The earliest form of echocardiography/cardiac sonography is A-mode. M-mode. 3D/4D. B-mode

The earliest form of echocardiography is M-mode.

M-mode echocardiography, or motion mode, was developed in the 1950s and is the earliest form of cardiac ultrasound. It provides a one-dimensional view of the heart's motion over time, allowing clinicians to measure structures and observe heart motion in a simplified manner. Although A-mode, B-mode, and 3D/4D techniques are essential in cardiac imaging and have been developed later, they are not considered the earliest form of echocardiography. M-mode remains a foundational technique in cardiac sonography, serving as a basis for more complex imaging modalities.