ULTRASOUND OF THE FETAL HEART - Normal


 

For the detailed scanning protocol

 

A 10 step approach

Step 1: Check the heart is beating

Step 2: M-mode heart rate - should be between 120 and 180 beats per minute

Hover your cursor over images to see highlighted anatomy or pathology

Step 3: SITUS


 Heart Orientation  Situs
The heart should be angled 45degrees to the left and occupy approximately 1/3 of the chest. Confirm that the heart is on the fetal left.

 

Step 4: 4 CHAMBER VIEW AND VALVES

                                                                                             

 

4 chamber heart
 

Valves
4 chamber heart.
  • LA= Left Atrium
  • LV= Left ventricle
  • RA= Right Atrium
  • LV left Ventricle
The prominant papillary muscles make the right ventricle appear to be a much smaller chamber.
  • The atrio-ventricular valves should arise from the crux of the heart as an offset cross.
  • The Foramen ovale is clearly seen.

 

  • 4 chamber view scan plane:scan plane
 

This image shows the scan planes to obtain:

  • 4 CHAMBER VIEW
  • LVOT
  • RVOT

From the 4chamber view, by angling crandially rather than sliding the probe the outflow tracts are easily seen.

 

VALVES visible on the 4 chamber view

 4 chamber

Atrioventricular Valves opening and closing
Angle the probe cephalad to get the 4 chamber view of the fetal heart.
The valvular movement should simulate birds wings.

STEP 5: Left Ventricular Outflow Tract  LVOT

 

 Left ventricular outflow tract  LVOT
SCAN PLANE LVOT
Left Ventricular Outflow Tract:
(Aortic Root)


STEP 6: Right Ventricular Outflow tract - RVOT

 RVOT  

Right ventricular outflow tract
RVOT
Right Ventricular Outflow Tract:
(Pulmonary Trunk

STEP 7: 3 Vessel view - PAV view

 PAV view  3 vessel view
3 vessel or PAV view
  • P = Pulmonary artery exiting the right ventricle
  • A = Ascending aorta
  • V = Vena Cava (superior)
These should be in order of descending size. (otherwise suspect coarctation of the aorta)
If the aorta and pulmonary artery are not in perpendicular planes, suspect transposition

STEP 8: INTERVENTRICULAR SEPTUM

 

False Positive Ventricular Septal Defect

 

 

 Ventricular Septum

 

 

Beware of false positives with the interventricular septum:
The part of the interventricular septum closest to the crux of the heart is the membranous portion and naturally tapers. If your angle is poor, it may be invisible simulating a venticular septal defect(VSD)
To avoid this, ideally, the integrity of the interventricular septum should be confirmed from a perpendicular approach.

STEP 9: AORTIC ARCH

 Aortic Arch  sagittal view aortic arch
Demonstrate the aortic arch as it leaves the left ventricle.
It will have a 'walking stick' curve.
Sagittal View of the Aortic Arch

 

 

STEP 10:  DUCTAL ARCH

 

 Ductal Arch  Ductus arteriosus
The ductal arch demonstrates the correct orientation and communication between the Aorta and the pulmonary trunk.
It will have a flatter curve like a 'hockey stick'.
Ductal Arch

 

 

 

Ultrasound of the Fetal Heart -Protocol

Role of Ultrasound

  1. To confirm normal anatomy to the best of our ability.
  2. To progress, or elaborate on, known foetal heart pathology.

Limitations

  • Fetal lie and large maternal habitus will inhibit the scan.
  • With patience, the difficulties posed by foetal postion can usually be overcome.

Equipment Selection

  • Depending on the gestational age and maternal habitus, a curvilinear probe between 3-5Mhz.
  • If 3rd trimester with very large maternal habitus, a 2.5Mhz annular array may be needed.
  • Low dynamic range B-mode
  • High PRF colour and doppler settings with low persistance.
(most machines will have an adequate factory preset, fetal heart setting)

 

 

Scanning Technique

1st Step: Check the heart is beating

2nd Step: M-mode heart rate - should be between 120 and 180 beats per minute

3rd Step:    Situs- check which is the left side of fetus then do a dual image in a tranverse axial plane of the fetus with firstly the thorax showing the hearts axis towards the left and the second image showing the stomach on the left ensuring the left and right side is labelled.

4th Step: Four Chamber View- Angling cephalad from a transverse axial view of the abdomen.

The ventricles should be of similar size and the atria should be of similar size.
Assess the AV valves (atrioventricular) ie The tricuspid valve on the right is more apical than the mitral (on the left)valve insertion onto the interventricular septum. (the "offset cross" appearance)
Watch ,in real time, the opening and closing of the valves in systole and diastole.
The pulmonary venous connections can be identified.

5th and 6th Step Outflow Tracts

5th Step:      LVOT

From the 4chamber view, angle further cephalad to see the Left ventricle and the aorta (Left outflow tract) in the same view.
The aorta will be coursing to the right posterior direction.It should be assessed in colour Doppler also looking for any stenosis.
6th Step: RVOT From the LVOT view, the probe is angled further towards the head and slightly towards the fetal left shoulder.
This show the pulmonary trunk heading directly posteriorly towards the spine. It will divide into the pulmonary arteries.
Image and look in bmode and Colour Doppler.

7th Step: 3 Vessel View This view is a slightly oblique, axial view.

It cuts the upper part of the arches and transversally the Superior Vena Cava.

    This is an image with
  1. A full length view of the Pulmonary Artery (P) which arises from the right ventricle.
  2. A cross section of the ascending aorta (A)
  3. The superior vena cava (V)

It is commonly labelled PAV on the image.
It is important to have the 3 vessels in line with each other in order of largest (P) to smallest (V).
The aorta and pulmonary artery must be perpendicular to each other, otherwise there is a serious heart defect such as transposition of the great vessels.

8th Step: Interventricular Septum
IVS (inter-ventricular Septum):
Should be assessed when the foetus is in a decubitus position so the ultrasound beam is perpendicular to the septum.
This will avoid anisotropy and a false positve for septal defect.
It should be assessed in both Bmode and Colour Doppler.

9th Step: Aortic Arch

The 'arches' are best assessed when the foetus is prone.


Aortic Arch: Turn the probe 90degrees to a para-sagittal plane on the foetus.
The Aortic arch arises from the centre of the heart and is commonly referred to as a "cane".
Coarctations may be visualised in this view.

10th Step: Ductal Arch

 

This is the ductus arteriosis: The junction between the pulmonary trunk and the aorta.
Utilise a similar scan plane to the aortic arch.
The ductal arch is referred to as a "hockey stick" appearance, with the arch arising from the anterior of the heart. Bmode and colour assessment.

 


 

Common Pathology

 

For fetal heart pathology

 


 

Basic Hard Copy Imaging


A foetal heart series should include the following minimum imaging:

  • Situs and orientation
  • 4 Chambers
  • Inter-ventricular septum
  • Left Ventricular outflow tract
  • Right ventricular outflow tract
  • 3 vessel view
  • Aortic arch V's ductal arch
  • Document the normal anatomy. Any pathology found in 2 planes, including measurements and any vascularity.

 

REFERENCES

  • Callen PW. Ultrasonography in Obstetrics and Gynecology, Fourth Edition. W.B.Saunders Company, 2000.
  • Nyberg DA, Kapur RP, Mahony B, Pretorius DH. Ultrasound of Fetal Anomalies. Mosby,Inc., 1995.
  • FOETAL HEART ULTRASOUND    “How,Why and When” June 2007 Catherine Fredouille, MD, Jean-Eric Develay-Morice, MD, Ultrasonographer
 
 

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