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. 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. The PLAX IVS measurement is rarely falsely low but there are several ways to get falsely high measurements. The first is that the cut through the IVS is oblique, rather than perpendicular. The second is that the RV moderator band inserts into the anteroseptum and may be included in the IVS measurement. Here is a good PLAX IVS measurement.

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

The PSAX may be used for IVS measurement if the view is clear because the measurement can be taken in the basal inferoseptum to avoid the moderator band. The following PSAX shows the moderator band joining the anteroseptum.

 

The ultrasound beam is somewhat parallel to the IVS in the PSAX so the endocardium may not be visualized well, leading to under-measurement of the IVS. Here is a PSAX IVS measurement in the inferoseptum.


 

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 hypertrophic cardiomyopathy. Here is a clip from a patient with a modest septal bulge.

 


The apical4 may show the IVS clearly, particularly when RV enhancement is used to get the beam more perpendicular to the IVS. In a true apical4 the view is through the inferoseptum so the moderator band is avoided. However, lack of good endocardial resolution in this window, due to the ultrasound beam still being mostly parallel to the endocardium, may result in under measurement of the IVS. Here is an IVS measurement in an RV enhanced apical4.

The SC4 view may be excellent for the IVS because the inferoseptum is seen, avoiding the moderator band, and the ultrasound beam is more perpendicular to the IVS. Remember that the standing patient position can optimize many aspects of the SC4 view when something is important. Here is a subcostal IVS measurement. However, notice that the left ventricular outflow tract and the aortic valve are partly in view, making it possible that the cut is anterior enough to risk moderator band confounding.

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 IVS and LVEDD measurements are taken toward the end of expiration when the LV is most full.

When measuring in the PLAX it is important to carefully observe the live B-mode 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. This can result in under measurement of LVEDD. Here is a PLAX LVEDD measurement.

Here is an RV enhanced apical4 LVEDD measurement.

As with the IVS measurement, a good SC4, perhaps with the patient standing, may give the best LVEDD measurement because the ultrasound beam is perpendicular to the LV walls. Here is a normal LVEDD in the SC4/5.

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 and 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.

Eyeballing of LV radial function is valid (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. Standard fractional shortening is an estimate of radial systolic function at only one particular LV site so isn’t used routinely.

E-point septal separation (EPSS) in the PLAX 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 in early diastole. 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) and confirm atrial contraction. When it is difficult to get M-mode perpendicular to the septum and motion of the valve leaflet, Venue has Anatomic M-mode that may get a more accurate measurement of EPSS. On all machines, optimizing the IVS image with depth, width, and focus position is important in difficult patients.

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 physician to time the respiratory cycle with the forearm on the patient’s chest/abdomen. The tracing is frozen at the end of expiration. The best complex for measurement is found near the end of the tracing. Here is a normal EPSS tracing.

If the anterior MV leaflet visually slaps the septum EPSS could be recorded as zero without M-mode measurement. However, the additional benefits of identifying systolic anterior motion of the mitral valve and the presence of left atrial activity (the presence of the A motion) justify routinely obtaining the tracing. In addition, with Venue we can quickly calculate the heart rate with the tracing. 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, on some machines without anatomic M-mode, an abnormal EPSS may result from a more oblique cut through the septum and valve leaflet.

 

Normal

EPSS (cm)

0 - 0.7

Longitudinal Systolic LV Function: Although longitudinal function comprises only about 10% of overall LV systolic function, it varies depending on the region of the LV and reduction in longitudinal LV function can be an early marker of various types of LV 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 vertically 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. An optimized image of the annulus can be very important for difficult patients. Anatomic M-mode may rarely be needed to be perfectly parallel to the annular motion. Position the cursor so it is best for end expiration, activate M-mode, and freeze at end expiration. Find the best complex towards the end of expiration and measure the difference between the peak and the valley of the annulus excursion.

