A person whose heart rate does not reach the expected level for age and gender at maximum exertion is said to have chronotropic incompetence.


predicted maximum heart rate =

= 220- (age in years)


Chronotropic incompetence may be defined as:

(1) failure to reach 85% of the predicted maximum heart rate

(2) failure to reach the 95% confidence limit (mean minus 2 SD) for age and gender


percent heart rate impairment =

= ((predicted value) - (maximum heart rate achieved)) / (predicted value) * 100%


Causes of chronotropic impairment:

(1) beta-blocker therapy

(2) elite aerobic athlete

(3) poor left ventricular function and severe coronary artery disease


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