Heart rate correction based on ‘universal’ regression equation—erroneous conclusions when studying cardiac mechanical function during stress

This paper studies the possible errors associated with the use of a 'universal' regression equation in heart rate correction when used on mechanical cardiac function parameters. Systolic time interval rate correction, using Weissler regression equations, is taken as an example. The measurements were made during the isometric handgrip test, the orthostatic test, the Valsalva manoeuvre and the cold pressor test. It was observed that in most measurements rate correction caused a significant correlation between the changes in heart rate and the rate-corrected systolic time interval. It is considered that this new dependence between heart rate and the rate-corrected parameter makes the physiological interpretation of results more difficult. Therefore it is recommended that in stress provocations mechanical cardiac function parameters should not be rate-corrected by methods based on a 'universal' regression equation between heart rate and the mechanical function parameter.