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 ( (center dot)VO2peak) following HIIT and M-VICT. Participants were randomized into HIIT or M-VICT after completing two baseline CPETs: one with cardiac stress technologists (CPETdiag) and the other with a research team of exercise specialists (CPETresearch). Additional CPET was completed following 12 weeks of twice-weekly training. The reliability of CPETdiag and CPETresearch was assessed by intraclass correlation coefficient (ICC) and dependent t tests. The MDC score was calculated for (center dot)VO2peak using a reliable change index. The proportion of participants achieving MDC was compared between HIIT and MVICT 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 (POpeak: 124 + 40 vs. 148 + 40 watts, p < 0.001) and HR (HRpeak: 136 + 22 vs. 148 + 30 bpm, p = 0.023) were significantly greater in CPETresearch than CPETdiag. Few participants achieved MDC in (center dot)VO2peak (5.6 mL/kg/min) with no difference between HIIT (0%) and M-VICT (10.0%, p = 0.244). POpeak and HRpeak 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 nonresponders.