How Fast versus effectiveness (Do Yo Want It Fast or Good?)
TomB, I missed the OP's distinction there. I was not responding to your post. Let me do so here.
In the first place, we weren't discussing how well the human animal tolerates high heart rates (which extremely variable) but rather how high a rate atrial fibrillation is capable of achieving.
If you are speaking about electrically only, that is one thing. If you are speaking about the in vivo condition of A-Fib, then myocardial tolerance and pulse are important too; beyond a certain point depending upon the patient's situation, the myocardium (et al) will not tolerate this because refill and discharge of the cardiac chambers will be insufficient. Formation of embolic clots will be more likely. I don't disagree with you, my accent and concern are just different.
I was simply pointing out that it depends on whether or not an accessory pathway is present.
NO argument. Excellent consideration.
Heart rates of 300 have been well documented (see the Guess the EKG thread which coincidentally shows 1:1 atrial flutter).
NO argument, but how long can a normal or even middle aged or elderly or diseased myocardium perform like this and support life? Also, even if the pt is living on the couch and sipping Ensure, can they get to the bathroom or feed themselves without help? Can you imagine how it would be to be purring along like that? Does "heart rate" mean strictly electrical activity (
in vitro) or effective pulses (
pro vivo)?
As for calculating the rate with atrial fibrillation you could always run a 60 second rhythm strip and count every complex if you're worried about the irregularity but in my experience computers are pretty accurate. For inpatients who are being continuously monitored the rate of AF is usually reported as a range like 60-90 or 110-140.
No argument again.
If you have an EKG, then yes. Electrically detected "QRS" is not the heart rate if you are speaking about how many physiologically EFFECTIVE pulses are generated. (PEA would by that token have pulses, whereas the pt and first responders will disagree).
Speaking from my creaky and low-rent experience, (including my physician's office), the human eye on the EKG is better than the machine; my a-fib was diagnosed by one machine as SVT with occasional PVC's, and the one across the hall (newer software and a concerned FNP) correctly diagnosed a-fib, which retrospective study of my EKG's by a cardiologist revealed a five year history of. Pulse ox machines could not figure out a pulse rate which accurately reflected the true pulse rate (pretty good at estimating the rate of EFFECTIVE pulses though).
EMT-B, or bedside nurse, is going to be taking the pulse, not doing 12 lead, so I referred to and am always concerned with the
in vivo, outside the hospital aspects. Good post, keep it up.
PS: To paraphrase, '
In the first case', I '
simply' am not '
worried'.
