Chapter 8
Holter Monitors, Event Monitors, Ambulatory Monitors, and Implantable Loop Recorders
1. What are the major indications for ambulatory electrocardiography (AECG) monitoring?
AECG monitoring allows the noninvasive evaluation of a suspected arrhythmia during normal daily activities. It aids in the diagnosis, documentation of frequency, severity, and correlation of an arrhythmia with symptoms such as palpitations, lightheadedness, or overt syncope. AECG monitoring can be extremely helpful in excluding an arrhythmia as a cause for a patient’s symptoms if there is no associated event during monitoring. AECG can also be used to assess antiarrhythmic drug response in patients with defined arrhythmias. Occasionally AECG is also used in other situations. The current major indications for AECG monitoring, from the American College of Cardiology/American Heart Association (ACC/AHA), are given in Box 8-1.
Box 8-1 SUMMARY OF THE AMERICAN COLLEGE OF CARDIOLOGY/AMERICAN HEART ASSOCIATION GUIDELINES FOR AMBULATORY ELECTROCARDIOGRAPHY
Class IIb (Usefulness/Efficacy Is Less Well Established by Evidence/Opinion)
Patients with episodic shortness of breath, chest pain, or fatigue that is not otherwise explained
To assess rate control during atrial fibrillation
Evaluation of patients with chest pain who cannot exercise
Preoperative evaluation for vascular surgery of patients who cannot exercise
Patients with known coronary artery disease and atypical chest pain syndrome
Patients with neurologic events, when transient atrial fibrillation or flutter is suspected
2. What are the different types of AECG monitoring available?
A Holter monitor constantly monitors and records two to three channels of ECG data for 24 to 48 hours. It is ideal for patients with episodes that occur daily.
Ambulatory real-time cardiac monitoring has various monikers. it has been termed ambulatory telemetry, real-time continuous cardiac monitoring, or mobile cardiac outpatient telemetry (MCOT). Ambulatory telemetry is a monitoring system that continuously records a 1- to 3-lead strip for 14 to 30 days. Depending on the vendor, the ECG data is either stored for offline interpretation or instantaneously transmitted for interpretation by a monitoring technician. In cases where the rhythm is monitored by a technician in real time, the patient or physician can be contacted immediately after an arrhythmia has been detected, to minimize delays in treatment. No patient action is necessary for an arrhythmia to be stored, and patient compliance can easily be assessed. These features facilitate the detection of silent or asymptomatic arrhythmias.
