  Aims. Clinical data indicating a heart rate (HR) target during rate control
therapy for permanent atrial fibrillation (AF) and assessing its eventual
relationship with reduced exercise tolerance are lacking. The present study
aims at investigating the impact of resting HR on the hemodynamic response to
exercise in permanent AF patients by means of a computational cardiovascular
model.
  Methods. The AF lumped-parameter model was run to simulate resting (1
Metabolic Equivalent of Task-MET) and various exercise conditions (4 METs:
brisk walking; 6 METs: skiing; 8 METs: running), considering different resting
HR (70 bpm for the slower resting HR-SHR simulations, and 100 bpm for the
higher resting HR-HHR simulations). To compare relative variations of
cardiovascular variables upon exertion, the variation comparative index (VCI) -
the absolute variation between the exercise and the resting values in SHR
simulations referred to the absolute variation in HHR simulations -was
calculated at each exercise grade (VCI4, VCI6 and VCI8).
  Results. Pulmonary venous pressure underwent a greater increase in HHR
compared to SHR simulations (VCI4 = 0.71, VCI6 = 0.73 and VCI8 = 0.77), while
for systemic arterial pressure the opposite is true (VCI4 = 1.15, VCI6 = 1.36,
VCI8 = 1.56).
  Conclusions. The computational findings suggest that a slower, with respect
to a higher resting HR, might be preferable in permanent AF patients, since
during exercise pulmonary venous pressure undergoes a slighter increase and
systemic blood pressure reveals a more appropriate increase.
