Intravalvular impedance sensor for next-generation smart prosthetic heart valves

Introduction: Complications after implantation of Prosthetic Heart Valves (PHVs) remain a substantial source of morbidity and mortality despite continuing advances in surgical care and prosthetic design. None of the current available PHVs, once implanted, is able to provide information on its functionality. We report our initial experience with a novel IntraValvular Impedance (IVI) sensor for next-generation smart PHVs to continuously monitor the operating status of the implanted prosthesis. Material and methods: The IVI sensor involves the use of electrodes integrated in the suture ring of PHVs to generate a local electric field (injection of current, and record electric field variations (ΔV) caused by the moving leaflets of the valve interfering with the electric field lines, from which IVI = Δ Forpreliminary in vitro evaluations we instrumented a mechanical heart valve (Carbomedics Orbis Aortic, Sorin Group) with two couples of copper electrodes (S1, S2, R1, R2) connected to an external impedance measurement system. The sensorized valve was immersed into a thorax model filled with saline solution and it was anchored to a mechanical simulator reproducing forward/backward movements that cause the cyclic opening/closing of the leaflets of the valve. IVI signal was continuously recorded by injecting current pulses (36 μA, 4 KHz) between S1 and S2 and measuring ΔV between R1 and R2. Results: The recorded IVI signal has shown a cyclic increasing/decreasing pattern which reflects the opening/closing dynamics of the leaflets and, ultimately, the functionality of the valve. Discussion: The novel IVI sensor proved to be a feasible tool for the continuous monitoring of the functionality of PHVs. It has great potential of reducing mortality of patients reporting IVI-based early warning of malfunctioning of the prosthetic valve due to thrombosis or pannus ingrowth. Additional efforts are required to achieve full integration of electrodes and microelectronic circuits for IVI measurement in commercially available PHVs.