So, in all iterations of D&D, HP have been handwaved away as a comparative score of a characters fortitude, combat effectiveness, heroism and luck prior to falling in a heap on the dungeon floor. (OD&D Magic Users were obviously quite un-heroic!)
That said, AW uses a similar comparative score, but most folks are generic in terms of their 'harm countdown clock'. The clock does have some nifty mechanical effects though - especially in lieu of healing times and recovery. I really like the commentary on Harm (p.163) where it gives the MC leeway in determining non- assisted healing in terms of 'in-time' and 'by itself' through the lens of the fiction at the table.
So I was thinking how to marry the concept of HP and the Harm countdown clock. Here's what I came up with:
*Rather than a clock (though you can still use it if you want, or a scale or a health 'bar', or a heart or whatever) I prefer a Harm 'hourglass' for DW. Draw one about the same size as your normal countdown clock. Avoid putting the clock numbers on your symbols as this will confuse you unless you have exactly 12HP!
*Mark your chosen symbol with the same segments as the clock from AW: at 1/2, at 3/4 and the last 1/4 into thirds (3X 1/12)
* Calculate 1/12 (round down) of your HP, which is usually 1HP, and mark the last three thresholds with the result. The remaining 3/4 and 1/2 thresholds are marked as noted with 1/2 and 3/4 of your total HP (round down). Write the results at the appropriate segment. (Yes this means if you have less than 12 HP the clock will effectively give you 1-3 extra HP!)
*As per AW, damage in the first half of the clock is less serious and will heal with time. In the third quarter it won't get better or worse by itself. - You'll need magical or practical healing. The last three segments will get worse if they are unstable (or bleeding), stay the same if they are stable, and only be healed through magical or medical help.
* as per AW, a player can opt to trade on of the last three thresholds for a permanent disability. If they do so, the clock will halt at the 3/4 HP threshold and they have to choose one of the following:
Shattered: -1 Str Bonus
Crippled: -1 Dex Bonus
Broken: -1 Con Bonus
Enfeebled: -1 Int Bonus
Traumatised: -1 Wis Bonus
Disfigured: -1 Cha Bonus
Mark the Stat, note the particulars of the disability and get used to it!