Cardiac foci: what are they, characteristics and possible causes

Heart sounds are the sound expression of the closing of the heart valves. Its operation, at a physiological level, is always unidirectional, which allows blood circulation in an adequate way without organic problems arising. Humans have about 4.5-5.5 liters of blood in our body and, surprisingly enough, the heart is capable of pumping almost all of the fluid in about 60 seconds.

The human heart beats, on average, about 80 times per minute, which translates into 3 billion involuntary contractions throughout our lives. 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 continue telling curious facts about the physiology of the heart for hours, because literally, we owe it our life and our own existence. In any case, today we find it useful to address a more complex and specific issue: stay, then we tell you all about heart foci and, specifically, the intracardiac echogenic focus (FEI).

• Related article: "The 13 parts of the human heart (and their functions)"

What are cardiac foci?

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

In the 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 muscles, which allow the pumping of blood to the entire baby. These are intracardiac echogenic foci (IEF).

The FEI (s) are believed to be normal and safe in most cases, as they are observed in 5% of fetuses during the second trimester and are not necessarily associated with pathologies at the time of birth or during development. In other words, cardiac foci alone do not endanger fetal health.

Curiously, It has been found that FEIs follow a certain ethnic pattern, as up to 30% of fetuses in Asian people can develop it, while the global average prevalence is 3-5%. It is more common in Asian, African and Middle Eastern babies, and in addition, almost 80% of the time the ultrasound "flash" occurs in the left ventricle. In 18% of the pictures it appears on the right side, while only 4% of the patients experience it in both at the same time.

Intracardiac echogenic foci and their relationship with chromosomal abnormalities

We have said that the spotlights 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. We tell you below what is known about it.

FEIs and trisomy 21

Down syndrome is a genetic condition that results from a chromosome abnormality, which results in the presence of a more partial or total copy of chromosome 21. Human beings present 2 copies of each chromosome in each of our cells and, therefore, we are diploid (2n). The rarity of trisomy 21, as its name suggests, is that during meiosis chromosome 21 is not distributed well. Therefore, the patient ends up with an accessory copy (2 + 1) and manifests the symptoms of Down syndrome.

90% of 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 one more copy of chromosome 21 and affects 10 out of 10,000 live newborns.

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

However, this is not to say that an EIF is not clinically important. By itself it is not a trait that should be supported by genetic analysis, but if the mother has certain risk factors, it is time to start performing accessory tests.

FEIs and trisomy 13

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

More than 90% of newborn children with trisomy 13 die before the first year of age, so we tell a very different story from the disorder named above.

Things get interesting, medically, when we discover that 39% of fetuses with trisomy 13 present microcalcifications in the papillary muscle (cone-shaped muscle projections, the bases of which are attached to the wall ventricular). It is believed that the cardiac foci correspond to these formations, that is, that the ultrasound detects that there is more calcium than normal in an area of ​​muscle tissue. Naturally calcified tissues, such as bones, appear brighter on ultrasound, so this correlation makes sense.

• You may be interested in: "Circulatory system: what is it, parts and characteristics"

Final notes

As mentioned previously, cardiac foci are considered "normal" when they occasionally present on ultrasound during 18-20 weeks. In any case, if there is no evidence of pathology, it is classified within isolated events., so it is not taken into account when making a diagnosis.

Also, many of the FEIs disappear before the third trimester, but others do not. This scenario is also considered normal, so monitoring of bright spots in heart tissue is not followed unless other warning signs appear. Beyond this, other studies cite that the correlation between trisomy 21 and FEI is 1%, so special emphasis is placed on not worrying when this event is found on ultrasound.

For all these reasons, there are no diagnostic tests for fetuses that show only isolated heart foci. Among the possible suspicious pathological events, we find the following:

• The age of the mother at the expected date of delivery. According to certain 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 from other fetal tests indicating a possible chromosomal mismatch.

If none of these criteria are met, the heart foci are considered innocuous and no accessory testing or monitoring is performed.

Resume

As you can see, very little is known about intracardiac echogenic foci, to the point that their causes are not even really known. It is stipulated that it is 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 physiological event alone does not indicate anything, so it should not alarm the parents of a baby when it occurs 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. TO. (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. TO. (2000). Echogenic intracardiac focus in 2nd-trimester fetuses with trisomy 21: usefulness as a US marker. Radiology, 216 (2), 450-456.