M-mode

Question 1

M-mode refers to….?

Answer 1

Motion mode.

Displays cardiac structures in a 1D plane.

Only the structures associated with the cursor are seen in the M-mode image.
(Fig 3.1, 3.2, 3.3)

The resulting M-mode image has depth through the heart on the Y axis and time on the X axis.

Question 2

Characteristics of M-mode images?

Answer 2

• 1D image of structures
• Only structures associated with the cursor are seen
• Depth on the Y axis
• Time on the X axis
• Records subtle changes in wall and valve motion
• Used for accurate measurements of size

Question 3

M-mode echo has a very high ……………… when compared to 2D imaging and is superior to RT images for measuring size and recording sublet changes in wall and valve motion.

Answer 3

M-mode echo has a very high sampling rate when compared to 2D imaging and is superior to RT images for measuring size and recording sublet changes in wall and valve motion.

Question 4

M-mode images used for accurate assessment of size and function are obtained at the levels of the ……………(3)?

Answer 4

M-mode images used for accurate assessment of size and function are obtained at the levels of:
the left ventricle,
the mitral valve and
the aortic root.

Question 5

Once a RT image of good quality is obtained there are only 2 main controls needed to obtain an M-mode image: Which ones?

Answer 5

Once a RT image of good quality is obtained there are only 2 main controls needed to obtain an M-mode image: Cursor positioning and sweep speed.

Question 6

M-mode: The mitral valve has an M shape on the M-mode when the cursor is placed over the tios of the mitral valve.
Rapid ventricular filling during early diastole forces the septal leaflet open. The mural leaflet moves down toward the wall. As pressures equalizes between the left atrium and left ventricle, flow decreases and the leaflets move toward an almost closed position.
As the left atrium contracts and flow into the left ventricle increases, again the mitral valve moves up toward the septum again.

Answer 6

M-mode: The mitral valve has an M shape on the M-mode when the cursor is placed over the tios of the mitral valve.
Rapid ventricular filling during early diastole forces the septal leaflet open. The mural leaflet moves down toward the wall. As pressures equalizes between the left atrium and left ventricle, flow decreases and the leaflets move toward an almost closed position.
As the left atrium contracts and flow into the left ventricle increases, again the mitral valve moves up toward the septum again.

Fig 3.2

Question 7

M-mode: A cursor placed over the aorta displays the aorta as 2 parallel lines.
The aorta moves downward, and the left atrium becomes smaller as it empties during diastole. A line in the middle of the aorta represents the closed cusps during diastole. The aorta moves upward during systole, and the left atrium enlarges as it fills during this time period.

The aortic valve opens toward the walls of the aorta with the onset of systole, remains there for the duration of systole, and then moves rapidly to a closed position at the end of systole.

Answer 7

M-mode: A cursor placed over the aorta displays the aorta as 2 parallel lines.
The aorta moves downward, and the left atrium becomes smaller as it empties during diastole. A line in the middle of the aorta represents the closed cusps during diastole. The aorta moves upward during systole, and the left atrium enlarges as it fills during this time period.

The aortic valve opens toward the walls of the aorta with the onset of systole, remains there for the duration of systole, and then moves rapidly to a closed position at the end of systole.

Fig 3.3

Question 8

Sweep speed controls …?

Answer 8

How fast an image moves across the screen. The M-mode image can be compressed or expanded along the X axis.

Typical sweep speeds are 25,50, and 100 mm per second.
At 25 mm/sec many cardiac cycles are include on one frozen frae. At a sweep speed of 100 mm/sec, fewer cardiac cycles are seen per frame.

An increased sweep speed of 50-100 mm/sec is usually necessary with the high heart rates of cats, in order to better separate the events of diastole and systole.

Question 9

The M-mode image depends on?

Answer 9

Where the cursor is positioned on the RT image.

A track ball is used to move the cursor over the 2D image. Whatever structures the cursor transects will be displayed on the M-mode image.

Question 10

M-mode: Left ventricle:
Right parasternal long-axis:

LV images are obtained by placing the cursor perpendicular to the inter ventricular septum and LV free wall at the level of the chordae tendinae, between the tips of the mitral valve leaflets and the LV papillary muscles (Fig 3.1-3.5). Imaging planes include the right parasternal long-axis LV inflow outflow plane and transverse plane at the level of chordae.

Answer 10

M-mode: Left ventricle:

LV images are obtained by placing the cursor perpendicular to the inter ventricular septum and LV free wall at the level of the chordae tendinae, between the tips of the mitral valve leaflets and the LV papillary muscles (Fig 3.1-3.5). Imaging planes include the right parasternal long-axis LV inflow outflow plane and transverse plane at the level of chordae.

