Performance comparison

To compare relative variations of the computational results, "variation comparative index" (VCI) was used. This index, evaluated for every cardiovascular variable at each exercise intensity (VCI₄, VCI₆ and VCI₈), is defined as the absolute variation between the exercise and the resting values in SHR simulations divided by the absolute variation in HHR simulations. Thus, for a general hemodynamic variable, q, VCI at a specific exercise intensity (ex = 4, 6, 8 METs), can be expressed as follows: VCI_ex = (q_ex—q_res)_SHR / (q_ex—q_res)_HHR, where the subscript res indicates the resting value (1 MET) of q.

Through VCI, we compare how the resting HR during permanent AF influences the exercise-induced modifications of cardiovascular variables. A VCI > 1 indicates that the studied variable undergoes a greater variation in SHR exercise simulation, while a VCI < 1 means that the greatest variation occurs in HHR exercise simulation. A variation was considered relevant when VCI ≥ 1.15 or ≤ 0.85, given the assumption that ±15% represents the estimated maximum variation between instrumental and operator-dependent measurements.