#399 - [Journal Club] - 📌 Are We Compressing the Wrong Ventricle in Neonatal CPR?

In this episode of Journal Club, Ben and Daphna review a thought-provoking study from the Archives of Disease in Childhood titled "Chest Compression in Newborn Infants: What Anatomical Structures Are We Compressing?". The hosts explore the anatomical findings suggesting that current neonatal CPR guidelines—recommending compressions over the lower third of the sternum—may actually be targeting the right ventricle and great veins rather than the left ventricle. They discuss the implications for the "cardiac pump" vs. "thoracic pump" theories and what this means for the future of resuscitation guidelines.

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Chest compression in newborn infants: what anatomical structures are we compressing? Chua CT, O'Reilly M, Surak A, Schmölzer GM.Arch Dis Child Fetal Neonatal Ed. 2026 Jan 16:fetalneonatal-2025-329582. doi: 10.1136/archdischild-2025-329582. Online ahead of print.PMID: 41545184

Transcript

[00:02.136] Ben Courchia MD Hello everybody, welcome back to the Incubator Podcast. We're back today for another episode of Journal Club. Daphna, good morning, how are you?

[00:11.15] Daphna Yasova Barbeau MD I'm doing well, what you got for us today?

[00:13.65] Ben Courchia MD Ooh, I'm gonna start this week with an interesting paper that I saw in the Archives of Disease in Childhood - Fetal and Neonatal Edition. The author is Catherine Chua. "Chest Compression in Newborn Infants: What Anatomical Structures Are We Compressing?". That is the title.

[00:31.502] Daphna Yasova Barbeau MD Well, my daughter's been working on her hooks for her writing. This was a hook for sure.

[00:37.526] Ben Courchia MD This is a hook, right? Yeah, I saw the title and I dived in. But very, very nice paper. The background is interesting—approximately 1% of infants require chest compression at birth. The aim, theoretically, of chest compression is to restore systemic circulation, optimize coronary blood flow, and improve myocardial perfusion. This is postulated to occur through two mechanisms. First, directly compressing the heart between the sternum and the spine forces blood to flow into the circulation with each compression, also known as the cardiac pump theory. The second hypothesis is that chest compression produces a rhythmic increase in intrathoracic pressure, generating the gradient necessary between the arterial and the venous compartment, resulting in forward flow—called the thoracic pump theory. So you're kind of sucking blood back into the thorax.

[00:37.526] Ben Courchia MDThe current consensus of science and treatment recommendations provides that neonatal chest compression should be centered over the lower third of the sternum and avoid the xiphoid process. Now, the authors of the paper note that observational cohorts of over 500 infants and young children show that the right ventricle or the left ventricle was directly located under the lower third or lower quarter of the sternum. However, no newborn infants were included in these studies, and the location of chest compression varies with age as the heart descends from infancy to adolescence. In children aged one year to puberty, the optimal site for targeting the left ventricle while minimizing injury is located one centimeter above the xiphisternal joint. Now, ultrasound imaging in a cohort of 64 adults showed that performing chest compression over the left sternal border at the inter-nipple line or the sixth intercostal space targeted the left ventricle in approximately 72% to 77% of participants. So, I mean, it's kind of mind-boggling that we might not be compressing the heart if we're doing chest compression where we're told to do chest compression.

[02:45.208] Ben Courchia MDThis suggests that an alternative chest compression location could potentially improve cardiopulmonary resuscitation effectiveness. This compression point might be more specific compared with the wide range of the lower third of the sternum as recommended by the current guidelines. So overall, there's limited understanding of the precise cardiac anatomy in the immediate newborn period, and little is known about which structure lies beneath the recommended compression site in newborn infants. So given this gap, they aim to identify the location of the left ventricle within the chest and identify the structures below the lower third of the sternum using transthoracic echocardiography.

[02:45.208] Ben Courchia MD For anybody doing echoes and hemodynamics, people will be like, "Oh, we know where it is." But it's true that it's funny to see it highlighted in the form of a paper. This is a prospective observational cohort study conducted in Edmonton in the province of Alberta in Canada. Newborn infants born at term admitted to the postnatal unit with likely normal heart anatomy were eligible for inclusion. Transthoracic echocardiography was performed and for each patient the chest circumference was measured at the inter-nipple line using tape. Then the tape was also placed along the sternum with the left edge of the tape aligning with the left border of the sternum, and the suprasternal notch and xiphisternum were palpated and marked on with tape.

[02:45.208] Ben Courchia MDNow the authors then followed the American Society of Echocardiography guidelines, got a bunch of views on echocardiography: a parasternal long axis, a parasternal short axis, an apical four-chamber view, and a subcostal view. Now, we'll talk a little bit more about how these views matter, but these views were used to delineate the location of the right ventricle and of the left ventricle and their projection on the chest wall. Small pieces of tape were placed on the skin to mark exactly where the optimal clip of each of the four views was obtained. Thereafter, the distance between the tape marking the long axis and the four-chamber view was measured, as well as the midpoint between the long axis and the four-chamber view to estimate the location of the left ventricle.

