The Fetal Medicine Foundation / 11-13 week scan / Tricuspid flow

11-13 week scan
Tricuspid flow

FMF Certificate of competence in assessment of tricuspid flow

The findings of recent studies suggest that examination of the fetal tricuspid flow at 11-13 weeks could have major beneficial implications in screening for both chromosomal abnormalities and major cardiac defects.

The FMF software which allows calculation of risk for both chromosomal and cardiac defects is provided free of charge to sonographers who have been appropriately trained and accredited in the assessment of the fetal tricuspid flow.

Requirements for Certification in assessment of tricuspid flow

The requirements for certification are:

1. FMF certification in measurement of nuchal translucency.
2. Attendance of the internet based course on the 11-13 weeks scan.
3. Submission of a logbook of 3 images including two with normal flow and one with tricuspid regurgitation at 11-13 weeks.

Protocol for the assessment of tricuspid flow

The gestational period must be 11 to 13 weeks and six days.
The magnification of the image should be such that the fetal thorax occupies most of the image.
An apical four-chamber view of the fetal heart should be obtained.
A pulsed-wave Doppler sample volume of 2.0 to 3.0 mm should be positioned across the tricuspid valve so that the angle to the direction of flow is less than 30 degrees from the direction of the inter-ventricular septum.
Tricuspid regurgitation is diagnosed if it is found during at least half of the systole and with a velocity of over 60 cm/s, since aortic or pulmonary arterial blood flow at this gestation can produce a maximum velocity of 50 cm/s.
The tricuspid valve could be insufficient in one or more of its three cusps, and therefore the sample volume should be placed across the valve at least three times, in an attempt to interrogate the complete valve.

Clinical application of tricuspid flow findings

The incidence of tricuspid regurgitation is related to NT and CRL as well as aneuploidy, being more common when the NT is high and the CRL is low. Therefore it is not possible to give simple numbers by which the presence of normal flow will reduce the risk for trisomy 21 and the presence of tricuspid regurgitation will increase the risk.
The FMF software firstly calculates a risk based on maternal age, fetal NT and maternal serum free β-hCG and PAPP-A. If the risk is more than 1 in 50 and tricuspid flow is normal the risk does not change. If the risk is 1 in 50 to 1 in 1,000 and the tricuspid flow is normal the risk is usually reduced. If there is tricuspid regurgitation the risk is always increased. In addition, there is an increased risk for cardiac defects and therefore such patients should have a follow up specialist fetal cardiac scan.

Quality review and ongoing Certification in assessment of tricuspid flow

Each sonographer must submit 3 images including two with normal flow and one with tricuspid regurgitation at 11-13 weeks for audit 12 months after obtaining the FMF Certificate of competence in assessment of tricuspid flow and the FMF software for the calculation of risks. In addition to the FMF audit, all sonographers are encouraged to perform their own internal quality assurance on a regular basis.
The audit involves examination of the images for each operator. Sonographers passing their audit will be re-audited and re-licensed on an annual basis thereafter.
If the images are not satisfactory the name of the sonographer will be removed from the FMF website list of holders of the Certificate of competence in assessment of tricuspid flow. A new audit can be carried out subsequently and the sonographer will only be reinstated on the FMF website list and the license renewed once the audit is considered satisfactory.