CHF question (can an MD answer?)

Discussion in 'Health and medical' started by E., Dec 17, 2003.

  1. E.

    E. Guest

    I'm a second year medical student and I've been reading about CHF. I've been trying to answer one
    simple question, and I've been having a lot of trouble getting a straight answer.

    My question is this: What causes the backup of fluid at the backdoor to the left heart? I understand
    that ventricular output is compromised in CHF. I also understand that compensatory mechanisms
    increase blood volume. However, it seems to me that a reduced cardiac output would result in a lower
    volume of blood returning to the heart. This would seem to prevent overloading of the left heart in
    itself, especially when the patient was standing. What's wrong with my reasoning here?

    Thanks.
     
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  2. "E." wrote:

    > I'm a second year medical student and I've been reading about CHF. I've been trying to answer one
    > simple question, and I've been having a lot of trouble getting a straight answer.
    >
    > My question is this: What causes the backup of fluid at the backdoor to the left heart? I
    > understand that ventricular output is compromised in CHF. I also understand that compensatory
    > mechanisms increase blood volume. However, it seems to me that a reduced cardiac output would
    > result in a lower volume of blood returning to the heart. This would seem to prevent overloading
    > of the left heart in itself, especially when the patient was standing. What's wrong with my
    > reasoning here?
    >
    > Thanks.

    Think Starling forces. A malfunctioning heart needs ever increasing preload to meet cardiac output
    demands. When this preload exceeds the threshold limits of the pulmonary vasculature, there will be
    pulmonary congestion.

    --
    Dr. Andrew B. Chung, MD/PhD
    Board-Certified Cardiologist
    http://www.heartmdphd.com/
     
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