General

Complete Heart Block: Symptoms, Causes, Diagnosis and Treatment

Posted on by Prof. Dr. İbrahim Cansaran TANIDIR

Complete atrioventricular heart block, also known as third-degree AV block, is a serious rhythm disorder in which the vital electrical communication between the upper chambers of the heart (atria) and the lower chambers that pump blood to the body (ventricles) is completely interrupted. In this condition, electrical impulses originating from the upper centers that determine the heart’s natural rhythm cannot reach the lower centers in any way, and the two sections of the heart begin to function entirely independently of each other. This cardiological condition, which can affect fetuses in the womb and children of all ages, means that the heart’s electrical bridge has been completely destroyed. This rhythm problem, which carries life-threatening risks if not treated early, requires multidisciplinary and meticulous medical follow-up.

How Does the Electrical System of Our Heart Normally Work and What Is Complete Heart Block?

The heart is not only a pump mechanism capable of contracting, but also an extraordinary organ that contains a flawless electrical network within itself. The starting point of this remarkable system is a special cluster of cells located in the upper right chamber of the heart, functioning like a natural generator or pacemaker. This generator produces small electrical signals at regular intervals. These signals first spread through the upper chambers of the heart, causing them to contract and pump the blood inside them toward the lower chambers. The signals then arrive at a special station that acts like a customs gate or bridge between the upper and lower chambers. This station delays the electricity for a very, very short period, allowing the lower chambers time to fill with blood. The electrical current is then transmitted to the lower chambers through special conduction cables, enabling the heart to contract very strongly and send blood throughout the entire body.

When complete heart block develops, this main customs gate or the electrical cables that follow it become completely nonfunctional. Since the electrical bridge is destroyed, the vital contraction commands coming from the upper chambers cannot pass to the lower chambers. To prevent the heart from stopping completely, some cells within the lower chambers become activated due to the miraculous structure of our heart and begin to produce weak electrical signals on their own. However, the rate generated by this backup system is much lower than the rate produced by the heart’s main generator. Because the heart beats much more slowly than it should, the blood needs of the body, brain, and other vital organs cannot be met. This enormous disconnection in the electrical system lays the groundwork for a series of compensatory mechanisms to become activated in the body and for various clinical complaints to begin.

Into Which Main Categories Is Complete Heart Block Seen in Children Divided?

Complete heart blocks encountered in infants, children, and adolescents are divided into two main groups depending on when and through which mechanisms the disease develops. This classification is the most important determinant of how the treatment of the disease will be planned. The first group consists of congenital heart blocks that begin to develop while the baby is still in the womb and are present when the baby is born. This condition is called the congenital form and usually occurs when certain antibodies transferred from the mother to the baby damage the heart or when the anatomical structure of the heart develops abnormally in the womb.

The second group consists of acquired heart blocks. In a child born with a completely healthy electrical system, this condition may develop later in life due to severe infections, immune system problems, inflammation of the heart muscle, or damage to the electrical pathways of the heart following open heart surgery performed to repair congenital heart defects. The clinical course, the complaints experienced by the patient, and the response to treatment in these two main categories have completely different dynamics.

What Are the Main Underlying Causes of the Development of Complete Heart Block in Babies in the Womb?

The most common and striking cause of congenital complete heart block developing in a fetus in the womb is autoimmune conditions in the mother’s immune system. Sometimes, even if the expectant mother feels no symptoms of any disease, certain antibodies with a tendency to attack her own tissues may be present in her blood. Particularly between the twelfth and sixteenth weeks of pregnancy, these antibodies in the mother’s blood cross the structure called the placenta and enter directly into the baby’s circulation. These antibodies entering the baby’s blood attack the cells forming the electrical system of the developing tiny heart as if they were foreign substances.

As a result of this attack, the balance inside the baby’s heart cells is completely disrupted. Conduction cells gradually begin to die. In the region where the dead cells are located, an intense inflammatory process that disrupts the natural structure of the heart is triggered. Especially in babies genetically predisposed to this damage, this inflammation turns over time into hardened scar tissue and calcifications instead of healing. This hard scar tissue physically and completely destroys the pathways carrying electrical signals. The autoimmune diseases that may be present in the mother and predispose to this destructive process include:

  • Systemic lupus erythematosus
  • Sjögren syndrome
  • Rheumatoid arthritis
  • Mixed connective tissue diseases

How Do Structural Anomalies in the Heart Predispose to Congenital Complete Heart Block?

