What is an Atrioventricular Block?

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  • Written By: Mary McMahon
  • Edited By: Kristen Osborne
  • Last Modified Date: 25 September 2019
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An atrioventricular block is a type of heart block, a condition where pacing signals do not travel throughout the heart and the ventricles fail to contract or contract slowly as a result. Atrioventricular blocks can be categorized by the degree of blockage, from first to third, with third degree blocks being the most severe. There are treatments available for patients with this condition and treatment is usually supervised by a cardiologist, a doctor who specializes in care for patients with heart conditions. Outcomes for patients may vary considerably on the basis of the treatment provided and the degree of the block.

In a patient with an atrioventricular block, the signals from the sinoatrial (SA) node, the heart's natural pacemaker, are not properly routed through the atrioventricular (AV) node. This results in a delay of the signal telling the ventricles of the heart to contract, causing a patient to have a slowed and/or irregular heartbeat. The variations in the heartbeat can be seen on an electrocardiograph (ECG), a visual display of the electrical signals in the heart.

Patients with a first degree atrioventricular block will simply experience a delayed ventricular contraction. Second degree blocks cause the ventricular contractions to become increasingly delayed until they do not occur at all, starting the cycle of the heartbeat all over again. In a third degree block, the signal is completely blocked. Third degree atrioventricular blocks can be life threatening for the patient and require immediate medical attention.


Some patients may not experience any symptoms from an atrioventricular block. Others may develop symptoms like nausea, shortness of breath, dizziness, faintness, and chest pain. A bradycardia or slow heartbeat will be discernible during physical examinations of the patient, allowing the doctor to identify the source of the symptoms. An ECG can be ordered to learn more about what is happening inside the heart on an electrical level, for the purpose of developing a treatment plan appropriate to the patient's needs.

When the heart's natural pacemaker is not working, the most common treatment is artificial pacing. In artificial pacing, a medical device is connected to the heart to provide regular electrical signals, controlling the heartbeats and addressing the block. External and internal pacing options are both available. Patients can discuss how pacing works and which kinds of devices may be suitable for them to decide on the best treatment for atrioventricular block. Treatments vary, depending on the severity of the block and the cause.


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