To understand what they are saying you need to be in the medical profession and to be able to understand the basics of cardiology, i cant believe they sent that letter to you!!

anyway basically when you have an ECG done they check for abnormalitys in the PQRST waves,, this may help.. http://www.tveatch.org/ekgs/pqrst.html...

& From that they can see many things, hence the shortened wave P & R, its just how they measure the waves LOL.

So in short you have something wrong with these waves and they way your heart runs, alot of the time things like this can be controlled by medicine but i dunno as you have the tumor i wouldnt like to say for sure.

HTH