Requesting review of calcification on CT angiogram (SVC?)

[AZHBent]

45yo male - 5'9" 235

Active - meaning I ran about my 50th half marathon a few months ago.  I'm up in weight and haven't been exercising much this year, but still knock out 4.5 miles pretty easily.  I'm a former Ironman (2014).

I had chest pains/heaviness for the first time starting a couple months ago.  I've been going through many tests as listed below:
EKGs always look good
Echocardiogram was reported as fine (I didn't receive any of those images)
Stress test was 'mildly abnormal'.  Something changed during my stress period (S-something or other).  I was told that it was abnormal, but not enough to worry about. (something about it only being 1mm and needs to be 2mm to be of concern)
Finally a CT angiogram.  

I was told "the ct looks great, no plaque and only a little calcification in your lung that I'm going to ask a colleague to comment on".

Curious as I am, I looked at the CT images and played with 3D modeling for the fun of it, and wanted to see where this calcification is...  

Here is my request:
The calcification, as best I can tell, is nearly blocking my superior vena cava and down into my right atria.

I'm an engineer, not in medicine.  I know zip about anatomy and hearts other than what I've read over the last few days.  I looked at it from many different angles, trying to find a different answer, and I just don't see one.

I've uploaded some screen shots to this public folder as I didn't see a way to attach images here.

https://drive.google.com/drive/folders/0B0P5ZFZp8l0MWHR5WDdYajNsTHM

I'd love for someone to look at these and let me know if my layperson assessment is correct.  If so, what does it mean for my health?

I have a call into my cardiologist asking for clarification and have not heard back.  

I'm freaking out a bit.