Variability of cardiopulmonary exercise testing in patients with atrial fibrillation and determination of exercise responders to high-intensity interval training and moderate-to-vigorous intensity continuous training.

Disabling atrial fibrillation (AF)-related symptoms and different testing settings may influence day-to-day cardiopulmonary exercise testing (CPET) measurements, which can affect exercise prescription for high-intensity interval training (HIIT) and moderate-to-vigorous intensity continuous training (M-VICT) and their outcomes. This study examined the reliability of CPET in patients with AF and assessed the proportion of participants achieving minimal detectable changes (MDC) in peak oxygen consumption (V̇O_2peak) following HIIT and M-VICT. Participants were randomized into HIIT or M-VICT after completing two baseline CPETs: one with cardiac stress technologists (CPET_diag) and the other with a research team of exercise specialists (CPET_research). Additional CPET was completed following 12 weeks of twice-weekly training. The reliability of CPET_diag and CPET_research was assessed by intraclass correlation coefficient (ICC) and dependent t tests. The MDC score was calculated for V̇O_2peak using a reliable change index. The proportion of participants achieving MDC was compared between HIIT and M-VICT using chi-square analysis. Eighteen participants (69 ± 7 years, 33% females) completed two baseline CPETs. The ICCs were significant for all measured variables. However, peak power output (PO_peak: 124 ± 40 vs. 148 ± 40 watts, p < 0.001) and HR (HR_peak: 136 ± 22 vs. 148 ± 30 bpm, p = 0.023) were significantly greater in CPET_research than CPET_diag. Few participants achieved MDC in V̇O_2peak (5.6 mL/kg/min) with no difference between HIIT (0%) and M-VICT (10.0%, p = 0.244). PO_peak and HR_peak differed significantly in patients with AF when CPETs were repeated under different settings. Caution must be practised when prescribing exercise intensity based on these measures as under-prescription may increase the number of exercise non-responders.