Chapter: LV Size and Function

LVH Septal Bulge LVEDD LV Function Athlete's Heart

LV Size & Function

This chapter provides an overview of quantitative assessment of the left ventricle's size and both systolic and diastolic function.

LV HYPERTROPHY

Detecting and quantifying LV hypertrophy with ultrasound is complex. There are different forms of hypertrophy which can be diffuse or localized. Diseases like amyloid, sarcoid, and Fabry cause hypertrophy of various types. Considering IMBUS equipment and exam time, only measurement of the interventricular septum (IVS) at end diastole is needed for most patients. End diastole is the image with maximum LV chamber size and the mitral valve just floating shut.

The PLAX is a standard view to measure the IVS, but there are several ways to get false measurements: not being at end-diastole, falsely including RV structures (e.g. moderator band) in the measurement, and being oblique rather than perpendicular to the septum. Nevertheless, with a good PLAX view the basal IVS (anteroseptum between mitral valve and papillary muscles) should be measured, as in the following image.

Here are the reference standards for the IVS.

 

Normal

Mild

Moderate

Severe

IV septum (cm)

0.6 - 1.0

1.1 - 1.3

1.4 - 1.6

≥1.7

In the patient just shown, the IVS was mildly increased in the PLAX, so confirmation was needed. The PSAX may sometimes be a little better view than the PLAX for IVS measurement if the view is clear. This measurement should also be taken in the basal IVS. Here is the PSAX measurement on the same patient, which seems to agree with the PLAX measurement.


 

Discrete upper septal thickening (DUST)/sigmoid septum/septal bulge/septal knuckle is relatively common, especially in older patients. It is associated with hypertension, but not hypertrophic cardiomyopathy, and should be less than 3 cm in length. Here is a diagram demonstrating the abnormality. The IVS measurement should be taken distal to this bulge but before the papillary muscles.

DUST is not completely cosmetic. It can cause turbulence in the outflow tract (resulting in a murmur) and hypovolemia or hyper-catecholamine states may cause temporary obstruction of the outflow tract with systolic anterior motion (SAM) of the anterior leaflet of the mitral valve. Thus, SAM is not specific to HCM. Here is a clip from a patient with a modest septal bulge.

 


The apical4 view may show the IVS more clearly, particularly when RV enhancement is used so the beam is more perpendicular to the IVS. However, lack of good endocardial resolution in the apical window, due in part to being parallel to the endocardium of the IVS, may result in under measurement of the IVS. Magnification is often helpful to accurately place the calipers. The measurement is taken in the basal inferoseptum. Here is an IVS measurement in the apical4 that was clear even without an RV enhanced view.

The IVS is not measured in every view when it is clearly normal. But, an abnormal width in any view should be validated in other views to avoid overcalling septal hypertrophy.


LV End Diastolic Diameter (LVEDD)

LVEDD varies with patient height and is measured at the same location and time as the IVS, measuring from endocardium to endocardium. Ideally, the measurement is taken toward the end of expiration when the LV is most full. If LVEDD measurements in different views don’t agree, report the largest measurement. Again, note the typical decrease in basal endocardial resolution when viewed from the apical window, and thus the potential to over measure the LVEDD in that window.

When measuring in the PLAX view it is important to carefully observe the live 2D images to be clear where the chordal structures of the posterior-lateral papillary muscle abut the inferolateral LV wall because the junction may be difficult to see in the end-diastolic frozen image. Here is a PLAX LVEDD measurement.

As with the IVS, equivocal or abnormal parasternal LVEDD measurements should be confirmed in good apical4 views. Here is an apical4 LVEDD measurement using a slightly LV enhanced view to be sure that the anterolateral LV wall was clearly seen.

The normal range for the LVEDD must consider the patient’s height to avoid misclassifying shorter and taller adults.

Left Ventricle

 

End Diastolic Diameter (cm)

3.8 - 5.8


LV FUNCTION

LV function is a complex mix of wall thickening, inward (radial) motion, longitudinal motion, rotatory motion, and active relaxation but an IMBUS exam can’t measure all of these. The rest of this chapter is complicated for an early learner. Yet, these analyses must be performed accurately or incorrect conclusions about a patient can be reached. A novice needs careful repetitions with a mentor to be proficient and to recognize the limitations of the methods.

Eyeballing of LV radial function works (categorizing as normal, mild/moderately, or severely reduced), but requires experience and an ability to integrate multiple views of the LV. Eyeballing should be supplemented with a few measurements most of the time. Ejection fraction by Simpson biplane method is not practical for IMBUS and has limitations. Fractional shortening is an estimate of radial systolic function at only one particular LV site so shouldn’t be an IMBUS standard.

