Estimating exercise intensity using heart rate in adolescents and adults with congenital heart disease: Are established methods valid?

Abstract

Background: Exercise training is important for people with congenital heart disease (CHD). However, accurate exercise intensity prescription remains challenging. We sought to evaluate the validity of using the percentage of peak HR (%HR_peak) and HR reserve (%HRR) methods to estimate exercise intensity in people with CHD.

Methods: Cardiopulmonary exercise tests from 2009 to 2017 were reviewed. Light, moderate, and vigorous exercise intensity were characterized using guideline-based percentage of peak oxygen uptake (VO₂) ranges, and corresponding HRs were averaged at each intensity. The estimated average HR for each exercise intensity category was calculated using the %HRR and %HR_peak methods. Differences between the average HR at each intensity (reference HR) and the estimated HRs were determined.

Results: 265 subjects were included (mean age, 29 ± 10 years, 48% females). The %HRR and age-predicted maximal HR (%HR_max) methods were the most accurate, but were still only within the guideline-defined HR ranges less than 65% of the time. Age-predicted %HR_max was the most accurate in the light and moderate-intensity categories, within the defined intensity range 59% and 63% of the time respectively. For vigorous-intensity exercise, %HR_peak was the most accurate, with the average HR within the defined intensity range 84% of the time. %HR_peak tended to underestimate exercise intensity, while %HRR overestimated it.

Conclusions: Using common HR methods for estimating exercise intensity may not be valid in many people with CHD. The %HRR and age-predicted %HR_max methods were the most accurate but were out of range for around one-third of the cohort.

Keywords: Cardiac rehabilitation; Cardiopulmonary exercise testing; Exercise intolerance; Exercise physiology; Exercise prescription; Exercise training.

Fig. 1

The frequency (expressed as a percentage) of when the average reference heart rate was withing, below, and above the defined intensity ranges according to guidelines in all participants. %HR_max, percent maximal heart rate; %HR_peak, percent peak heart rate; %HRR, percent heart rate reserve.

Fig. 2

The frequency (expressed as a percentage) of when the average reference heart rate was withing, below, and above the defined intensity ranges according to guidelines in participants with a normal chronotropic response A) and chronotropic incompetence (CI) B). %HR_max, percent maximal heart rate; %HR_peak, percent peak heart rate; %HRR, percent heart rate reserve.