ULTRASOUND OF THE FETAL HEART - Normal
|For the detailed scanning protocol|
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
|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.|
|4 chamber heart.
This image shows the scan planes to obtain:
From the 4chamber view, by angling crandially rather than sliding the probe the outflow tracts are easily seen.
|Angle the probe cephalad to get the 4 chamber view of the fetal heart.
||The valvular movement should simulate birds wings.|
|SCAN PLANE LVOT
||Left Ventricular Outflow Tract:
||Right Ventricular Outflow Tract:
|3 vessel or PAV view||
If the aorta and pulmonary artery are not in perpendicular planes, suspect transposition
|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.|
|Demonstrate the aortic arch as it leaves the left ventricle.
It will have a 'walking stick' curve.
|Sagittal View of the Aortic Arch
|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'.
Ultrasound of the Fetal Heart -Protocol
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.
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
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.
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
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.
A foetal heart series should include the following minimum imaging: