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

From the Guidelines

First-degree atrioventricular (AV) block typically requires no specific treatment as it is generally benign and asymptomatic. This condition, characterized by a prolonged PR interval greater than 200 milliseconds on an ECG, represents a delay in electrical conduction from the atria to the ventricles but does not usually affect cardiac output or cause symptoms. However, according to the acc/aha/hrs 2008 guidelines 1, permanent pacemaker implantation is reasonable for first- or second-degree AV block with symptoms similar to those of pacemaker syndrome or hemodynamic compromise, although this is not typically the case for asymptomatic first-degree AV block. Some key points to consider in the management of first-degree AV block include:

• If the first-degree AV block is caused by medications such as beta-blockers, calcium channel blockers, digoxin, or certain antiarrhythmics, the physician may consider reducing the dose or discontinuing these medications if clinically appropriate.
• Regular cardiac monitoring is recommended to ensure the condition doesn't progress to higher-degree AV blocks.
• In rare cases where first-degree AV block is associated with symptoms like fatigue or exercise intolerance, or if the PR interval is extremely prolonged (>300 ms), further evaluation may be warranted. The benign nature of first-degree AV block stems from the fact that all atrial impulses still conduct to the ventricles, maintaining proper synchronization between the heart chambers despite the delay.

From the Research

Treatment for First-Degree Atrioventricular (AV) Block

The treatment for first-degree AV block depends on the presence of symptoms and the severity of the block.

• For asymptomatic patients with first-degree AV block, no specific treatment is required 2.
• However, for patients with symptoms similar to those of pacemaker syndrome or with hemodynamic compromise, permanent pacemaker implantation is a reasonable treatment option 2.
• The current guidelines suggest that pacemakers may not improve survival in patients with isolated first-degree AV block, but they can alleviate symptoms 2.
• Recent studies have shown that first-degree AV block may be a risk marker for more severe intermittent conduction disease, and insertable cardiac monitors can help detect progression to higher grade block or bradycardia requiring pacemaker implantation 3.
• For patients with marked first-degree AV block (PR > 0.30 s), conventional dual-chamber pacing may be beneficial, especially for those with normal left ventricular function 4.
• Biventricular DDD devices may be considered for patients with marked first-degree AV block and left ventricular systolic dysfunction 4.
• Pacemaker programming in patients with first-degree AV block should be individualized, and the choice of pacing mode can affect long-term pacing burden and outcome 5.

Pacemaker Programming

• The optimal way of pacing in patients with first-degree AV block is not well established, and firm guidelines are lacking 5.
• A study found that most patients with first-degree AV block had their pacemakers programmed to atrial pacing (AAI/DDD +/-R), while a smaller percentage had their pacemakers programmed to AV-sequential pacing (DDD) or ventricular pacing (VVI) 5.
• Patients with pacemakers programmed to AAI had a lower ventricular pacing percentage at follow-up, which can influence outcome 5.

Medications

• Slow channel blockers and beta blockers can affect AV nodal function and may prolong conduction and refractoriness in the AV node 6.
• Verapamil and diltiazem have been shown to prolong AV nodal conduction and refractoriness, while nifedipine has minimal effect on the AV node 6.
• Beta blockers can also prolong the AH interval and AV nodal refractory periods, but rarely cause more than first-degree AV block in patients receiving maintenance therapy 6.