Cardiac Preload and Afterload - page 3
by orca1 123,265 Views | 22 Comments
Hi, I need help from the professionals :) I am being tested tomorrow on cardiac and was wondering if anyone in the critical care field can explain preload and afterload in student nurses terms;) I am a bit confused and... Read More
- 1Sep 11, '10 by xXtjhcXxThank you for taking time to explain and give analogies about preload and afterload! I have an exam covering cardiac this coming Tuesday. I was so confused about the whole concept, but after reading many posts of caring nurses, I do understand it now! Thanks alot!
- 0Jul 29, '12 by CBLNurse2BeQuote from joeyzstjWonderful explanation! I have a deep love for cardio! That's a good way of putting it, thanks! I'm only a student, so my deep love may very well change. But, I can honestly say that cardio is one of the only things that I can sit down to read and be completely locked into and intrigued by. I'm a cardio nerd! Heh. Thanks, again! I'll remember this.Think of preload in relation to a rubber band. If you remember back to Anatomy and Physiology class, there is an optimal point in which you can stretch a muscle fiber and it will have the most effiency. I belive its 120% of the orginal length of the muscle fiber. Sooooo..........think of a rubber band. You stretch it a little and let go and it barely moves. You pull it back farther and farther it really starts to snap back hard. You pull it back unti you cant pull it anymore and it snaps the strongest. This is the same concept as preload............you are Preloading the cardiac muscle sarcomere (muscle fibers) by giving volume we stretch the heart far enough that we get a good snap from the heart. Afterload is the resistance that the heart pumps against when it ejects the blood. Its actually the measurement of Left ventricular wall tension during systole. SO, we preload the heart with a certain volume and then we eject it. Now, afterload will be high if we have to eject that volume through something the size of a coffee stirer. Afterload will be low if we eject the volume through a vessel the size of a car tire. On a extra note, CHF is similar to us stretching that rubber band sooooo far that it loses its optimal stretch. We stretch it out so far that it is beyond that 120% point and is too lose and streched out to recoil well. That is CHF in essence.