Another aspect of congenital complete heart block is the physically abnormal development of the heart in the womb. When the chambers, vessels, or valves of the heart form abnormally, the electrical conduction pathways running through the inner walls of the heart are also affected by this defect. The electrical pathways either do not form at all, are directed toward completely incorrect locations, or become physically interrupted at some point. Heart blocks seen together with structural heart diseases are among the most feared scenarios in medicine. This is because the heart already has difficulty pumping blood due to an anatomical abnormality, and when a slow heart rate is added, the baby’s risk of developing heart failure increases exponentially.

These structural defects usually occur during the first weeks of pregnancy and cause the heart to develop with a completely different architecture. In situations where the conduction system is directly physically interrupted or changes direction, the baby has to struggle with both the structural problem in the heart and a serious rhythm disorder. The structural heart anomalies most commonly accompanying congenital complete heart block include:

  • Congenitally corrected transposition of the great arteries (ccTGA)
  • Atrioventricular septal defects (AVSD)
  • Left atrial isomerism (LAI)

What Causes Acquired Complete Heart Block Developing Later in Childhood?

Even if the child’s heart and electrical system develop completely normally in the womb and the birth proceeds without complications, complete heart block may develop in later years due to the effects of various external factors. By far the most common cause of acquired heart block in childhood is surgical intervention. During open heart surgeries performed to close a congenital heart defect or replace a problematic heart valve, the surgeon inevitably has to work only a few millimeters away from the electrical pathways. A stitch placed in this region, the traction force created by surgical instruments, or fluid accumulating in the tissues after surgery can place serious pressure on the electrical pathways. Although this swelling often subsides within a few weeks and relieves the conduction system, sometimes the damage becomes permanent and complete block becomes established.

Apart from surgical trauma, severe infections that directly target the heart muscle and electrical pathways, as well as certain poisonings, can also cause acquired heart block in children. In such cases, the conduction pathways of the heart are invaded by inflammatory cells and signal transmission stops completely. Medical conditions that may cause acquired complete heart block in childhood apart from surgery include:

  • Acute rheumatic fever
  • Viral myocarditis
  • Lyme disease
  • Infectious mononucleosis
  • Rickettsial infections
  • Cardiac tumors
  • Drug intoxications

What Is Type 2 Atrioventricular Block and How Is It Related to Complete Heart Block?

There is a very critical stage on the path toward complete heart block. This rhythm disorder, referred to in medical terminology as Type 2 2:1 atrioventricular block, describes a special condition in which the bridge has not been completely destroyed but has suffered very severe damage. In this condition, not all electrical signals coming from the upper chambers are blocked; instead, within a certain pattern, for example, only one out of every two signals can be transmitted to the lower chambers. While the upper part of the heart contracts twice, the lower part manages to contract only once.

Although this condition is not a “complete” block, it poses a danger clinically at least as serious as complete block. This is because this weak and damaged bridge may suddenly collapse at any moment without any warning and transition to complete heart block by causing the heart to stop completely. It is vitally important for children diagnosed with this type of rhythm problem to be monitored extremely carefully for enlargement or weakening of the heart muscle, since they are at constant risk of progressing to complete block. Whether patients are able to remain balanced on this fine line must be kept under continuous control with technological imaging devices.

With Which Serious Symptoms Does Complete Heart Block Present During Infancy?

In infants who are not yet able to express themselves, the signs of complete heart block consist entirely of the body’s physical responses to oxygen deprivation and a slow heart rate. When the heart cannot pump a sufficient amount of blood, the tissues are deprived of oxygen and the severe condition called heart failure gradually begins to make itself felt. For babies, the greatest exertion during the day is the feeding process. While a healthy baby can breathe comfortably while breastfeeding, a baby with complete heart block becomes tired very quickly, frequently stops feeding and feels the need to rest, and sweats profusely during this time because the body is exerting excessive effort.

