In apical 4 chamber view, one may appreciate the RV, LV function and size. Here we see the free wall of the RV, the inter-ventricular septum and the lateral wall of the left ventricle. One can appreciate the size of the mitral and tricuspid valve. It is a view to also measure the RV basal, mid-cavity and longitudinal dimensions in diastole. EF by Simpsons may be calculated using the apical-4-chamber view. The biplane methods also evaluation in the Apical-2-chamber view. The apical 4 chamber view (A4C) is also useful to assess longitudinal function of the Right ventricle.
In this LV focused view (A4C), one may appreciate the systolic and diastolic dimensions of the left ventricle.
Here, one may see the apical-2-chamber (A2C) view, where we can appreciate the mitral valve, as well as the LV end-diastolic and end-systolic dimensions. One may use this view to calculate the biplane EF by Simpson's disc method. We can also appreciate the blood flow through the mitral valve by colour.
Ejection fraction (EF)
EF(%) = (LVEDV − LVESV)/LVEDV × 100
- Assumes a bullet shape geometry of the LV
- May not be true if high PVR; abnormal septal geometry; LV hypoplasia
- EF preserved despite abnormal regional subclinical disease
- Decreased areas of contractility tethered by more healthy myocardium
- Multiple methods based on mathematical models assuming a bullet shape appearance
- Limitation of this assumption in the context of high PVR or Pulmonary Hypertension (flattening or dyskinesia of septum)
- Variability of measurements is within the 10–15% range. A reduction in EF of >10% in the normal range (>55%) and >5% if <55% is clinically significant.
Ref: Lai, W. W., Mertens, L. L., Cohen, M. S., & Geva, T. (2015). Echocardiography in pediatric and congenital heart disease: from fetus to adult. John Wiley & Sons.
Colour box may be applied on the tricuspid valve of the A4C - as such, in this clip, we can appreciate some tricuspid regurgitant jet (blue - away) when the tricuspid valve is closed. One may interrogate the TRJ to evaluate the RV-RA velocity gradient. This gradient may allow to estimate end-systolic RV pressures. If there is no RVOT obstruction, this can be used as a surrogate of systolic MPA pressure.
Tricuspid Regurgitant Jet (TRJ) Velocity
- During systole, tricuspid valve is closed (prevents backflow in RA)
- As RV afterload starts rising - RV dilates, tricuspid annulus dilates and coaptation of valve becomes less competent
- TR appears: blood flow from high pressure RV to low pressure RA generates a velocity of flow
- Measuring speed using Doppler allows to estimate the “gradient” (difference) between RV and RA chamber at peak of systole
- Simplified Bernouilli equation tells you that :
- Pressure difference between the 2 cavities = 4 x velocity2
- True if the opening of jet is a narrow point.
- Assuming RA pressure – 0-5mmHg (will increase with diastolic RV dysfunction)
- TR = 5.45 m/s à 4v2 = 119 mmHg at peak of systole à RV-RA gradient of 119 mmHg
- Assuming RA pressure about 5 mmHg: estimate of systolic PAP = 119+5 = 124 mmHg
One may also use the enveloppe of the tricuspid regurgitant jet (CW) to calculate the systolic to diastolic time ratio, an indicator of ventricular function. Indeed, the S/D ratio is increased in ventricular dysfunction since there is prolongation of the systolic duration and a reduction in the diastolic time period. Similarly, the enveloppe may be used to calculate the dp/dt of the RV (especially useful in the context of single RV - such as in HLHS). As per Csecho.ca: "The RV contractility dP/dt can be estimated by using time interval between 1 and 2 m/sec on TR velocity CW spectrum during isovolumetric contraction. (...) Although the time from 1 to 2 m/s is most commonly used, the best correlation between echocardiographic and invasive measures was found by using the time for the TR velocity to increase from 0.5 to 2 m/s. In this case the numerator for the calculation is 15 mmHg."
Example of a TRJ with RV-RA gradient of 5.45 m/s, which gives 119 mmHg of RV-RA gradient. This can be seen in significant RV hypertension, such as in pulmonary hypertension or pulmonary embolus. More examples are provided in the pulmonary hypertension section.
