I'm glad you have this question, i'm very interested in ekg's. I'll tell you what I can...
Sinus tachycardia means that you have an fast heart beat. Normal beats are 60-100.. It says yours was 108.. It's not as bad as it may seem, it's only abnormal. Critical heart beats are anything less than about 35 and anything (adult) over 180. - estimate.
When they looked at your ekg strip, they noted that the qrs intervals are abnormal. That means somewhere in the bundle of hiss - I don't know if I spelled that right- there is a block (blood clot). I know that a heart attack is a blood clot anywhere in the veins and arteries of the heart.. But in the bundle of his you'd have to ask your doctor... I'm not sure what the numbers mean on your question.. I just wish I could see the strip for sure...
The left atrial is a chamber of your heart.. The strongest part of the heart, the part that pumps all the blood throught your body. It says it was enlarged.. Again, i'm not sure what that means " enlarged" you'd have to ask your doctor.