[05:00.758] Ben Courchia MDSo just for a review—since we're talking about hemodynamics again, we're considering doing some educational series on hemodynamics if you are interested, let us know. But when they talk about these parasternal long axis views: the heart sits in the chest kind of like a fist aiming at your nipple, I guess. And a parasternal long axis view is kind of like looking at the heart from the profile. So like you're looking at an elongated view of the left ventricle. The apical four-chamber view is kind of like the way you imagine the heart in your head, like two atria above, two ventricles below. The parasternal short axis view is kind of difficult to describe. And then the subcostal view is kind of like an apical four-chamber, just taken from a different angle from below the diaphragm. So basically, you don't really need to know so much about these views. You just need to understand a little bit that they provide different perspectives on the heart anatomy, and that basically kind of like recreating a 3D structure by putting all these pictures together, you can delineate exactly where the heart is located.

[05:00.758] Ben Courchia MDSo they took a convenience sample of 50 infants. They had a gestational age of about 39 weeks. 3.4 kilos was about the birth weight, and the echoes were performed within the first day of life. So the distance between the long axis and the apical four-chamber view was about 3.5 centimeters. The midpoint between the two was about 1.9 centimeters. And then they had all these different projections where they looked at different measurements. And there's a very... actually, you know what, Daphna? Since we are on... since we're going to be on YouTube, as my grandmother used to say, I'm going to show you exactly what is meant by that. Let me see if I can share my screen. You see, people, how unsophisticated we are. We'll do it this way.

[06:39.435] Daphna Yasova Barbeau MD Yeah, show me. Show us.

[06:53.996] Ben Courchia MD So basically they have a bunch of measurements and what they come to is kind of this figure. Can you see? So they come to this figure and what they see is that the left ventricle is located at the third left sternal border in one infant or 2%. It was located at the fourth left sternal border in 22 infants or 44%. It was located at the fifth left sternal border in 25 infants or 50% of the cohort, and at the sixth left sternal border in 4% of infants.

[07:34.233] Ben Courchia MD So basically, when you look at it and you look at the lower third, you're really not compressing the left ventricle. And you're kind of right over the right ventricle, which is very interesting. And that's not really the intention. So the authors state that their study provides newborn-specific anatomical data. Some people might say that the sample size is not big enough. To be fair, if you look at doing hemodynamics, this is where we expect some of these structures to lie anyway, so I don't think they're off. I think they're absolutely correct in how they delineated the position of the heart.

[08:10.965] Daphna Yasova Barbeau MD Okay, but I have a dumb question. Again, I was just teaching the cardiac exam last month. And I mean, this is kind of true in adults also , that the left ventricle is to the left of the patient's sternum.

[08:33.707] Ben Courchia MDYeah, but the difference is that really what they're looking at is the position in terms of its height in the chest. And I feel like what gets missed is that it almost feels like when you are born your heart is more midline, its axis is a bit rotated, and over the course of the years it kind of lands on the diaphragm and sort of starts sitting on the diaphragm. Yeah, and I think that this is something that informs the chest compressions in adults where it is you are compressing the heart. When we are talking about babies, we're really looking at maybe one structure.

[09:03.403] Ben Courchia MDSo I just want to get through this discussion and this conclusion. But really, the authors talk about the fact that the left ventricle does not lie directly beneath the midline of the sternum, but projects predominantly under the fourth or fifth left sternal border corresponding to the lower third of the sternum. The longitudinal extent and projection of the ventricle indicates that standard midline compressions are unlikely to directly overlay the left ventricle in most newborns. Instead, based on their measurements, chest compression applied to the recommended lower third of the sternum would primarily compress midline structures such as the right atrium and the right ventricle, the superior vena cava and the ascending aorta.

[09:31.253] Ben Courchia MDThe authors note that current recommendations are based on cohort studies including mostly infants and children, rarely newborns. Analysis of 210 radiograph images of children from birth to 12 years of age revealed that the heart descends with age, as we just mentioned, and the heart is positioned under the sternum in infants and then migrates to the lower third of the sternum in adolescence. They conclude that chest compression delivered at the currently recommended lower third is likely to compress the right heart, the great veins, and that this anatomical relationship challenges the cardiac pump-based rationale underlying the 3:1 compression-to-ventilation ratio. Together with the evidence supporting the thoracic pump mechanism and the benefits of continuous chest compression with sustained inflation, these results highlight the need to re-examine both the optimal compression site and the ratio of compression to ventilation to optimize blood flow and improve outcomes. I think this is very interesting. And wondering if maybe, yeah, we need to have different points of compression based on the age of the patient, which sounds like a terrible thing to establish, but yeah.

[11:14.487] Daphna Yasova Barbeau MD I'm gonna reference our Delphi quote for this year, which was, "Innovation consists of seeing what everybody else has seen and thinking what nobody else has thought". That's exactly what this is, saying like, this is something we do pretty routinely—have we ever thought about the underlying mechanisms? And it's like these little things that like, I mean, if we changed the way we did CPR, that would be earth-shattering, right? Potentially. And I think that's very cool. And it makes sense.

[11:52.341] Ben Courchia MDYeah. And like I said, what's mind-boggling is that if you ask anybody who ultrasounds hearts all day, they'll be like, "Yep, yeah," they'll be like, "Yeah, this is exactly right". Right? I mean, this is also what I was thinking of when I was thinking about it, because I could imagine myself doing chest compression and was like, "How did that never dawn on me?". So kudos to this group for making us see what others have not.

[12:21.741] Daphna Yasova Barbeau MDFor sure. Love that. Good one. Okay, bye everyone.

[12:25.529] Ben Courchia MDAlright buddy, I'll see you tomorrow.