Pediatric Cardiology

Acquired Complete Atrioventricular (AV) Block: Symptoms, Causes and Treatment

Posted on by Prof. Dr. İbrahim Cansaran TANIDIR

Acquired complete atrioventricular block in children is a serious heart rhythm disorder that occurs when the vital electrical communication between the upper chambers of the heart (atria) and the lower chambers that pump blood (ventricles) becomes completely interrupted later in life. This condition, which is not a congenital defect, develops as a result of damage to the heart’s electrical network, which had previously functioned perfectly, due to various causes. When the signals are blocked, the upper and lower parts of the heart begin to work independently of one another in an incompatible rhythm. This electrical interruption, which suddenly endangers healthy blood circulation in the body, is a critical health problem that directly affects children’s quality of life and requires professional intervention without delay.

How Does the Electrical Network of Our Heart Work and What Does Acquired Complete AV Block Mean?

The human heart can be thought of as a magnificent engine with its own flawless electrical network, rhythmically contracting and relaxing thanks to these electrical currents. Under normal conditions, there is a natural generator located in the upper right chamber of the heart called the “sinus node.” This generator produces electrical signals according to the body’s current needs, for example slowly during sleep and rapidly while running. These signals travel from the upper chambers of the heart and pass through a special bridge called the “atrioventricular node,” or AV node for short. The signals passing through this bridge reach the powerful lower chambers of the heart that actually pump the blood. Thanks to this flawless electrical communication, the heart pumps blood in an extremely rhythmic, regular, and powerful manner.

In acquired complete AV block, however, this electrical bridge or the conduction pathways immediately below it become completely damaged due to a disease that develops later, surgical trauma, or severe inflammation. The electrical signals originating from the generator above cannot pass to the lower chambers in any way. In this state of disconnection, the lower chambers of the heart develop an extraordinary defense mechanism and begin to produce electricity on their own so that they do not remain completely unstimulated and motionless. However, the backup rhythm produced by these lower chambers is much slower and highly unreliable compared with the natural generator. As a result, while the upper chambers contract at their own rapid rhythm, the lower chambers work independently and at a much slower rate. This lack of communication prevents the heart from pumping sufficient blood to the body and may lead to life-threatening consequences.

What Are the Main Causes That Trigger the Development of Acquired Complete AV Block in Children?

There are many different factors underlying the development of complete block in a heart that previously functioned completely normally during childhood. These factors may be anatomical, infectious, or related to externally ingested substances.

The main causes of the disease are:

  • Surgical trauma
  • Cardiac catheterization procedures
  • Viral infections
  • Inflammatory diseases
  • Progressive muscle diseases
  • Neurological syndromes
  • Drug poisoning
  • Electrolyte disorders

In clinical practice, the most common and critical cause of acquired complete heart block is open heart surgery performed to correct congenital heart diseases. Procedures such as closing defects between the ventricles, relieving obstructions beneath the aortic valve, or repairing valves are carried out within millimeters of the heart’s electrical pathways. Direct contact of sutures with the conduction tissue during the operation, physical stretching of the tissue in that region, or temporary oxygen deprivation of the tissue during surgery may lead to permanent heart block. Sometimes, even if there is no direct damage during surgery, temporary blocks may be seen during the first weeks after the operation due to excessive edema and tissue inflammation developing around the suture line during the healing process. Although a significant proportion of these temporary blocks resolve spontaneously, some may become permanent and require lifelong support.

In addition, myocarditis, which means inflammation of the heart muscle and conduction tissue due to viral agents, is also a very critical cause. Viruses entering the body initially attack the heart cells directly and damage them. However, the real danger begins in the second stage, when the immune system mistakenly attacks its own heart tissue while fighting the virus. This autoimmune reaction may cause severe swelling and tissue death in the heart’s electrical cables, completely interrupting conduction. Other infections such as acute rheumatic fever or Lyme disease may also leave temporary or permanent damage in the conduction pathways through a similar mechanism. Progressive muscle and nervous system diseases may cause deterioration and calcification of the heart’s electrical pathways over time, leading to block. In addition, accidental overdose of certain blood pressure and rhythm medications may stop conduction, but this condition usually resolves completely once the drug is eliminated from the body.

