In horses, cardiac diseases are frequently occurring and arrhythmias are an important cause of sudden death, which has a major impact on rider safety. In human and small animal medicine, diagnosis and treatment of cardiac disease often involve minimally-invasive techniques that use precisely placed catheters in the heart. In order to ensure success and safety, accurate visualization of these catheters is essential. This is problematic in horses, and at the same time the reason why such important techniques have barely been developed. The standard imaging techniques needed for accurate catheter placement, such as CT & MRI scan or radiography, cannot be applied in horses because they are too large. The aim of this research project is to develop adapted catheterisation techniques, fully guided by echocardiography as imaging technique, in order to enable more efficient treatment of cardiac disease. The study will start by creating lifelike, 3D-printed, ‘plastic’ models of the equine heart. The models will be placed in a water bath allowing us to develop new echography-based imaging techniques of both heart and catheters and to develop new catheterisation procedures. In the last phase, after optimizing the required techniques and sufficient practicing, the catheterisation procedure will be performed in horses. This project will provide new, standardized techniques for minimally-invasive diagnosis and treatment of heart diseases in horses.