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Objectives: The current study was performed to determine whether pulmonary vein isolation (PVI) improves nocturnal hypertension in patients with paroxysmal atrial fibrillation (PAF)., Background: Abnormal night-time blood pressure (BP) fluctuation is a risk factor for atrial fibrillation. Imbalance of autonomic nervous function is a risk factor common to both of these abnormalities. PVI can reportedly modify the autonomic nervous function balance in patients with atrial fibrillation., Methods: The study population comprised 50 consecutive patients (mean age, 69.8 ± 7.5 years; 35.0% male) with PAF scheduled for PVI. Both 24-h ambulatory BP monitoring and heart rate variability analysis were performed before and at 3 months after PVI., Results: Patients were classified into two groups according to the presence of nocturnal BP dipping before PVI: the normal dipping group (n = 27) and the nondipping group (n = 23). The low-frequency spectrum power and the ratio of low-frequency spectrum power to high-frequency spectrum power (low-frequency spectrum/high-frequency spectrum) were higher in the nondipping than the normal dipping group (low-frequency spectrum: 219.9 ± 210.2 vs. 92.7 ± 50.5 ms, respectively, P = 0.03; low-frequency spectrum/high-frequency spectrum: 1.8 ± 1.9 vs. 0.9 ± 0.8, respectively, P = 0.05). In the nondipping group, the elevated night-time BP disappeared in eight (35%) patients at 3 months after PVI, which was associated with an increase in high-frequency spectrum power. These patients did not develop atrial fibrillation recurrence during follow-up (mean, 568 ± 218 days)., Conclusion: Among patients with PAF, the nondipping group showed greater sympathetic activity (higher low-frequency spectrum power and low-frequency spectrum/high-frequency spectrum) than the dipping group. Restoration of BP dipping after PVI is associated with increased parasympathetic activity (higher high-frequency spectrum power) and reduced recurrence of arrhythmic events.