For the first time, researchers have mapped the electrical wiring of a heart with Tetralogy of Fallot—revealing a delicate network that surgeons have been operating around blindly for decades. Scientists at UCL and the European Synchrotron in Grenoble, France, used a groundbreaking imaging technique to scan 18 whole human heart specimens and reconstruct in stunning three-dimensional detail the cardiac conduction system, the specialized fibers that carry electrical signals through the heart muscle.
Tetralogy of Fallot is one of the most common congenital heart diseases, affecting around 1% of the population worldwide. Many babies born with it require life-saving surgery shortly after birth, and survival rates are now high. But a troubling pattern has emerged: many patients develop complications later in life, particularly abnormal heart rhythms or contraction patterns. Surgeons have long suspected that these problems arise when the heart's electrical conduction system—invisible during surgery—gets disturbed during repair. Until now, they've had no clear map to guide them.
The breakthrough came through Hierarchical Phase-Contrast Tomography, or HiP-CT, an advanced imaging method that harnesses the European Synchrotron's Extremely Brilliant Source. This new generation synchrotron produces an X-ray beam intensity up to one million times higher than conventional hospital CT scanners, allowing researchers to scan whole organs non-destructively and zoom in to near-cellular resolution—down to two microns, about 50 times thinner than a human hair.
What the scans revealed was striking. In healthy hearts, the electrical wiring of the right ventricle—the main chamber affected by Tetralogy of Fallot—follows an expected pattern. But in hearts with the disease, the wires are both thinner and spread out across the septum, the wall separating the ventricles, in a pattern that resembles fabric draped loosely over a surface. This anatomical difference explains why electrical disturbances are so common in these patients.
Andrew Cook, a professor of cardiac anatomy at UCL and senior author of the study, offers a simple analogy for why this map matters: "I often compare it to renovating a house: You wouldn't want to start drilling into a wall without knowing where the electrical wires are. The same principle applies to the heart." Until now, surgeons have relied on "anatomical landmarks" to navigate around the conduction system—educated guesses based on general patterns. The new research revises those landmarks with precision based on actual anatomy.
This research is part of the Human Organ Atlas, an international collaboration aimed at visualizing the body's structures in unprecedented detail. The HiP-CT technique, developed at the European Synchrotron by a team led by UCL, finally bridges a gap that has persisted for more than a century: radiology and histology have always offered very different views of the body. HiP-CT synthesizes both, revealing anatomy that was simply invisible before.
The implications ripple outward. Surgeons can now use these maps for surgical training, learning exactly where to navigate and where to avoid. For the patients themselves—infants born with one of the most common birth heart defects—the prospect is clearer: better-informed surgery today could mean fewer complications and better outcomes tomorrow. What was once a mystery written in invisible wires is finally coming into focus.