Flatline Plotline

"I did not come to medical school to murder my class mates no matter how deranged they might be."

—Randy Steckle, Flatliners

A character or group of characters make it so they die for a certain amount of time (often times by simulating a heart attack) and then are revived. Sometimes this is so they can have an out-of-body experience or see if there's an afterlife or become a ghost for a certain amount of time. Sometimes this will result in their nightmares becoming real or sometimes it's a plot for one of the characters to kill another without getting caught. May be part of a Faking the Dead plot.

Extra fail points occur if the victim actually does flatline. Only about 10% are successfully brought back once their cardiac cells have stopped channeling enough electricity to trigger an ECG blip, with preemptive treatment. Clinical death actually means cessation of breathing and circulation and is not the same as flatlining. Bonus fail points if the victim is then revived with defibrillation, since a flatline by definition has no heart rhythm to "defibrillate".

Most of the time, this requires some Artistic License: Biology.

Not to be confused with Faux Death—that's when the character never really dies in the first place—or with Flatline. Compare Revival Loophole.

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Flatline Plotline include:

Anime

This is done to Sasuke in Naruto after he defects from the Leaf Village in order to raise the power of the cursed seal Orochimaru gave him.
Unsurprisingly, the Faking the Dead version has shown up in Black Jack at least once. In one story he temporarily induces clinical death in the President he's operating on in order to fool the terrorists who are holding Pinoko hostage so he'll throw the operation.
In Descendants of Darkness, during the King of Swords story arch, Muraki does this as the ultimate alabi.
An early episode of Pokémon has Ash and Pikachu go through this, temporarily turning into ghosts after being crushed under a fallen chandelier. This proves key in helping Ash bond with the ghostly trio of Haunter, Ghastly and Gengar.
In Seikimatsu Occult Gakuin, Kozue goes through one to try to get a glimpse of the afterlife and ends up leaving part of her soul behind.

Comic Books

In Elf Quest there's a scene where Leetah the healer confronts death by bringing herself to its very brink. It's a huge risk because she aims to revive herself at the exact split-second before she dies. But it's a flashback story so we know she lives.
One of Batman's plans in The Dark Knight Returns.

Film

Flatliners, the Trope Namer.
In The a Team, "Hannibal" Smith does this while in prison.
In Ghost Town, Ricky Gervais's character briefly becomes one of the ghosts he sees.
Happened in Constantine.
The Frighteners: Frank Bannister does it to experience afterlife first-hand instead of communicating with it, as he did as a medium.
In the Italian film Diabolik (the final episode of Mystery Science Theater 3000), Diabolik's elaborate Batman Gambit to rescue Eva and keep the emeralds he stole for her involved ingesting a pill that would make him appear dead for 12 hours, but would kill him if he didn't take the antidote before then. When does Eva bring him the antidote? 11 hours, 57 minutes.

Literature

It is the plot of Bernard Werber's Thanatonauts. The protagonists work on a way to trigger NDEs (Near Death Experiences) and to make them progressively longer so as to go further into the afterlife. The book starts as hard-ish science fiction, with several test subjects dying in the process, then proceeds into Werbery philosophical tale with a good dose of silliness when they actually find Heaven and start regularly going there and back.
Connie Willis's Passage is about a doctor experiment with a drug that can trigger NDEs, although it's not dangerous at all. That is until the doctor takes it and finds herself on the Titanic. It's much better than it sounds.
Terry Bisson's short story Necronauts. The main character is an artist hired to produce paintings of his experiences during the NDEs.
God Bless You, Dr. Kevorkian by Kurt Vonnegut, is a series of interviews with the dead conducted by a reporter getting repeatedly nearly killed by the Doctor.
The Scott Lynch novel The Lies of Locke Lamora features a cult devoted to the goddess of death which, as part of its initiation, requires extensive experimentation with near-death experiences. The protagonist, whose mission is to infiltrate the cult, essentially says "the hell with this" and leaves that night.
In The Dresden Files, ghosts are effectively echoes sticking around to take care of unfinished business, not necessarily the actual spirit or soul (or what not) of the deceased. So, when one was kicking his ass, Harry came up with the plan to die just long enough for a ghost to be created, then have his friends resuscitate him so that he could team up with his own ghost to beat the baddie.
In Terry Pratchett's Nation, it's a way to pay a visit to the local death god.
In Beyond Varallan, Cherijo does this in order to break up with Xonea (since that's about the only way one can back out of a Jorenian engagement). Justified in that not only is she essentially immortal, but it's decidedly rough on her.

