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By Steve Dassel, MD
April 2009: Electrocardiology
This quarter I had a conversation with Dr. Terry Chun, MD, an electrocardiologist in the Division of Cardiology at Seattle Children's Hospital. Terry grew up in Southern California, attended Pomona College, took his medical degree in Philadelphia at Hahnemann University, and did a pediatric residency at Cedars-Sinai in Los Angeles and a pediatric cardiology fellowship at Cincinnati Children's. That was followed by a fellowship in both pediatric and adult electrophysiology - a combined program through Stanford and University of California, San Francisco. He has been at Seattle Children's since 2004 and is an assistant professor (up for associate) at the University of Washington.
Dr. Terry ChunQ: Terry, what is new in pediatric electrocardiology over the last several years?
A: Well, in the last 15 to 20 years, this field has evolved from being mostly diagnostic to the addition of interventional treatments as well. Examples are ablation of arrhythmias by catheterization, and inserting pacemakers and defibrillators. We can really improve the quality of life for kids with arrhythmias with these interventions. The medical management of arrhythmias has also become much more sophisticated with newer treatments for old problems.
Q: What are some examples?
A: Take the use of adenosine for the conversion of supraventricular tachycardia. This allows the quick conversion to take place in the emergency room or by paramedics, rather than a more intensive process, with more drugs in the hospital as we sometimes did before. Nowadays, we take for granted how easy it is. Another example is the use of amiodarone, a very powerful antiarrhythmic that can control life-threatening arrhythmias such as ventricular tachycardia, junctional ectopic tachycardia and sometimes supraventricular tachycardia. Many children will have a catheter ablation as first-line therapy for their arrhythmia these days, where in the past, that was only offered when they failed multiple drug therapy. So we can actually cure their arrhythmia instead of just treating the symptoms.
Q: Anything new in the way of diagnostic capabilities?
A: Yes, there are also new ways to diagnosis old problems. For example, electrocardiograms have been used for a long time to diagnose conditions like hypertrophic cardiomyopathy and long QT syndrome. Sometimes we can even use the tracing to stratify who is at highest risk, even in these groups.
Q: How about this computer analysis of electrocardiographic tracing?
A: Yes, nearly all electrocardiographic equipment comes with a computer that analyzes and prints out an interpretation.
Q: So is this going to put you out of business?
A: I'm not worried. It is so sensitive, it has a tendency to over-read minor things. On the other hand, it also rejects data that is out of its experience, so it can also under-read.
Q: Explain that to me.
A: The computer algorithm is highly sensitive, in order not to miss any pathology, but the cost of this is over-reading and reporting a lot of relatively benign minor variations that do not need to be treated, such as "nonspecific ST wave abnormalities."
Q: And under-reporting?
A: For example, if the QT interval is prolonged, it will report it. But when that measurement is severely prolonged, outside of the computer's parameters, it will report it as normal.
Q: It can say "normal electrocardiogram," but then under that it will have some phrase that confuses the normal electrocardiogram statement. How can I avoid that?
A: Well, let me give you a list of terms you may see that are normal or normal variants and do not require further workup unless clinical symptoms, exam or history suggest cardiac involvement. Phrases such as "sinus bradycardia," "sinus arrhythmia," "sinus tachycardia," "right ventricular conduction delay or incomplete right bundle branch block without right ventricular hypertrophy or right axis deviation," "isolated intraventricular conduction delay," "early repolarization," "nonspecific ST-T wave changes," "juvenile T wave pattern" - all of these are only minor variations that usually don't have any clinical significance in kids, assuming they don't have any history or exam to suggest actual cardiac disease. Right axis deviation can be normal in the 8-or-less-year-old. A corrected QT that is greater or equal to 0.45 by the computer but normal by hand calculation or a "borderline QT interval" of 0.44 to 0.45 can also be considered within normal limits.
Q: That ought to do it. Shifting focus a bit, should all athletes have a screening electrocardiogram?
A: That's a tricky question. It apparently works for the Italians. They screen all athletes down to school age, regardless of sport. Of course, the only way to do this is by establishing screening centers run by the state that are designed to look at all medical conditions that athletes can face - in particular, looking at all of these electrocardiograms obtained on everyone.
Q: And what is their yield?
