Higher resting heart rate relates to greater rise in pulmonary vein pressure under exercise during permanent atrial fibrillation: a computational study

BACKGROUND. Clinical data indicating a heart rate (HR) target during rate control therapy for permanent atrial fibrillation (AF) and regarding its eventual relationship with reduced exercise tolerance are lacking. OBJECTIVE. The present study aims at investigating the impact of resting HR on cardiovascular response to exercise in permanent AF patients by 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) starting from different resting HR (70 bpm for the slower resting HR-SHR-simulations, and 100 bpm for the higher resting HR-HHR-simulations). To allow comparison of 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 (VCI 4 , VCI 6 and VCI 8). RESULTS. Pulmonary vein pressure (VCI 4 = 0.71, VCI 6 = 0.73 and VCI 8 = 0.77) underwent a greater increase, while systemic arterial pressure variations (VCI 4 = 1.15, VCI 6 = 1.36, VCI 8 = 1.56) experienced a less sustained increase than expected in HHR compared to SHR simulations. CONCLUSIONS. In terms of exercise tolerance, a slower resting HR could be preferable in permanent AF patients, since pulmonary vein pressure undergoes a slighter increase and systemic blood pressure a more appropriate increase with respect to a higher resting HR