# What happens to the nerves during heart surgery? **URL:** \ **Category:** Factual Questions\ **Created:** [September 11, 2004, 2:41am UTC](https://boards.straightdope.com/t/what-happens-to-the-nerves-during-heart-surgery/263992 "2004-09-11T02:41:01Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Limbo\_Donni](https://avatars.discourse-cdn.com/v4/letter/l/5f8ce5/32.png) [@Limbo\_Donni](https://boards.straightdope.com/u/Limbo_Donni)\ **Post date:** [September 11, 2004, 2:41am UTC](https://boards.straightdope.com/t/what-happens-to-the-nerves-during-heart-surgery/263992/1 "2004-09-11T02:41:01Z")
When they remove the heart for surgery, do they have to cut a lot of nerves? How are those repaired? ---
**Author:** ![Joe\_Random](https://avatars.discourse-cdn.com/v4/letter/j/e8c25b/32.png) [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)\ **Post date:** [September 11, 2004, 3:45am UTC](https://boards.straightdope.com/t/what-happens-to-the-nerves-during-heart-surgery/263992/2 "2004-09-11T03:45:33Z")
> [@Limbo Donni](#): > > When they remove the heart for surgery, do they have to cut a lot of nerves? I would assume that the only time the heart is actually _removed_ is when the patient is receiving a transplant, and so that would probably be the only time that any nerves would have to be cut. > [@](#): > > How are those repaired? They aren’t. From [this site](http://www.heartmath.org/research/science-of-the-heart/soh_4.html): “In a heart transplant, these nerve connections do not reconnect for an extended period of time, if at all; however, the transplanted heart is able to function in its new host through the capacity of its intact, intrinsic nervous system.” ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [September 11, 2004, 3:57am UTC](https://boards.straightdope.com/t/what-happens-to-the-nerves-during-heart-surgery/263992/3 "2004-09-11T03:57:36Z")
> [@Joe Random](#): > > “In a heart transplant, these nerve connections do not reconnect for an extended period of time, if at all; however, the transplanted heart is able to function in its new host through the capacity of its intact, intrinsic nervous system.” Thats very interesting. But how is blood pressure and pulse rate regulated? Do people who had transplant need a pacer for that job? ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [September 11, 2004, 4:06am UTC](https://boards.straightdope.com/t/what-happens-to-the-nerves-during-heart-surgery/263992/4 "2004-09-11T04:06:47Z")
I mean, how does the heart know that it’s time to speed up or speed down? Since it doesn’t receive an external signal from the brain, it won’t speed up when the patient is running or speed down when he’s sleeping. ---
**Author:** ![Joe\_Random](https://avatars.discourse-cdn.com/v4/letter/j/e8c25b/32.png) [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)\ **Post date:** [September 11, 2004, 4:28am UTC](https://boards.straightdope.com/t/what-happens-to-the-nerves-during-heart-surgery/263992/5 "2004-09-11T04:28:11Z")
> [@Dog80](#): > > I mean, how does the heart know that it’s time to speed up or speed down? > > Since it doesn’t receive an external signal from the brain, it won’t speed up when the patient is running or speed down when he’s sleeping. Well, according to [this site](http://my.webmd.com/content/article/51/40688.htm?src=pemedscape): > [@](#): > > “Because the nerves leading to the heart are cut during the operation, the transplanted heart beats faster (about 100 to 110 beats per minute) than the normal heart (70 beats per minute). The new heart also responds more slowly to exercise and doesn’t increase its rate as quickly as before.” IANAD, but I would venture to guess that pulse regulation can be achieved by the use of hormones (such as adrenaline) alone, without having the vagus nerve connected. I also managed to find [this article](http://my.webmd.com/content/article/51/40688.htm?src=pemedscape), which mentions the effects of hormones on _decreasing_ the heart rate: > [@](#): > > “In the cardiovascular system, ANP [atrial natriuretic peptide] decreases heart rate and preload and promotes venodilatation and arterial relaxation. When activated in arteries and veins, ANP causes pronounced vasodilatation by promoting guanylyl cyclase activity. Guanylyl cyclase then triggers the production of cyclic guanosine monophosphate, which leads to smooth muscle relaxation.[sup]5[/sup] The dilatation that occurs shifts fluids from the heart into the vessels. ANP appears to decrease heart rate by augmenting the action of the vagus nerve” Notice that ANP _augments_ the action of the vagus nerve. That would indicate that it can affect a change in heart rate on its own, even though the effect wouldn’t be as pronounced.