One-Dimensional Echocardiography: Still Needed or Already Outdated?

There is a widespread lack of knowledge about onedimensional echocardiography (M-mode) by the current generation of echocardiographers.Has two-dimensional echocardiography (B-mode) and Doppler made M-mode outdated?M-mode provides information that cannot be obtained by using B-mode or even Doppler-be it spectral, color, or tissue Doppler-for two reasons:1) M-mode provides temporal resolution of a structure at 2,000 frames per second, whereas B-mode provides only 30-100 frames per second.Sudden movement or amplitude definition is compromised on B-mode, but not on M-mode;2) Doppler defines the velocity of the flow, whereas the temporal variations of a structure visualized via M-mode show the volumetric changes of that flow.Now let us consider some conditions that can only be detected by M-mode and not by B-mode or Doppler, which can aid in the diagnosis via B-mode or in the understanding of pathologies.In left ventricular (LV) diastolic dysfunction, approximately 70% of LV filling occurs in the first third of diastole, the so-called rapid filling period of the LV.In impaired relaxation, this initial flow is slowed, and ventricular filling occurs predominantly in the last twothirds of diastole at the expense of atrial contraction. 1,2M-mode continuously displays the left atrium (LA) in a left parasternal section behind the aorta from the end of LV ejection, when it is at its largest, to after atrial contraction, when it is at its smallest diameter.In this way, it is possible to determine whether LA emptying (and thus LV filling) occurs mainly in the first-third of diastole or in the last two-thirds.If it occurs in the last two-thirds, the rapid filling phase of the LV is absent, which suggests an impaired relaxation.This is also seen in the region where the posterior valve merges with the mitral annulus, forming a prominence between the ventricular and atrial walls.This elevation, seen on M-mode, is pulled toward the apex during systole and returns to its original position at the end of diastole.This return occurs as the LV relaxes.If it returns less in the first third and more in the last two-third, LV relaxation is impaired.The key point is not the rate of return (detectable