ECG waveform generator

I have been working extremely hard to come up with a heartbeat Simulator that can generate an ECG waveform. I almost tried everything from timer LM555 to CD4017, and UJTs anything I?ve heard of. Please if anyone has an idea I can try the due time almost up
THANK YOU ALL

you have two options. Or create a pure analog system with an rlc and controling the damping. Its not perfect but is a solution. It has been made many many years ago. The second ... Just use a dac. as ecg frequency is low.. This might be very simple

Is it possible to specific on using RLC, is it a pulse shaping process, because I can create a 30 seconds pulses but I need to shape them and have amplitude modulation plus a creating a negative part too.

See if you can help thank you