One of the earliest forms of cardiac ultrasound is Motion or “M”-mode echocardiography. Utilizing a rapid updating of more than 1,000 Hz, a single crystal rapidly goes back and forth transmission and receiver modes. Because of this, the monitoring of structures that move rapidly inside the body such as valve leaflets is made possible, thereby allowing the examiner to appreciate the characteristic motions that the structures make. The data collected through M-mode can be either be recorded on paper or, using a sweep speed of 50–100 mm/s, displayed on a video monitor. Previously, dedicated crystals were used to perform this technique, but now, M-mode beam is typically done with the use of 2D imaging guidance.
A great advantage of M-mode echocardiography is its high temporal resolution which makes possible the identification of even the most subtle changes or abnormalities in the cardiac structures such as anterior mitral leaflet fluttering due to aortic insufficiency or vegetation movement. Add to this, measurements of cardiac dimensions such as endocardial thickness, chamber size, and even the detection of cardiomegaly can be done as well.