I have watched this video, where Kasparov explains the variations after his knight sacrifice. However, the position he analyses starting from 3:08, I think I am missing something.
Kasparov vs Karpov, 1990 World Finals
[FEN "r3qb1k/1b4p1/p2pr2p/3n4/Pnp1N1N1/6RP/1B3PP1/1B1QR1K1 w - - 0 1"] 1. Nxh6 Rxh6 2. Nxd6 Qxe1+ 3. Qxe1 Rxd6 4. Qe4 Nd3
What if black plays
[FEN "r4b1k/1b4p1/p2r4/3n4/Pnp1Q3/6RP/1B3PP1/1B4K1 b - - 0 1"] 1... Nf6
instead of Nd3? Can't he both attack queen and defend h7 square? His chances of survival is so low, obviously, but I think Nf6 is better than Nd3, and worth analyzing.