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Cardiac Equipment (ECGs, Loop Recorders and Holter Monitors) to Diagnose Arrhythmias Part I of IV

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There are many common diagnostic equipment that a physician uses to evaluate patients suspected of having an arrhythmia.
Electrocardiogram (ECG): An ECG is the most basic tool used to evaluate patients with a suspected arrhythmia.  It is usually the initial test performed because it is the least invasive test.  An ECG detects and records the electrical activities of the heart.  To record these electrical activities from different angles, electrodes (sticky patches) are placed on the arms, legs, and over the chest.  With each and every heartbeat the electrical activities can be detected by the voltage difference between pairs of electrodes and translated into a graphical display.  Today’s standard ECG utilizes 12 electrodes, thus the name “12-Lead ECG.”  An ECG is useful in diagnosing an ongoing arrhythmia at the time the ECG is being performed.  This test has an extremely low diagnostic yield, when the symptoms suspected to be due to arrhythmia, are no longer present at the time of the evaluation.


12 lead ECG

Holter monitor: Holter monitors are ECG recorders that continuously record every heartbeat from a patient for a period of 24 – 48 hours.  Rather than having 12 leads, Holter monitoring is done with 3 leads.   Patients are hooked up with Holter monitors while in the physician’s office, hospital or clinic wearing it for 24 – 48 hours.   The patient may not shower and should avoid strenuous activities (unless specifically instructed by the physician) during the recording period.   At the end of the 24 -48 hour period, the patient may remove the unit and bring the unit back to the office for analysis.

The recording of the heart rhythm is made in a continuous fashion onto an electronic media, which is then subsequently downloaded into a computer and every beat analyzed by a technician.  This test is most useful if an arrhythmia occurs frequently enough to be “caught on tape” during that 24-48 hour period of recording.  It is very important for the patient to write down in a diary the symptoms that occurred during the recording period. This helps the physician to correlate the symptoms to actual arrhythmias found on the recording.  One important limitation of a Holter monitor is that it records only during that 24 -48 hours of time and may miss an infrequent arrhythmia. An arrhythmia that occurs only a few times a year is unlikely to be caught by chance during any single 24-hour period of recording.  In those cases, a loop recorder may be the preferred choice of test.


Digitrak XT Holter Monitor

Loop Recorder: Loop recorders are long-term (usually 14 days) monitoring devices that record patient activated events.   Similar to an ECG or Holter monitors, loop recorders record the electrical activities of the heart via electrodes placed on the patient’s chest.   The electrodes and wires are attached to patient’s chest and can be taken off and replaced as needed for a shower.   Unlike a Holter monitor, which records continuously, the loop recorder mostly records when activated by patients.   While the monitor continuously keeps a loop memory, the recording of the heartbeat and writing of the data onto the electronic media occurs only when patient activates the recording by pressing a button on the unit.   This allows the physician to correlate patient’s symptoms to what is recorded, thus confirming the cause of patient’s symptoms.  Another major advantage of a loop recorder is that it always keeps the preceding 40-60 seconds of data in the loop memory.   This allows the patient who was not able to trigger the recording immediately at the time of the symptoms, can do so a short time later and data will still be useful.


The newer types of loop recorders have automatic recording capability.   This is most useful in patients with suspected atrial fibrillation.  However, the automatic recording is not used to help explain patient’s symptoms as it is not patient-triggered.  It is only able to detect silent arrhythmias.   Once a recording is made successfully, the data can then be downloaded through the telephone to a centralized station, where a technician analyzes the ECG tracings and sends to the physician.   The physician can then correlate findings on the recording with patient’s symptoms.   After 14 days of monitoring, patients would usually make an appointment with the physician to review the results.


Braemar ER920 Loop Event Recorder

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