The colour box indicates some mitral regurgitation (blue flow when mitral valve is closed). In this case, the patient had hypoxic ischemic encephalopathy and some signs of LV dysfunction. Papillary muscles are often the watershed part of the myocardium and MR may appear in patients with LV dysfunction. Furthermore, when facing moderate to severe MR, assessment of LV function by echocardiography is very challenging. Indeed, the LV contracts against the lower pressure chamber (left atrium) and as such, the use of markers such as ejection fraction or shortening fraction may not reflect adequately underlying performance. In this case, the MR was judged as mild.
Pulmonary venous flow visualized by colour Doppler. Often, it requires to decrease the Nyquist (velocity) in order to visualize by colour the flow.
The best view in newborns to visualize pulmonary venous flow is in the "crab view" (suprasternal with a posterior angulation to visualize the left atrium). However, one may appreciate some of the pulmonary venous flow in the A4C. As such, colour velocity ("Nyquist") may need to be decrease din order to capture the low velocity pulmonary venous flow as it enters the left atrium. Typically, the PW Doppler is used to probe the pulmonary veins at their osteum. High velocity may occur in the context of increased pulmonary venous flow (example: left to right ductus arteriosus with significant Qp:Qs) or secondary to obstruction with flow acceleration (example: pulmonary venous stenosis). A pulmonary venous atresia may be difficult to diagnose by echocardiography, since it is associated with interruption of flow.
E/A velocities ratio
A PW Doppler may be sampled at the inflow of the right or the left ventricle. Filling of the ventricle typically occurs during 2 phases - mostly in early diastole (passive early phase - E phase), and in late diastole by the atrial contraction (late diastolic atrial phase - A phase). These phases may fuse in the context of fast heart rate (such as in newborns). The early peak velocity is typically higher than the atrial velocity in compliant ventricles. In patients with restricted filling (diastolic dysfunction), the ratio of these velocity may become inverted. It is not uncommon for newborns to have a reversed profile, especially in the first few days of life. Indeed, in the context of post-natal adaptation, the ventricles are less compliant compared to the expected compliance of the pediatric/adult ventricles. Hence, the RV is more muscular than the thin walled RV found later in life.
Example here of some of the cycles with fusion of the E and A wave and some cycles with E < A velocity from the tricuspid valve inflow.
Example of E<A velocities of a left ventricle in a premature newborn with some degree of LV hypertrophy.
Left Ventricular Velocity of Propagation as a marker of LV diastolic assessment has been described, mostly in the adult population, but not well studied in the pediatric population. As per the ASE: "Color M-mode measurements of the early diastolic flow propagation velocity from the MV to the apex correlate well with t and provide another means by which to evaluate LV filling; as LV relaxation becomes abnormal, the rate of early diastolic flow propagation into the left ventricle decreases."
Ref: Lopez L. et al. Recommendations for Quantification Methods During the Performance of a Pediatric Echocardiogram: A Report From the Pediatric Measurements Writing Group of the American Society of Echocardiography Pediatric and Congenital Heart Disease Council. J Am Soc Echocardiogr 2010;23:465-95.
LV inflow velocities may also be assessed in the A2C.
Apical 5 chamber view in 2D. This view is essential to evaluate LVOT and rule out sub-aortic obstruction. It is the view in which we also obtain PW-Doppler at the level of the tip of the aortic valve.
In this view, one may appreciate the flow from the left atrium to the left ventricle, as well as from the LV to the aorta.
In this view (apical 5 chamber view), one may apply the colour Doppler and see the flow through the LVOT. Presence of aortic insufficiency or stenosis can be appreciated in this view, if present. As well, presence of sub-aortic stenosis (such as in infants of diabetic mother with septal hypertrophy) can lead to flow acceleration that may be noticed in this view
At the tip of the aortic valve, one may probe with PW-Doppler the LVOT in order to estimate the LVOT-VTI (stroke distance). The VTI can also be used to estimate stroke volume and resultant cardiac output. In the presence of poor LV performance, or significantly increased LV afterload, one may appreciate a decrease in the stroke distance by VTI.
- LV: Velocity time integral of the LVOT
- Cardiac Output (CO) = SV × HR = VTI × CSA × Heart Rate
- The normal values are 150–400 ml/kg/day in infants and children.
- Important to assess output in situations of poor cardiac contractility, abnormal excessive preload (PDA), or underfilling (pulmonary hypertension) or risk of LVOT obstruction (infant of diabetic mother, intracardiac mass, etc).