Question

(1) The physiology behind Einthoven triangle. Please be sure to comment on why lead placement is important.

(2) How the signal is collected and processed. Please be sure to comment on what specific signal is being measured.

(3) How, based on the collected data, one could use frequency analysis to determine the number of heartbeats per minute.

(4) Would a developing fetus have an increased or decreased cardiac frequency and compared to a healthy adult?

Answer 1

(1) Einthoven's triangle is basically an imaginary formation of three limb leads in a triangle used in electrocardiography​​​​​​, formed by two shoulders and the pubis.

The physiology behind Einthoven's triangle is the shape forms an inverted equilateral triangle with the heart at the center that produces zero potential when the voltages are summed. Einthoven's used these measuring points, by immersing the hands and foot in pails of salt water, as the contacts of his string galvanometer, the first practical ECG machine.

Lead placement is so important because it is the significant source of electrocardiographic error that may lead to faulty diagnosis and improper clinical action.

(2) Each lead measures electric field created by heart during depolarization and repolarization of myocytes. The specific electric field signals can be represented as vector that changes continously and can be measured by recording the voltage difference between electrodes.

(3)