 Now let's take a minute to discuss the concept of heart dominance, okay? You'll recall from early in the video that approximately 90% of the population has their posterior descending artery coming off their right Coronary artery. We call these patients right heart dominant as you can see in this diagram here because their PDA comes off the right coronary artery and in the remaining approximately 5 to 10 percent of the population we call these patients left heart dominant because the PDA comes off the left circumflex artery. So let's take the example of a right heart dominant patient, okay? And let's say they have a clock buildup in the left coronary artery and now it's occluded There's no blood flow coming through here That means we lost blood supply to our left circumflex artery and our left anterior descending artery, okay? And you'll also recall from early in the video that the left circumflex artery supplies the lateral aspect of The left ventricle and the left anterior descending artery supplies the interior aspect of the left ventricle, okay? So now we've lost blood supply to both of those locations, but luckily this patient's right heart dominant So they still have some blood supply through their right coronary artery into the posterior descending artery The posterior descending artery as you'll recall supplies the inferior aspect of the left ventricle So in the setting of a left main coronary artery occlusion, this right heart dominant patient would still have some residual left ventricular function, okay? Whereas now let's take the example of one of these left heart dominant patients This posterior descending artery is actually a branch of the left circumflex artery So if the left coronary artery is occluded now, we've lost blood supply to the lateral aspect The interior aspect and the inferior aspect of the posterior descending artery So this patient essentially has no left ventricular function and thus it would be a much more severe Myocardial infarction in the case of a left main coronary artery occlusion That's why we need to distinguish between left dominant and right dominant patients When we're discussing coronary artery anatomy and it is also important to note that in another approximately 5 to 10 percent of the population They have their PDA arising from Getting blood supply from the right coronary artery and the left circumflex artery and we call these patients co-dominant And that's kind of the best case scenario For a patient because they have collateral circulation if the left main coronary artery or the right main coronary artery is occluded and that's hard