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) following HIIT and M-VICT. Participants were randomized into HIIT or M-VICT after completing two baseline CPETs: one with cardiac stress technologists (CPET) and the other with a research team of exercise specialists (CPET). Additional CPET was completed following 12 weeks of twice-weekly training. The reliability of CPET and CPET was assessed by intraclass correlation coefficient (ICC) and dependent tests. The MDC score was calculated for V̇O 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: 124 ± 40 vs. 148 ± 40 watts,  < 0.001) and HR (HR: 136 ± 22 vs. 148 ± 30 bpm,  = 0.023) were significantly greater in CPET than CPET. Few participants achieved MDC in V̇O (5.6 mL/kg/min) with no difference between HIIT (0%) and M-VICT (10.0%,  = 0.244). PO and HR 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.