Afterload – Cardiac Mechanics

by Thad Wilson, PhD

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    Now, let’s move to afterload. Afterload is a resistance. It's how much you are pushing against the aortic valve to open it up. So, you need to open the valve up. The heart needs to overcome the resistance that's in the cardiovascular system and to push out any blood. If it couldn't open the valve up, no blood would move. And the absolute way you quantify afterload is in the amount of pressure it generates at a certain wall stress. A little bit more complex, but sometimes it’s important to not just think of the valve opening, but it’s the amount of pressure the left ventricle needs to contract on to open that valve. The most important thing to think about with afterload is how it affects the velocity of contraction. This should make inherent sense to you. This more weight you have on a muscle when you try to contract it, it will contract slower simply because you're trying to overcome a greater weight. The heart is working on a very similar principle. It is trying to open up the aortic valve. The more resistance there is to opening up the valve, the less velocity the contraction will be. If there is easy time to open that valve, velocity will be very rapid. So, the velocity of contraction always affected on how much afterload it needs to overcome. You can think about this, even with something like a weight. So, if you are trying to lift up, let’s say, a table and you went to lift that table up and the table was really light, you can move it rapidly. If that table, however, was a big oak table and had stuff stacked on it and you were trying to lift it up, you would lift...

    About the Lecture

    The lecture Afterload – Cardiac Mechanics by Thad Wilson, PhD is from the course Cardiac Physiology.

    Included Quiz Questions

    1. Decreases stroke volume
    2. Increases stroke volume
    3. Does not change stroke volume

    Author of lecture Afterload – Cardiac Mechanics

     Thad Wilson, PhD

    Thad Wilson, PhD

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