What Are the Symptoms of Acquired Complete AV Block in Children of Different Age Groups?

The clinical picture that develops when acquired complete AV block occurs varies greatly depending on the rate of the slow backup rhythm generated by the heart itself, the location of the block within the heart, and the child’s age group. If the heart’s backup rhythm can pump enough blood to the brain and vital organs, the child may continue daily life for a long time without any symptoms. However, when blood flow becomes insufficient, very clear age-specific warning signs emerge.

Symptoms during the neonatal period include:

  • Feeding difficulty
  • Easy fatigue
  • Rapid breathing
  • Marked pallor of the skin
  • Bluish discoloration of the lips
  • Excessive sweating

In newborn babies, the heart normally needs to beat very rapidly. When complete block develops and the heart rate falls below critical levels, the baby may suddenly become breathless, struggle to breathe, and stop feeding halfway through the most basic physical activity of breastfeeding or bottle-feeding. Pallor or bluish discoloration may appear on the skin because sufficient oxygen cannot reach the body. In the most severe cases, extensive fluid accumulation may develop throughout the baby’s body.

Symptoms during infancy include:

  • Unexplained restlessness
  • Uncontrollable crying episodes
  • Refusal to breastfeed
  • Developmental delay
  • Facial swelling

In infants who are a few months old, a continuously low heart rate tires the heart and creates a constant state of restlessness in the child. Parents usually notice that their child is no longer as eager to feed as before, becomes drenched in sweat while nursing, and cries continuously. If the heart cannot pump blood adequately, mild swelling may begin around the eyelids and face.

Symptoms during school age and adolescence include:

  • Reduced exercise capacity
  • Shortness of breath during exercise
  • Sudden dizziness
  • Chest pain
  • Sensation of palpitations
  • Darkening of vision
  • Sudden fainting

In older children and adolescents, the clinical picture is much more dramatic. While running with friends, climbing stairs, or playing basketball, the child may suddenly become breathless and unable to keep up with peers. They often describe palpitations as though a bird were fluttering inside the chest. During those few seconds when the heart slows excessively or pauses completely, blood does not reach the brain, and the child may suddenly collapse and faint without any warning symptoms. These fainting episodes are highly dangerous and require emergency medical intervention.

What Is the Relationship Between Acquired Complete AV Block and Heart Failure?

Excessive slowing of the heart in children dangerously reduces the total amount of blood the heart pumps to the body in one minute. When organs and tissues do not receive enough blood, the body enters a kind of survival and panic mode. In this panic mode, the sympathetic nervous system and certain hormonal mechanisms in the kidneys are rapidly activated. In the hope of raising the falling blood pressure again, the body constricts the blood vessels like a sponge and begins retaining water and salt.

However, this well-intentioned defense mechanism actually increases the workload of the already very slow, strained, and weak heart many times over. Because the heart cannot pump this additional fluid load accumulating in front of it, full congestive heart failure develops. Fluid backs up from the heart and begins to accumulate in the lungs, liver, and legs. Blood tests in these children show markedly elevated levels of certain enzymes that indicate how hard the heart is working and how much stress it is under. On physical examination, the liver is found to be much larger than normal, and fluid accumulation may be detected between the membranes surrounding the lungs. Especially when the heart rate falls below fifty beats per minute, it becomes almost impossible for the heart to tolerate this burden, and if timely intervention is not provided, a much more severe condition called cardiogenic shock may develop.

Which Medical Methods Are Used to Diagnose Acquired Complete AV Block?

