Ambulatory Electrocardiographic Monitoring
Ambulatory electrocardiographic monitoring can be useful for the detection and quantification of arrhythmia burden. Many arrhythmias are transient, making capture via a 12-lead EKG difficult or impractical. Many of these arrhythmias can be harmless, but symptoms of palpitations or syncope in patients with a history of structural heart disease can be particularly worrisome. Ambulatory monitoring is particularly useful to correlate symptoms with the presence of an arrhythmia (detection) and to assess the success of medical therapy on arrhythmia burden. Two broad categories of ambulatory electrocardiographic monitoring covered in this discussion include:
- Continuous ambulatory EKG recording (Holter monitor)
- Patient-triggered, symptom-related EKG recording (Event monitor)
An ambulatory 24- or 48-hour Holter monitor, or continuous extended EKG recording, is a diagnostic option in those cardiac arrhythmias that are transient and difficult to capture. However, as with an Event monitor, these devices capture only two or three EKG leads, thus providing your physician with much less information regarding the electrical activation of the heart. This may make the precise diagnosis of your arrhythmia difficult. Patients are instructed to maintain a Holter“diary”, recording both the symptoms and the time they occur for correlation with downloaded data. The efficacy of medical therapy, in particular antiarrhythmics, on arrhythmia burden can be inferred with these continuous EKG recordings. In addition, cyclic variations in arrhythmia or overall heart rate trends can also be determined. For instance, this can be important in the analysis of the heart rate response to medications for the control of the ventricular rate during episodes of atrial fibrillation.
Patient-triggered, symptom-related Event monitors allow for the episodic capture of symptomatic arrhythmias. These monitors can be used for extended periods, especially useful for symptomatic arrhythmias that are difficult to capture given their rare and unpredictable occurrence. Current devices allow the patient to record an EKG strip during a symptomatic episode, store it for a limited time in the device, and then transmit the information via telephone to a central server. This data is then decoded and formatted for transmission to your physician, typically via facsimile.
Due to the transient nature of many of these arrhythmias, “loop monitors” have been designed to continuously record electrocardiographic data. Once the patient-triggered button is activated, it can record data from seconds to minutes prior to the event, up to several minutes thereafter for transmission. This allows your physician a clear view of the onset of the arrhythmia and possibly even termination.
Ambulatory monitoring is a valuable, widely employed tool useful to quantify transient symptomatic events in patients. It is a harmless and painless technique for not only arrhythmia detection, but also arrhythmia burden and its response to medical intervention.