Been to the er 3 times with 5 ekgs first 4 were normal along with all normal tropin levels in blood but last ekg said sinus tachycardia septal infarct when compared with other ekg in my chart. is this a serious issue i should return to the er for?

I assume you went to the ER because of chest pain or similar symptoms. If 4 ECGs and troponins were normal, the likely cause of the ECG "abnormality" could be incorrect lead placement. This is a common problem. It is appropriate for you to speak to your physician who treated you, or your primary physician with all the ECGs and lab reports for their explanation and reassurance. Good luck.