Various technological and medical imaging methods are used together to definitively document this electrical disconnection in the child’s heart, determine where the damage is located, and understand whether there are any accompanying structural problems.

The main diagnostic tools used are:

  • Electrocardiography (ECG)
  • 24-hour rhythm Holter monitoring
  • Echocardiography (ECHO)
  • Computed tomography (CT)
  • Cardiac magnetic resonance imaging (MRI)
  • Catheterization procedures
  • Tissue biopsy

Electrocardiography is the most basic, completely painless, and most definitive diagnostic method. Small adhesive electrodes placed on the child’s chest, arms, and legs amplify the weak electrical signals produced by the heart and record them on paper. When the electrocardiogram of a child with complete heart block is examined, it is very clearly seen that there is no rhythmic relationship between the electrical waves of the upper chambers and the contraction waves of the lower chambers. While the upper chambers beat very rapidly, the lower chambers beat very slowly and entirely on their own.

However, electrocardiography captures only a ten-second snapshot. To understand how the child’s heart behaves during normal daily life, twenty-four-hour Holter monitoring is essential. A small recording device is attached to the child’s waist, and all heartbeats are recorded continuously for one day while the child sleeps, plays, and eats. This long-term recording is vital for determining the average heart rate, the lowest rate during sleep, and especially the duration of dangerous moments when the heart stops completely. Echocardiography is an ultrasound examination of the heart and works entirely with sound waves. With this device, structural defects in the heart, the contraction strength of the heart muscle, and whether the heart is enlarged are examined in detail. In much more complex situations or when surgical planning is required, advanced imaging techniques such as magnetic resonance imaging, which creates a three-dimensional map of the heart, are used. In very rare cases, in severe inflammation of the heart muscle where the diagnosis cannot be confirmed, a microscopic tissue sample taken from inside the heart may need to be examined.

At Which Stages Is a Permanent Pacemaker Required in the Treatment of Acquired Complete AV Block?

After the disease is diagnosed, the treatment approach is carefully planned according to the child’s immediate emergency condition and the expected long-term performance of the heart. If the child is brought to the hospital with a very low pulse, confusion, or unconsciousness, the first goal is to eliminate the life-threatening danger. The child’s breathing is supported, and if necessary, a thin wire is advanced through a vein in the neck or groin to the heart; through this wire, a temporary pacemaker ensures that the heart beats at a normal rate and circulation is stabilized.

After the emergency has passed and the patient’s condition has stabilized, permanent treatment planning begins. Since the decision to place a permanent pacemaker directly affects the child’s quality of life and chance of survival, it is made within the framework of very precise rules established by medical guidelines. These rules are divided into various classes.

Conditions that definitely require a pacemaker include:

  • Marked reduction in the heart’s blood-pumping capacity (hypotension)
  • Extremely slow heartbeat
  • Frequent recurrent fainting episodes
  • Very low heart rate without structural heart disease
  • Presence of dangerous rhythm disorder episodes
  • Severely reduced exercise capacity

If the heart’s backup rhythm originates from a very deep and unsafe region of the lower chambers, if fainting episodes occur, or if the average pulse rate falls below fifty beats per minute in a heart that appears structurally normal, a permanent pacemaker must be implanted without delay. Similarly, in children with a congenital heart anomaly, even if the heart rate remains at higher levels, the pacemaker decision is made earlier because the heart is considered unable to tolerate additional burdens. During infancy, if complete pauses lasting several seconds are detected between heartbeats, immediate intervention is required because this condition may endanger the baby’s brain development and life.

On the other hand, the decision is somewhat more flexible in children whose hearts contract completely normally, who have no complaints, who experience no problems while running and playing, and whose heart rates remain at acceptable levels. These children are monitored very closely, and the pacemaker decision may be postponed to a later date according to the child’s physical development and the results of exercise tests in subsequent years. Pacemaker implantation is generally not recommended in mild forms of block that cause no complaints.

