Center of Excellence: Ambulatory Cardiac Arrhythmia Monitoring

Types of electrocardiogram ECG monitors

• Holter monitor: A Holter monitor is usually indicated for people who have symptoms daily or almost daily. The monitor continuously records the heart’s electrical activity for up to 14 days. Electrophysiologists may also ask patients to keep a diary of their symptoms while wearing the monitor. After the prescribed time, the cartridge (with data on it) will be taken and uploaded to a server for the electrophysiologist to assess the data and determine next steps.
• Event monitor: Event monitors are usually preferred for people with less frequent symptoms and when a comprehensive view of all heart activity is not needed. These monitors can record the heart’s electrical activity over a more extended period of time. Unlike a Holter monitor, the event monitor only records cardiac events that are triggered by a patient or that are automatically trigged when there is an arrhythmia. Event monitors transmit data via a wireless network to a remote monitoring system.
• Mobile cardiac outpatient telemetry monitor: A mobile cardiac outpatient telemetry monitor (MCOT) is usually preferred for people with less frequent symptoms and when a comprehensive view of all of the heart’s electrical activity is needed. This device records and transmits data to a central monitoring station that is attended 24/7 by trained technicians. These monitors offer the potential for real-time identification of arrhythmias while immediately notifying the ordering electrophysiologist.
• Internal monitor: Internal monitors, such as insertable cardiac monitors (ICM) and implantable loop recorders (ILR), are usually indicated for people with infrequent symptoms that can be dangerous (such as fainting), for people who have not had success with other monitoring methods, or to evaluate cryptogenic stroke. Many times, people can also become frustrated with needing to wear ECG or event monitors multiple times; ILRs can alleviate this need.
  • The small device is placed under the skin in the left chest area via a minor outpatient procedure. The electrophysiology procedure is performed using local anesthesia, only requiring a very small incision and taking about 1-2 hours.
  • The monitor can be triggered by the patient or caregiver and can automatically trigger when an arrhythmia is detected. The monitor sends signals wirelessly to a remote monitoring location attended 24/7 by trained technicians. This data can be accessed by the ordering electrophysiologist. There are several EP studies showing that remote monitoring helps to detect cardiovascular changes. These small devices can usually record activity for up to 3 years.
• Loop recorders:
  • Atrial fibrillation: Atrial fibrillation can be symptomatic or asymptomatic, brief or long lasting, and frequent or less frequent, making it challenging to identify by an electrocardiogram, Holter monitor, or event monitor. Loop recorders can be helpful in the diagnosis of infrequent and asymptomatic episodes of atrial fibrillation. Also, compliance with conventional monitoring beyond 2-4 weeks can be difficult for many people and EP studies show that the longer we monitor the heart rhythm of people at risk for atrial fibrillation, the higher the likelihood of diagnosis. Loop recorders can also provide valuable information after a catheter ablation. They can help an electrophysiologist decide when to stop blood thinners and detect if there is any continued asymptomatic atrial fibrillation.
  • Syncope: Implantable loop recorders (ILRs) are commonly used to evaluate the cause of recurrent fainting. These devices are especially useful if fainting is less frequent or if ECG monitors have not been able to reveal the cause of the heart’s electrical activity. When using a loop recorder, the detection rate of an underlying cause is about 75% and multiple EP studies have shown that the devices result in earlier diagnosis. One EP study showed that loop recorders help in diagnosing bradycardia (slow heart rate) in 55% of people versus 19% with other conventional testing methods.
  • Cryptogenic stroke: Stroke is a leading cause of death and disability. The majority of strokes are caused by a blood clot that blocks or narrows an artery depriving the brain of blood and oxygen. The initial diagnosis of stroke involves evaluation by the admitting doctor(s), a neurologist, and telemetry. Testing often includes a CT of the brain, MRI of the brain, 12-lead EKG, echocardiogram (TTE/TEE), and a carotid artery evaluation by doppler or magnetic resonance angiogram. After this, about 25% to 40% of stroke cases have no well-defined cause and are labelled as cryptogenic.
    • Atrial fibrillation can be a hard-to-detect cause of cryptogenic stroke and loop recorders can be a valuable tool to aid in diagnosis. In the CRYSTAL AF trial, 441 patients with cryptogenic stroke and no evidence of atrial fibrillation during 24 hours or more of ECG monitoring were randomly assigned to prolonged monitoring with an implantable loop recorder or to a control group with conventional follow-up. At six months, atrial fibrillation detection was significantly higher in the monitored group (8.9% versus 1.4% in the control group).
    • It has been clearly shown that oral anticoagulation in patients with atrial fibrillation and CHA2DS2-VASc score higher than 2, reduces stroke risk by about 65%. In cryptogenic stroke patients presenting with sinus rhythm, prolonged cardiac monitoring with an ILR can significantly increase the detection of occult atrial fibrillation. Such monitoring will allow physicians to reduce recurrent stroke by prompting the appropriate use of long-term anticoagulation.

Remote monitoring of cardiovascular implantable electronic devices

Remote monitoring of cardiovascular implantable devices (CIEDs) including loop recorders, pacemakers, and defibrillators, allows the electrophysiology care team to check a device without the patient having to go into the clinic. Remote monitors also check for device battery life and proper functioning

The implant site and device are usually checked in the clinic at about one week post-implantation. After that, a patient is usually not required to come to the clinic for subsequent device checks.

Remote monitors use a home transmitter that are plugged into an electrical outlet in the bedroom. They do not require a telephone or internet connection. The transmitter will be provided to the patient after device implantation.

Commercially available wearable cardiac monitoring devices

Wearable devices are becoming more popular, and as technology advances they may become increasingly useful in the diagnosis and management of arrhythmias. These devices include:

• Smart watches
• Smartphone camera-based apps
• Smartphone ECG cases