PVARP functions in some pulse generators may need to be adjusted to optimize pacing during activity 5.