Cardiorespiratory fitness in individuals with and without atrial fibrillation
Authors: Johnson K E , Sellevold A B , Roedal L , Loennechen J P , Wisloff U , Dalen H , Letnes J M , Nes B M 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Liaison Committee for Education, Research and Innovation in Central Norway (Samarbeidsorganet).

Background
Cardiorespiratory fitness is an important marker of cardiopulmonary health. The majority of published data is however based on healthy individuals. To improve clinical decisions and tailor exercise as treatment for patients with atrial fibrillation (AF), knowledge on impact of AF with and without other cardiovascular diseases (CVD) is essential.

Purpose
To explore impact of age, sex, presenting rhythm during cardiopulmonary exercise testing (CPET) and presence of other CVDs on directly measured peak oxygen uptake (VO2peak) in participants from a general health-survey with and without AF.

Methods
We used cross-sectional data from the HUNT4 Fitness Study, a subsample of the Trøndelag Health Study (HUNT, 2017-2019). All participants (n = 2548, 49 % women) completed a standardized CPET with ECG monitoring. We stratified participants into categories of validated AF diagnosis (yes/no) and whether the CPET was performed in sinus or AF rhythm among those with AF. As we did not have precise data for subtype of AF, cardiac rhythm under testing was used as a proxy for permanent/persistent AF or non-permanent AF. Other CVD (yes/no) was defined as stroke, coronary heart diseases, or heart failure, using validated diagnoses from hospital registries for those with AF and self-reported diagnoses for non-AF participants. We used a general linear model to investigate the differences in predicted means for VO2peak per category of AF, other CVD, age, and sex testing for interaction between covariates.

Results
In total, 355 participants had valid AF, and among them 139 performed CPET with AF rhythm (Table 1). Mean VO2peak was 26 and 35 mL/kg/min for women and men, respectively, with non-permanent AF (sinus) and 22 and 26 mL/kg/min for women and men with permanent AF. Results from the general linear model are shown as predicted means with 95% confidence and prediction intervals in Figure 1. VO2peak decreased with higher age for both women and men, with and without other CVD, and were generally lower for women than for men. For both sexes and categories of CVD, participants with permanent/persistent AF, and hence AF during CPET, had lower VO2peak than those with non-permanent AF tested in sinus rhythm, and those without AF. The difference was more prominent in the younger age groups. There were, however, only small differences between participants with non-permanent AF and those without AF. Predicted means for VO2peak were lower for women and men with other CVD than without other CVD.

Conclusion
VO2peak was similar in participants with AF performing CPET in sinus rhythm to those without AF when no other CVD was present. Permanent/persistent AF and presence of other CVDs were the two factors with the most negative impact on VO2peak for both men and women across age groups.