Ex vivo monitoring of rat heart wall motion using piezoelectric cantilevers

We report on an experimental exploration of ex vivo measurements and real-time monitoring of the motions of heart wall for perfused rat hearts, by employing a surface-contact type of electromechanical probes based on piezoelectric transduction. In a hybrid experimental apparatus consisting of a conventional heart perfusion system and external electromechanical probing devices and circuitry, prototyped piezoelectric cantilever devices are calibrated and tested. We demonstrate that the external piezoelectric cantilevers are capable of monitoring the dynamic behavior of the isolated heart ex vivo, by measuring the motions of the heart wall. For typical rat hearts with heart rates in the range of ~150-250bpm (beats per minute), cantilevers with dimensions of t × w × L ≈ 130μm × (0.3-8)mm × (1-19)mm yield electrical signal of ~50-400mV. Measured data can also help identify signatures of various regimes (e.g., from healthy to fatigued, to expiring) in the dynamical evolution during the perfused heart´s lifetime. Preliminary tests on parallel multichannel monitoring with probes positioned at multiple locations on heart surface prove to be valid and useful in obtaining information of regional displacement of heart wall.