E-point septal separation (EPSS) in the PLAX view is a screening measurement that assesses a combination of LV size, function, and anterior mitral valve (MV) leaflet movement. It measures the gap between the closest approach of the anterior mitral leaflet tip to the basal anteroseptum. M-mode through the end of the leaflet best visualizes this gap because of the higher frame rate. This technique can also detect systolic anterior motion of the MV (SAM).

LV filling and output are maximal toward the end of expiration because of respiratory effects on left heart capacity and pulmonary venous return. EPSS is optimally done by activating M-mode and positioning the cursor for correct alignment
in late expiration. This requires the examiner to direct a patient’s breathing (“breathe in, breathe out”). The tracing is started by hitting the M-mode button again at the onset of an expiration and then frozen at the end of expiration. The best complex for measurement is found near the end of the tracing by using the left arrow key at the top right or by using the trackpad. Here is a normal EPSS with a small gap between the leaflet and the IVS. Calipers were then used to measure the width of the gap.

With any M-mode or Doppler tracing, there is a thumbnail image at the top that shows the gate position at the time the tracing was initiated, but this is infrequently the position for the complex that was measured and saved. Thus, the thumbnail cannot reliably indicate whether an M-mode or Doppler gate placement was optimal, but it can raise a question about gate placement.

If the anterior MV leaflet clearly slaps the septum during live 2D, EPSS is recorded as zero without M-mode measurement. An EPSS progressively greater than 0.7 cm is increasing evidence that something is abnormal with LV size/function or with the leaflet (e.g. mitral stenosis or eccentric aortic regurgitation). However, an abnormal EPSS may occasionally result from an oblique, rather than perpendicular, view through the septum, so further evidence is needed to determine the cause of an abnormal EPSS.

 

Normal

EPSS (cm)

0 - 0.7

Longitudinal LV Function: Although longitudinal function comprises only about 10% of LV systolic function, reduction in longitudinal LV function is an early marker of systolic dysfunction and of more advanced diastolic dysfunction. Mitral annular plane systolic excursion (MAPSE) with M-mode in the apical4 view is the easiest way to assess longitudinal function. It measures the amplitude of the MV annular movement.

Understanding the location of the MV annulus is important for MAPSE and also for tissue Doppler imaging that is covered in the next section of this chapter. The annulus is a ring of fibrous tissue (a little more hyperechoic than myocardium) that supports the MV apparatus. On the screen, the septal part of the annulus in the apical4 view lies medial and a little apical to the base of the septal leaflet. It is not a particularly thick ring and is in continuity with the annulus of the aortic valve. The annulus lies between the IVS and the interatrial septum and is passively moved by the myocardium in both chambers. The following drawing shows the location of the septal and lateral mitral annuli, but only the septal annulus is used with IMBUS.

For MAPSE, the M-mode line needs to go through the annulus and be as parallel as possible to the vertical motion of the annulus. Magnification may sometimes help better position the line. Position the cursor so it is best for the latter part of expiration, as in the following clip.

Activate M-mode at the start of expiration and if complexes look good, freeze at end expiration and scroll back to identify the best complex towards the end of expiration. Measure the height of the peak and the valley by starting a caliper, hitting Select, and moving the left index finger directly down on the track pad to take the caliper to the bottom of the screen. Subtract the valley height from the peak height to get MAPSE. In the following patient, MAPSE was 1.7 cm, which is high-normal.

 

Normal

MAPSE (cm)

1.2 - 1.8


 

DOPPLER EVALUATION OF LV FUNCTION

Doppler analysis of LV function is difficult to do well and inaccurate measurements may do more harm than good. The IMBUS technique with an Edge machine measures the velocity of blood flow into the LV through the mitral valve and the velocity of septal mitral annulus tissue movement. Together, these values give information about longitudinal LV function, the stiffness of the LV, and peak left atrial pressure (LAP). Interpretation of these measurements will be further discussed in a future chapter on diastology and volume assessment. The IMBUS exam cannot replicate all the parameters determined by a high level echocardiography lab, but should result in overall conclusions that are consistent with such a lab.

LV Inflow Analysis measures the maximum velocity of the E-wave (early diastolic inflow caused by the LV suction and LA pressure gradient) and the A-wave (late diastolic inflow from atrial contraction). These velocities are usually maximum near the tips of the open mitral valve leaflets at end expiration. The exam starts with a good apical view of the LV and LA with both mitral leaflets visible. The end of expiration also usually gives the best view of the LV inflow area.

Step 1: The left heart must be adjusted so the angle of flow through the mitral valve into the LV is as parallel as possible to the Doppler cursor coming from the upper center of the screen. This usually requires moving the LV toward the middle of the screen along with a bit of RV enhancement of the septum.

