Thanks for the replies one & all.
The incident I alluded to was a collapse mid Atlantic and the cabin crew did CPR for 2.5 hours (including descent and landing) to CYQX. The unfortunate pax did not survive but the crew did a great job (Czech Air ?). I doubt I could do CPR for that length of time - I managed 35 minutes once and I was knackered!.
According to the autopsy report the pathologist didn't reckon much of his heart was left to work.
Rgds
CB