I think in my head I always thought that the coronary artery circulation was much more complicated than it really is. The simple way to boil it down is that the right coronary artery (RCA) does the right ventricle and the back of the heart. While the left coronary artery (LCA) does most of the anterior and some of the back depending on the circumflex artery and individual variation.

SA Node: usually supplied by the RCA (in 60% of people) but can also be supplied by the LCA
AV Node: supplied by the RCA

Dominance of circulation

Right-dominant (80%): Posterior interventricular (PIV) & at least 1 posterolateral branch arise from the RCA
Left-dominant (15%): PIV & at least 1 posterolateral branch arise from left circumflex artery
Balanced (5%): dual supply of posteroinferior LV from RCA and circumflex

So what this means is that if you see a inferior MI pattern on an ECG, there is likely a posterior infarct as well. Not to mention that you should be worried about both your AV and SA node.