ECG records heart activity through suction cups or pad electrodes placed on the skin. Portable ECG units were developed in the 1990s and can be connected to personal computers. Holter monitors were an earlier version of portable ECGs. Handheld portable ECGs record heart activity and can be connected to a computer to print or save snapshots. They are less expensive than standard hospital machines but cannot match their high-quality graphics.
Electrocardiography (ECG or ECG) consists of making a recording of heart activity. This is done by placing suction cups or pad electrodes on the skin, with the main electrodes labeled leads 2 and 3. Additional electrodes, labeled aVR, aVL, aVF, and V1-V6, are also used. Each lead records signals generated by different areas of the heart, which are interpreted in the form of a graph produced by the ECG machine. The large equipment used for this monitoring was the only method available until the development of a portable ECG unit capable of recording heart activity using miniature electronic sensors.
After being invented in the early 1900s, ECG machines have standardized over time to the 12-lead unit used in medical facilities. Testing of precursors for portable ECGs was conducted in 1964 by the United States Public Health Service when nurses obtained four-lead ECGs from patients in their homes and telephoned them to a medical computer. In 1991, ECG readings were computerized, based on an analytical program called the Louvaine algorithm. This led to the development of portable ECG diagnostic units using standard 12-leads that could be connected to personal computers (PCs) and carried from room to room in hospitals and clinics.
A variant of portable ECG units was the Holter monitor, which had sensing leads attached to the patient’s chest and connected to a small recording unit worn on the belt. This allowed conditions such as irregular heartbeats to be monitored during daily activities outside of clinical trials. Holter monitors were an expensive and tedious means of monitoring, however, and smaller, battery-powered portable ECG monitoring units were developed to monitor heart activity more flexibly. Some of these were even capable of 12-lead recording; complete graphs can be stored on the unit and later printed with a PC printer.
A typical handheld portable ECG records heart activity by simply pressing it against the chest or palm of the hand to activate it. An actual heart rate graph does not appear on the display screen. It typically shows a one-channel graphical trace of your heart activity, which can be switched to show only a digital heart rate display.
Cardiac activity can be recorded at various durations and up to 400 “snapshot” waveforms can be recorded before the memory card becomes full. The portable ECG can then be connected to a computer and the software provided with the unit can be used to print or save the snapshots as a computer file.
Less expensive portable units have become a popular way to make a noninvasive recording of heart rhythms. Even with the optionally attached cables, however, they can’t match the high-quality graphics that can be obtained from standard hospital machines. There are also warnings against use on anyone who is pregnant or has a pacemaker.
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