Holter Versus Event Monitor
Holter Monitoring has been the gold standard for ambulatory cardiac monitoring for nearly 4 decades. A traditional Holter monitor is generally prescribed for patients that complain of a variety of symptoms that can result from electrical instability in the heart. Such symptoms may include chest pain, shortness of breath, fatigue, palpitations, light headedness and syncope (fainting).
A Holter monitor is generally worn for a period of 24 hours but there is increasing evidence that more information can be captured if worn for an extended length of time. For instance, there is now a 14 Day Holter which is similar to a 24 hour but newer technology can now record this continuous ECG for up to 336 hours. Long term Holter can be useful in asymptomatic and transient arrhythmias that occur less frequently than a 24 hour period. Further, there is emerging clinical evidence that suggests that long term Holter monitoring can be useful in the detection & management of atrial fibrillation.
Cardiac Event Monitoring (also known as event monitoring) is a recording device that is worn for an extended period of time to capture cardiac abnormalities. Event monitoring is similar in length to a 14 day Holter monitor but the event recording device only captures a specified length of ECG. Event monitors do not record continuous ECG data but rather designed to capture the actual abnormality only.
Cardiac Event monitors can come in a variety of forms. There are standard loop recorders, auto detect recorders, wireless event monitors and post event monitors. The most common of all event monitors is the loop recorders. A loop monitor uses a loop recording methodology where it is constantly capturing data but only permanently stores data when the patient presses the ‘event’ button. Once the ‘event’ button is pressed by the patient, the monitor will store 90 seconds pre-event and 90 seconds post (after) the event button was pressed. The 3 minutes of ECG data that is then sent to the diagnostic laboratory for analysis.
After analysis of the stored cardiac event, the captured data is forwarded to the ordering physician or hospital. In many cases, the captured ECG event can lead to pharmacological therapies or other life saving procedures such the implantation of pacemaker in case of Bradycardia (slow heartbeat) or an ICD in case of Tachycardia (fast heartbeat). Event monitors areare very effective and efficient in detecting atrial arrhythmias and flutter i.e. fast heartbeat in the upper chambers of the heart.
Holter Monitoring Versus Event Monitoring
Event monitoring is generally prescribed for patient whose arrhythmic episodes that are transient or intermittent. As the patient is put on traditional Holter monitor for only a day, such episodes go missed or undetected. Event monitors are more effective as they are worn for a period of up to 30 days which in theory can capture wide range of heart rhythms and abnormalities.
Due to the long duration of event monitoring, it is logical that it may capture wide variety of heart rhythms are captured which helps in proper analysis and diagnosis. Studies suggest that the yield of symptomatic event monitor device is 50—60% as compared to that of Holter device whose yield is just 10%. Reason for the same is the variation of duration for which a patient is put on the two devices.
Event monitoring can often be a preferred method of cardiac monitoring compared to traditional Holter monitoring method due to its efficacy and easy to use features and extended battery life to capture events up to 30 days. Event monitoring can be very useful for syncope as this is a clear and distinct symptom felt by the patient. Syncope, as known in medical terms, is loss of consciousness. A person who has fainting spells may or may not return to full consciousness depending on whether he has benign or malignant syncope. Cardiac Event monitoring can help physicians identify the cause of the fainting spell which could be risks of sudden cardiac arrest