{
  "abstract": "Background Atrial fibrillation (AF) is associated with reduced exercise capacity, but the physiological mechanisms underlying this limitation remain unclear. Cardiopulmonary exercise testing (CPET) enables integrated assessment of cardiovascular performance during exertion. We aimed to determine whether reduced exercise capacity in AF is attributable to impaired heart rate augmentation or altered cardiovascular efficiency compared with sinus rhythm controls.Methods Sixty-seven participants prospectively recruited from two clinical studies with identical CPET protocols underwent symptom-limited CPET on a cycle ergometer for this prospective observational study. In a post hoc analysis, patients with symptomatic AF in the last 12 months (n=38) were compared with sinus rhythm controls (n=29). Peak oxygen consumption (VO 2 peak), anaerobic threshold (AT), peak workload, heart rate response, chronotropic response index, and oxygen pulse were assessed. Subgroup analysis compared patients in AF at the time of testing with those in sinus rhythm with no history of AF. Between-group comparisons were performed using unpaired Student’s t-test.Results As summarised in table 1, indexed peak VO2 was significantly lower in patients with AF compared with controls (17.45 ± 3.74 vs 20.65 ± 4.91 mL·kg–1·min–1, p=0.0027). Peak workload, AT, and absolute VO2 achieved were similar between groups. Heart rate at rest, at AT, and at peak exercise did not differ, nor did the chronotropic response index (0.98 ± 0.60 vs 0.88 ± 0.25, p=0.41), which was preserved in both groups. Oxygen pulse at peak exercise was comparable. Patients in AF at the time of testing also demonstrated lower peak VO2 compared with those in sinus rhythm with no history of AF (17.8 ± 2.83 vs 20.65 ± 4.65 mL·kg–1·min–1, p=0.044), despite similar chronotropic response and similar achieved workload. Achieving anaerobic threshold, workload and variance in VO2 peak did not differ between those in AF and not in AF groups (T=2.52 p=0.11).Conclusions AF was associated with reduced peak oxygen consumption despite preserved heart rate augmentation and workload during exercise. These findings suggest that exercise limitation in AF may not be primarily driven by chronotropic impairment but may reflect reduced cardiovascular efficiency. CPET appears feasible and physiologically interpretable in this population.Abstract 515 Table 1Results of CPET analysis",
  "authors": [
    {
      "affiliations": [
        "University of Bristol, Bristol, UK"
      ],
      "name": "G Calthorpe"
    },
    {
      "affiliations": [
        "Cardiology, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK"
      ],
      "name": "D Murphy"
    },
    {
      "affiliations": [
        "Cardiology, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK"
      ],
      "name": "J Graby"
    },
    {
      "affiliations": [
        "Department for Health, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK"
      ],
      "name": "JCL Rodrigues"
    },
    {
      "affiliations": [
        "Cardiology, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK"
      ],
      "name": "A Khavandi"
    }
  ],
  "title": "515 Contrasting cardiopulmonary exercise testing in patients with atrial fibrillation vs sinus rhythm",
  "uid": "426e4563-d6fd-594d-84af-7015fb18aaa9"
}