I say combo of heart attack and time change erasure because his agony started after the brass handle of his cane smashed him in the chest in the vicinity of his heart.
I'm sure it was a time erasure more then heart attack but the agony that they showed him in can be called both.
As to disappearing vs. changing, who knows how time travel and changing things really works? Would the old version simply disappear along with people's memories and be replaced by the revised version or do they transform on the spot along with everyone's memories?
is it a slow ripple effect that spreads out from the source of the time change or is it just the blink of an eye?
Many writers. many different views.
Babylon 5: thanks to the time rift they got to see glimpses of the dark alternate future that would occur if they did not succeed in taking B4 into the past and Sinclair becoming Valen. Note: for those that never watched babylon 5 you missed some good story telling. Valen hints were dropped through season 1 and 2 and it culminated in a nice season 3 two parter where past/present/future collided.
Star Trek TNG: Enterprise D finds a time rift, the Enterprise C emerges from it into the present and suddenly everything ripples and changes.
BTTF 2: Biff changes his past and returns to the same future as the temporal change/ripple effect had not reached that year. Marty and Doc end up in the alternate 1985 as the ripples have spread from 1955.
BTTF 3: Marty learns Doc dies in the old West. He has the photo of his headstone and after going back, they inadvertently change things when they save Clara from going into the ravine. They figured Doc would die on a certain day, then Buford nearly shoots him in the back stating it would take days for Doc to die.....Marty steps in and later the pic of the tombstone changed to show his alias instead of Doc. Future changed and the ripples were already in motion. Marty then changes it for good by beating the tar out of Buford and smashing what would have been the headstone. The polaroid alters again from the ripple affect. Marty remembers it as he was the cause/epicenter of the changes along with Doc. Also the ravine was renamed from the time change to Eastwood Ravine.
Doctor Who: a franchise that plays fast and loose with time travel to the extreme. We do know that fixed points cannot/must not be changed due to the paradox effect and that IF they are changed the Time Lords need to work to stabilize the paradox. This was shown in Doc 9 when Rose saved her father from the car. No Time Lords to stop the Paradox effect. All 13 Doctors later unite and revised the end of the Time War to save Gallifrey but due to timelines out of synch and the ripple effect, all of Doc 9 and 10's adevntures stay the same and only Doc 11 and above will know the truth about what was done to end the Time War. War Doc, 9 and 10 all still think Gallifrey was nuked.
Old episode of Challenge of the Superfriends, Legion of Doom goes to the future to conquer and rule as there are no Superfriends. Of course Riddler leaves clues behind and they go too far in the future, but they figure things out and stop the Legion and Superman shows them a book from the future that shows how the Legion was defeated by the Superfriends. Foreknowledge of what was to come, the Superfriends had to simply go and fulfill it.
Another old Challenge of the Superfriends episode, Apache Chief and I think Aquaman got stuck in prehistoric times. So they find the exact spot where the hall of justice will one day be built and bury their distress signal (which has infinite power it seems), and then in the present they get the signal, trace it to under the hall of justice and then carbon date the device and Superman goes to get them. The device suddenly appeared under the HoJ after they buried it in the past.
Beast Wars Season 2 ends with a massive time storm after Megatron mortally wounds optimus Prime. The cosmos was collapsing and would have rebuilt itself in a new time line had it not been stopped.
90' FLASH series, Barry gets blasted 10 years into the future and sees the dark future that was created because he quite being the FLASH and didn't stop Pike from taking over the town. he goes back and changes the critical point which will alter the future. No time storm, but to resolve the paradox of two Flashes they merge into one and basically Barry from the future overwrites his past self.
Current Flash series, barry time warps back a day and again to avoid two Barry's his past self is over written and erased. No time storm. Barry changes the day by shutting down the Weather Wizard and locking him up. But as Stein points out, that was 24 hours vs the 15 years Barry would need to travel to save his mother. Barry chooses the wiser course and not save her despite the agony he suffered. Wise choice as he likely realized that 15 years of time changes would be too much. However Eddie starts the ball rolling when he kills himself to erase RF. RF is erased and the time storm starts. Only Rip Hunter can stop this.
All GREAT points! Another thing here that escapes me is RF-Thawne said he was born 135 years from now -- hence why Eddie is his Great, Great, Great, Great Grandfather BUT how is it Barry/Flash is his nemesis in the future when he born 22-23 years prior to the present? So unless Barry somehow travels into the future at some point how would he and RF-Thawne have ever crossed paths?
I do think something comes of Eddie being sucked into the black hole that will be told. Barry getting Iris would be enough to make him an enemy. Notice how Wells/Thawne doesn't disclose WHY he and Barry are enemies.
One of the things here that seems an issue in other time-travel stories is you can't ever touch yourself (YES, HEARD IT! LOL) like when Flash saves his younger self, something about same matter not able to occupy same space.