Study Sheds New Light On Pediatric Heart Conditions

Registry Points To Genetics In Some Cases

A report from a data registry on the sometimes-fatal childhood condition called pediatric cardiomyopathy provides insights into this disease.

It also points the way toward better diagnosis and perhaps even treatment, says an expert who started the registry.

The report finds the rare condition is more likely to strike boys than girls, and is more common among African Americans and Hispanics than Caucasians.

Cardiomyopathy consists of a family of conditions that affect the heart muscle. About 1,000 children are born in the US each year with a form of cardiomyopathy.

Progress in Treatment Is Lacking

While enormous strides have been made in treating conditions caused by problems with the heart's blood vessels, little progress has been made on heart muscle problems. A transplant is the only hope for many young cardiomyopathy patients.

"The time to transplantation or death for children with cardiomyopathy has not improved during the last 35 years," says a new report in the New England Journal of Medicine.

That report provides precise information about pediatric cardiomyopathy, such as when it is diagnosed, its incidence in different ethnic groups, and the percentage of the different kinds of cardiomyopathy. The regions of the country covered in the report are New England and the central southwest, which includes Texas, Oklahoma, and Arkansas.

Those numbers alone represent something new, says study author Dr. Steven E. Lipshultz, who started the Pediatric Cardiomyopathy Registry when he was at Boston Children's Hospital. He is now a professor of pediatrics at the University of Rochester School of Medicine in New York.

"If you look at some of the current textbooks in pediatric cardiology, you will find they state that hypertrophic cardiomyopathy [in which the heart muscle is abnormally thickened] is rare in adolescents," says Dr. Lipshultz, after reflecting on new information from the registry. "That is not true."

The registry says 42 percent of cases are hypertrophic, while 51 percent are dilated, in which the heart muscle expands abnormally, with scattered other causes accounting for the remainder.

Families May Consider Screening

And while pediatric cardiologists said in a survey the condition could be detected at almost any age, the registry shows most cases being diagnosed in the first year of life, Dr. Lipshultz says.

"That suggests that many of the causes are genetic, while in adults many cases are related to health habit issues," he says.

Other indicators that genetics is important are striking differences in incidence between the sexes and ethnic groups.

The incidence is 1.32 per 1,000 in boys compared to 0.92 per 1,000 in girls, in large part because several genes for neuromuscular disease that can also cause cardiomyopathy are more common in boys.

The condition is more common in African-American children (1.4 cases per 1,000) and in Hispanics (1.41 per 1,000) than in Caucasians (1.06 per 1,000). The incidence was about 50 percent higher in the Southwest than in New England, a finding that leaves the researchers puzzled.

The effect of genetics can be important in early detection, Dr. Lipshultz says. It is important to screen other family members when a case is diagnosed, he says, to pick up cardiomyopathy that may be causing few or no symptoms.

Second Study Finds Similar Trends

What Lipshultz also finds striking is that a study done in Australia, and reported in the same issue of the journal, produces very similar numbers.

"These two studies, done without knowledge of each other, have come up with almost the same results," Dr. Lipshultz says.

That study, led by Dr. Robert G. Weintraub of the Royal Children's Hospital in Melbourne, covered all known cases diagnosed in children 10 and under between 1987 and 1996.

It found about the same overall incidence, 1.24 per 1,000, the same concentration of diagnoses in the first year of life and the same higher incidence in a minority group, in this case Australian aborigines (2.47 per 1,000).

"It is remarkable" the studies have similar results, but also fortunate, Dr. Weintraub says. "We think that the two studies serve as external validation to each other."

Dr. Weintraub is director of the heart transplant program at Royal Children's Hospital, which serves all of Australia. He says the study was undertaken "to better gain an appreciation of how to plan heart transplantation for those children who require it."

The study has helped to give "a better appreciation of how these cases present and behave, so we can make long-term predictions about which children will require transplants," he says.

Always consult your physician for more information.

What Is Cardiomyopathy?

Cardiomyopathy is any disease of the heart muscle in which the heart loses its ability to pump blood effectively.

In some instances, heart rhythm is disturbed, leading to irregular heartbeats, or arrhythmias. There may be multiple causes of cardiomyopathy, including viral infections. Sometimes, the exact cause of the muscle disease is never found.

Cardiomyopathy differs from many of the other disorders of the heart in several ways, including the following:

• Cardiomyopathy can, and often does, occur in the young.
  
• The condition is fairly uncommon, affecting only about 50,000 Americans (adults and children).
  
• Cardiomyopathy is a leading cause for heart transplantation.
  
• The condition tends to be progressive and sometimes worsens fairly quickly.
  
• It may be associated with diseases involving other organs, as well as the heart.

Always consult your physician for more information.

Online Resources  

American Academy of Pediatrics

American Heart Association

Centers for Disease Control and Prevention (CDC)

National Heart, Lung, and Blood Institute (NHLBI) 

National Institutes of Health (NIH)        

• irregular heart rhythms
• risk of blood clots
• congestive heart failure

Various infections (including viral) which lead to an inflammation of the heart muscle (myocarditis) can cause this type of cardiomyopathy.

Contact with toxins or very powerful therapeutic drugs, such as certain types of chemotherapy given to fight cancer, have been known to cause dilated cardiomyopathy.

Heredity can also be a factor. Twenty percent of people with dilated cardiomyopathy have a parent or sibling with the disease.

In many cases, a specific cause for this type of the disease is never identified.

Because the heart muscle is weak and unable to pump enough blood to meet the body's demands, the body tries to preserve blood flow to essential organs such as the brain and kidneys by reducing blood flow to other areas of the body, such as the skin and muscles.

The following are the most common symptoms of dilated cardiomyopathy. However, each child may experience symptoms differently.

Symptoms may include:

• pale or ashen skin color
• cool, sweaty skin
• rapid heart rate
• rapid breathing rate
• shortness of breath
• fatigue
• irritability
• chest pain
• poor appetite
• slow growth

hypertrophic cardiomyopathy (Also known as hypertrophic obstructive cardiomyopathy, HOCM; asymmetric septal hypertrophy, ASH; or idiopathic hypertrophic subaortic stenosis, IHSS.)

In this type of cardiomyopathy, the muscle mass of the left ventricle of the heart is larger than normal, or the wall between the two ventricles (septum) becomes enlarged.

These abnormalities obstruct the blood flow from the left ventricle.
The thickened muscle or septal wall can also affect one of the leaflets of the mitral valve, which separates the left atrium and the left ventricle. The valve leaflet becomes leaky, allowing blood to move backwards from the left ventricle into the left atrium, instead of forward to the body.

Hypertrophic cardiomyopathy is often hereditary. One-half of children with the disease have a parent or sibling with varying degrees of left ventricular muscle or ventricular wall enlargement, although relatives may or may not have symptoms.

Children with hypertrophic cardiomyopathy may have symptoms that increase with exertion or symptoms may be unpredictable.

Symptoms may include shortness of breath on exertion; dizziness; fainting; chest pain; or abnormal heart rhythms. However, each child may experience symptoms differently.

Consult your child's physician for more information regarding the specific outlook for your child.