 

Normal

MAPSE (cm)

1.2 - 1.8


 

DOPPLER ANALYSIS OF LV FUNCTION

Doppler analysis of LV function can be difficult to do well and inaccurate measurements may do more harm than good. The IMBUS technique 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 systolic longitudinal LV function, LV diastolic active relaxation, peak left atrial pressure (LAP), and left atrial function. Additional interpretation of these measurements will be discussed in several future chapters. The IMBUS exam will not measure 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 through the mitral valve measures the maximum velocity of the E-wave (early diastolic inflow caused by the suction/pull of active relaxation and the push of LA pressure) 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 apical4 view of the LV and LA with both mitral leaflets visible.

Step 1: The left heart may need adjustment so the angle of flow through the mitral valve into the LV is roughly parallel to a Doppler gate line. Venue has angle correction for spectral Doppler so the gate can easily be made parallel to inflow.

Step 2: Color Doppler (Color) is activated, the sector box width is optimized for the LV inflow area, and the probe is then fanned “anterior/posterior” to find the plane with maximum intensity of the inflow signal (red flush) during expiration. Here is good red flush LV inflow signal along with blue LV outflow signal.

Step 3: Continuous wave Doppler (CW) is activated. CW measures velocity all along the line. The center of the line contains a “region of interest” which should be placed near the tips of the open mitral valve. This sharpens the tracing for this particular location. The best gate line position is usually a little lateral, rather than right in the center of the LV. This position also helps avoid the left ventricular outflow tract. Use the Color signal to get the gate line roughly parallel to the strongest flow through the valve. Then, tap the CW button again to activate the tracing and do final angle correction as needed. The Baseline, Scale, Gain, or Sweep Speed may occasionally need tweaking. The active B-mode thumbnail in Venue (Duplex mode) may need to be watched carefully with faster heart rates to be clear where diastole begins on the tracing. Then, Duplex can be turned off to have a more defined tracing. The tracing is frozen at the end of expiration and the complex with the maximum and clearest E wave is selected. Here is a normal tracing with the E and A waves measured (Venue calculates the E/A ratio).

Messy tracings usually mean that chordal elements have entered the gate line and the gate may not be parallel to inflow. We have also seen an eccentric aortic regurgitation jet appear in between the E and A waves.

E-wave velocities are usually < 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 increased so higher peaks can be measured.

E-waves vary more than A-waves with changes in LA pressure and LV function, so the E/A ratio is dynamic. E, A, and E/A vary substantially with age. The following table shows the weighted mean values (by decades) from a metanalysis of these values. The E velocity falls as the LV suction decreases with age and the A velocity increases as there is more dependence on the atrial contraction to empty the increased residual volume in the left atrium.

LV Inflow

20 - 29 yr

30 - 39 yr

40 - 49 yr

50 - 59 yr

60 - 69 yr

70 - 79 yr

80 - 89 yr

E

83

78

73

67

67

66

64

A

45

51

55

61

71

78

90

E/A

1.91

1.56

1.37

1.16

0.99

0.87

0.73

 

Left atrial dysfunction: dysfunction of the left atrium with preserved sinus rhythm does occur. Both idiopathic heart failure with preserved ejection fraction and amyloidosis are reported to reduce atrial function without causing atrial fibrillation. This can decrease the A-wave velocity below what is expected for age. This becomes important in analyzing an elevated E/A ratio as discussed in the Diastology chapter.

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 accurately derive an average E-wave velocity. This is tedious, so the utility of IMBUS LV inflow analysis in an atrial fibrillation patient is only to quickly identify patients with very high E-wave velocities indicating one of the several conditions noted above.

PW LV Inflow analysis: The CW tracing with Venue is rarely suboptimal. The analysis is then performed with PW, which measures just at the small gate, rather than along the whole line. Careful placement of the PW gate is essential. The gate line positioning steps described above for CW are still needed and the PW gate is carefully placed just past the tips of the open mitral valve. If the gate is too distal or proximal in the LV, lower velocities may be recorded so exploration with the gate in Duplex mode is often needed to be sure the maximum velocities are found.

The PW tracing should also be optimized for Baseline, Scale, Gain, and Sweep Speed and Duplex turned off for the final tracing .The tracing is frozen at the end of expiration. The complex with the highest E-wave toward the end of expiration is selected for measurement of E and A as in the following tracing.

