An Atrial Septal Defect, or ASD, is a hole in the wall between the right and left atria (atrial septum). In the presence of an ASD, blood flows from the higher pressure left atrium to the lower pressure right atrium.
When this happens, the oxygen-rich blood of the left atrium is redirected through the right side of the heart and back to the lungs. The right atrium, right ventricle, and pulmonary artery may enlarge due to the increased blood flow through these structures.
Long-term side effects of an untreated ASD include atrial arrythmias (loss or abnormality of rhythm), ventricular dysfunction, and pulmonary vascular obstructive disease (a condition in which the pulmonary arteries become thickened due to high blood flow). For these reasons, it is preferential to close even small ASDs early in life to prevent complications later in life.
Three Types of ASD
Secundum-type ASDs are the most common, comprising approximately 85% of all ASDs. In many cases, infants and young children are asymptomatic and the ASD may not be detected until school age or later. Approximately 20% of secundum-type ASDs close spontaneously in the first year of life. Often, a heart murmur, associated with the increase in blood flow across the pulmonary valve, is the symptom that causes a physician to investigate further. The diagnosis of an ASD is confirmed by echocardiography.
In a secundum-type ASD, the hole is located in the central part of the atrial septum. The methods of treatment for a secundum-type ASD consist of surgical repair or a catheter technique. Options for surgical repair involve suture closure (reserved for small ASDs) or patch closure. The patch material may be a portion of the patients own pericardium (the sac around the heart) or a synthetic material. The catheter technique involves closure of the ASD with a synthetic device that plugs the hole. The device is introduced through a heart catheter which is passed through a vein in the leg that leads up to the heart. Initially, the device is held in place by the natural pressures created within the atria. Over time, the device acts as a framework over which normal tissue grows.
Sinus venosus atrial septal defects constitute 5% to 10% of all ASDs. In a sinus venosus ASD the hole is located in the upper portion of the atrial septum. This type of ASD is often associated with anomalous drainage of the right, upper pulmonary veins. In other words, the pulmonary veins, which normally carry oxygenated blood from the lungs to the left atrium, drain into the right atrium instead. There is no chance for spontaneous closure of this type of ASD. For this reason, surgical repair is necessary for patients with this type of ASD.
Primum-type ASDs constitute between 5% and 10% of all ASDs. In a primum-type ASD the hole is located in the lower part of the atrial septum. Frequently, abnormalities of one or more heart valves (most often the mitral valve) are associated with this defect. Unlike the secundum-type ASD, symptoms of this type of ASD are seen during early childhood. Surgical repair is the only method of treatment for a primum type ASD since there is no chance of spontaneous closure.
What Is Normal Cardiac Anatomy?
When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.
Heart With Normal Cardiac Anatomy
When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.
The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.
There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.
Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.
Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.
From Nemours' KidsHealth
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An arrhythmia is an abnormal heart rhythm usually caused by an electrical "short circuit" in the heart.
The heart normally beats in a consistent pattern, but an arrhythmia can make it beat too slowly, too quickly, or irregularly. This can cause the heart muscle's pumping function to work erratically, which can lead to a variety of symptoms, including fatigue, dizziness, and chest pain.
What Causes Arrhythmias?
The heart has its own conduction system, or electrical system, that sends electrical signals around the heart, telling it when to contract and pump blood throughout the body. The electrical signals originate from a group of cells in the right atrium, called the sinus node. The sinus node functions as the heart's pacemaker and makes sure the heart is beating at a normal and consistent rate. The sinus node normally increases the heart rate in response to factors like exercise, emotions, and stress, and slows the heart rate during sleep.
However, sometimes the electrical signals flowing through the heart don't "communicate" properly with the heart muscle, and the heart can start beating in an abnormal pattern — an arrhythmia (also called dysrhythmia).
Arrhythmias can be temporary or permanent. They can be caused by several things, but also can occur for no apparent reason. Arrhythmias can be congenital (meaning kids are born with it), sometimes due to a birth defect of the heart but sometimes even when the heart has formed normally.
Other causes of arrhythmias in kids include chemical imbalances in the blood, infections, or other diseases that cause irritation or inflammation of the heart, medications (prescription or over-the-counter), and injuries to the heart from chest trauma or heart surgery. Other factors (such as illegal drugs, alcohol, tobacco, caffeine, stress, and some herbal remedies) also can cause arrhythmias.
Signs and Symptoms
Because arrhythmias can cause the heart to beat less effectively, blood flow to the brain and to the rest of the body can be interrupted. If the heart is beating too fast, its chambers can't fill with the proper amount of blood. If it's beating too slowly or irregularly, the proper amount of blood can't be pumped out to the body.
If the body doesn't get the supply of blood it needs to run smoothly, these symptoms can occur:
- palpitations (a feeling of fluttering or pounding in the chest)
- shortness of breath
- chest pain
Arrhythmias can be constant, but usually come and go at random. Sometimes arrhythmias can cause no detectable symptoms at all. In these cases, the arrhythmia can only be discovered during a physical examination or a heart function test.
What's a Normal Heart Rate?
Heart rate is measured by counting the number of beats per minute. Normal heart rate varies depending on factors like age and whether the person leads an active lifestyle or not. (For example, athletes often have a lower resting heart rate).
