echocardiography - lv function

Echocardiography:LV Systolic Function

David M. Whitaker, MD

“I need a stat echo…”

LVEF – most common reason for echo

2nd most common – pericardial effusion

3rd most common - RVSP

The “early days”

Before there was 2D echo M-mode

M-mode was a useful tool but with many limitations

Offered superior temporal resolution

M-mode

LV function was determined using linear measurements

Even as 2D echo advanced, linear measurements still made to assess LV function

Linear Measurements

M-mode

Early limitations related to “quality” of echo image – difficulty separating blood pool from endocardial interface

Improvements in gray scale technology improved this

Other M-mode Limits

Ice Pick evaluation

Leaves out potential regional wall motion abnormalities

May overestimate or underestimate overall LV function

Other M-mode Limits

Because the M-mode line often intersects the LV in a tangential fashion – the minor axis is often overestimated

Could argue that for a given pt the degree of overestimation remains constant and thus could be used for serial evaluation

More Linear M-mode

Other measurements for LV performance Rates of systolic wall thickening of post wall Calculation of velocity of circumferential shortening

(which assumes the LV is a perfect circle) Descent of the base measurement

Descent of the Base

During ventricular contraction – base moves toward apex

Magnitude of this motion directly proportional to systolic function

Same principle that TDI is based on

Indirect Markers of LVEF

Increased E-point septal separation

Gradual end systolic closure of the aortic valve

E-point Septal Separation

Magnitude of MV opening (E wave height) correlates with transmitral flow and with LV stroke volume – if MR is not bad

Internal dimension of LV diastolic volume

So… the ratio of the mitral excursion to LV size reflects the EF

E-point Septal Separation

Normally the MV E-point within 6 mm of the LV septum

In severely depressed EF, this distance is increased…

Aortic Valve Closing Pattern

If the LV stroke volume is decreased, there may be a gradual reduction in forward flow in late systole

Results in “gradual” closing of the AV in late systole

M-mode will show a rounded closure rather than the box cars

2D Measurements

A number of 2D views are used to provide LV function

Some rely exclusively on area measurement

Others rely on calculation of volume from the image

2D Measurements

All the general formulas based on the assumption that ventricle will adhere to a predictable shape

If there are regional wall motion abnormalities, the accuracy of these methods decreases

Simplified Method

Get minor axis measurements in diastole and systole at base, mid and distal LV.

Combine these with assessment of the apex to get EF

Simpsons Method

A.k.a. the “Rule of Disks”

Requires apical 4 or 2 chamber view, outlining the endocardial border in diastole and systole

Ventricle is mathematically divided along its long axis into a series of disks of equal height

Simpsons Method

Individual disk volume is calculated Height x disk area

Height = total length of LV / # of disks

Disk surface area determined for LV diameter at that point

Adding the disk volumes give LV volume

Simpsons Method

Tangential or foreshortened imaging of LV apex will most often overestimate EF

If the LV is assymetric, a bi-plane determination improves accuracy

Simpsons Method

Determine the stroke volume (LV diastolic – LV systolic)

EF = stroke volume / end diastolic volume

LV Mass

Determined using a number of echo formulas and algorithms

Carries significant prognostic importance in all forms of heart disease

LV Mass – Earliest Method

Teichholz Method or Cubed Formula

Based on M-mode measurement of septal and posterior wall thickness as well as LV internal dimension measurement

Again, symmetric geometry is assumed that LV is a sphere

Calculates outer dimensions of sphere, then inner dimension. The difference = presumed LV volume

Cubed Formula

LV Mass =

(IV septum + LV interior + post wall)3 ---

(LV interior)3

This gives volume of stylized sphere of myocardium which, multiplied by SG of muscle (1.05 g/cm3) estimates LV mass

Abnormal LV Mass

Conentric Remodeling

Contentric Hypertrophy

Eccentric Hypertrophy

After 100 Echos