What does "M-mode" echocardiography measure?

M-mode echocardiography specifically focuses on evaluating the motion of cardiac structures over time, allowing for detailed analysis of the movement of the heart's walls and valves. This mode sends a single beam of ultrasound and documents the motion of structures as a continuous line, producing a one-dimensional time-motion graph. By capturing these movements, clinicians can assess how well the heart is functioning and identify any abnormalities in cardiac structure motion, such as in conditions like aortic stenosis or mitral valve prolapse.

The other options discuss aspects of echocardiography but do not accurately define M-mode. For instance, measuring blood flow velocities across valves pertains to Doppler echocardiography. Static images of cardiac structures relate to two-dimensional echocardiography, which provides snapshots but does not illustrate motion over time. Evaluating electrocardiographic heart rhythms falls under a completely different domain of cardiac diagnostics focused on electrical activity rather than the mechanical function observed in M-mode. Understanding these distinctions is crucial for comprehending the varied echocardiographic techniques used for assessing cardiac performance.