Case
Hi, thanks for taking my call. I have a 3 year-old boy in my office today who I am seeing for a well-child check. I have been following him since he was born and he really hasn’t had any issues. His parents are great and come in for routine follow ups. He is keeping up with his developmental milestones and he is up to date with all his immunizations. But I am listening to him today and his heart rate seems kind of slow. I don’t know what to make of it. His parents say that he is an active three year old and has lots of energy. They have noticed nothing out of the ordinary or concerning to them- but this heart rate just gets me. When I count it out, I get a rate of 70 bpm at rest. We have a blood pressure machine here and he has a normal blood pressure for age, but it reads a heart rate of 65 bpm! What do you think? Should I send him to you for evaluation? Am I missing something?
What am I thinking?
Heart rates in children can be so varied. Here, we have a toddler that is asymptomatic, doing well, growing well, and there is no real concern, but the heart rate was found to be low for age. Here, my advice would be to “trust your gut” because, in most cases, your “gut” is right! The patient’s clinical status should always be the guiding principal in any concern for rhythm-related issues and the fact that this toddler is doing well should not alarm us about a low heart rate for age. The lack of symptoms is the key. There are evaluations that we can perform but overall, nothing particularly worrisome here.
| Differential diagnosis |
|---|
| Likely |
| Sinus bradycardia for age Normal sinus arrhythmia |
| Possible |
| Nonconducted premature atrial beats |
| Rare |
| 2nd or 3rd degree AV block, congenital 2nd or 3rd degree AV block, acquired
|
History and physical
As with all potential arrhythmias, the first thing to establish is the symptomatology of the patient. In the scenario of bradycardia, the concern is that the heart rate that drives cardiac output is insufficient. In this rare case, the patient may experience dizziness, fatigue with activity, and/or syncope. Most often, patients are asymptomatic at presentation but any suggestion of inadequate cardiac output warrants further investigation. Eliciting history of a previous viral illness or sick contacts in the prior 2 weeks may suggest a rare myocarditis picture when combined with established conduction disease. Travel history to areas endemic to tick-borne illnesses such as Lyme disease should be obtained. Lastly, the family history of any individuals with conduction disorders with the need for a pacemaker should be asked about.
Physical examination may be entirely normal except for heart rate. Upon auscultation of the heart rate, assessment of the rhythmic beating can be a distinguishing feature. Contrast a consistent sinus bradycardia rate versus that of varying rates related to normal sinus arrhythmia (see Fig. 8.1 ). Here, the heart rate increases with inspiration and decreases with expiration. A helpful finding is to determine heart rate response to activity. Asking the child to be active and then listening to the heart rate to determine if there is an appropriate tachycardic response is reassuring.
