Peak aortic acceleration-derived contractility index (ICONTM) to monitor left ventricular contractility in preterm infants: a pilot, prospective, cohort study.
In a pilot prospective cohort study of preterm infants, the electrical cardiometry-derived contractility index (ICON™) demonstrated a weak but significant correlation with echocardiographic measures of left ventricular function, suggesting its potential utility as a continuous monitoring tool that complements rather than replaces standard echocardiography.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the delicate world of newborn intensive care, watching a tiny heart work is a constant challenge. For premature babies, whose bodies are still finishing their development, the heart must pump blood with enough force to reach every cell, yet it is often too small and fragile for the heavy-duty tools used on adults. Doctors rely on ultrasound machines, which use sound waves to create moving pictures of the heart, to see how well the muscle is squeezing. This method is the gold standard, but it has a flaw: it is like taking a photograph. It captures a single moment in time, requires a skilled operator to hold the probe in just the right spot, and cannot tell the doctor if the heart is struggling or improving the very next second. In a busy nursery, waiting for a new picture every time a baby's condition changes is not always practical.
Scientists have long looked for a way to watch the heart's strength continuously, without interrupting the baby or needing a specialist at the bedside every minute. One such method involves measuring how electricity moves through the chest. As the heart beats, the blood inside it rushes forward, and this movement changes the way electricity flows through the body. A device can detect these tiny shifts and calculate a number that represents how hard the heart muscle is contracting. This approach is non-invasive, meaning it uses only stickers on the skin, and it provides a steady stream of data. The question for researchers was whether this electrical number could truly reflect the actual strength of the heart muscle, or if it was just a rough guess that might mislead doctors.
A team of researchers in France set out to test this idea in a group of premature infants. They focused on babies who had already passed the most dangerous first few days of life and were stable enough to be studied without putting them at risk. The goal was simple: to see if the continuous electrical reading matched the detailed pictures taken by the ultrasound. The team recruited fifty-nine preterm babies, most born before thirty-six weeks of pregnancy, who were already in the hospital and needed a standard heart ultrasound for their regular care. The researchers did not change how the babies were treated; they simply added a new layer of observation.
While the babies were resting quietly on their backs, the medical team placed four small stickers on each infant. Two went on the forehead and thigh, and two on the neck and chest. These stickers sent a very weak, high-frequency electrical current through the baby's body, a current so small it could not be felt. A portable monitor connected to these stickers watched how the electricity changed as the heart pumped. From these changes, the machine calculated a specific number called the contractility index, which is meant to show how forcefully the left ventricle is squeezing. At the same time, a highly trained specialist performed the standard ultrasound, taking clear images of the heart to measure how much blood it was pumping out with each beat. This specialist did not know what the electrical monitor was reading, ensuring that the comparison was fair and unbiased.
The researchers then compared the two sets of numbers. They found that the electrical reading did move in the same direction as the ultrasound measurements. When the heart was stronger on the ultrasound, the electrical number was also higher. However, the connection was not a perfect match. The electrical number was only weakly linked to the ultrasound results, meaning that while they generally agreed on the trend, they did not tell the exact same story. More importantly, the electrical device tended to give higher numbers than the ultrasound. It consistently overestimated how strong the heart was, and this overestimation became more noticeable when the heart was already pumping quite well.
The study confirmed that the electrical method is not a perfect replacement for the ultrasound. It cannot simply swap out the detailed pictures for a single number, because the two methods measure the heart in different ways and the electrical device is prone to exaggerating the strength. Yet, the findings suggest a different kind of value. Because the electrical monitor can run continuously, it might be able to spot when a baby's heart is starting to weaken or getting stronger over time, even if the absolute numbers are not perfectly accurate. This could be especially useful in smaller hospitals or during transport, where a specialist with an ultrasound machine is not always available.
The authors concluded that this electrical tool should be seen as a companion to the ultrasound, not a substitute. It offers a way to keep a constant watch on the heart's rhythm and force, filling the gaps between the snapshots taken by the ultrasound. While it needs more testing to see how well it tracks changes in sick or unstable babies, this initial study shows that in stable premature infants, the electrical signal does reflect the heart's true effort, even if it speaks in a slightly louder voice than the ultrasound. For now, the best approach remains using both tools together, letting the continuous monitor warn of changes while the ultrasound confirms the details.
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