The heart is a pump. It's divided into a right and left side, each with an upper and lower section. The upper section, called an atrium, receives blood from the body and pumps it through a one-way valve into the lower section, called a ventricle. These valves prevent the backward flow of blood inside the heart. The right side of the heart receives the “blue” oxygen-poor blood from the body and pumps it to the lungs where oxygen is added. All the oxygen-poor blood pumped to the lungs returns to the left side of the heart as “red” oxygen-rich blood in an equal volume. This red oxygen-rich blood leaves the lungs and enters the left side of the heart. It's then pumped into the aorta, which distributes it throughout the body to provide necessary oxygen and nutrients for growth and normal body functions. As the body removes oxygen, the now oxygen-poor blood returns back to the right side of the heart and the cycle continues. A wall, called a septum, separates the two sides of the heart. In this way, there is no mixing of the red and blue blood. The heart muscle receives oxygen-rich blood from special blood vessels called the “coronary arteries.” The pumping function of the heart is controlled by an internal electrical system much like a battery and internal wires.
What Is Heart Failure?
For a child to grow and develop, the heart needs to maintain normal pump function, to provide optimal blood flow throughout the body. However, sometimes the heart of a child may not function normally. The term “heart failure” describes a heart that's not functioning properly. It does not mean that the heart has stopped working, but that it is not working as well as it should. Heart failure occurs in adults due to effects of smoking, high blood pressure, diabetes, coronary artery disease and bad heart valves. It can also occur in newborns, infants, toddlers and teenagers for other reasons. Since heart failure has different causes and outcomes, it's important to recognize how it's diagnosed, treated and even cured in younger children.
There are two primary causes for heart failure. The first, called “overcirculation failure,” occurs when blood mixes inside the heart due to a congenital heart defect. The second, call “pump failure,” occurs when the heart muscle becomes damaged and no longer contracts normally.
What Causes Heart Failure in Children?
- Overcirculation Failure: About 1 percent of all newborn infants will have some type of structural heart defect. In some of these defects, there are holes between the right and left chambers inside the heart. Because of these holes, the blue and red bloods mix inside the heart. A defect of blood vessels in the head or other parts of the body (AV malformation) can cause similar mixing of the blue and red blood but outside the heart. Abnormal heart valves can also cause heart failure. An abnormally formed valve that does not close properly causes blood to leak backwards. Rarely, a Strep throat infection can result in damage to otherwise normal heart valves, causing them to leak as well. Finally, low blood (anemia) can also result in heart failure. These defects lead to overcirculation failure. In each instance, an overload blood flow pattern occurs in one or more of the sections of the heart. The normal forward blood flow is interrupted and the heart becomes an inefficient pump.
- Pump Failure: As in the adult, a child’s heart may develop pump failure. This can be caused by a virus infection that damages otherwise normal heart muscle or from problems with the coronary arteries that occur from birth or are the result of infection and prevent effective blood flow to the heart muscle itself. Older children and teenagers may complain of becoming tired quickly, especially if a virus infection has caused heart muscle damage. Certain drugs, some necessary to treat other medical problems (like cancer or leukemia) can also damage the heart muscle. The heart’s electrical system also may be abnormal from birth or damaged by infection, causing the heart to beat too slow or too fast. Sometimes one of the heart valves does not open properly causing pressure to back up inside the heart chambers. Rarely, severe chest trauma may damage the heart. Children with muscular dystrophy may eventually also develop problems with their heart muscle. In all of these situations, the heart muscle fails to function normally and the heart becomes an inefficient pump.
How Is Heart Failure Identified?
In infants, heart failure often presents with breathing trouble, poor feeding, poor growth, excessive sweating or even low blood pressure. At times, heart failure can look like other problems such as colic, pneumonia, or other respiratory infections. Often parents may note that an infant takes longer to feed or becomes uninterested in feeding after a short time. If heart failure is caused by too rapid a heartbeat, parents may feel the rapid heartbeat through the chest wall when the infant is sleeping or resting quietly.
If your physician suspects that your child may be experiencing symptoms of heart failure, a chest x-ray may help to determine if the heart is enlarged. You also may be referred to a pediatric heart specialist (pediatric or congenital heart cardiologist) for further evaluation and testing. Additional tests can include an electrocardiogram (EKG) (more on EKG's) to evaluate the heart rhythm or an ultrasound of the heart (echocardiogram) [more on echocardiograms] to evaluate heart structure and function. Both of these tests are simple, typically performed in the physician’s office or clinic and are not painful for the child. However, depending on the child’s age and ability to cooperate, light sedation may be necessary to obtain the best test results.
Sometimes, older children (usually over age 4) may be asked to perform an exercise stress test to evaluate heart-lung function. At times a more detailed and invasive test, called a heart catheterization study, may be required. In this test, a small plastic tube (catheter) is placed inside the heart from a blood vessel in the leg or arm to record pressures and the amount of oxygen in the different parts of the heart. Commonly a small amount of an x-ray dye (contrast) material is injected to make a movie of the heart function and coronary arteries. The child usually receives deep sedation to ensure the best test results. Since this test is performed in a special catheterization procedure room or laboratory, a short admission to a hospital is often necessary.
How Is Heart Failure Treated?
If heart failure is caused by overcirculation due to a congenital heart defect, surgery is often necessary to repair the defect. Often your physician may initially treat your child with medications to help unload the excessive volume, lower blood pressure resistance and allow the heart’s pump function to improve. At times your child may need to be hospitalized to begin this treatment. These medications may include diuretics (water pills) and afterload reducers. Since overcirculation causes poor growth, your physician may consider nutritional supplements to ensure that your child is receiving enough calories to compensate for the increased energy requirements. Other dietary changes such as low salt and low fat diets may be discussed. Following appropriate treatment, your child’s condition and symptoms may improve. This is called compensated heart failure. However, the underlying cause may persist. If heart surgery is required, you will have the opportunity to discuss the types of surgery or other treatments available.
If the heart failure is caused by pump failure, the same medications listed above may be used. Sometimes other medications that lower blood pressure help the heart pump better. Hospitalization may be necessary to further improve heart function. At times, surgery may also be required, such as replacing a damaged heart valve.
Pump failure caused by too slow a heartbeat often requires a pacemaker (more on pacemakers). These small battery-operated devices are like tiny computers and are implanted under your child’s skin with a small wire connected to the heart. This requiresa surgical procedure. Pacemakers remind the heart to maintain a normal heart rate. If the pump failure is caused by the heart beating too fast, your child may require medications to control the heartbeat. At other times, a specialized heart catheterization procedure called radiofequency ablation may be recommended to correct the abnormal heart rhythm by applying short bursts of radio waves to the area of heart muscle causing the rapid heart beat.
Rarely, if pump failure is caused by irreversible muscle damage, heart function may not improve with medication but may continue to get worse. In this situation, a special pacemaker, mechanical pump (LVAD) or ECMO (extracorporeal membrane oxygenator) may be necessary to temporarily improve heart pump function. If heart muscle function continues to deteriorate despite therapy, your heart specialist may discuss the need for a heart transplant.
Heart failure can happen to all children. However, it is not necessarily a hopeless condition. Many of the causes can be repaired. It's important that parents and family members understand the causes and treatments of heart failure in children and to ensure that proper medical care is provided. As newer techniques and medications become available, most children with heart failure should be able to grow and lead active lives.