I do wish Slashdot would let you edit posts, then I wouldn't have to reply three times!
I'll group the answers.
Then why doesn't it happen more often?
Well, you need to stick needles into the body quite big and deep to have a good contact (the probes mentioned in this Darwin award). And apply a sufficient voltage to them, for a long enough time. That's quite a convoluted way that doesn't happen in every day life.
(I hardly see example how it could happen, except deliberately as in the example).
Actually a healthy heart will regain rhythm easily.
Generally speaking, yes, I agree. A healthy heart should restart.
That's in fact the principle which is used by defibrillators:
- a firbillation: is a big electrical mess where the cells a completely desynchronised and are firing mostly at random each triggered by the mostly random fires of their neighbours. Electrically, the heart gives a signal that looks like white noise. Mecanically, the heart isn't beating in a coordinated manner, but instead its surface is more or less kind of "vibrating" making tons of small uncoordinated local micro-contraction (that's what fibrillation means).
- fire a charge a the heart
- the charge cause all the muscle cells (and the specialized muscle cells that serve as the heart's equivalent of nerves) to contract at the same time and stay contracted for the short duration of the charge.
- after the shock, most of the cell are more or less at the same position in the cycle. (and thus none will start miss firing due to other nearby miss-fires). They are more or less in "waiting state".
- natural rhythm generator generates impulse as usual, and now all the cell should follow the same impulse travelling along the heart (and its nerve-like specialised fibers).
- heart should contract in a coordinated manner and beat as it should.
In the Darwin awards example, the current is constant. Which doesn't cause a "resync" as the single pulse that a defibrillator's shock is. Also, given the low resistance of the salty water medium, the current is probably quite high which is dangerous. (I mean relatively speaking).
There's a much higher risk of the heart going into fibrillation in this case.
Of course adding some heart disease could increase the likely hood of dying.
But the absence of disease isn't a definite guarantee to die from such shocks.
I've had quite a few jolts from 240 volt mains from one hand to the other. Explain why I'm not dead.
Basically: you got lucky.
Probably the shocks where short. Or by luck the travel path of the current didn't happen to reach the heart (I've once had a thunder struck patient that survived exactly because of that: the heart wasn't touched).
The fact that you survived previous shock and the fact that you don't have a heart disease doesn't necessarily make you immortal and doesn't guarantee that you won't die next time.