Question 11

An M-mode cursor placed throughout a tipped (apex up) LV outflow plane is often diagonal through the ventricle. Adjust the image so the inter ventricular septum and anterior aortic wall line up almost horizontally across the sector image.
Where should the M-mode cursor be placed?

Answer 11

The M-mode cursor is placed perpendicular to the inter ventricular septum and left ventricular wall below the tips of the mitral valves at the largest ventricular chamber size.
Take care to generate the M-mode from the best longitudinal image possible.
Do not foreshorten the ventricle; the LV wall and septum should be parallel to each other, the aortic valve should be seen, and mitral valve motion should show good excursion toward the septum.

Question 12

M-mode: On transvere images the cursor should be placed over the septum and free wall dissecting the image into perfect right and left halves. Which plane is the desired one for M-mode image generation?

Answer 12

fan the transducer from mitral valve to papillary muscle and the plane intercepting the chordae tendinae between both of these standard planes is the desired one for M-mode image generation of the left ventricle. Fig 3.5

Question 13

The right ventricle should be seen at the top of the sector image. What if it is not seen?

Answer 13

It it is not seen or the M-mode does not have a clearly defined top to the septum, the transducer is probably located too close to the apex of the heart.
Slide cranial an intercostal space, perhaps two in a large dog, and dorsal in the ic space (toward the heart base) in order to correct this problem. The crystals will probably have to be pointed a little more caudally as well after this move.

Question 14

M-mode LV: Imaging planes?

Answer 14

Right parasternal transverse LV

Right parasternal long axis LV outflow view

Question 15

M-mode Imaging technique: Place the cursor perpendicular to the septum and wall on all views.

The cursor should be between tips of the mitral valve and the papillary muscles at the level of the chordae and the largest LV dimension.
On transverse views the ventricle should be divided into equal and identical halves.

Answer 15

Place the cursor perpendicular to the septum and wall on all views.

The cursor should be between tips of the mitral valve and the papillary muscles at the level of the chordae and the largest LV dimension.
On transverse views the ventricle should be divided into equal and identical halves.

Question 16

The …………….., widest left ventricular chamber on long-axis imaging planes and the …………. circular left ventricle at the level of the chordae on transverse views should be used for M-mode images.

Answer 16

The longest, widest left ventricular chamber on long-axis imaging planes and the smallest circular left ventricle at the level of the chordae on transverse views should be used for M-mode images.
This sounds contradictory, but if the imaging plane is slightly lateral to midline on a long axis, the chamber will be smaller, and if the imaging plane is oblique to the transverse plane and not perpendicular to it, the left ventricle will be larger.

Question 17

The pericardium on an M-mode image is always a very bright line just below the LV free wall.

Answer 17

The pericardium on an M-mode image is always a very bright line just below the LV free wall.

Question 18

In many cases there is a slight ……………. dip of the posterior wall and a small ……………motion of the ventricular septum with atrial contraction. This will not be appreciated with fast heart rates.

Answer 18

In many cases there is a slight downward dip of the posterior wall and a small upward motion of the ventricular septum with atrial contraction. This will not be appreciated with fast heart rates.

Question 19

M-mode: mitral valve

Imaging planes:?

Answer 19

Right parasternal long-axis left ventricular view

Right parasternal transvere mitral valve view.

Question 20

Cursor position over the tips of the mitral valve leaflets produces an M-shaped structure on the M-mode image. The cursor should be positioned perpendicular to the septum and mitral valve leaflets.

Which views may be used?

Answer 20

The right parasternal long-axis left ventricular inflow outflow view or transverse view at the level of the mitral valve may be used.

Question 21

M-mode mitral valve: Imaging technique. How should this be performed on the long axis view and the transverse views?

Answer 21

Place the cursor perpendicular to the septum over the tips f the mitral valve on the long axis view.

On transverse views: place the cursor perpendicular to the valves as it divides the image into equal and similar halves.

Question 22

When using the long-axis image; make sure what?

Answer 22

Make sure the septum and free wall are parallel to each other, that the aortic valve is seen, and that the mitral valve leaflets move well.

Question 23

Initial motion of the valve reflects early diastole and rapid ventricular filling. The first peak of an M-shaped line, the …… point (for early filling) should almost touch the septum as it does on real-time images.

Answer 23

Initial motion of the valve reflects early diastole and rapid ventricular filling. The first peak of an M-shaped line, the E point (for early filling) should almost touch the septum as it does on real-time images.

Question 24

The early filling phase of diastole is driven by…..

