Atrioventricular Block: Symptoms, Causes and Diagnosis

Written by Medicover Team and Medically Reviewed by Dr Pabba Anish , Cardiologists

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1. Causes 2. Find a Doctor 3. Diagnosis 4. Treatment 5. FAQs

Atrioventricular block (AV block) is a condition characterized by impaired conduction of electrical impulses from the atria to the ventricles. This disruption can lead to a variety of symptoms and complications, and its management depends mainly on the underlying cause and severity of the block.

What are the Types of Atrioventricular Block?

The atrioventricular block is categorized into three types based on the extent and nature of the conduction delay:

First-Degree Atrioventricular Block

In first-degree AV block, the electrical impulses are delayed but eventually reach the ventricles. This delay is typically identified by a prolonged PR interval on an electrocardiogram (ECG) exceeding 200 milliseconds. Patients are often asymptomatic, and this type of block is generally considered benign.

Second-Degree Atrioventricular Block

The second-degree AV block is further divided into two subtypes:

Mobitz Type I (Wenckebach Block): Characterized by progressively lengthening PR intervals until an atrial impulse is completely blocked, leading to a dropped ventricular beat. This type is often transient and may not require treatment.
Mobitz Type II: In this subtype, PR intervals are constant, but occasional impulses fail to reach the ventricles, causing dropped beats. Mobitz Type II is more serious and often necessitates medical intervention.

Third-Degree Atrioventricular Block

Third-degree AV block, or complete heart block, occurs when no atrial impulses are conducted to the ventricles. The ventricles generate their escape rhythm, which is usually slow and unreliable. This type of block can result in severe symptoms and requires immediate attention.

What are the Causes of Atrioventricular Block?

Understanding the underlying causes of AV block is essential for accurate diagnosis and effective treatment. The causes can be broadly categorized into intrinsic and extrinsic factors.

Intrinsic Causes

Intrinsic causes originate within the heart itself and include:

Ischemic Heart Disease: Reduced blood flow to the heart muscle can damage the conduction pathways.
Cardiomyopathy: Diseases affecting the heart muscle can impair electrical conduction.
Congenital Heart Defects: Some individuals are born with abnormalities in the heart's conduction system.
Fibrosis and Sclerosis: Age-related changes can lead to fibrosis (scarring) and sclerosis (hardening) of the conduction system.

Extrinsic Causes

Extrinsic causes are external factors that affect the heart's conduction system:

Medications: Certain drugs, including beta-blockers, calcium channel blockers, and antiarrhythmic agents, can induce AV block.
Electrolyte Imbalances: Abnormal levels of potassium, calcium, or magnesium can disrupt electrical conduction.
Infectious Diseases: Conditions such as Lyme disease, myocarditis, and endocarditis can affect the conduction pathways.
Surgery and Trauma: Cardiac surgeries or trauma can damage the conduction system.

What are the Symptoms of Atrioventricular Block?

The symptoms of AV block can vary widely depending on the type and severity of the block. In some cases, individuals may be asymptomatic, while in others, they may experience significant discomfort and complications.

Common Symptoms

Fatigue: Reduced cardiac output can lead to generalized tiredness.
Dizziness and Syncope: Impaired blood flow to the brain can cause lightheadedness and fainting.
Palpitations: Patients may feel abnormal heartbeats or fluttering sensations.
Shortness of Breath: Inefficient heart function can lead to respiratory distress.
Chest Pain: In some cases, chest discomfort may be present.

When to See a Doctor for Atrioventricular Block?

If you experience symptoms of Atrioventricular (AV) Block, consult a cardiologist promptly. Untreated AV Block can severely impact daily life, causing dangerous drops in heart rate, fainting episodes, or heart failure requiring hospitalization.

You should see a doctor if you have:

Persistent fatigue, dizziness, or lightheadedness that interferes with daily activities
Unexplained shortness of breath or chest discomfort during mild exertion
Noticeably slow or irregular heartbeat (bradycardia) lasting more than a few minutes

Get medical help immediately if:

You suddenly faint or lose consciousness without any warning signs
You experience severe chest pain, pressure, or signs of a heart attack
Your heart rate drops dangerously low, causing confusion or an inability to stay awake

These could be signs of a serious complication like Atrioventricular Block, which needs urgent care.

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How is Atrioventricular Block Diagnosed?

Accurate diagnosis of AV block is crucial for determining the appropriate treatment. The diagnostic process typically involves several steps:

Medical History and Physical Examination

A thorough medical history and physical examination can provide valuable insights into potential risk factors and underlying conditions contributing to AV block.

Electrocardiogram (ECG)

An ECG is the primary tool for diagnosing AV block. It records the heart's electrical activity and can reveal the type and severity of the block based on characteristic patterns and intervals.

Holter Monitor

A Holter monitor is a portable ECG device worn by the patient for 24 to 48 hours. It provides continuous monitoring of the heart's electrical activity, capturing intermittent blocks that may not be evident during a standard ECG.

Electrophysiological Study

In some cases, an electrophysiological study (EPS) may be conducted to assess the electrical pathways of the heart in greater detail. This invasive procedure involves threading catheters through blood vessels to the heart to record electrical signals directly.

What are the Treatment Options for Atrioventricular Block?

The treatment of AV block depends on its type, severity, and underlying cause. Here are some commonly employed strategies:

Observation and Monitoring

Regular monitoring may be sufficient for asymptomatic patients with first-degree AV block or Mobitz Type I second-degree block. These patients typically do not require immediate intervention.

Medications

In cases where AV block is caused by medications, adjusting or discontinuing the offending drug can resolve the condition. Additionally, medications such as atropine may be used temporarily to improve heart rate and conduction.

Pacemaker Implantation

Pacemaker implantation is often necessary for patients with symptomatic AV block, particularly third-degree block or Mobitz Type II second-degree block. A pacemaker is a small device implanted under the skin that sends electrical impulses to regulate the heart's rhythm.

Treating Underlying Conditions

Addressing the root cause of AV block is crucial for long-term management. This may involve treating ischemic heart disease, managing electrolyte imbalances, or addressing infectious diseases.

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What Is the Recovery Process for Atrioventricular Block?

Recovery from atrioventricular (AV) block depends on the type and severity of the heart block, its underlying cause, and the treatment received. Mild cases may improve after treating the underlying condition, while advanced AV block often requires permanent pacemaker implantation. With appropriate treatment and regular follow-up, many people can lead normal, active lives.

Take all prescribed medications as directed and do not stop them without consulting your healthcare provider.
Attend regular follow-up appointments, including electrocardiograms (ECGs) and pacemaker checks if a device has been implanted.
Gradually return to normal activities after treatment or pacemaker surgery, following your doctor's recommendations.
Maintain a heart-healthy lifestyle by eating a balanced diet, exercising appropriately, avoiding smoking, and controlling blood pressure, cholesterol, and diabetes.
Avoid strenuous activities or heavy lifting for the recommended period after pacemaker implantation to allow proper healing.
Monitor for symptoms such as dizziness, fainting, fatigue, chest pain, or shortness of breath and report them promptly to your healthcare provider.
Seek immediate medical attention if you experience recurrent fainting, severe chest pain, persistent shortness of breath, or signs of pacemaker malfunction.