A: They have had this program for about 25 years. They recently published their experience - that they have significantly reduced the number of cardiovascular deaths on the playing field, and in the last few years have had no deaths from hypertrophic cardiomyopathy. Their incidence of sudden death in nonathletes was unchanged. And their rates of sudden death from other kinds of heart disease did not change much.
Q: How would this translate to the United States?
A: We have an incidence of sudden death of approximately 1 in 300,000, which comes out to anywhere between about 1,000 to 7,000 sudden deaths in children yearly, from all causes. Fewer than 10% of these are from cardiac causes. About one-third of these are due to hypertrophic cardiomyopathy. Number 2 would be a long QT syndrome. A close number 3 is an abnormal coronary artery pattern, which of course would not be picked up by an electrocardiogram. A recent analysis of sudden deaths in young competitive athletes found the nationwide rate of sudden cardiac deaths to be about 50 to 100 cases per year. So there are obviously other populations that have a risk as well.
Q: The Italian program sounds impressive. Are you advocating that we do that?
A: No. It would be a huge manpower problem and very costly. Several people in the sudden-death research community have suggested that we would get far more bang for our buck investing that kind of money into immunizing kids who are underimmunized. Some small communities have tried to do similar programs, but the problem is sustainability on a large scale.
Q: Japan has routine electrocardiograph screening too. How does that work?
A: The Japanese are even more ambitious. They screen every newborn and every child - not just athletes - every five years, into adolescence.
Q: Are there problems with that approach?
A: Yes. In the first place, the newborn has normal variations, which correct in time and don't require treatment. In the second place, problems such as hypertrophic cardiomyopathy may not show until much later in life. That sort of program is best at picking up things like long QT syndrome. But there are a lot of false positives, as you can expect. Physical examination and pulse oximetry are far more useful in picking up structural heart disease in general.
Q: About a year ago there was a big flap about getting electrocardiograms on all kids who have ADHD before starting stimulant medication therapy. Comments on that?
A: The data did not support that recommendation, and the media picked up on it before it was reviewed. We saw an increase by tenfold in the number of electrocardiograms requested of us in the first week. As you know, a discussion followed between the American Heart Association, the American Academy of Pediatrics and the American Academy of Child and Adolescent Psychiatry. Subsequently, the American Heart Association modified its recommendation, and now everyone agrees a good history - including a good family history - be taken along with a physical examination, and if negative, an electrocardiogram is not necessary. I think everyone has come to their senses and has gotten the message. After a year, the requests for electrocardiograms are almost back to baseline.
Q: Are there any other reasons for doing a screening electrocardiogram?
A: We can see severe electrocardiographic abnormalities with extreme feeding issues. QT prolongation leading to ventricular arrhythmias have been reported in severe malnutrition such as anorexia nervosa and also with ketogenic diet for seizures.
Q: What is the pathophysiology of that?
A: No one knows for sure, but it probably has something to do with alteration in potassium metabolism.
Q: So all patients with anorexia nervosa should have an electrocardiogram?
A: I think it would be useful if there are signs of cardiac involvement, especially if they have bradycardia. Then one would follow with electrocardiograms, as well as doing whatever else one was doing to correct the underlying condition.
Q: Along the line of intervention, what do you do if you find hypertrophic cardiomyopathy?
A: You need to screen family members, consider beta blockers and restrict high-intensity athletics. In patients that seem to have a very high risk, we will implant a defibrillator to prevent sudden cardiac death.
Q: What about long QT syndrome?
A: Again, beta blockers, modified lifestyle with no high-intensity sports - and if there is syncope or extreme QT prolongation, consider defibrillator implantation. Genetic studies and family history help to separate high-risk long QT syndrome from those at lesser risk, and that subset of severe QT population may benefit from defibrillator implantation.
Q: What about the low-risk subset?
A: They would be candidates for a beta blocker.
Q: If screening for cardiac disease is deemed necessary, would echocardiography be a better way to go?
A: No, in general, electrocardiographic screening will have a higher yield. There are many causes of sudden cardiac arrest that would not be detected by echocardiogram. If the physical exam or electrocardiogram suggests it, an echocardiogram would be warranted. But echocardiograms are not an effective screening tool.
Q: Thanks, Terry.