[afraidfortherepublic]

Are there ways to induce a massive heart attack on someone so that it does not show up in an autopsy?

Yes, if you believe Murder She Wrote, Matlock, Law & Order, NCIS, or any of a dozen other "crime" shows.

[spokeshave]

Are there ways to induce a massive heart attack on someone so that it does not show up in an autopsy?

Spike of the Australian stonefish.

[sweetiepiezer]

What about Sarin Gas?

http://www.bt.cdc.gov/agent/sarin/basics/facts.asp

I met Andrew once, very nice and a gentleman.
Rest In Peace Andrew.

Prayers for your beloved family.