Identifying and Treating First-Degree AV Block (First-Degree Heart Block)

An atrioventricular (AV) of a 1st degree AV block is also known as a heart block. This blockage takes place because electrical conduction is delayed through the AV node of the heart. It slows down the impulse between the atria and the ventricles. However, the conduction between the atria and the ventricles does not have any interruption. With the help of a first-degree AV block, this delay occurs due to a defect in AV conduction occurring at or below the AV node. If the interval of the PR is less than 0.30 seconds, the rhythm does not disrupt the patients. However, if the interval is greater and exceeds 0.30 seconds, then it can lead to an increased development of symptoms. This can be due to reduced ventricular filling within the heart.

This rhythm is due to an increased legal tone, whereas in older patients, the rhythm is frequently due to fibrosis within the cardiac conduction system. Identify this rhythm on an electrocardiogram (ECG), as patients do not have any symptoms.

What are the first degree heart block ECG characteristics?

• P wave for every QRS complex
• No beats are dropped in the rhythm.
• If PR extends for more than 0.30 seconds, then it is considered marked’.
• If the PR interval is extended for more than 0.30 seconds, it is considered ‘marked’.
• Do not drop these beats in this rhythm.

What signs or symptoms are present?

Most patients with a first-degree AV block do not have symptoms. However, patients who extend beyond 0.30 seconds often experience symptoms such as dyspnea, syncope, and lightheadedness.

What causes a first-degree AV block?

The rhythm can be a normal variant for an individual.

The risk factors include the following:

• Cardiac surgery
• Myocardial infarction
• Scleroderma
• Electrolyte abnormalities such as hypokalaemia
• Scleroderma
• Rheumatoid arthritis
• Increased vagal tone

First degree AV block treatment

Patients with a first-degree AV block are asymptomatic. This rhythm is incidental on an ECG, as patients are unaware of this rhythm disturbance. This rhythm does not require treatment for most patients with a first-degree AV block.

However, if the adult patient with bradyarrhythmia such as first-degree AV block is symptomatic and has a heart rate that is less than 50 beats per minute, use the Advanced Cardiovascular Life Support (ACLS) Adult Bradycardia Algorithm to determine the signs and symptoms. If so, this is then considered unstable bradycardia.

Signs and symptoms of unstable bradycardia

• Hypotension
• Altered mental status
• Acute heart failure
• Ischemic chest pain
• Shock

If the patient does not demonstrate signs or symptoms of poor perfusion, observe the patient and monitor for any potential change in their clinical condition. However, if the adult patient with bradyarrhythmia is symptomatic, unstable, and has a pulse, follow the ACLS adult bradycardia algorithm to guide further evaluation and treatment.

The ACLS adult bradycardia algorithm recommends that the ACLS primary assessment be completed to treat and identify the underlying causes of the patient’s condition. Some of the necessary elements involve managing the patient’s airway, offering supplemental oxygen, and assessing the patient’s cardiac rhythm. It also involves monitoring their vital signs.

Additionally, to establish intravenous (IV) access, a 12-lead ECG and healthcare provider must consider possible hypoxic and toxicological (H’s and T’s) causes for the clinical condition of the patient. The healthcare provider may utilize multiple interventions while monitoring for any changes to prevent the condition from deteriorating.

Medications 

If the patient is symptomatic and does not have any reversible causes, it demonstrates signs of poor perfusion due to bradyarrhythmia. According to the ACLS adult bradycardia algorithm, administer atropine. Consider the medication at a dose of 1 mg intravenously and repeat it for 3-5 minutes until it reaches 3mg. Utilize dopamine or epinephrine as secondary options for managing symptomatic bradyarrhythmia.

Pacing

When the patient experiences bradyarrhythmia and displays signs and symptoms of unstable bradycardia, use transcutaneous pacing. By transmitting an electrical stimulus from an external power source, apply it to the surface of the patient’s skin in the right places.

ACLS providers can perform TCP; however, it can be painful. Sedate the patient, if possible. Consider an intervention and bridge the treatment until transferring the patient to a higher level of care. However, this situation is not very common.

What are the next steps to follow?

Patients with a sinus bradycardia first-degree AV block often do not experience hemodynamic instability. Hence, they do not need any treatment. If medications develop rhythm, you can modify and remove them as per the medication of the patient. As patients with a first-degree AV advance in age, atrial fibrillation develops with increased progressive AV blocks. Continued monitoring can help patients identify any cardiac emergencies throughout their lifespan.

Conclusion

Identifying and treating 1st degree AV block is critical for maintaining cardiovascular health. By detecting the condition early through ECG monitoring, allowing healthcare experts to implement the interventions and prevent any complications. Understand the diagnosis and manage the disorder to boost patient outcomes.