One of the oldest chestnuts in the AH genre, which can easily become a cliché if used recklessly and without any thought put into it.
Simply put, whenever an author needs to get rid of a historical personality whose further existence, work and deeds might prove inconvenient to the author's timeline in some way, said author usually opts for solutions like giving the person in question a heart attack, a sudden onset of deadly health problems, a mortal injury in some serious accident, or have him/her get accidentally killed or willfully assasinated.
As with most writing conventions and tropes, the overuse of this solution to a narrative or POD problem can easily cheapen its value and level of impact, both in a general sense, and in the specific story where it occurs. Too many convenient sudden deaths in a work - especially if they are contrived (even increasingly so) - is proof of the author being unable to come up with different solutions to what to do with historical personalities that might not be important to the timeline's story or might become a hindrance to its further progression.
A subtype of this cliché is that it often manifests itself in the oddly specific case of the person dying of a heart attack at just the right / wrong moment. Even if the person had a history of heart disease in real life (and in many examples they didn't!) wouldn't a much more likely cause of death at a random moment be a transport accident?
Rather than having all unneeded characters drop dead like flies by the dozens (often for the mere “sin” of the author having a grudge against them), it is generally recommended to attempt finding more creative ways on how a “burden character” can be sidelined without having to outright kill him/her off. These popular alternative options include, e.g. the personality achieving less success in his/her career than in OTL, or working in a different profession altogether, lessening the personality's impact on world history, etc., etc.