Personalized Low-Energy Smart-Defibrillators Through Feedback Based Re-synchronization Therapy in Langerdorff-perfused Rabbit Hearts

Ilija Uzelac and Flavio Fenton
Georgia Institute of Technology


Aims: Ventricular fibrillation (VF), is a life threatening cardiac arrhythmia requiring defibrillation in order to restore normal sinus rhythm through administration of strong electric shocks. These shocks are seldom optimized in strength, timing and duration, and may cause AV node burnout, tissue damage through electroporation, formation of scars, and painful experience in conscious patients. In this study we presents feedback-based controlled delivery of re-synchronization therapy through administration of series of low-energy shocks based on feedback monitoring of ventricular electrical activity.

Methods: Isolated rabbit hearts were Langendorff perfused and stained with Di-4-ANBDQPQ Vm dye. For validation of the technique, series of images were obtained at 128 x 128 pixels at 500 FPS. Activation of the ventricles was monitored with locally placed photo-diodes connected to a controller board with based on 32-bit ARM micro-controller. The entire control algorithm was implemented in the micro-controller, and depending on the sensory input, a single shock parameters were calculated. Timing of the shock was based on desynchronous activity of the left and right ventricles during VF. Time between successive shocks was synchronized with the dominant VF frequency, and strength of each pulse was determined as proportional to the differences in the activation times between the ventricles.
Each shock was delivered with a custom based real-time controlled trans-conductance amplifier and each subsequent shock was re-calculated based on the observed VF dynamic.

Results: Feedback based re-synchronization therapy resulted in reduction of defibrillation energy by order of magnitude during ventricular tachycardia in comparison to a single shock. With more complex polymorphic VF, reduction of necessary defibrillation energy less, typically 3-5 times.

Conclusions: Feedback-based re-synchronization therapy is aimed towards design of advanced strategies for VF termination, and patient specific through assessment of VF dynamics resulting in reduction of defibrillation energy. Lower energy is associated less myocardium damage.