High-power current source with real-time arbitrary waveforms for in vivo and in vitro studies of defibrillation

Defibrillators are standard tools for treating cardiac fibrillation; however, the mechanisms by which they terminate deadly cardiac arrhythmias are still not fully understood, and optimizations to lower energies are very desirable. Clinical defibrillators do not provide a precise control of shock timing, duration, and voltage (current), and operate with fixed waveforms. Therefore, they are not suitable for research, particularly when studying low-energy defibrillation methods that require an examination of arbitrary and strictly timed waveform shocks of varying strength and duration. We present a custom-made microcontroller voltage-to-current converter (V2CC) with an output isolated from the Earth ground, capable of delivering up to 1 A continuously and up to 5 A into a 40 Ω load for >500 ms in a pulsed regime. For currents lower than 5 A, the load resistance can be higher, so that the product current times resistance is guaranteed to be up to 200 V. Bandwidth is in excess of 1 kHz, timing accuracy, response time, and rise and fall times are better than 10 μs. In addition, multiple safety mechanisms are implemented to protect the device and the operator. In our feedback control experiments the device has been tested successfully on isolated rabbit hearts. The V2CC is primarily designed to be used in ex vivo cardiac experiments, but is suitable for a wide variety of settings that require a high-current source of arbitrary waveforms.