Cardiac Arrhythmias and Holter Monitoring:
As we have understood in the section of Pacemakers, the electrical circuit of the heart plays an important role in the synchronized functioning of the heart. Any abnormality in this electrical system of the heart is called as an ‘Arrhythmia’ as it disturbs the rhythm of the heart.
Arrhythmias can be broadly of 2 types. Tachyarrhythmia and Brady-Arrhythmia. When the rhythm disturbance is associated with a significant increase in heart rate, it is called as a Tachyarrhythmia and an arrhythmia in which the heart rate slows down to abnormal lows, it is called as a Brady arrhythmia.
What do the Arrhythmias do?
As the arrhythmias disturb the synchrony of the heart, the end effect is that the heart fails in its function of perfusing the organs of the body. When the arrhythmias are of a moderate severity, they cause symptoms of dizziness, black outs or palpitations in which the patient becomes aware of his or her own heart beat. When the arrhythmias are of a significant severity, they result in reduced perfusion of the brain which can cause transient loss of consciousness or syncope or even death.
How do doctors evaluate the Arrhythmias?
Usually a resting ECG is not sufficient to diagnose a clinically significant arrhythmia. This is because most arrhythmias are transient and may not be present when the resting ECG is being taken. Hence, for the diagnosis of these arrhythmias, a continuous ECG recording is needed. This can be done using the Holter Monitoring system or the Loop recorder systems.
What is Holter Monitoring?
Holter monitoring device is a gadget which is attached to the body for 24 to 48 hours. It records the entire electrical activity of the heart over this duration, which can be interpreted after the device is removed. The device is of the size of a small camera and can be worn around the neck. The lead wires are connected to the skin. All routine day to day activities can be performed. In fact, the purpose of Holter monitoring is to record the ECG during the routine activities.
The patient is asked to maintain a diary during the period of monitoring in which he or she is asked to record the timing of the symptoms. This can be used to correlate the symptoms with the ECG findings at the time of the symptoms and can aid the diagnosis of symptomatic arrhythmias.
The only drawback of a 24-48 hour Holter monitoring is that those arrhythmias may get missed which don’t occur in this time period of monitoring. For this purpose, the loop recorders are which can record for longer time periods.
What are loop recorders?
Loop recorders are ECG recording devices with a longer storage capacity and battery life. There are 2 types of loop recorders viz. External Loop Recorder or ELR or Implantable Loop Recorder or ILR. The implantable loop reorders have battery longevity of up to 3 years and a recording ability of up to 50 minutes. The loop recorders are programmed to detect certain types of rhythm disturbances to start recording them at the same time, the recording can be activated by the patient when he or she notices the symptoms.
Essentially, the loop recorders help to record data over a longer period of time and hence are more productive in diagnosing symptomatic rhythm disturbances.
The Holter and Loop Monitoring systems help to find out:
- Whether your symptoms are correlating with the ECG disturbances
- Whether your medicines for prevention of rhythm disturbances are acting appropriately
- Whether there is a risk of arrhythmias after the acute phase of a heart attack is over
- Whether there are certain arrhythmias which come and go intermittently. Such arrhythmias are an important cause of strokes or paralytic attacks.
Care to be taken during long term ECG monitoring:
- Generally, during Holter monitoring, it is advisable to prevent water contact with the gadget. Hence showers or baths or swimming is to be avoided.
- Electromagnetic fields such as metal detectors, magnets, microwave ovens, electric blankets, and electric razors and toothbrushes can interrupt the signal from the electrodes to the Holter monitor.
- Cellphones and electronic music players are to be kept at least 6 inches away from the device to avoid interruptions in the signals.
All in all, the Holter and Loop Monitoring Systems are a big boon for Modern Medicine as they help to diagnose certain disturbances which are not very obvious on the surface and hence can help in preventing unexplained deaths.