A 3D-Printed Heart That Actually Beats - and Surgeons Can Operate On It

Before a surgeon repairs a leaky heart valve, she may have practiced on a pig heart or reviewed images on a screen. Neither option lets her feel a beating organ, handle realistic tissue, or rehearse the specific anatomy of the patient on her table tomorrow. A team at Washington State University has spent years trying to change that.

Their latest result: a soft, 3D-printed model of the left side of the human heart that contracts, beats, and - crucially - can be operated on.

Why the left side of the heart is the hardest to practice on

The left heart handles the highest pressures in the circulatory system. Its mitral valve, positioned between the left atrium and left ventricle, tends to become leaky as people age - a condition called mitral regurgitation, in which blood flows backward instead of forward. Surgeons fixing this valve often do so through minimally invasive procedures, working through small incisions while the heart continues to pump. The skill required is considerable, and there are few good ways to build it before operating on a living person.

Previous synthetic models exist, but they are mostly made by molding - a process that limits how complex the shapes can be. "There have been other, synthetic models that are mostly mold-casted, and one of the main limitations there is that they cannot do some of the more complex curvatures that you see in the heart," said Alejandro Guillen Obando, a PhD candidate in WSU's School of Mechanical and Materials Engineering and first author on the study.

Printing a heart layer by layer

The WSU team started with a scan of a real human heart and used it to 3D print a replica of the left side, including the atrium, ventricle, and mitral valve. The result has a soft texture meant to approximate real cardiac tissue. Inside the model, tiny pneumatic actuators pump the structure rhythmically, and string-like filaments manage mitral valve movement in a way that mimics the real organ's chordae tendineae. When artificial blood flows through it, sensors on the model monitor simulated blood pressure.

"Our layer-by-layer approach in 3D printing allows us to add more curvature and make the chambers simulate a real heart," said Guillen Obando.

To test whether the model could actually be used for surgical training, the researchers did something ambitious: they deliberately created a defective mitral valve within the model and then fixed it. They built a repair device similar to commercially available clips used in real procedures and inserted it into the faulty valve. Sensors showed increased pressure in the left ventricle, a sign the valve was closing properly. Ultrasound imaging confirmed that artificial blood was no longer regurgitating back into the chamber.

The study appeared in Advanced Materials Technologies.

What makes this different from a computer simulation

"It's very useful for doctors and surgeons to practice when the heart is still beating, especially for minimally invasive surgery," said corresponding author Kaiyan Qiu, Berry Family Assistant Professor in the School of Mechanical and Materials Engineering. "In our case, this model is the first fully synthetic model that, without any assistance of animal models, mimics the complete left side of the heart. We were able to incorporate both the anatomic features and the dynamic functions."

The last point matters. Computer-based training shows you a procedure but does not put a tool in your hand while a pulsing structure resists. Animal models are closer to reality but are not patient-specific, cannot be reused, and raise ethical concerns. A synthetic model that can be printed from any patient's scan - and re-printed if needed - occupies a different space entirely.

The road to all four chambers

The team has filed a provisional patent and is now working toward a complete four-chamber, four-valve heart model. They also plan to work with medical professionals and students to conduct patient-specific pre-surgical rehearsals on the model for different valve diseases.

The obvious question is whether the feel and mechanical response of a 3D-printed model, however sophisticated, is close enough to real tissue for training to transfer meaningfully. That validation will require studies with surgeons who use the model and then operate on real patients - research that has not yet been done. The WSU work is funded by the National Science Foundation and WSU internal funds, and represents an early proof of concept rather than a validated training tool.

Still, the fact that a valve repair performed on this model produced measurable, ultrasound-verifiable results suggests the physics of the system are doing real work. That is a necessary first step.