A silicone phantom heart that can be tuned to mimic HFpEF

HFpEF, the form of heart failure where the heart still squeezes but loses its ability to relax and fill, has been hard to study in the lab. The contraction looks healthy on an echocardiogram, so the dysfunction hides until the patient is already short of breath. A team at the University of New South Wales in Sydney built a phantom that lets researchers dial that relaxation, called compliance, up and down on demand. The device is a beating replica of the left side of the human heart, cast in silicone with soft robotic artificial muscles wrapped around it to drive the motion. Inside, it carries the structures most heart devices are designed to fix: artificial valves, papillary muscles (the small inner-heart muscles that anchor the valves), and chordae tendineae (the tendon-like cords that tether the valves to those muscles).

The model is described in two peer-reviewed papers: a Nature Communications article on compliance modulation in HFpEF and a companion Advanced Science paper on the platform itself. A UNSW press release and a Robohub re-report present the work as a new way to study heart disease and test life-saving devices before they reach patients.

HFpEF is not one disease. It is a cluster of syndromes in which the ventricle stiffens and cannot fill properly, even though the ejection fraction (the percentage of blood squeezed out with each beat) stays normal. Roughly half of all heart-failure patients fall into this category, and existing drugs help only a subset. Previous phantoms and animal models could mimic the squeeze but not the give, which is why device development has been slow. A valve repair that works on a stiff phantom may fail on a compliant one, and a stiff-phantom test of a new HFpEF-specific implant gives the wrong answer by construction.

The UNSW model decouples those two variables. Silicone membranes form the internal chambers, and soft robotic muscles wrapped around the outside drive the beating. The team can shift the model from healthy compliance to the stiff, poorly-filling regime that defines HFpEF, and the same setup can replay regurgitation, the process in which a valve leaks and blood flows backward, by reproducing the geometry of valves, papillary muscles, and chordae tendineae inside the model. That is the specific capability the Nature Communications paper anchors: a soft robotic atrioventricular model of HFpEF whose compliance can be modulated to study the disease and test devices against it.

The team is led by Scientia Associate Professor Thanh Nho Do in UNSW's School of Biomedical Engineering and Medical Robotics Lab. Stated goals include better understanding of heart conditions, reducing reliance on animal testing, and patient-specific models that doctors can use to plan procedures. The published work shows a platform rather than a deployed clinical workflow, and the patient-specific claim rests on the thinnest evidence of the three.

The falsifier is sharp. If the model does not reproduce clinical HFpEF filling dynamics measured in patients, or if existing phantoms already covered compliance modulation, the headline claim collapses. The Nature Communications paper reports compliance modulation as the contribution, so the question worth tracking is which clinical signatures the model reproduces and across what compliance range.

For now, the most concrete use of the model is in the device-development pipeline: a soft-robotic left heart that can fail the way a real one does, on demand, in a lab.