M-mode echocardiogram in left ventricular dysfunction

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Assessment of left ventricular function is one of the very few instances when M-mode echocardiography is being used currently. In the beginning of the era of echocardiography when only M-mode was available and no 2D (two dimensional) imaging was available, detection of pericardial effusion was one of the important uses for it. Pericardial effusion used to be detected by the presence of anterior and posterior echo free space beyond the heart.

M-mode echo showing B hump in mitral valve tracing
M-mode echo showing B hump in mitral valve tracing

This is an M-mode cut taken from the parasternal view, guiding the position of the cursor using the parasternal long axis 2D view, which is seen in the top panel. It is immaterial whether the cursor is placed in the parasternal short axis view or long axis view as the M-mode imaging is one dimensional – an icepick of the heart. The cut in this case is through the tip of the mitral valve rather than at the chordal level which is used for measuring left ventricular dimensions and estimating the ejection fraction. Here the cut has been taken at the tip of the mitral valve to demonstrate other features of left ventricular dysfunction in this case.
The top most echo band below the chest wall represents the movements and thickness (vertical axis) of the right ventricular free wall (RVFW). The horizontal axis in this case represents time. M-mode was also called TM (Time-motion) mode and later abbreviated to M-mode. Downward excursion indicates the systolic contraction of the RV free wall. The echo free space below that represents the right ventricle, usually near the outflow region. Terminating the echo free region of the RV is the band of echoes from the interventricular septum (IVS). Normally the septal echo moves downwards to the left ventricular posterior wall (LVPW) in systole, though the motion is not totally in phase with that of the posterior wall. Here the amplitude contraction of the IVS is diminished and the pattern is somewhat biphasic. Below the IVS, within the left ventricular cavity (LV), the movement pattern of two leaflets of the mitral valve are visible.

M-mode echo in left ventricular dysfunction due to anthracycline related cardiomyopathy - annotated
M-mode echo in left ventricular dysfunction due to anthracycline related cardiomyopathy – annotated

C is the systolic closure point of the mitral valve. CD segment represents systole. Some systolic separation between the anterior and posterior leaflets could indicate mitral regurgitation, though this finding is not that specific. The motion of anterior mitral leaflet (AML) is M shaped while that of posterior mitral leaflet (PML) has a complementary W shape. In systole both meet and form a single line without any separation in normal case. The amplitude of excursions of PML are less than that of AML, which is also a larger leaflet. When the left ventricular function is normal the opening excursion (DE) reaches almost upto the IVS, with very little separation between the two. The separation is called E point septal separation (EPSS), which is less than 5 mm normally. In this case the separation is increased due to the left ventricular dysfunction and is over 9.5 mm. E wave occurs during the early diastolic opening of the mitral valve. The nadir of the E wave represents the F point. The EF slope is reduced in mitral stenosis, with almost a horizontal EF in severe mitral stenosis. A wave occurs during atrial systole and is absent in atrial fibrillation. Beyond the A wave, a B hump may be visible in cases with left ventricular dysfunction and an elevated left ventricular end diastolic pressure as in the current illustration. The contractions of the posterior wall are also diminshed due to global left ventricular dysfunction, in this case due to doxorubicin related cardiomyopathy.

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