The resting heart rate decreases as kids get older. Typical normal resting heart rate ranges are:
- babies (birth to 3 months of age): 100–150 beats per minute
- kids 1-3 years old: 70-110 beats per minute
- kids by age 12: 55-85 beats per minute
Your doctor should help you determine whether or not your child's heart rate is abnormally fast or slow, since the significance of an abnormal heart rate depends on the situation. For example, an older child or adult with a slow heart rate might begin to show symptoms when his or her heart rate drops below 50 beats per minute. However, trained athletes have a lower resting heart rate — so a slow heart rate in them isn't considered abnormal if no symptoms are associated with it.
Types of Arrhythmias
There are several types of arrhythmias, including:
Premature Atrial Contraction (PAC) and Premature Ventricular Contraction (PVC)
Premature contractions are usually considered minor arrhythmias, in which the person may feel a fluttering or pounding in the chest caused by an early or extra beat. PACs and PVCs are very common, and are what happens when it feels like your heart "skips" a beat. It doesn't skip a beat — an extra beat actually comes sooner than normal. Occasional premature beats are common and considered normal, but in some cases they can indicate an underlying medical problem or heart condition.
Tachycardias are arrhythmias that involve an abnormally rapid heartbeat. They fall into two major categories — supraventricular and ventricular:
- Supraventricular tachycardia (SVT): is the most common significant arrhythmia, it's characterized by bursts of fast heartbeats that originate in the upper chambers of the heart. The bursts can happen suddenly, and episodes can last anywhere from a few seconds to several days. Specific treatment is usually recommended if incidents of SVT are long-lasting or happen often.
- Ventricular tachycardia: is a serious but relatively uncommon condition that originates in the lower chambers of the heart and can be dangerous.
Bradycardias — arrhythmias characterized by an abnormally slow heartbeat — include:
- Sinus node dysfunction: is when the heart's sinus node isn't working correctly, most commonly following surgery to correct a congenital heart defect. An abnormally slow heartbeat is typically seen in this condition; however, episodes of rapid heartbeat due to SVT also can occur.
- Heart block: is often caused by a congenital heart defect, but also can be the result of disease or injury. Heart block happens when electrical impulses can't make their way from the upper to lower chambers of the heart. When this happens, another node in the lower chambers takes over and acts as the heart's pacemaker. Although it sends out electrical impulses to keep the heart beating, the transmission of the signals is much slower, leading to a slower heart rate.
Doctors use several tools to diagnose arrhythmias. It's very important to know your child's medical history and give this information to your doctor, who will use it, along with a physical examination, to begin the evaluation.
If an arrhythmia is suspected, the doctor will probably recommend an electrocardiogram (EKG) to measures the heart's electrical activity. There is nothing painful about an EKG — a series of electrodes (small metal tabs) are fixed to the skin with sticky papers, then information about the electrical activity of the heart is transferred to a computer, where it's interpreted and drawn as a graph.
The doctor might recommend the following types of EKG tests:
- Resting EKG. This measures resting heart rate and rhythm, and lasts about a minute.
- Exercise EKG (also called a stress test). This measures heart rate and rhythm while exercising, like riding a stationary bicycle or walking on a treadmill.
- Signal-average EKG. This measures heart rate much like a resting EKG. The only difference is the signal-average EKG monitors the heartbeat over a longer time period (around 15–20 minutes).
- Holter monitor. This is an EKG done over a long period of time, usually 24 hours or more. The electrodes are connected to the chest, and the wires are attached to a portable EKG recorder. The child is encouraged to continue normal daily activities, but must be careful to not get the electrodes wet (for example, no swimming, showering, or activities that cause a lot of sweating). The two kinds of Holter monitoring are: continuous recording, which means the EKG is on throughout the entire monitoring period; and event monitoring, which means data is recorded only when the child feels symptoms and then turns the Holter monitor on.
Many arrhythmias don't require treatment; however, some can pose a health problem and need to be evaluated and treated by a doctor.
Depending on the type and severity of the arrhythmia, one of these options might be recommended:
- Medications. Many types of prescription anti-arrhythmic medications are available to treat arrhythmias. The doctor will determine which is best by considering the type of arrhythmia, possible underlying medical causes, and any medications a child is taking. Sometimes, anti-arrhythmic medications can increase symptoms and cause unwanted side effects, so their use and effectiveness should be closely monitored by the doctor, you, and your child.
- Pacemakers. A pacemaker is a small, battery-operated device implanted into the body (near the collarbone) through a surgical procedure. Connected to the heart by a wire, pacemakers can help treat bradycardia. Through a sensing device, a pacemaker can detect if the heart rate is too slow and sends electrical signals to the heart to speed up the heartbeat.
- Defibrillators. Like a pacemaker, a defibrillator can deliver electrical impulses to the heart. A small battery-operated implantable cardioverter defibrillator (ICD) can be implanted near the left collarbone through a surgical procedure. Wires run from the defibrillator to the heart. It senses if the heart has developed a dangerously fast or irregular rhythm and delivers an electrical shock to restore a normal heartbeat.
- Catheter ablation. "Ablation" literally means removal or elimination. In the case of catheter ablation, a catheter (a long, thin wire) is guided through a vein in the leg to the heart. Arrhythmias are often caused by microscopic defects in the heart muscle. Once the problem area of the heart is pinpointed, the catheter heats or freezes the muscle cells and destroys them.
- Surgery. Surgery is usually recommended only if all other options have failed. In this case, the child is put under anesthesia, the chest is opened, and the heart is exposed. Then, the tissue causing the arrhythmia is removed.
When to Call the Doctor
Although many arrhythmias are minor and don't represent a significant health threat, some can indicate a more serious problem. If your child has been having symptoms of an arrhythmia, call your doctor.
Reviewed by: Joel D. Temple, MD
Date reviewed: August 2012