In several published reports, CW measurements of E and A waves were about 10% higher than PW measurements and the IMBUS-COC experience supports this. A 2009 joint statement by the European and American echocardiographic societies noted, “CW to assess peak E and A velocities should be performed before applying the PW technique to ensure that maximal velocities are obtained.” Thus, the IMBUS routine for LV inflow analysis is to use CW and only move to PW if the CW tracing is suboptimal.


Tissue Doppler (TDI) analysis of the septal mitral annulus can be difficult and the subtleties need to be known to avoid misclassification of patients. It measures the velocity of movement of the mitral annular tissue, including the positive s’ (longitudinal systolic function), negative e’ (active relaxation of diastolic function), and negative a’ (atrial contraction) waves. For PW 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. TDI analysis should probably not be performed on an atrial fibrillation patient. TDI should also not be done when there is significant mitral annular calcification, previous mitral valve repair or replacement, abnormal basal septal wall motion, significantly impaired right ventricular function, or ≥ moderate mitral or aortic regurgitation.

Step 1: Optimize the B-mode image of the mitral annulus. On Venue, the standard PW gate is first positioned over the mitral annulus, including the use of angle correction to be parallel to the motion of the annulus. Measurements should be performed in later expiration. Fortunately, this is usually when the best views of the annulus are obtained.

Step 2: After the gate is positioned, activate TDI. Freeze at the end of expiration and 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. Most suboptimal tracings are caused by suboptimal gate placement. The s’, e’, and a’ peak velocities are measured and the e’/a’ ratio is calculated by Venue. The following is a good TDI tracing with measurements.

The s’ from a good tracing may be a modestly better measure of longitudinal systolic LV function than MAPSE, but having both is good when LV function is particularly in question for a patient. The s’ (like MAPSE) doesn’t vary with age (0.08-0.13 for all ages).

Trap: There is a part of LV contraction called isovolumetric contraction (IVc), which occurs in earliest systole when all valves are still closed. No change in LV volume occurs during this very brief event. The IVc can be seen in the TDI tracing above and is the initial brief up and down deflection. There is no IMBUS utility in measuring the usually small IVc peak or duration. However, the following TDI tracing demonstrates what can happen when the IVc velocity is higher than typical. The physician chose the IVc peak of 0.11 as s’, when the true s’ peak was about 0.06.

The LV inflow section above noted that reduced LA pressure reduces E more than A resulting in a fall of the E/A ratio. While reduction in LA pressure can also modestly reduce e’ and a’, the fall is proportional in most patients so the e’/a’ ratio may be a more consistent measure of LV stiffness than is the e’ when LAP might be reduced. Both e’ and the e’/a’ ratio fall as patients age. The a’ velocity can also decrease when left atrial function deteriorates and this causes an increase in the e’/a’ ratio. All of this will be pulled together in the Diastology chapter. Here are the normal ranges for s’, e’, and e’/a’. There is not a well-established, published range for a’ but we typically see values of 0.08-0.12 m/sec.

Mitral Annulus TDI

16 - 20 yr

21 - 40 yr

41 - 60 yr

> 60 yr

s’ (m/sec)

0.08 - 0.13

0.08 - 0.13

0.08 - 0.13

0.08 - 0.13

e’ (m/sec)

0.12 - 0.17

0.13 - 0.18

0.10 - 0.14

0.08 - 0.12

e’/a'

2.4

1.1 - 2.1

0.8 - 1.4

0.65 - 1.05

 

Unfortunately, this table lumps all patients over the age of 60 together in one group. This is not optimum because important changes continue with increasing age. From the metanalysis noted above in the E and A discussion, the weighted mean e’ for more elderly patients was:

70-79 yo:.0.07
80-89 yo: 0.05

This means that about half of patients in their 70s meet the standard definition for diastolic dysfunction and a strong majority of patients in their 80s have stiff hearts!


A NOTE ABOUT THE ATHLETES HEART:

This condition usually 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.