I should have known this was coming sooner or later, given my unhealthy living style and other health risk factors, but it did come, quietly on padded feet in the hushed hours of early morning. I had a silent heart attack. I woke up to take a piss but was unable then to fall back asleep. I kept waking up again to gasp for breath, which was weird. After perhaps thirty minutes of this, I gave up and arose to poke at the Internet for clues. Carbon monoxide poisoning was a possible cause, but then why were alarms not ringing...