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Monday, April 27, 2015

Standard maximal heart rate prediction formula may result in an underestimate

For stress tests purposes ( regular treadmill and nuclear exercise imaging) physicians  typically use the formula : Maximal heart rate =220-age.

Another formula is the Tanaka formula; Maximal heart rate =209-.7age

More recently based on a Norwegian study by Nes  and co workers the following formula is suggested :

Maximal heart rate= 211-.64 with an error term of +/- 10.8. See here for reference.

For the three formulas applied to a 75 year old we get maximal heart rate predictions of
145,156 and 163 . (Standard,Tanaka,Nes)

Frequently stress tests are terminated at when the patient reaches 85% of the predicted max heart rate.
For the three formula we get :


The validity of a stress tests depends in part on having the patient exercise to a high enough level to induce some degree of stress into the stress tests and use of 220-age formula would seem to make  false negative tests more likely.This is not breaking news, Tanaka said as much in his 2001 article in the American College of Cardiology Journal  but still some  stress test facilities still use the 220 formula . See here.

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