Step 2: Color Doppler (CD) is activated, the sector box size is optimized for the LV inflow area, and the probe is then fanned “front to back” to find the plane with maximum intensity of the CD signal during late expiration.

Step 3: Doppler is activated and continuous wave Doppler (CWD) is selected with the button at the top left. CWD measures velocity all along the line. The center of the line contains a “diamond”, which is the focal point that should be placed near the tips of the open mitral valve. Next is a clip showing correctly positioned CWD during expiration.

When the CWD tracing is first activated on a default Edge machine, the settings need adjustment before measurements are obtained. The Line needs to be moved at least half the way down the screen because positive waves will be measured but negative waves still need to be seen. The Scale is almost always moved to the lowest setting to measure velocities < 100 cm/sec. Finally, the Sweep speed should be adjusted to Slow while the tracing is running so multiple complexes can be seen, unless a patient is particularly tachycardiac, when Medium speed should be used. After the settings are correct, Update is selected to confirm correct gate position and then Update is pushed again at the start of an expiration. The tracing is frozen at the end of expiration when good complexes have been seen. Scroll back through the end of expiration and choose the complex with the maximum and clearest E wave. The following patient did not have a negative systolic wave, so it was acceptable to lower the baseline to the bottom for measurement of E and A.

The closing of the mitral valve leaflets may be seen in the tracing as a vertical line right after the A-wave, but multiple vertical lines through the tracing usually mean that chordal elements have entered the tracing and the gate line may not be parallel to inflow. If mitral regurgitation is present, a negative wave will be seen during LV systole if the gate is through the regurgitant jet. A negative wave may also be seen if the gate line passes through part of the LV outflow tract, usually indicating that the gate is not optimally parallel to LV inflow.

E-wave velocities are usually ≤ 125 cm/sec (1.25 m/sec), but there are conditions with higher velocities (well hydrated athletic heart, mitral stenosis, mitral regurgitation, decompensated heart failure). In these situations, the Scale is raised to see the higher peak of the E wave. In IMBUS patients, the main purpose of the LV inflow analysis is calculation of the E/A ratio, which the examiner does with a cell phone calculator or the cardiac calculations package on the machine.

E-waves vary substantially more than A-waves with changes in LAP, so the E/A ratio is dynamic. The E/A ratio is also importantly age-dependent, as shown in the following table.

Mitral Inflow PWD

16 - 20 yr

21 - 40 yr

41 - 60 yr

> 60 yr

E/A

1.4 - 2.3

1.1 - 1.9

1.0 - 1.5

0.8 - 1.1

Atrial fibrillation patients lack an A-wave, so all that can be measured is E. This measurement may have utility, but the difficulty is the beat to beat variation in the E wave. Multiple E waves must be measured to derive an average E wave velocity. This is tedious, so the utility of IMBUS LV inflow analysis in an atrial fibrillation patient is probably only to quickly identify patients with clearly high E wave velocities indicating one of the several conditions noted above.

PWD LV Inflow analysis: The CWD tracing may be suboptimal because the gate line cannot be aligned parallel to the LV inflow. The analysis is then performed with PWD, which is the technique used by most formal echo labs because they need the additional detail in the waves to calculate other parameters. PWD, which was described in the Carotid chapter, measures just at the small gate, rather than along the whole line. Careful placement of the PWD gate is essential. The positioning steps described above for CWD are still needed and the PWD gate is carefully placed between the tips of the open mitral valve. As a last step, hit Select to activate track pad adjustment of the gate angle correction line to get optimally parallel to the LV inflow. If the gate is too distal or proximal in the LV, lower velocities may be recorded. Here is a correctly positioned PWD gate that was parallel to LV inflow without needing the final gate angle correction adjustment. Gate angle correction uses a mathematical formula to correct the measured Doppler value. Therefore, all efforts should be made to be parallel to flow without using the angle correction when possible.

The PWD tracing should also be optimized with Line, Scale, and Sweep speed adjustments. The tracing is begun at the start of expiration and frozen at the end of expiration. The complex with the highest E wave toward the end of expiration is selected for measurement as in the following tracing. The E/A ratio is calculated (1.25 in the displayed patient).

In several published reports, CWD measurements of E and A waves were about 10% higher than PWD measurements and the IMBUS experience with the Edge machine supports this. A 2009 joint statement by the European and American echocargiographic societies noted, “CWD to assess peak E and A velocities should be performed before applying the PWD technique to ensure that maximal velocities are obtained.” Thus, the IMBUS routine for LV inflow analysis is to first try CWD and then move to PWD if the CWD tracing is suboptimal.

