M-Mode Echocardiographic Measurements

M-Mode Echocardiographic Measurements

M-Mode Echocardiographic Measurements
M-Mode Echocardiographic Measurements

M-Mode Echocardiography has good temporal resolution. Hence measurements of the left ventricle are often taken with M-Mode. End diastolic and end systolic volumes are estimated from these measurements. the stroke volume and ejection fraction are also calculated from these measurements. Usually M-Mode cursor is guided by a two dimensional image in the parasternal long axis view (seen as inset above). The position of the cursor corresponds to the M-Mode cut. The cut is at the chordal level for left ventricular measurements. The following measurements are marked out in the M-Mode tracing:

LVPWs: Left ventricular posterior wall, systolic

LVIDs: Left ventricular internal diameter, systolic

IVSs: Interventricular septum, systolic

LVPWd: Left ventricular posterior wall, diastolic

LVIDd: Left ventricular internal diameter, diastolic

IVSd: Interventricular septum, diastolic

From these measured values, other estimates are calculated by the computerized algorithm of the echocardiograph:

EDV: End diastolic volume.

IVS / LVPW: Ratio of thickness of IVS and LVPW in diastole. In asymmetric septal hypertrophy due to hypertrophic cardiomyopathy, this ratio is increased. It is reduced in septal thinning due to anterior wall myocardial infarction.

IVS %: Percentage systolic thickening of the interventricular septum. Systolic thickening is reduced in scars of myocardial infarction as well as in hypertrophic cardiomyopathy.

FS: Fractional shortening.

ESV: End systolic volume.

EF: Ejection fraction – the most important and popular measure of left ventricular systolic function. It is the ratio of stroke volume to end diastolic volume, expressed as percentage.

LVPW %: Systolic thickening of the left ventricular posterior wall – reduced in scarring due to myocardial infarction.

M-Mode measurements of the right ventricle (RV) are seldom taken as this view cuts only through the right ventricular outflow tract and does not assess the major part of the right ventricle. Calculation of ejection fraction of the right ventricle is difficult due to its complex shape.

Ideally the M-Mode tracing has to be timed with simultaneous ECG. But this is often not done as it is cumbersome to connect ECG leads in a busy echocardiography laboratory. If an ECG is attached, correct timing of end systole and end diastole is possible.

M-Mode measurements have an inherent limitation in that it is one dimensional. Better methods of assessing left ventricular function would be two dimensional or preferably three dimensional in modern echocardiographs. But it is often restricted to the research scenario, again due to constraints of time.

Measurements can be indexed according to body surface area (BSA) to allow comparison between individuals with different body sizes [1]. According to the American Society of Echocardiography and the European Association of Cardiovascular Imaging guideline 2015, 2D echocardiographic images are preferred to avoid oblique sections of the ventricle [1]. Theoretically, anatomical M-Mode in which computer software  corrects the obliquity, can give better M-Mode measurements. But errors could be there if the angle correction is high.

Vivek Sullere et al have published the data of 707 healthy Indian adults for echocardiographic measurements including M-Mode, among other modalities [2].

References

  1. Lang RM, Badano LP, Mor-Avi V, Afilalo J, Armstrong A, Ernande L, Flachskampf FA, Foster E, Goldstein SA, Kuznetsova T, Lancellotti P, Muraru D, Picard MH, Rietzschel ER, Rudski L, Spencer KT, Tsang W, Voigt JU. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2015 Jan;28(1):1-39.e14. doi: 10.1016/j.echo.2014.10.003. PMID: 25559473.
  2. Sullere V, Jain D, Sullere S, Anthony C. Global longitudinal strain, ejection fraction, effort tolerance and normal echocardiography measurements in healthy Indians. Indian Heart J. 2018 Sep-Oct;70(5):637-641. doi: 10.1016/j.ihj.2018.05.018. Epub 2018 Jun 14. PMID: 30392501; PMCID: PMC6204477.