When Maya started wigging out there was all this super loud heartbeat sound. I couldn't make out if that was just the effect of Maya's power at the time and just the sound of him starting to die when she used it..or was it his super hearing?

nah... i dont think sylar was able to use his powers yet.

It was part of the musical score.

I agree, because if Sylar had heard
Maya's heart beat, then he would have
tried some other power.

Yeah, that was definately just sound effects or the score. If Sylar's hearing returned, he would have cut open both of their skulls and that would have been that