If the block progresses enough to cause heart failure while the baby is still in the womb, fluid begins to accumulate in all body cavities, the lungs, and the abdominal region of the baby. This extremely fatal condition is called hydrops fetalis. In the postnatal period, fluid may accumulate in the lungs due to the excessively slow heart rate, breathing becomes rapid, and visible retractions begin in the baby’s chest. The main clinical symptoms caused by complete heart block during infancy include:

  • Becoming tired quickly during feeding
  • Stopping breastfeeding early
  • Excessive sweating
  • Rapid breathing
  • Chest retractions
  • Restlessness
  • Mottling of the skin
  • Episodes of cyanosis

Why Do the Complaints of Complete Heart Block Differ in Older Children and Adolescents?

As children grow and their physical activity increases, the body’s energy and oxygen needs become completely different compared with infancy. Interestingly, if the backup generator in the lower chambers of a child with complete heart block can produce an impulse once per second (approximately 60 times per minute), and the child’s cerebral blood flow can be adequately maintained at this rate, the child may grow for years without experiencing any serious complaints. However, with the growth period, when physically demanding activities such as playing sports, running, or climbing stairs begin, the situation changes.

A normal heart accelerates during exertion and pumps more blood to the body. In complete heart block, although the upper chambers accelerate, the electrical signals cannot travel downward, so the lower chambers continue to remain at the same slow rhythm. When the body’s increased demand for blood cannot be met, the brain and muscles do not receive enough oxygen. When blood flow to the brain suddenly falls below a critical level, the child may abruptly lose consciousness and collapse. Fainting (syncope) episodes are among the most life-threatening symptoms for these children and require emergency intervention. Due to the heart rate slowing even further during sleep, the brain may be deprived of oxygen, which may cause children to frequently wake from sleep after having nightmares. The main symptoms of complete heart block seen during play age and adolescence include:

  • Becoming breathless while climbing stairs
  • Shortness of breath during exertion
  • Becoming tired easily
  • Dizziness
  • Weakness
  • Fainting
  • Having nightmares during sleep

Which Imaging Methods Are Used to Diagnose Complete Heart Block in the Womb?

Thanks to the possibilities offered by technology, even highly complex rhythm problems in the fetal heart can now be detected with great accuracy while the baby is still in the womb. Everything usually begins during a routine obstetric examination, when the obstetrician notices on the ultrasound device that the baby’s heart rate is much slower than expected. A tiny heart that should normally beat between 120 and 160 times per minute is observed to have slowed to levels of 50-60 beats per minute. Upon this suspicion, the expectant mother is immediately referred to a pediatric cardiology or perinatology (high-risk pregnancy) specialist.

The most important technological tool used at this stage is fetal echocardiography. This method, which sends sound waves through the mother’s abdomen and displays the baby’s internal heart structure, chambers, valves, and most importantly electrical rhythm on the screen in high resolution, can be safely performed at any stage of pregnancy, but provides the clearest results between the 16th and 24th weeks. Using the device’s special Doppler and M-Mode features, the timing of contraction of the upper chambers and the timing of contraction of the lower chambers are examined simultaneously on the same graph. When this examination clearly demonstrates that the upper and lower chambers are completely disconnected and functioning independently of each other, a definitive diagnosis is made for the baby in the womb.

Which Modern Medical Tests Are Performed to Diagnose Complete Heart Block After Birth?

After the baby is born or when a child suspected of having complete heart block at an older age is brought to the outpatient clinic, painless, completely noninvasive, and highly reliable diagnostic methods are used to prove that the electrical communication within the heart has been completely interrupted and to determine the extent of the existing damage.

The medical tests used by the physician as the main diagnostic tools include:

  • Electrocardiography (ECG)
  • 24-hour rhythm Holter monitoring
  • Transthoracic echocardiography (ECHO)
  • Exercise stress test

How Is Complete Heart Block That Begins in the Womb Managed Medically?

If the development of heart block in the womb has not yet reached the stage of complete interruption or if the inflammatory process has just begun, a time-sensitive medical treatment process is initiated to prevent the electrical bridge in the heart from being completely destroyed. Since direct intervention on the baby is not possible during this period, medications are delivered to the baby through the placenta via the mother’s body. If the mother has an immune system problem and intense inflammation is detected in the baby’s heart, potent steroids administered intravenously to the mother are intended to cross the placenta and extinguish the inflammation in the baby’s heart.

