Microsensors for Continuous Monitoring of Heart Function

We are developing two new sensor systems for continuous monitoring of the cardiac function during and after surgery. The first system uses triple-axis accelerometers to measure motion of the epicardial surface, while the second system uses miniature ultrasound transducers fastened to the heart surface to measure the contraction pattern of the heart muscle. The systems have been tested in animal experiments and in patient trials. Both systems have proven their ability to deliver high quality measurements of the heart’s motion and contraction, and to detect changes caused by occlusion of an artery. The ultrasound probes deliver very local information from where the transducer is fastened, while the accelerometer data seem to be more linked to global heart function. The ultrasound system requires high data rates and heavy processing, but the processed results are straightforward to interpret. For the accelerometer, the required data transfer rates and processing power is quite low. The optimal processing scheme for the accelerometer recordings is not so straightforward, but different schemes have been tested with promising results. The two systems are integrated with ECG and pressure measurements to a “multi-sensor system for the heart”.