Sea, you make a good point, but I’d counter with the argument that this is exactly how we’re supposed to think: That two such contrasting elements couldn’t possibly be connected. I don’t see your comment “slamming the brakes down” on this, but adding at least one more layer to speculation. (After all, if someone from the 14th century transported to our time and saw someone click something on a mobile phone, and the owner’s house lights turned on — 5 miles away — that 14th century individual would think the connection absurd. Time, distance, or apparent relative importance may not be as critical as we think, or have been conditioned to think.)
In the intact heart, preload, afterload and inotropy do not remain constant. To further complicate matters, changing any one of these variables usually changes the other two variables. Therefore, the above PV loops, although they illustrate the independent effects of these three variables, they do not represent what happens when the heart is in the body. However, if one understands the independent effects of these variables, then it is relatively easy combine the loops to illustrate what occurs when multiple variables change. To learn more about these interactions, CLICK HERE .