Case

I have a 4-month old male in my office today for a well-infant check, who is growing well and doesn’t appear to have any clinical concerns but when I listen on cardiac exam, I am hearing some extra beats or changes in rhythm that seem a bit off. I’m thinking I should send him to you for evaluation. Should I order an event monitor or something first?

What am I thinking?

The first piece to the presentation is that the baby does not appear to have any clinical concerns which is usually a good sign. Hearing extra beats most commonly presents as a benign finding of a premature atrial beats or possibly premature ventricular beats. Sometimes the extra beat may not have anything to do with a change in rhythm and could represent just an extra auditory sound. Ordering the right test is important, but in an infant this young, obtaining a good family history for any inheritable disease is just as important.

History and physical

An infant history can clue any examiner to a potential etiology for extrasystoles noted on examination. Family history is a critical component to any evaluation within pediatrics, but particularly in the world of pediatric cardiology and electrophysiology. Understanding the familial patterns in the pediatric patient allows for a greater understanding for the potential of disease. It is often recommended to conduct a comprehensive family history including a genetic pedigree. As genetic disease may be undiagnosed or not shared with family members, asking questions focused on symptoms may be helpful. For example, obtaining a history for tuberous sclerosis may be focused on not only the existence of the diagnosis itself in the family history but also eliciting a history of seizures. When asking about family history of sudden death, it is helpful to elaborate on different forms including unexplained drownings, unexplained car accidents, or death while playing sports. The art of asking questions is a skill that must be practiced and configured to the clinical scenario. Asking questions surrounding serious conditions that may result in sudden death could raise unnecessary concerns in parents. Therefore, it is advised that asking the right questions should be equally coupled with actively listening for the right answer. Reading the situation, the patient, and the family can mean the difference between being led to a diagnosis versus being led astray.

Auscultation on the cardiac exam is what leads to the noted change in rhythm. Listening for an extended period of time and counting the number of extra beats may be helpful to determine the frequency. Auscultating for other cardiac sounds such as cardiac murmur may help indicate the possible presence of congenital heart disease. Additionally, if the extra beat is heard during every cardiac cycle (systole + diastole), this is likely to indicate a tie to an anatomic etiology. Arrhythmia-related changes usually are accompanied by a pause in rhythm and do not occur with every cardiac cycle. Stigmata for other diseases should be evaluated for physical examination (e.g., Ash Leaf macule).

Diagnostic testing

As mentioned previously, a standard electrocardiogram is the best initial test to order. If there are concerns for the possibility of structural heart disease from history and/or physical examination, an echocardiogram would be diagnostic. In the clinical scenario presented, the physician asks about an event monitor as the appropriate test to order. The answer depends on the frequency of the arrhythmia and the symptomatology presented by the patient. Different types of outpatient monitoring devices can be utilized for the recording of arrhythmias in patients, and a review of these devices is presented.

• (1)
  

  Holter monitor: A Holter monitor is a continuous monitoring device meaning that the rhythm of the patient will be recorded for the extent that the monitor is programmed and in contact with the patient. Most Holter monitors present with multiple leads to provide multichannel recording and can record between 24 and 48 h. Most Holter monitors are equipped with a button to signal the presence of a symptom by the patient, however, the button has no impact on the recording. For patients who have frequent rhythm concerns that are short-lived, with or without symptoms, a Holter monitor may be the best choice. Once completed, the monitor is returned for evaluation of all recorded rhythms and a report is provided.

  
  
• (2)
  

  Event monitor: An event monitor is a device that records on a continuous loop and stores the rhythm recorded when a button is pressed indicating when the patient felt a symptom. For those that remain on the skin surface, the total time before pressing the button and after pressing the button can be programmed (e.g., 2 s prerecording, 6 s postrecording) to help provide onset of arrhythmia. Other event monitors that do not remain on the skin surface can be placed on the skin if there are symptoms felt by the patient. These can be helpful in scenarios where the arrhythmia is felt to last for several seconds to minutes allowing time for the patient to obtain the monitor, connect it to the skin, and press the recording button. The onset of arrhythmia would not be recorded in such a scenario; however, the convenience of not wearing the monitor can be a benefit. These monitors are generally administered for 30 days at a time. Some monitors can connect to the monitoring center once a recording is obtained, via either a phone line or internet connection.

  
  
• (3)
  

  Intermediate-term monitoring: In recent years, there have been a number of technological advances that have allowed for the miniaturization of devices coupled with advances in skin adhesion that may allow for longer monitoring times. These devices are inconspicuous but usually accompanied by the trade-off of multi-lead for single-lead recording. Some may connect to a monitoring center while others must be sent after completion of the recording for analysis. Usually, these devices can act as both an event monitor and Holter monitor providing symptom-specific recording along with long-term recording. Monitoring can last anywhere between 2 weeks and 30 days but frequently depends on the length of time that the device is adhered to the skin.

  
  
• (4)
  

  Implantable loop recorder: An implantable loop recorder is a device that is implanted underneath the skin in a surgical procedure that will record under a continuous loop for up to 3 years. Recent advances have allowed the device to reduce in size to that of a large paper clip and only a few millimeters in thickness that can be implanted within minutes. The device can be programmed to monitor for any significant arrhythmias which will record if detected, regardless of patient symptoms. Patients are also provided with an activator that can be placed over the recorder implant location that can activate recording in the case of symptoms. These devices can be interrogated using specified computer systems either in person or from home. While costly, these devices may be helpful in patients who do not have frequent presentations but are potentially at risk for significant or life-threatening arrhythmias.

Action plan

The most common presentation for an infant with extrasystoles is that of premature atrial beats. This is usually diagnosed by electrocardiogram. Premature atrial beats may be conducted or nonconducted (blocked) through the AV node (refer to Chapter 2, Figure 2 and Chapter 1, Figure 2, respectively). Those that are conducted may result in aberrant conduction within the ventricle that may mimic a premature ventricular beat. As previously mentioned, infants with premature atrial beats have a normal prognosis and self-resolve over time. Premature ventricular beats should be monitored but generally also self-resolve. If the beat reflects a single reentrant beat, continued monitoring will often reveal short salvos of supraventricular tachycardia.

Conditions such as cardiac tumors do require regular monitoring and should have the participation of a pediatric cardiologist. In the setting of tuberous sclerosis, these rhabdomyomas will often reduce in size with time and will not require any form of surgical intervention. Rhabdomyomas are mostly located within the ventricle and should be monitored for the development of ventricular arrhythmias. Surgical intervention is reserved for those tubers that interfere with cardiac valve function, hemodynamic consequences, or recalcitrant arrhythmias. Fibromas generally do not reduce in size and often require surgical intervention for removal.