In children with attention deficit hyperactivity disorder (ADHD), there has been some concern about the use of stimulant medicines and the need to have an electrocardiogram (ECG). As the number of children on stimulant medicine has increased, more doctors (and patients) are interested in when an ECG would be warranted.

Ronald Kanter, MD, discusses research studying the connection between ADHD medications and heart problems, and how ECG might be used to help detect problems.

-- Dennis Clements MD, PhD, MPH

Ronald J. Kanter, MD

Attention deficit hyperactivity disorder, or ADHD, is a commonly diagnosed condition in school-age children, especially boys. It is characterized by difficulty concentrating at a given task, increased and unwanted physical activity, and poor school performance.

The American Academy of Pediatrics has repeatedly emphasized the importance of identifying and treating children with ADHD, due to the higher likelihood of school failure if untreated.

Pediatricians are especially competent at diagnosing ADHD, especially since the advent of validated screening tools. The treatment for ADHD consists of both behavioral approaches and medication therapy.

Through scientifically sound clinical trials, medications known as amphetamines and amphetamine-like stimulants have been proven to help many children affected by ADHD. It is currently estimated that more than 2.5 million youngsters in the United States receive these drugs.

The medications under consideration include mixed amphetamine salts (Adderall XR), dextroamphetamine (Dexadrine), and methylphenidate (Ritalin, Metadate, Concerta, Focalin). They are chemically similar to the natural human stress hormones, adrenalin and noradrenalin; to the decongestants long used in over-the-counter cold remedies, pseudephedrine (“Sudafed”) and phenylpropanolamine; and to the now banned weight-losing dietary supplement, ephedra (also known as ma huang).

These chemicals all have the effects of raising blood pressure, raising heart rate, and increasing the oxygen requirements by body organs, especially the heart.

In people with certain types of heart disease, high levels of such chemicals can theoretically cause dangerous rapid heart rhythms and even sudden death. There have been several such events from ephedra use in high profile individuals, as recently as 2003.

In 2005, sudden unexpected deaths in 12 children receiving Adderall were reported to the United States Food and Drug Administration (USFDA) by a voluntary reporting organization of health care providers, known as the Adverse Event Reporting System. Five of those 12 children turned out to have underlying and previously undiagnosed structural heart disease. This event, plus the report of seven additional deaths in children receiving methylphenidate, prompted the USFDA to mandate distribution of a parental guide to the parents of any child for whom one of these medications has been prescribed.

This guide lists certain medical conditions that disqualify a child from receiving a stimulant drug: moderate-to-high blood pressure, overactive thyroid gland, a history of drug abuse, and certain psychiatric conditions. It also recommends careful consultation with the child’s provider, if the child has known heart, liver, or kidney disease; certain other psychiatric disorders; or seizures.

Screening to Identify Risk

Parents may wonder, “Why even take a chance, if these drugs are so dangerous?” Well, for the vast majority of children, they are quite safe. It should be emphasized that the tragic deaths reported above were from among tens, perhaps hundreds, of thousands of children using stimulant drugs.

Nevertheless, health care officials and investigators are developing techniques to screen children prior to initiating medical therapy, in hopes of identifying those who are at special risk, especially of heart disease.

The results from a major USFDA-sponsored study, which was designed to evaluate cardiovascular risk factor identification from among more than 500,000 children having ADHD, is expected to be available later in 2010.

Electrocardiograms

A laboratory test, which has long been used to diagnose a variety of heart conditions and (in adults) to screen for overall risk of heart disease, is the electrocardiogram (ECG). This simple, painless, and relatively inexpensive test records the heart’s electrical activity.

Previous studies have shown that children having ADHD ordinarily have a normal ECG, and stimulant medications do not cause appreciable changes in the ECG. You may hear of children having ADHD and other conditions undergoing an ECG prior to starting medications. However, the accuracy of the ECG as a screening tool for heart disease in children prior to medication use is controversial.

There has long been interest in using the ECG to screen for heart disease in young athletes, as part of the “pre-participation” evaluation. In that experience in the United States, over-diagnosis of serious conditions by ECG that are not present and under-diagnosis of conditions which are serious have been impediments to widespread ECG use.

So, at least for now, prior to stimulant use, the standard of care requires that the provider performs a comprehensive medical history, family history, and physical examination, with emphasis on heart disease. If there are features which raise questions of cardiovascular disease, an ECG, and perhaps even an echocardiogram may be ordered.

-- Ronald J. Kanter, MD, is director of pediatric electrophysiology in Duke Pediatrics Division of Cardiology.

-- Dennis Clements, MD, PhD, MPH, is the chief of primary care pediatrics at Duke Children's Hospital.