you've never heard of them because you've not been listening. Of course noone in the places that have them call them that...
In the UK there's the inaptly named NICE, which determines what can and cannot be treated and supplied to patients. If they decide something's not to be treated, it's a death sentence (for example, they've banned the distribution of a large number of cancer treatments, meaning a lingering death for tens of thousands of sufferers).
In the Netherlands there's an upper limit on the number of heart operations (and similar in many other countries), and panels (made up on paper of doctors but including bureaucrats of course) to determine which patients are most worthy of receiving one of the few slots available each year. They decide you're not to be treated, you're dead unless you have the money to pay out of hand for an operation abroad.
There's "working groups" determining what medication is allowed for which condition based not on medical necessity but purely on cost. This had the effect that my parents would now both be dead if they'd not have had the money to pay for the pills themselves that they needed to stay alive.
The list goes on and on.
Insurers in the US refuse to insure people for certain conditions unless they can pay enough to cover the risk involved. That's a business decision, and no death panel. If you want to pay enough, they'll cover it. Over here, the government sets limits on what they're allowed to cover, and what they're required to cover, then goes ahead and determines that although covered it won't be provided.
The UK is now going one step further and decides to refuse treatment at all to people who "live an unhealthy lifestyle", but by law they're still required to pay up. So the UK NHS and NICE are handing out death sentences to people based on factors like whether you smoke or not or whether you're overweight or not (irrespective of the reasons why), which can be arbitrarilly expanded to cover most anything. Next up they might well decide to not cover respiratory illnesses for people living near highways (because those people are at an increased risk from those, and thus have an unhealthy lifestyle by living there).