Echocardiography, ECG

Electrocardiogram. potential differences derived from the heart or its environment, which occur between different parts of the skin of the thorax and the extremities due to excitation of the heart muscles. The ECG provides information on heart rate, regularity of heart rhythm, excitation formation, propagation and regression of excitation and heart position, from which the causes of any disturbances can be deduced directly or indirectly.

https://de.wikipedia.org/wiki/Echokardiografie _{(Wikipedia CC-by-sa-3.0)}