Live-Action TV

The A-Team does this at the start of the last season, by getting shot by a firing squad with replaced, nonlethal bullets.
The Medium episode "Things to Do in Phoenix When You're Dead" had a doctor doing this so he could travel as a ghost to see rich people doing bad things and then blackmail them.
An episode of Tru Calling called "Haunted."
House once shocked himself and was clinically dead for 97 seconds so he could see what another guy was talking about about the afterlife. He saw nothing, which confirmed for him that there was no afterlife. He did this despite the fact that he'd experienced clinical death before and seen visions, which he'd already rejected as proof of an afterlife.
In an episode of Sliders, the team lands on a world where the Egyptian dynasties never ended, and people are conducting afterlife experiments by temporarily killing test subjects. Naturally, one of our heroes gets caught up in it.
Fringe keeps dancing close to this line.
In Star Trek: Voyager episode "Barge Of The Dead", B'Lenna didn't actually die, but she had a near-death experience and ended up in Klingon Hell. Then after she got revived she asked the Doctor to put her in another near-death experience, because she wanted to save her mother from Klingon Hell (which she knew full well existed).
This was on an episode of Smallville.
Exactly the same idea as The Frighteners had been inverted about 20 years earlier by Randall and Hopkirk Deceased. In that case, they needed the man they were interrogating to have a near-death experience so Hopkirk (the dead one) could talk to him.
Red Dwarf tries this once. Except they almost forget one important bit... Kryten: MR LISTER!!!
Parodied in an episode of Upright Citizens Brigade; Anton is trying to improve his chess-playing skills by hooking himself up to a machine that briefly renders him clinically dead every time he makes a bad move. It doesn't work out well.
Supernatural:
- To figure out why the people in a town have stopped dying, Sam and Dean decide to try astral projection so they can see ghosts and reapers.
- In Appointment in Samarra Dean has himself temporarily killed so he can contact and make a deal with Death According to the man conducting the procedure he has a 60% success rate.
Charmed: At least once a season.
Diagnosis Murder had an episode featuring this trope - where a group of medical students induced cardiac arrests in themselves and then gradually increased the amount of 'flatline time' on each occasion to try and make themselves more resistant to death. Then one of the medical students decides to murder another by not reviving him and it goes on from there....
The subject of an episode of Forever Knight. Nick too crosses over, in order to find if he's damned forever.
The TV miniseries House of Frankenstein 1997, featuring various horror-staple monsters, had a scene where a man carries a dying wolf (his werewolf girlfriend) into the ER and forces the doctors at gunpoint to attend to the animal. He lays her on the operating table, then insists that they let her die, at which point she reverts to human form. They rush to resuscitate her; upon awakening, she remains human and is cured of the curse, as it's the wolf that died.
In a season 3 episode of Sanctuary Will has himself flatlined in order to make connection to a certain abnormal running amok at the time. This is presented as a last resort after performing a Bollywood-style dance fails.
In one episode of Merlin, the only way to break a spell is to make Uther cry, and the only way to make Uther cry is to kill Arthur. Of course, he'll be just fine provided he gets the antidote within 30 minutes. 29 minutes later...

Tabletop Games

The limited-run Orpheus RPG by White Wolf was all about this trope. The titular corporation flatlined its agents through cryogenics, who would become ghosts and be able to interact with the spirits of the recently deceased on behalf of well-paying clients.

Video Games

Mass Effect 2: Both played with and parodied. The parody is when a security officer states that being dead for a year is a popular tax-dodge.
Metal Gear Solid
- In Metal Gear Solid, Snake is able to lay in a pool of ketchup to convince a guard that he has died.
- In Metal Gear Solid 3, Big Boss can do a similar trick by using a fake Cyanide Pill to cause a temporary state of "death". However if you don't use the revival pill before a certain time limit, he dies permanently, causing a Time Paradox.
- Lastly in Metal Gear Solid 4 it is possible to lay among a group of corpses after a battle and play dead. This usually causes any passing guards to ignore you.

Web Comics

The Adventures of Dr. McNinja: Happens in one of the major arcs. Dracula helps Benjamin Franklin create an elixir of immortality, so that he can die and come back (as a Headless Horseman) and tell him what the afterlife is like... he's gotten tired of his own immortal existence, and wants to know what the next world is like, so he can make an informed decision about passing on. Turns out that Purgatory is a restaurant with terrible service. The worst.
- Dracula was pretty pissed when he learned that Benjamin didn't even experience the true afterlife because the service of Purgatory was so slow. The elixir kicked in right after he finished his meal, as Death came to make him move on.
  - ...So he tried to get Dr McNinja to do it because he's already faced death and gotten out of it. Dr McNinja claimed that they were Only Flesh Wounds.
A Girl Genius short story has Agatha investigating a team of construct con artists who do this: the front man, if caught by the authorities, collapses and dies. A week or so later, his/her friends, who weren't caught, dig up and revive the body, and they go to play their moneymaking tricks somewhere else.
- Later on, Agatha, Gilgamesh, and Tarvek all contract a disease, and the best plan for curing it involves killing and resuscitating themselves.

Western Animation

In an episode of Justice League, Flash tricks a captor by speeding up his heart rate until it looks like he's flatlined.
An episode of Moral Orel involves Orel killing himself in order to talk to God.

Real Life

Some scientists have managed to replace the fluid in dogs with a solution that places them in a state of suspended animation of sorts (they're clinically dead). By then replacing that solution with the proper fluids, the dogs could be revived. Other methods have also been experimented with.
Nikki Sixx is famous for flatlining and then resurrecting.