Eshuis G, Hock J, Marchie du Sarvaas G, van Duinen H, Neidenbach R, van den Heuvel F, Hillege H, Berger RM, Hager A.Heart. 2021 May 14:heartjnl-2020-318928. doi: 10.1136/heartjnl-2020-318928. Online ahead of print.PMID: 33990411
Take Home Points:
- Peak VO2 was reduced at all ages compared to healthy controls (70% of predicted at age 6)
- The annual deterioration in peak VO2 was significantly faster in rTOF compared to controls with a value of -0.24% of predicted point per year
- Female patients had a lower peak VO2 than males at any age
- The exercise limitation seen in adults with rTOF originates mainly in adolescence due to the normal growth and maturation of the musculoskeletal system
Commentary from Dr. Blanche Cupido (Cape Town, South Africa), chief section editor of ACHD Journal Watch: The use of cardiopulmonary exercise testing (CPET) has been used increasingly as surveillance in patients with congenital heart disease (CHD). The peak VO2 (maximum oxygen consumption) servs as both a diagnostic and prognostic tool in assessing clinical deterioration and is being incorporated into clinical guidelines, particularly related to valve replacement in patients with repaired Tetralogy of Fallot (rTOF). Many factors however affect peak VO2 including age, height- and weight gain inn adolescence, and peaks in adulthood before declining as patients age, mainly related to a loss of muscle mass and a reduction in chronotropic competence over time.
Previous studies showed rTOF to have a reduced peak VO2 of ± 60-80% of predicted. However, few longitudinal studies of peak VO2 exist in this cohort. To adequately interpret serial CPET studies, a knowledge of peak VO2 across a wide age and gender spectrum is needed. This multi-center cohort study at 2 tertiary institutions in Germany and the Netherlands aimed to describe the natural spectrum of peak VO2 from childhood to elderly adulthood in a cohort of patients with rTOF. Patients seen between September 2001 and December 2016 were retrospectively included. Clinical, demographic and cycling CPET data were included. Those with treadmill CPET were excluded.
The primary outcome was peak VO2 expressed in absolute ml/min or as a percentage of predicted. The absoluter peak VO2 was compared to subject-specific references based on 2 prediction models (Bongers et al and Mylius et al). A total of 586 patients were included with 1175 valid CPET’s available for analyses. 46% of the cohort was female.
The cohort was divided into age-based quartiles. At baseline, median age was 21 years with youngest being age 6 and the oldest age 63. The median follow-up time between CPET tests was 24 months.
Above is depicted the scatterplots of repeated peak VO2 measurements and their subject-specific references, showing an increase during adolescence – yet faster in reference population than in the rTOF group. The maximum peak VO2 was reached at around age 20- 25 in both reference and rTOF group after which it gradually declined with age. At all ages, patients showed a reduced peak VO2 compared to references and the decline is accelerated inn rTOF patients compared to the reference group.
Figure 5 above shows the absolute peak VO2 stratified for sex. At the age of 6, no significant difference between male and female was noted. The steep linear increase in peak VO2 is accelerated in males compared to females, with a greater peak in males compared to females. The gradual annual rate of decline is similar in both sexes.