Tissue Doppler (TDI) analysis of the septal mitral annulus is difficult to do well. It measures the velocity of movement of the mitral annular tissue, including the positive s’ (systolic), negative e’ (early diastolic), and negative a’ (late diastolic) waves. The current Edge TDI is a form of PWD, but some labs use color tissue Doppler. For PWD TDI, the gate must be carefully placed to encompass the annulus and be parallel to its movement. The gate target is the same that was used above for MAPSE, which on the screen means medial and a little apical to the base of the septal leaflet. However, the vertical gate position is also critical. If the gate is a little above or below the annulus, the waves change, almost always with a disproportionate reduction in the e’. This means that equivocal or low e’ values always need careful confirmation of correct gate placement. Analogous to the LV inflow analysis, the main goal of the TDI analysis is the calculation of the e’/a’ ratio. TDI analysis should probably not be performed with an IMBUS exam of an atrial fibrillation patient. TDI of the mitral annulus should also not be done when there is significant mitral annular calcification, previous mitral valve repair or replacement, abnormal basal septal wall motion from various causes, or ≥ moderate mitral or aortic regurgitation.

Step 1: PWD is selected and the TDI button at the central top is toggled. The default settings with the Edge machines are appropriate for most patients, but more vigorous hearts may need the gate size increased from 3 mm to 5 mm to cover the excursion of the annulus. As with MAPSE and LV inflow analysis, TDI measurements should optimally be performed in later expiration to be optimal. Fortunately, this is usually when the best views of the annulus are obtained. Find the apical window that is best for expiration and plan to have the patient stop breathing in later expiration when the view is most clear.

Step 2: A vertical or slightly RV enhanced septum is needed to get the TDI gate line as parallel as possible to the direction of annular movement. Magnification on the annulus should be used to position the gate optimally. Make sure the Scale and Sweep speed are correct with a trial run. Here is a TDI gate that was correctly positioned for at least some of the cycles.

Step 3: After the settings are correct, Update to confirm the gate position and then activate again at the start of expiration. Have the patient stop breathing toward the end of expiration with clear complexes. Freeze after a handful of seconds and let the patient breathe. Scroll back to pick the complex with the largest, clearest e’ wave. A falsely high e’ is rare, but it is easy to get a falsely low e’ with suboptimal gate placement. The default Edge TDI settings have optimized filters and gain, so turning the gain up or down more than a notch risks error. Most suboptimal tracings are caused by suboptimal gate placement. The s’, e’, and a’ peak velocities are measured with calipers and the e’/a’ ratio is calculated. Don’t place the calipers at the farthest wispy tip of any wave, but don’t exclude the fading parts of waves or under measurement may occur. The following is a good TDI tracing.

The s’ from a good tracing is a modestly better measure of longitudinal LV function than MAPSE, but having both is good when LV function is particularly in question for a patient. A low s’ certainly needs a confirmatory MAPSE and a low s’ with a normal MAPSE requires confirmation of correct TDI gate placement. The s’ doesn’t vary with age (8-13 for all ages).

The LV inflow section above noted that reduced LAP reduces E more than A resulting in a fall in the mitral inflow E/A ratio. While reduction in LAP can also modestly reduce e’ and a’, the fall is proportional so the e’/a’ ratio is a more consistent measure of LV stiffness than is the e’. However, e’ and the e’/a’ ratio both fall as patients age. Here are the normal ranges for s’, e’, and e’/a’.

Mitral Annulus TDI

16 - 20 yr

21 - 40 yr

41 - 60 yr

> 60 yr

s’ (cm/sec)

8 - 13

8 - 13

8 - 13

8 - 13

e’ (cm/sec)

12 - 17

13 - 18

10 - 14

8 - 12

e’/a'

2.4

1.1 - 2.1

0.8 - 1.4

0.65 - 1.05

E/e’ can be useful to estimate left atrial pressure (if E and e’ are valid measurements). Formulas to convert to estimated wedge pressure are probably not necessary in most patients and we should be a little cautious in atrial fibrillation and sinus tachycardia. But the following scheme works well for the great majority of patients.

Mitral

Normal LAP

Indeterminate

Elevated LAP

E/e’

< 8

8 - 15

> 15

Interpretation of diastolic findings changes periodically. A new consensus statement about diastolic function was published in 2016 and we have a separate chapter that tries to clarify our approach to diastology.


A NOTE ABOUT THE ATHLETES HEART:

This condition results from prolonged, intensive endurance training. The septum is rarely over 1.3 cm and both the right and left ventricles may be slightly above normal diameter. Radial LV function can appear low normal by eyeball and even by EF, but just having a patient squeeze a ball hard can improve the radial function. Specific LV longitudinal and diastolic function is normal to supra-normal in these athletes, eliminating the eyeball concern about reduced LV function.