What does an elevated t wave mean on an ecg? what conditions could it be?

Many causes: Elevated t-waves can have a variety of causes. Heart conditions, such as poor blood flow through coronary arteries, can cause elevation. So can abnormalities of different chemistries in your body, for example, an elevated potasium level. Many of these things have many causes, so you need to work with your doctor to first find out what abnormality might be causing it, and then why you have that.

Many things...: It means many things, one of which is lack of blood supply to the heart...But it is not the only possibility, other conditions can do the same. Ecg is very non-spefiic.