Thanks for writing in.
I am a qualified and certified cardiologist. I read your mail with diligence.
Unless a heart attack
was diagnosed by a competent doctor based on recognized criteria your assumption that you have had heart attack might as well be wrong. There is no term as "longer ST waves". To answer your specific question treatment for your back with the drugs you named and steroids
will not adversely affect your heart you can take my word for it. As far as diagnosis of 'heart attack' is concerned I will urge you to consult a doctor, who would thoroughly examine you, see your EKG may be order a test like echocardiography
then tell you whether what you are assuming is correct or not. Best of Luck.
With Best Wishes.
Dr Anil Grover