Can anyone Help me out with this question ???

  1. i was hoping someone out there could help me gain a better understanding of the exact physiology/interdynamics of the use of iabc.

    i recently started a position in the cticu~i have done medical icu, ccu, interventional cardiology, ed to name a few areas in my background. however, i have not worked directly with balloons !

    i am aware that it is used to: decrease the workload of the heart & to increase coronary perfusion.

    where i stumble is exactly how it does this ? my best understanding is that the balloon inflates during diastole (when the coronaries receive most of their purfusion) & deflates just prior to systole (just before the aortic valve opens) .

    is it so that the inflation of the balloon during diastole causes an increased backflow of blood which increases coronary perfusion ???

    how does the deflation of the balloon just prior to systole decrease afterload ??? is it as simple as a sudden decrease in pressure ??? this does not make sense to me, as "afterload" refers to the resistance the lv must overcome to push out through the aortic valve ???

    can anyone help

    frustrated rn
    Last edit by Elicia RN on Dec 8, '07
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  2. 2 Comments

  3. by   suanna
    You seem to have an adequate understanding of the process. The heart gets its blood flow to the coronary arteries during diastole. The balloon inflating pushes blood forcefully back toward the heart providing maximal filling of the coronary arteries. Yes, it is as simple as the sudden drop in pressure as the balloon deflates that reduces afterload. 80% of the hearts workload is in the initial 1/3 of ejection; opening the aortic valve and overcoming the resistance of forcing blood through the aorta. By deflating the balloon just before myocardial contraction you form a relative negative pressure in the decending aorta greatly reducing the work in opening the a valve and starting blood flow. Timing is critical. If the blood has a chance of refilling the aorta by backflow from the dista aorta before the heart contracts you have lost the benifit of the IABP for afterload reduction. If the balloon is still inflated when contraction starts you make afterload MUCH MUCH higher and can cause harm. Most IABPs now have an "R wave deflate" safety to reduce the chance of this. Since contraction is delayed from the electrical "Rwave" event when the balloon sees what may be an R wave it will automaticaly deflate to get out of the way of the comming contraction.
    Last edit by suanna on Dec 10, '07
  4. by   Elicia RN
    Dear Suanna;

    Thanks so much for your reply!!! It was very helpful. I tend to get very obsessive when I don't understand something in it's entirety !!

    Many Thanks again;

    Elicia, R.N.

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