External Loop Recording
The equipment that we use for recording the heart in patients who have symptoms suggestive of cardiac arrhythmias that occur intermittently and are short lived, is called a loop recorder. Essentially this is the same piece of equipment that we use for the cardiomemo recordings except in this case we place three electrodes (ECG leads) on the patient's chest and connect this to the event recorder. The recorder is now set to continuously record the patient's heart rhythm. As the symptoms are short lived and intermittent we set the recorder so that it functions rather like a black box recorder in an aeroplane. That is, it stores the record of the heart rhythm for a set amount of time and then starts to overwrite it from the beginning.
When the patient becomes aware of their symptoms they press a button on the device which then stores in its memory a portion of the heart recording including the moment the button was activated but also preceding and after the event. This ECG can then be sent electronically from the patient's home down a standard telephone line to an analyser which prints it out in the cardiology department.
The tracing illustrated is of a page of ECG obtained this way showing a rhythm abnormality called an SVT (supraventricular tachycardia).