What is the treatment for First-degree (1st degree) atrioventricular (AV) block?

From the Guidelines

First-degree atrioventricular (AV) block typically does not require treatment as it is usually asymptomatic and benign, and observation with regular cardiac monitoring is the standard approach for most patients. The decision to treat first-degree AV block is influenced by the presence or absence of symptoms directly attributable to bradycardia, as stated in the 1998 guidelines 1. According to the 2019 guidelines, patients with first-degree AV block do not typically require pacing, unless they have symptoms suggestive of intermittent AV block, in which case an AV block diagnostic algorithm should be followed 1.

The 2013 guidelines also support a conservative approach, stating that marked first-degree AV block can lead to symptoms even in the absence of higher degrees of AV block, but pacing is usually not indicated unless the patient is symptomatic 1. The treatment approach should prioritize addressing any underlying conditions that may have caused the heart block, such as coronary artery disease, myocarditis, or electrolyte abnormalities. Patients should follow up regularly with their cardiologist to monitor for any changes in their condition or progression to higher-degree heart blocks.

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

• Discontinuation of any medication that may be causing the condition, such as beta-blockers or calcium channel blockers
• Close monitoring for patients with significantly prolonged PR intervals (>300 ms) or those who develop symptoms like dizziness or fatigue
• Assessment for underlying conditions that may be contributing to the heart block
• Regular follow-up with a cardiologist to monitor for changes in the condition or progression to higher-degree heart blocks.

Overall, the management of first-degree AV block should prioritize a conservative approach, with treatment focused on addressing underlying conditions and managing symptoms, rather than immediate pacing or other interventions, as supported by the guidelines 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 for First-degree (1st degree) atrioventricular (AV) block may involve atropine if vagal activity is the cause, as it may lessen the degree of partial heart block. However, this is not a direct answer to the question as the label does not explicitly state that atropine is used to treat first-degree AV block. 2

From the Research

Treatment for First-degree AV Block

The treatment for first-degree atrioventricular (AV) block is primarily focused on managing symptoms and preventing progression to higher-grade block.

• According to 3, marked first-degree AV block (PR ≥ 0.30 s) can produce a clinical condition similar to that of the pacemaker syndrome, and clinical evaluation often requires a treadmill stress test.
• Uncontrolled studies have shown that many symptomatic patients with normal left ventricular (LV) function improve with conventional dual-chamber pacing (Class IIa indication) 3.
• For patients with marked first-degree AV block and LV systolic dysfunction, a biventricular DDD device may be considered 3.
• Insertable cardiac monitors (ICMs) can be used to detect progression of 1st-degree AV block to a higher grade block or bradycardia requiring pacemaker implantation 4.
• In some cases, patients with first-degree AV block may require pacemaker implantation, especially if they experience symptoms or have underlying heart disease 4.

Pacemaker Management

Pacemaker management is crucial in patients with first-degree AV block, as they may require adjustments to their pacing settings to optimize their cardiac function.

• Patients with suboptimally programmed pacemakers may develop functional atrial undersensing, and a relatively short postventricular atrial refractory period (PVARP) can often be used at rest with little risk of endless loop tachycardia 3.
• However, special PVARP functions in some pulse generators may negate the usefulness of a short PVARP, and careful programming is necessary to avoid desynchronization 3.

Considerations for Cardiac Resynchronization Therapy

First-degree AV block can affect the outcome of cardiac resynchronization therapy (CRT), and patients with this condition may have a poorer response to CRT.

• According to 3, first-degree AV block during CRT predisposes to loss of ventricular resynchronization, especially in association with a relatively fast atrial rate and a relatively slow programmed upper rate.
• Patients with first-degree AV block may experience more episodes of undetected "electrical desynchronization," which can negatively impact their response to CRT 3.