What condition would cause someone who is sitting down to suddenly feel an electrical shock sensation in the center of their chest. not a pinch. or stab. but a zap like real electricity and then suddenly a tachycardia event for 20 min? what is this?

Tachycardia: We don't know if the rapid heart rate was a true tachyarrhythmia like SVT or simply a nonspecific sinus tachycardia due to your reaction to the chest discomfort. A fleeting electricity sensation in the chest is not characteristic of cardiac discomfort by was most likely a superficial nerve irritability. If similar episodes recur, consult a cardiologist for evaluation and advice.