How Is a Pacemaker Implanted for Acquired Complete AV Block in Children?

In childhood, placing a pacemaker, meaning the generator that produces electricity for the heart and the thin wires that carry that electricity to the heart, requires much more delicate and precise surgical planning than the methods used in adults. The most decisive factors are the child’s age, weight, physical size, and the width of the vascular system.

Methods used for younger children include:

  • Surgical opening of the chest
  • Suturing the electrodes to the outer surface of the heart muscle
  • Placing the generator behind the abdominal muscles

Especially in newborn babies and infants with very low body weight, the blood vessels in the body are extremely thin. Passing a pacemaker lead through these narrow vessels to reach the heart may damage the vessels and, in children with congenital defects in the heart, may create a risk that tiny blood clots forming on these leads could pass through the defects and reach the brain. To eliminate these life-threatening risks, a different approach called the epicardial method is preferred. In this method, the outer surface of the heart is reached surgically, and the conductive wires are securely sutured directly onto the outer muscle tissue of the heart. Since there is no room in the chest, the generator device, which produces the electricity and is slightly larger than a matchbox, is hidden behind the muscles in the abdominal region so that it is protected and not visible from the outside.

Methods used for older children include:

  • Using the veins beneath the collarbone
  • Advancing the electrodes through the veins into the heart chambers
  • Securing the leads to the inner wall of the heart
  • Placing the generator under the skin in the chest region

In older children and adolescents who have largely completed their growth, the endocardial method, similar to that used in adults, is applied. Using the large veins passing just beneath the collarbone, the conductive leads are safely advanced into the right upper and right lower chambers of the heart and gently screwed into the inner wall of the heart. The generator box is placed into a small pocket created under the skin in the chest region.

These devices implanted in children are specially manufactured to keep pace with their high metabolic rates and energetic lifestyles. They are much lighter and smaller. However, there is another important detail that should be known; traditional pacemakers stimulate only from the right ventricle. Because children’s hearts beat much faster, the pacemaker works far more intensively than in adults. Years of this one-sided electrical stimulation may sometimes disrupt the harmony between the right and left sides of the heart, leading to fatigue and reduced activity of the heart. If such a weakening in pumping capacity is noticed during follow-up, the existing pacemaker system is replaced with a more advanced technology, allowing both sides of the heart to work simultaneously with perfect synchronization and enabling the heart to regain its former strength.

What Should Be Considered During Pacemaker Follow-Up After Acquired Complete AV Block?

The process of pacemaker implantation is not actually the end of the disease, but rather the healthy beginning of a brand-new and much safer life that requires extremely careful follow-up. Although the surgical wound closes superficially in approximately ten days, it takes about two months for the device to fully adapt to its pocket under the skin and for the thin leads inside the heart to completely integrate with the heart tissue.

Points that require attention especially during the first two months include:

  • Avoiding excessive upward and sideways lifting of the arm
  • Avoiding carrying weight with the arm on the side of the procedure
  • Avoiding heavy school bags
  • Avoiding movements that may cause impact to the shoulder region
  • Protecting the pacemaker area from hard impacts
  • Always carrying the pacemaker identification card

For children who have had a pacemaker implanted in the chest through a vein, it is extremely important not to raise the arm on the side of the procedure more than ninety degrees to the side or use that arm to pull themselves upward, so that the leads do not become displaced from their newly formed attachment points. Children are also restricted from lifting heavy objects during this period. After the critical two-month healing period is successfully completed and physician approval is obtained, most of these physical restrictions are removed and the child returns to normal life. However, children and their families must always carry the pacemaker card containing all the technical specifications of the device so that it can be shown during travel and emergencies.

Routine device checks begin with the first detailed test performed approximately one and a half months after surgery. During this test, computers communicate with the device to evaluate how well the leads have attached to the tissue and the energy consumption of the pacemaker. If everything is normal, follow-up visits are generally scheduled every six months.

