Wednesday, September 17, 2008

Whither Heartbeat?

A few weeks ago I saw something somewhere (funny how context eludes you, even when alluded to), possibly in a nature show or something like that, which suggested that we have a finite number of heartbeats. That, with corrections of course made for use & things like accidents (although wouldn't it be weird if you died early but you heart had to fulfill its contractual obligation to beat for the amount of time for which it was programmed?), our hearts will pump as long as they are supposed to pump. & the implication (or at least the meaning I took away from the television show/article/podcast/whatever) was that pretty much all mammals have the same number of heartbeats per life. Thus, little critters whose hearts beat way faster live shorter life spans, while behemoths live longer. That got me thinking about heartbeats.

Is it true? Here's an excerpt from a quick web search looking for that answer, in a silly article about human longevity:

Mice and elephants lead very different lifestyles — one ponderous, the other manic — yet rodents & pachyderms share the same pervasive pattern of aging. Individuals who survive the perils of daily life, from disease to predators, inevitably begin declining after finishing about half a billion heartbeats. Elephants live much longer than mice, but their hearts also beat far slower, so the total allotment stays remarkably similar. Few mammals live to celebrate their billionth pulse.

...[T]hat billion heartbeat limit that seems to confine all mammals, from shrews to giraffes [is] a pretty neat correlation, till you ponder the chief exception.

Us. Most mammals our size and weight are already fading by age twenty, when humans are just hitting their stride. By eighty, we've had about three billion heartbeats!


Of course we're the exception to the rule. We invented Accupril, Lopressor, Vasotec, Cardizem, Anacanapanasan, Vaxadrin & the rest. Duh!

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