EP Lab Digest - May 2008 - (Page 60)

60 ECG 101 MAY 2008 ECG 101: Ambulatory ECG Monitoring Rakesh Latchamsetty, MD, and Abraham G. Kocheril, MD, FACC, FACP University of Illinois at Chicago Chicago, Illinois T he goals of this ECG 101 article are to define ambulatory electrocardiographic (ECG) monitoring, identify clinical scenarios where ambulatory monitoring has proven useful, and discuss the different types of monitoring available. We will highlight the three major categories of devices: Holter monitors, event recorders, and implantable loop recorders. Although implanted pacemakers and defibrillators also have monitoring capabilities, they are beyond the scope of this discussion. By the end of this article, the reader will be aware of the types of monitoring devices available and be able to select the appropriate device for a given clinical scenario. ECG provide a wide array of recording options. The type of patient and clinical indication will dictate which device and recording options are most appropriate. What is Ambulatory Monitoring? Ambulatory ECG monitoring is the continuous recording of ECG signals from patients while they are at home and engaged in routine daily activities. These are non-invasive or minimally invasive diagnostic exams that have been shown to be very efficacious and cost-effective in the right clinical scenario. From the pioneering work of Dr. Norman Holter, who published his landmark article in Science1 (1961) discussing a new technique for continuous portable electrocardiography, ambulatory ECG monitoring has evolved to include myriad device designs that What are Some Scenarios Where ECG Ambulatory Monitoring has Proven Useful? The most common indication for ambulatory ECG monitoring is to evaluate patients with symptoms (such as palpitations, atypical angina, or syncope) that suggest a possible arrhythmia or other electrocardiographic abnormality. The correlation of symptoms with the time of a recorded arrhythmia can often firmly establish or eliminate an etiology. The method of initiation for an arrhythmia is also often captured and can help identify the arrhythmia and guide therapy. ECG monitoring can also identify suspected abnormalities even when the patient remains asymptomatic. Another important use of ambulatory ECG monitoring is to monitor efficacy of antiarrhythmic therapy — both pharmaceutical and procedural. Many patients can be asymptomatic with rhythm disturbances (such as atrial fibrillation or ventricular tachycardia), and ambulatory monitoring may be necessary to identify the existing burden of the arrhythmia. This can help the clinician identify the success of the current therapy and guide any potential changes or additions to management. Ambulatory ECG monitoring has also been used to prognosticate patients with certain underlying cardiac conditions such as ischemic2 or nonischemic cardiomyopathy and congenital abnormalities.3 The presence of ventricular arrhythmias, abnormal heart rate variability, late potentials, and T wave alternans can all help identify patients at risk for potentially harmful arrhythmias. Silent ischemia can also be elucidated through ST segment changes found on monitoring. Despite this potential to effectively identify such disorders, it is important to remember that ambulatory monitoring is not indicated for patients who are clinically unstable. Patients with active and significant hemodynamic, ischemic, or arrhythmic compromise should be admitted directly for further evaluation and treatment. Given the large number of clinical uses for ambulatory monitoring, it is important to select the right test for the right clinical scenario. Next, we will discuss the three major categories of ambulatory monitoring: Holter monitors, event recorders, and implantable loop recorders. Holter Monitors Holter monitors are typically a continuous recording of several ECG channels for 24 to 48 hours. Any number of standard ECG leads are adhered to a patient’s chest and connected by wire to a digital or analog recording device. Patients are instructed to wear loose-fitting clothes over the leads and perform their usual activities, provided they keep the device dry. They are also asked to keep a log of their symptoms, noting both the nature of the symptoms and their time of occurrence.This log is then used to correlate the symptoms with the ECG recordings at that time. While the device is worn, Holter monitors provide a continuous and complete recording similar to full disclosure on inpatient telemetry. From the recordings, algorithms identify rhythm strips that are automatically selected and displayed to the reading clinician. Typically, highlighted rhythms include significant bradycardia or tachycardia outside of set heart rate limits, or significant heart rate variability within a short period of time. Other abnormalities such as heart block or rhythm irregularity can also be automatically identified. Also generated is an electronic statistical summary that includes heart rate ranges as well as frequencies of premature atrial and Ambulatory ECG monitoring is a safe and effective means of monitoring a patient’s heart rhythm on an outpatient basis. Figure 1. Female with ischemic cardiomyopathy was experiencing palpitations. Event recorder showed PVCs and episodes of sustained ventricular tachycardia. Figure 2. Male with recurrent syncope received an event recorder showing high-degree heart block.

Table of Contents Feed for the Digital Edition of EP Lab Digest - May 2008

EP Lab Digest - May 2008 Is There an Under-Referral of Women for Atrial Fibrillation Ablation? A Hybrid Approach to the Cure of Atrial Fibrillation Contents Letter from the Editor Spotlight Interview: University of Michigan Health System 10-Minute Interview: Amit J. Shanker, MD Modular EP Units: Are They Possible? One Hospital’s Experience All About My Job: Technician Supervisor (New Column!) Alcohol Septal Ablation in the Cath Lab: What is it All About? About the Canadian Heart Rhythm Society: Interview with Martin J. Gardner, MD, FRCP(C), FACC Email Discussion Group: May 2008 Second Annual Salary Survey My First Year in Electrophysiology: What Have I Got Myself Into? Highlight on Technology: Video-Audio Integration for the EP Lab On the Horizon: A New Remote Catheter Manipulation System Striving for Excellence in the Care of Cardiac Patients Five Reasons to Participate with a Professional Organization Suspected Shunting of Defibrillation Energy in the EP Lab Can Digital Music Players Cause Interference with Implantable Devices? ECG 101: Ambulatory ECG Monitoring Events Calendar Industry News and Products Classifieds Advertisers Index

EP Lab Digest - May 2008

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