In fetuses whose heart rate has become very slow and who are beginning to develop heart failure as a result, special heart-stimulating medications called sympathomimetics may be administered to the mother to accelerate the heart rate. In addition, antimalarial medications are available for preventive use throughout pregnancy in subsequent pregnancies of mothers who have previously given birth to a child with congenital heart block, in order to prevent the same distressing condition from recurring. Medical treatments used to protect the baby in the womb and stop the progression of the block include:

  • Corticosteroids
  • Sympathomimetic medications
  • Betamimetic agents
  • Hydroxychloroquine prophylaxis
  • Plasmapheresis

Why Must the Delivery Process of Babies With Complete Heart Block Be Planned So Comprehensively?

The moment of birth of a baby diagnosed with complete heart block in the womb must be managed with the seriousness of a fully equipped medical operation, far beyond an ordinary delivery. Although the baby somehow survives in the womb by relying on the mother’s oxygen through the placenta, once the umbilical cord is cut, the baby will be left alone with its own slowly beating heart. A slow heart rate carries the risk that the newborn will be unable to send enough blood to the lungs during the process of adapting to life outside the womb and that the entire body may go into shock.

If widespread fluid accumulation due to heart failure (hydrops fetalis) has begun in the fetus while still in the womb, the baby’s survival until that point is already a great miracle, and in such cases, lung-maturing medications are administered and an earlier emergency cesarean delivery is planned. Delivery must take place in a tertiary healthcare center with an advanced neonatal intensive care unit, where pediatric cardiac surgery and pediatric cardiology are available 24 hours a day. In addition to the obstetrician, a pediatric cardiologist, perinatologist, and neonatologist must be present in the team receiving the baby in the delivery room. Emergency interventions should be performed immediately after birth, and if necessary, a temporary pacemaker should be inserted without delay.

According to Which Criteria Is Permanent Pacemaker Treatment Decided in Children With Complete Heart Block?

Despite all technological advances in medicine, unfortunately there is still no medical treatment option capable of restoring a completely interrupted and calcified electrical conduction system with pills or syrups. The only universally accepted, life-saving, and definitive treatment for complete heart block is the implantation of a permanent pacemaker. However, the decision to implant a pacemaker is not made at the same pace for every child; this critical decision is based on extremely precise measurements shaped entirely by scientific data, the child’s age, the structural condition of the heart, and the complaints caused by the disease.

If the child faints, shows signs of heart failure, or even remains completely asymptomatic but the awake heart rate during the day falls far below a certain safety threshold, a pacemaker must unquestionably be implanted. In addition, if silent periods lasting several seconds are detected between heartbeats on Holter recordings, or if the heart has completely lost its ability to accelerate during an exercise test, the decision for surgery is made without delay. The critical criteria considered by pediatric cardiology specialists when deciding to implant a pacemaker include:

  • Signs of congestive heart failure
  • Low cardiac output
  • Fainting episodes
  • A resting heart rate below fifty beats per minute in newborns without heart disease
  • A resting heart rate below seventy beats per minute in newborns with heart disease
  • A resting heart rate below forty beats per minute in adolescents
  • Pauses exceeding three seconds on Holter recording
  • Progressive left ventricular dilatation or left ventricular dysfunction
  • Persistence of the block in children who have undergone heart surgery despite the fact that 7 days have passed after the operation

How Is Pacemaker Implantation Performed for Complete Heart Block in Infants and Older Children?

Pacemaker operations in children require a completely different level of surgical skill and planning compared with adults. The form of treatment is carried out using two entirely different techniques depending on the patient’s age and weight. In newborn babies who are only a few days old or have a very low body weight, the blood vessels are too thin and delicate to allow a wire to pass through them. Therefore, a special surgical technique called the epicardial method is used in infants. Through a small window opened in the chest or beneath the ribs, the outer surface of the heart is reached, and the delicate wires that will transmit the electricity produced by the pacemaker are gently sutured directly onto the outer muscle tissue of the heart. The battery of the pacemaker device is usually placed in a pocket hidden between the muscles under the skin in the baby’s abdominal region.

As the child grows and reaches adolescence, the endocardial method is used, just as in adults. In this method, there is no need to open the chest. One of the large veins just below the collarbone is entered, and thin wires are advanced through the vein to the lower right chamber of the heart and secured to the heart tissue from the inside. The battery unit is placed directly into a skin pocket beneath the collarbone. This surgical technique takes much less time and greatly accelerates the child’s discharge from the hospital.

