What is the management approach for first degree heart block?

From the Guidelines

First degree heart block typically does not require specific treatment as it is generally benign and asymptomatic. Management of first degree heart block focuses on identifying and addressing underlying causes such as medication side effects, electrolyte abnormalities, or cardiac disease. If the heart block is caused by medications like beta-blockers, calcium channel blockers, or digoxin, these drugs may need to be discontinued or their dosages reduced 1. Regular cardiac monitoring is recommended to ensure the condition does not progress to higher-degree heart blocks. Patients should undergo a thorough cardiac evaluation including ECG, echocardiogram, and possibly stress testing to rule out structural heart disease. Electrolyte levels, particularly potassium, calcium, and magnesium, should be checked and corrected if abnormal. While first degree heart block itself rarely causes symptoms, patients should be educated about the condition and advised to report any symptoms like dizziness, syncope, or exercise intolerance, which might indicate progression to a more severe conduction disorder 1. The benign nature of first degree heart block is due to the fact that all electrical impulses still conduct to the ventricles, just with a delay (PR interval >200 ms), which typically does not affect cardiac output or hemodynamic stability. Some specific conditions, such as severe first-degree atrioventricular block or first-degree atrioventricular block with an accompanying neuromuscular disease, may require more careful consideration and potentially pacing, as outlined in the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. However, for the majority of patients with first degree heart block, a conservative approach focusing on monitoring and addressing underlying causes is appropriate, as supported by the most recent and highest quality guidelines 1.

Some key points to consider in the management of first degree heart block include:

• Identifying and addressing underlying causes
• Regular cardiac monitoring
• Thorough cardiac evaluation
• Electrolyte level checks and correction
• Patient education on symptoms to report
• Consideration of pacing in specific conditions as outlined in recent guidelines 1.

It's also important to note that the management approach may vary depending on the presence of other cardiac conditions or symptoms, and should always prioritize minimizing morbidity, mortality, and improving quality of life 1.

From the Research

Management Approach for First Degree Heart Block

The management approach for first degree heart block involves several considerations, including the presence of symptoms, the degree of PR interval prolongation, and the presence of underlying heart disease.

• The current guidelines state that permanent pacemaker implantation is reasonable for first-degree AV block with symptoms similar to those of pacemaker syndrome or with hemodynamic compromise 2.
• However, there is little evidence to suggest that pacemakers improve survival in patients with isolated first-degree AV block 2.
• Patients with first-degree AV block are at greater risk of death, stroke, or heart failure hospitalization, and may experience more episodes of undetected "electrical desynchronization" 3, 4.
• The optimal way of pacing in patients with an indication for pacing and concomitant first-degree AV block is not known, and firm guidelines on this topic are lacking 5.
• The choice of pacing mode affects long-term pacing burden, which in turn has been shown to influence outcome 5.

Pacemaker Programming

Pacemaker programming in patients with first-degree AV block is crucial to prevent adverse effects.

• The majority of patients with first-degree AV block have their pacemakers programmed to atrial pacing (AAI/DDD +/-R), whereas a smaller percentage have their pacemakers programmed to AV-sequential pacing (DDD) or ventricular pacing (VVI) 5.
• Patients with pacemakers programmed to AAI have a lower ventricular pacing percentage at follow-up compared to those programmed to DDD or VVI 5.

Underlying Causes

First-degree AV block can be caused by a delay in the AV nodal/His conduction and/or the right intra-atrial conduction (RIAC).

• RIAC delay is a common underlying cause of first-degree AV block in patients with atrial fibrillation and atrial flutter 6.
• The prevalence of first-degree AV block is higher in patients with atrial flutter (41%) and atrial fibrillation (21%) compared to a reference group of patients with AVNRT/AVRT (8%) 6.