Cardiac foci: what are they, characteristics and possible causes?

Let us see what is known about cardiac foci and how they are associated with certain chromosomal abnormalities.

Heart sounds are the sonorous expression of the closure of the heart valves. Their functioning, at the physiological level, is always unidirectional, which allows Blood to circulate properly without organic problems. Humans have about 4.5-5.5 liters of blood in our body and, surprising as it may seem, the heart is capable of pumping almost all the fluid in about 60 seconds.

The human heart beats, on average, about 80 times per minute, which translates into 3 billion involuntary contractions in our lifetime. With the size of a fist and the greatest possible resistance, this organ filters about 7,000 liters of blood every 24 hours (or more).

We could go on telling curious facts about the physiology of the heart for hours, since we literally owe life and our very existence to it. In any case, today we find it useful to address a more complex and specific topic: stay, because we will tell you all about cardiac foci. we tell you all about the cardiac foci and, specifically, the intracardiac echogenic focus (IEF).

What are cardiac foci?

Cardiac foci, more specifically intracardiac echogenic foci, are small bright spots seen in the heart of a fetus on ultrasound examination (sonography).. We recall that ultrasound uses sound waves to produce images of internal areas of our body, so this technique is very useful for observing the development of the fetus throughout pregnancy.

In second trimester ultrasound, the structure and function of the heart and fetus are routinely evaluated. In this type of examination, special attention is paid to the 4 chambers of the organ (right atrium, left atrium, left ventricle and right ventricle). As we have said, sometimes small bright "spots" are observed in the heart, generally in the ventricular musculature, which allows the pumping of blood to the whole baby. These are intracardiac echogenic foci (IEFs).

The IEF(s) are thought to be normal and harmless in the majority of casesThey are seen in 5% of fetuses during the second trimester and are not necessarily associated with pathology at birth or during development. In other words, cardiac foci alone do not endanger fetal health.

Interestingly, it has been found that EIF follows a certain ethnic pattern, as up to 30% of fetuses in Asian individuals may develop EIF, while the global average prevalence is 3-5%.while the average worldwide prevalence is 3-5%. It is more common in Asian, African and Middle Eastern babies and, moreover, in almost 80% of cases the ultrasound "flash" occurs in the left ventricle. In 18% of cases it appears in the right ventricle, while only 4% of patients experience it in both at the same time.

Intracardiac echogenic foci and their relation to chromosomal abnormalities

We have said that foci are not bad per se, but science has a lot to argue about this issue. Specifically, research such as Significance of an Echogenic Intracardiac Focus in Fetuses at High and Low Risk for Aneuploidy have shown that, unfortunately, there is a correlation between EIF and trisomies on chromosomes 21 and 13.. Here is what is known about it.

EIF and trisomy 21

Down syndrome is a genetic condition resulting from a chromosomal abnormality, which translates into the presence of a partial or total extra copy of chromosome 21. Humans have 2 copies of each chromosome in each of our cells and are therefore diploid (2n). The rarity of trisomy 21, as the name suggests, is that during meiosis the chromosome 21 is not well distributed.. As a result, the patient ends up with an accessory copy (2+1) and manifests the symptoms of Down syndrome.

Ninety percent of the cases are due to these meiotic errors, while 4% and the remaining percentage are the result of problems such as balanced translocation and errors after fertilization. In short, this condition causes there to be one extra copy of chromosome 21 and affects 10 out of every 10,000 live newborns.

According to the research cited above, cardiac foci are present in approximately 18% of fetuses with a trisomy 21, compared to 5% of foci experienced in normal babies.. This might indicate that IEFs could be minor markers for detecting trisomy, but this correlation does not always hold true.

In any case, this does not mean that an SIF has no clinical significance. On its own, it is not a trait that needs to be supported by genetic testing, but if the mother has certain risk factors, it is time to start accessory testing.

SIF and trisomy 13

Trisomy 13 follows the same premise as the previous case, i.e. the patient has a copy of more than one of the somatic chromosomes, this time number 13. It can manifest in a total, partial or mosaic form, but it is enough to know that the extra genetic material interferes with the normal development of the patient.

More than 90% of newborns with trisomy 13 die before the first year of life.So we tell a very different story from the previously named disorder.

Things get interesting, on a medical level, when we discover that 39% of trisomy 13 fetuses have microcalcifications in the papillary muscle (cone-shaped muscle projections whose bases attach to the ventricular wall). The cardiac foci are thought to correspond to these formations, i.e. ultrasound detects that there is more calcium than normal in an area of muscle tissue. Naturally calcified tissues, such as bone, appear brighter on ultrasound, so this correlation makes sense.

Final notes

As previously mentioned, cardiac foci are considered "normal" when they occur occasionally on ultrasound during the 18-20 weeks. However, if there is no evidence of pathology, it is classified as an isolated event, so it is not taken into account.so it is not taken into account when making a diagnosis.

In addition, many of the SIFs disappear before the third trimester, but others do not. This scenario is also considered within normality, so monitoring for bright foci in cardiac tissue is not pursued unless other warning signs appear. Beyond this, other studies cite that the correlation between trisomy 21 and SIF is 1%, so special emphasis is placed on not being concerned when this event is found on an ultrasound.

For all these reasons, no diagnostic tests are available for fetuses showing only isolated cardiac foci. Among the possible suspicious pathological events, we find the following:

• The age of the mother at the expected date of delivery. According to some studies, an older woman is more likely to give birth to a child with this syndrome.
• Alarming triple test results: this test is performed to quantify the probability that the infant has chromosomal aneuploidies.
• Evidence of other fetal testing indicating a possible chromosomal mismatch.

If none of these criteria are met, the cardiac foci are considered harmless and no ancillary testing or monitoring is performed.

Summary

As you have seen very little is known about intracardiac echogenic foci, so much so that even their causes are not really known.. It is stipulated to be due to characteristic microcalcifications in the heart muscle, but there is not even a clear idea about the etiology of the event.

On the other hand, some investigations associate trisomy 13 or 21 with cardiac foci, while others do not dare to make clear correlations. This physiologic event alone does not indicate anything, so it should not alarm parents of an infant when it presents in isolation.

Bibliographic references:

• Bethune, M. (2008). Time to reconsider our approach to echogenic intracardiac focus and choroid plexus cysts. Australian and New Zealand Journal of Obstetrics and Gynaecology, 48(2), 137-141.
• Bromley, B., Lieberman, E., Laboda, L., & Benacerraf, B. R. (1995). Echogenic intracardiac focus: a sonographic sign for fetal Down syndrome. Obstetrics & Gynecology, 86(6), 998-1001.
• Rodriguez, R., Herrero, B., & Bartha, J. L. (2013). The continuing enigma of the fetal echogenic intracardiac focus in prenatal ultrasound. Current Opinion in Obstetrics and Gynecology, 25(2), 145-151.
• Winn, V. D., Sonson, J., & Filly, R. A. (2003). Echogenic intracardiac focus: potential for misdiagnosis. Journal of ultrasound in medicine, 22(11), 1207-1214.
• Winter, T. C., Anderson, A. M., Cheng, E. Y., Komarniski, C. A., Souter, V. L., Uhrich, S. B., & Nyberg, D. A. (2000). Echogenic intracardiac focus in 2nd-trimester fetuses with trisomy 21: usefulness as a US marker. Radiology, 216(2), 450-456.