What Should Be Considered in the Daily Lives of Children Living With a Pacemaker Due to Complete Heart Block?

Pacemaker treatment is one of the most extraordinary medical interventions connecting children with fatal rhythm disorders to a normal, healthy, and long life. Families’ concern, “Will my child be able to live a normal life?” is generally unfounded. Children with pacemakers can attend school, run, play, and grow without feeling any physical difference from their peers. There are only very clear but simple safety rules that must be followed in daily life to avoid disrupting the pacemaker’s operating mechanism or causing physical damage to the area where the battery is located.

Today’s modern pacemakers are manufactured with highly advanced shielding so that they are absolutely unaffected by standard electromagnetic fields emitted by household appliances such as smartphones, tablets, microwave ovens, or televisions. However, very strong magnetic fields may temporarily disrupt the heart’s rhythm settings or reset the pacemaker. In addition, sports involving direct severe blows to the chest must absolutely be avoided to prevent permanent lead damage. Situations that children with pacemakers should avoid or approach with caution include:

  • Heavy sports with a high risk of trauma
    • American football
    • Boxing
    • Wrestling
    • Karate and similar martial arts
  • Airport security detectors
  • Shopping mall security gates
  • High-voltage transformer stations
  • Magnetic resonance imaging (MRI) devices

Why Is Long-Term Follow-Up of Children Diagnosed With Complete Heart Block Vitally Important?

Complete heart block and the pacemaker treatment that follows are not conditions in which the patient’s file is closed after a successful operation and the patient is never seen again; on the contrary, they mark the beginning of a close lifelong partnership between physician and patient. The batteries that provide power to the pacemaker do not last forever; depending on the child’s growth rate and the intensity of device use, these batteries are depleted on average within five to ten years. When the device battery becomes weak, the external generator unit must be replaced with a new one through a minor operation. Therefore, patients must return to the center every six months for device measurements.

In addition, the contraction dynamics of the heart tend to become fatigued over the years due to external electrical stimulation. Unlike normal physiology, receiving continuous electrical stimulation from the lower right chamber may cause the heart muscle in some children with complete heart block to gradually enlarge and its pumping strength to weaken in later years, leading to a condition called dilated cardiomyopathy. Continuous follow-up with echocardiography by pediatric cardiology specialists is an indispensable necessity so that this cardiac fatigue can be detected well in advance and heart-supporting medications can be initiated or pacemaker settings can be adjusted.

Frequently Asked Questions

Complete heart block is the complete interruption of electrical conduction between the atria and ventricles. As a result, the heartbeat may slow down and the blood circulation required by the body may not be adequately maintained.
Dizziness, fainting, extreme weakness, shortness of breath, easy fatigue, a sensation of palpitations, and reduced exercise capacity are among the most common symptoms of complete heart block.
Complete heart block may be congenital, or it may develop later due to age-related conduction system disorders, heart diseases, myocarditis, heart surgeries, or certain medications.
Yes, congenital complete heart block can occur in children. Complete heart block may also develop after certain congenital heart diseases, infections, or cardiac surgeries.
Electrocardiography (ECG) is the primary diagnostic method. Holter rhythm monitoring, echocardiography, and, when necessary, advanced cardiological examinations are also used to investigate the cause of the disease.
Yes, because the heart beats very slowly, sufficient blood may not reach the brain. This can lead to dizziness, darkening of vision, and sudden fainting episodes.
If left untreated, it may cause serious rhythm disorders, heart failure, and life-threatening complications. Therefore, early diagnosis and regular follow-up are of great importance.
Treatment is planned according to the underlying cause. While temporary causes are corrected when possible, permanent pacemaker treatment is usually applied in patients with persistent conduction disorders.
A pacemaker helps prevent fainting, weakness, and serious circulatory problems by ensuring that the heart beats regularly and at a sufficient rate. It is the primary treatment option for many patients.
Individuals suspected of having complete heart block should consult a Cardiology specialist. In pediatric patients, the diagnosis, treatment, and follow-up process should be managed by Pediatric Cardiology specialists.
Güncellenme Tarihi: 13.10.2026

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