This chapter discusses the use of M-mode (movement/motion mode) and its role in neonatal functional echocardiography, as well as common measurements obtained with two-dimensional (2D) imaging.
The original description of M-mode echocardiography in 1953 by Dr. Inge Edler and physicist Hellmuth Hertz marked the beginning of a new noninvasive diagnostic technique. This technique was initially used primarily for the preoperative study of mitral valve stenosis. M-mode is also frequently referred to as an “ice pick view of the heart” for the following reason: Dr. Edler, while pioneering this “new” technology, had realized that a characteristic pattern of echo signals was obtained in patients who displayed mitral stenosis. Determined to find the origin of these signals, he initially performed experiments on calf hearts and later, to verify his observations, he performed ultrasound examinations on dying patients. Upon completion of an examination, he marked the direction of the ultrasonic beam on the patient's chest. After the patient died, he reportedly passed an ice pick through the chest wall in the direction taken by the ultrasonic beam. On postmortem examination, Edler found that the needle had pierced the anterior wall of the right ventricle, had passed through the right ventricular outflow tract, the interventricular septum, and the upper part of the left ventricle, and had entered the left atrium via the mitral valve. Dr. Edler realized that the anterior cusp of the mitral valve was responsible for the echo signal in question.1
Another key element in the development of medical ultrasonography was making ultrasound waves visible on the screen. In other words, the returning echoes needed to be displayed in a way that would enable visualization of the cardiac structures. The first display mode was called the amplitude modulated or A-mode display. In A-mode, the presence of a “structure” on the ultrasound beam's path is represented on the screen by a positive deflection (spike) and the strength of the returning signal is represented by its height (amplitude). In intensity modulated display—also known as B-mode (B = brightness)—the signals are converted from spikes to dots. The taller the spikes (the greater the amplitude of the signal), the brighter the dots. This forms the basis of M-mode as well as 2D imaging (Figure 5-1).
FIGURE and VIDEO 5-1.
Schematic drawings showing the 2D parasternal short-axis view of the heart at the level of the mitral valve leaflet tips with corresponding illustrations of A-mode, B-mode, and M-mode assuming single ultrasound beam. Abbreviations: RV, right ventricle; LV, left ventricle.
Video 5-1: Normal Systolic Function (> 30% change in radius)
Since the cardiac structures are constantly moving, the echo dots from these moving ...