Answer 24

A pressure gradient.

Question 25

What creates the downward motion seen after the E point?

Answer 25

The left ventricle has just finished emptying while the left atrium has just completed its filling phase. As the left ventricle fills and the pressure differential decreases, flow through the valve decreases. This creates the downward motion seen after the E point as the valve leaflets do not remain fully open secondary to the decreased flow through the valve.

Question 26

The valve remains partially open during mid-diastole as blood flows slowly through it into the ventricles. Toward the end of diastole as the left atrium contracts, the valve leaflets are forced ……………………. by the rush of blood into the left ventricle associated with atrial systole.

Answer 26

The valve remains partially open during mid-diastole as blood flows slowly through it into the ventricles. Toward the end of diastole as the left atrium contracts, the valve leaflets are forced up toward the septum and down toward the wall again by the rush of blood into the left ventricle associated with atrial systole.

Question 27

Why is the A point of the “M” lower than the E point in a normal heart?

Answer 27

Since flow volume associated with atrial contraction is less during this phase, the amplitude of the second peak of the M, referred to as the A point (for atrial contraction), and is lower than the E point in a normal heart.

Question 28

What is the C point?

Answer 28

Following atrial contraction the leaflets move toward a closed position = the C point for closure, where they are displayed as multiple straight lines that move in a slightly upward direction on the M-mode throughout systole.

Question 29

Fig 3.9:
The mitral valve looks lika an M on the M-mode images. The ….. point represents maximum opening due to rapid ventricular filling. The …… point represents maximum excursion following atrial contraction. The valve is represented by ……..during systole.

Answer 29

The mitral valve looks lika an M on the M-mode images. The E point represents maximum opening due to rapid ventricular filling. The A point represents maximum excursion following atrial contraction. The valve is represented by multiple lines during systole.

Question 30

What happens with the “M” when heart rates are high?

Answer 30

When heart rates are high, the two phases of ventricular filling coincide (as in the first three beats on this M-mode in Fig 3.10) and the mitral valve no longer has an M shape.

Question 31

What happens with the “M” when heart rates are slow?

Answer 31

Fig 3.11. Slow heart rates separates the two phases of ventricular filling.

Question 32

Aortic root: Positioning the cursor through the aorta and left atrium produces an M-mode of the base of the heart. How is this obtained?

Answer 32

This is obtained from the right parasternal long-axis left ventricular inflow outflow or transverse view of the aorta and left atrium (Fig 3.12).

Question 33

Using a long-axis inflow outflow view, place the cursor …….?

Answer 33

Using a long-axis inflow outflow view, place the cursor perpendicular to the aortic walls and throughout through the aortic valve.
The inflow outflow view should be as long as possible with the wall and septum perpendicular to each other, and there should be a good aortic and mitral valve motion. If positioned correctly, the cursor should then be located through the largest portion of the left atrium.

Question 34

How should the transverse image be optimized?

Answer 34

On transverse images, allt three aortic valve cusps should be clearly and symmetrically seen. The intertribal septum and left auricle should also be clearly seen.
Place the cursor throughout the middle of the aorta and through the left atrium. The cursor can be located close to the junction of the left auricle and atrium but not in the auricle. Fig 3.12

Question 35

Transverse M-mode images: The right atrium is at the ….. of the image, followed by the anterior and posterior aortic walls. These walls move parallel to each other. Below the aorta is the…………

Answer 35

The right atrium is at the top of the image, followed by the anterior and posterior aortic walls. These walls move parallel to each other. Below the aorta is the left atrium. The left atrium fills during ventricular systole, and this is one reason the aorta moves upward at that time. There should be very little posterior left atrial wall motion.

Fig 3.3, 3.13

Question 36

The aortic valves are a line in the center of the aorta during ……….. With …………., the valve cusps move rapidly toward each wall and remain there until the end of ventricular ejection when they move back to the center of the vessel and close. This creates a box-like image on the M-mode. Aortic valve motion is often easier to record from ……………..images.

Answer 36

The aortic valves are a line in the center of the aorta during diastole. With systole, the valve cusps move rapidly toward each wall and remain there until the end of ventricular ejection when they move back to the center of the vessel and close. This creates a box-like image on the M-mode. Aortic valve motion is often easier to record from short-axis images.

Question 37

M-mode: Mitral annular motion (MAM):

Recoded from the …………….

Answer 37

Recoded from the left parasternal apical 4-chamber view of the heart.
The M-mode cursor is placed along the interventricular septum and motion of the annulus is displayed (Fig 3.14). During systole annular motion is upward. During diastole annular motion is downward.
Fig 3.15