Product Development and Test Systems
Biomedical invitro tests of prosthetic heart valves required a left ventricular pulse duplicator designed and developed by SAI to precisely replicate invivo LVP waveforms. The duplicator accurately reproduces atrial fibrillation LVP waveforms for test and evaluation of forces, stresses, and vibro-acoustics in mechanical heart valves and components. »«Example of atrial fibrillation LVP waveforms, as recorded through a catheter at the Cleveland Clinic invivo and reproduced invitro in the SAI pulse duplicator (top, plotted simultaneously). The recorded instantaneous invitro aortic pressure and LV volume are also displayed.
Accelerated fatigue testing of pacemaker leads at 10 times anatomical rates is accomplished in a test system assembled at SAI. The leads are mounted in groups of 30, with stresses calculated from stroboscopic biplane photography and analysis to accurately measure lead curvature and compute component stresses under the applied conditions of each test. The system operates under computer control, driven by dual stepper motors that produce synchronized motion simultaneously both in-plane and out-of-plane for the leads. »
«In vivo pacemaker lead stresses as a function of time and position along the distal end of the lead, calculated from lead curvature in situ. The curvature along the lead is computed from bi-plane fluoroscopic cines taken from individual patients.
SAI personnel have worked extensively with animal studies, implanting telemetry systems for real-time acquisition of left ventricular pressure, stresses in mechanical implants, and high fidelity acoustic and EKG monitoring signals. »
«Expertise and experience in implant instrumentation includes the encapsulation of strain gages, pressure transducers, signal conditioning and RF telemetry transmitters, and the development and use of skin buttons, connectors, and implanted acoustic sources.
An acoustic array of accelerometers arranged in a pattern optimized for measurement of cardiac sounds. The array is shown in an invitro test configuration on the surface of a cast of ballistic gelatin. A tube simulating blood flow through a stenotic coronary artery runs 5cm beneath the fourth sensor from the left. »
«Transparent view of the chest showing line element arrays positioned over the heart. Cross-spectral amplitude and phase (delays) are used in beamforming to improve signal-to-noise ratio, and indicate presence of localized cardiac sound sources throughout the cycle.
Sensor designs using PVDF film produce high sensitivity with very low noise. Elements can be closely spaced, adhesive backed, and disposable. This linear array was designed by a sensor team at MedAcoustics™. »
«Spectral analysis of signals obtained from mechanical heart valves can provide evidence of features in time and frequency indicative of valve condition. The closing sound spectrogram shown here shows features that indicate valve integrity.
Mechanical heart valve instrumentation for invitro testing may include optical proximity sensors to measure the displacement, velocity, and acceleration of the valve occluder disc, seen here at the 2 o'clock position. Micro-miniature strain gages, miniature accelerometers, and acoustic sensors are used to simultaneously monitor mechanical interactions and sound. Signal analysis is then used to evaluate cause-and-effect relationships between mechanical interactions and the sound signature. »