Conditions requiring emergency medical assistance include:

  • Redness of the skin over the pacemaker pocket
  • Abnormal warmth in the area
  • Purulent or clear discharge
  • The device becoming visibly prominent by thinning the skin
  • Unexplained persistent fever
  • Unexplained night sweats
  • Recurrent sensation of fainting
  • Unexpected slowing of the heart
  • Siren or beeping sounds coming from the device

If signs of infection such as redness or discharge are seen at the wound site, or if the child experiences fever and chills lasting for days despite no identifiable source of infection, the hospital should be contacted immediately without waiting for the routine follow-up date. Likewise, no time should be lost if the child experiences faintness as before or if an alarm, vibration, or beeping sound is emitted from certain advanced pacemakers. These sounds are vital warnings indicating that the device’s battery is running low or that a technical problem has been detected in the leads.

When Can Children Begin Sports After Acquired Complete AV Block?

In children who develop block due to temporary causes such as inflammation of the heart muscle, the electrical pathways of the heart often return completely to normal and the block disappears once the inflammatory process ends. However, even if externally recorded electrocardiograms appear completely normal, full healing of damage in the microscopic depths of the heart takes a considerable amount of time. To prevent small hidden electrical imbalances in the heart from turning into severe rhythm disorders while healing continues, children must medically avoid competitive sports, intensive training, and physical education classes for at least six months from the day the illness begins.

Evaluations that must be performed before deciding on a return to sports at the end of the six-month rest period include:

  • Detailed electrocardiography
  • Assessment of contraction with echocardiography
  • Twenty-four-hour rhythm Holter analysis
  • Capacity measurement with an exercise test
  • Advanced imaging of the heart muscle

If all these tests prove that there are no rhythm pauses in the heart and the heart muscle has regained its former flexibility, the child is allowed to gradually return to sports. Regular exercise is also very important for the physical and mental health of children with permanent pacemakers. However, children with permanent complete block must undergo an exercise treadmill test before starting sports, and it must be assessed whether their pacemakers can accelerate sufficiently to meet the increased oxygen demand during exercise. In addition, experts recommend choosing more individual and low-contact sports instead of combat sports or sports involving hard physical contact, in order to prevent damage to the pacemaker from a severe external impact.

Frequently Asked Questions

Acquired complete AV block is the complete interruption of electrical conduction between the atria and ventricles of the heart. It is not congenital, develops later, and may cause a serious slowing of the heart rhythm.
Dizziness, fainting, extreme weakness, shortness of breath, a sensation of palpitations, and reduced exercise capacity are the most common symptoms. In some patients, symptoms may appear suddenly.
Heart muscle diseases, myocarditis, heart surgeries, certain medications, age-related conduction system disorders, and electrolyte imbalances may cause acquired complete AV block.
Yes, it can also occur in children. It may develop especially after heart surgery, due to infections such as myocarditis, or as a result of certain rare heart diseases.
Electrocardiography (ECG) is the primary diagnostic method. Holter rhythm monitoring, echocardiography, and, when necessary, advanced cardiological examinations may also be used.
Yes, because the heart rate slows significantly, sufficient blood may not reach the brain. This may lead to dizziness, brief loss of consciousness, and fainting episodes.
Treatment is planned according to the underlying cause. While temporary causes are corrected when possible, pacemaker implantation may be required in patients with permanent conduction disorders.
Permanent pacemaker treatment may be used to ensure that the heart beats at a sufficient rate and to prevent complications such as fainting, heart failure, or serious rhythm problems.
If left untreated, it may lead to serious rhythm disorders, fainting, and, rarely, life-threatening complications. Therefore, early diagnosis and regular follow-up are of great importance.
People suspected of having acquired complete AV block should consult a Cardiology specialist. In pediatric patients, the evaluation and treatment process should be managed by Pediatric Cardiology specialists.
Güncellenme Tarihi: 13.10.2026

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