Blood Supply of HEART

Blood to the heart is supplied by two coronary arteries (right and left) in majority of patients, variations include (a) may have 3 coronary arteries, Right, Left and posterior. (b) may have only one coronary artery which supplies entire heart

Right coronary artery:  Divides into Right marginal and PDA (aka posterior interventricular artery)Right atrium, Right Ventricle , Posterior wall of left ventricle(near posterior IV groove) and posterior 1/3 rd of interventricular septum

Left coronary artery:  divides into Circumflex and LAD (aka anterior interventricular artery)

Circumflex: supplies  LA and  lateral part of Left ventricle

LAD: supplies anterior 2/3 rd of interventricular septum and anterior walls of both ventricles

Dominance : Whosoever gives rise to PDA is dominant, The dominant one supplies the AV node

85%  RCA gives rise to PDA so Right dominant
15% LCA gives rise to PDA so Left dominant.

So if you are left dominant and occlude your LCA you will infarct in the Anterior, Lateral AND POSTERIOR or INFERIOR (PDA) walls of Left Ventricle as opposed to  only anterior and lateral.

SA node 60% of cases by RCA 40% by LCA