Left Ventricular Function

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Indications

Estimation of left ventricular (LV) function is a useful application but has a steep initial learning curve. Its main indications are below:

  • Undifferentiated dyspnea/respiratory failure
  • Suspected pulmonary edema
  • Undifferentiated chest pain
  • Hypotension/Shock

Acquisition

In order to estimate LV function it is imperative to generate a quality parasternal long axis (PLAX), short axis (PSAX), and apical four chamber view (A4C). For the more advanced practitioner alternative approaches using additional apical views (e.g. the two and three chamber views) as well as the subcostal short axis can act as stand-ins for the core views but this is not recommended for those new to focused echocardiography. For details on acquiring the basic views please see our tutorial here.

In each view we will assess specific qualitative aspects of how the LV functions to generate a global interpretation.

PLAX

In the PLAX we will assess for three things. First, does the interventricular septum (IVS) thicken more than 30% during systole at the mid cavity (which is normal)? Below we represent this with a yellow line at the IVS and visually in appears to nearly double in thickness indicating robust contraction.

Next we assess whether the diameter of the LV cavity reduces by at least ~20% during systole. Estimation of the change in diameter is based on the quantitative method of fractional shortening where the diameter of the LV is measured just below the mitral valve leaflets in end diastole and end systole and the percentage change calculated. A change of <18% (when measured in 2D) correlates with an EF of <30%. An example is shown below. We just eyeball this however, no busting out the callipers here.

Last we look to the anterior leaflet of the mitral valve and judge its distance from the inter-ventricular septum during early diastole otherwise known as the E point septal separation (EPSS). EPSS of >7 mm when measured using M-mode correlates with a reduced EF. We judge this visually in 2D by assessing whether it comes close to the septum or touches it (normal), or is not close at all (significantly abnormal).

PSAX

In the PSAX at the mid papillary level we look subjectively at whether there is circumferential thickening of the myocardium and if the chamber collapses by ~30% or more. This is based on the method of fractional area change, where the internal area of the LV is traced during peak diastole and the percentage change versus peak systole calculated (normal is 35-65%). Eyeballing this is essentially seeing if the myocardium is thickening and moving towards the centre uniformly with about a 30% decrease in chamber side.

A4C

In the A4C we observed for the if the anterolateral wall of the LV (i.e. the free wall in this view) is moving towards the septum as well as the longitudinal motion of the lateral mitral annulus towards the apex. The latter is based on the M-mode measurment known as MAPSE or mitral annular plane systolic excursion; in general <11 mm is abnormal for males and <13 mm for females.

Interpretation

The first point in terms of the interpretation of left ventricular function is what we are trying to achieve in terms of stratifying individuals. It is not particularly clinically useful to know precise EF when making decisions regarding resuscitation or volume removal and hence while we acknowledge the diagnostic groups of EF (American Society of Echocardiography grades are listed below on the left) we instead stratify more broadly.

ASE EF Grading Focused Echocardiography EF Grading

In the following series of images we will demonstrate features that help to sort LV function into these various categories.

Hyperdynamic

This image set shows clear hyperdynamic LV with near complete chamber collapse seen in the PLAX, PSAX (with papillary muscles touching) and EPSS of 0 with the anterior mitral valve leaflet slapping the septum. The A4C shows extremely vigorous movement of the mitral annulus towards the apex and the chamber is obliterated in this view as well with the anterolateral wall touching the septum.

Normal

In the PLAX view with normal LVEF there should be easily discernible fractional shortening of the LV cavity and the anterior mitral valve leaflet should come close to, if not fully touch, the septum in early diastole. In the short axis there should be appreciable circumferential contraction with a change of at least one-third of diastolic area. In the A4C there should be inward movement of the anterior lateral wall vigorous movement of the lateral mitral valve annulus towards the apex.

Moderately Reduced

The toughest to call, and in terms of clinical relevance it is more important to recognize those LV’s that are closer to 30% than the nearly normals (as the above example demonstrates). In the PLAX the LV cavity change is more subtle and the anterior mitral valve leaflet remains fairly distant from the septum. In the short axis there is still circumferential contraction but it is less robust. Similarly in the A4C there is still inward movement of the anterolateral and longitudinal movement of the mitral valve annulus towards the apex but it is less vigorous than in normal LVEF.

Severely Reduced

In the PLAX view in severely reduced LVEF there should be almost no fractional shortening of the LV cavity and the anterior mitral valve leaflet will not even be close to the septum (though this is usually a mix of dilated ventricle as well as impaired function). In the short axis there is almost no circumferential contraction and in the A4C there will be little if any inward movement of the anterolateral wall and the lateral mitral valve annulus is almost static.

Pitfalls

Fractional shortening, area change, and EPSS all have similar challenges whether by ‘eye balling’ or direct measurement. The main pitfall is they are dependent on measuring in the right area with an optimal image; foreshortening or not imaging the LV in perfect long axis/short axis/apical axis can result in artificially increased EF due to the ‘cylinder effect’. Basically, if you measure near the edge of the LV you make the cavity smaller and accentuate the contraction making the EF higher than it truly is, so a properly acquired image is paramount.

Additionally a dilated LV can still have a relatively preserved EF but will tend to prompt us to overestimate severity especially with EPSS where the MV is physically pulled away from the septum due to the dilation.

Regionality is another challenge as if a single vascular territory is significantly hypokinetic or akinetic our eye has a hard time accounting for how this impacts function globally.

Dysrhythmia can also make EF estimation difficult as tachycardia can artificially make EF look higher and bradycardia lower. Irregular rhythms such as atrial fibrillation or premature beats create substantial variation in EF from beat to beat.

Specifically for EPSS LV chamber dilation as well as mitral valve restriction can render this measurement completely useless. Significant aortic regurgitation can also can push down on the anterior leaflet leading to underestimation.