Abstract: The invention provides a system for determining a real-time valve function of a subject. The system comprises a processing unit adapted to: obtain a numerical model of a cardiac system, the numerical model being a 0D numerical model or a 1D numerical model, wherein the numerical model is adapted to receive physiological data as an input and output a simulated function of the cardiac system in real-time, wherein the simulated function of the cardiac system comprises a simulated function of a valve within the cardiac system. The processor is further adapted to obtain a continuous stream of physiological data from the subject; provide the continuous stream of physiological data as an input to the numerical model of the cardiac system, thereby generating a simulated real-time function of the cardiac system of the subject; and determine a real-time valve function of the subject based on the simulated real-time function of the cardiac system of the subject.