Changes in Glucose-6-phosphate Dehydrogenase Activity in Paroxysmal Atrial Fibrillation

Background: The antioxidant defense system has been subject to investigations in various cardiovascular diseases. The studies of its status in paroxysmal atrial fibrillation are scarce. The enzyme glucose-6-phosphate dehydrogenase is the main source of reducing equivalents and its activity is crucial for the antioxidant defense system of the cell. Purpose: To study the activity of glucose-6-phosphate dehydrogenase in dynamics as an indicator of the antioxidant defense system in patients with paroxysmal atrial fibrillation (<48 hours). Patients and methods: The enzyme was studied in erythrocytes of 51 patients (59.84±1.60, 26 males) immediately after hospitalization, 24 hours and 28 days after sinus rhythm restoration. It included also 52 healthy controls (59.50±1.46, 26 males), matching the patients by gender and age. The rhythm regulation was achieved by propafenone. The enzyme activity was determined spectrophotometrically. Results: The mean duration of atrial fibrillation episodes prior to hospitalization was 8.1 hours, the majority of the patients being hospitalized on the 5th hour from the arrhythmia onset. Upon admission, the patients' enzyme activity was lower as compared to the controls (2.50±0.10 vs 2.90±0.15 nmol NADP+ min/mg Hb, p<0.05). The difference was retained for twenty-four hours after rhythm regulation (2.41±0.09 vs 2.90±0.15 nmol NADP+ min/mg Hb, p<0.05). On the twenty-eighth day, there was no significant difference (2.63±0.08 vs 2.90±0.15 nmol NADP+ min/mg Hb, p>0.05). Conclusion: In the early hours of its clinical manifestation, paroxysmal atrial fibrillation is associated with reduced glucose-6-phosphate dehydrogenase activity, which persists after sinus rhythm restoration and is slowly increased with time. In essence, the changes in enzyme activity reflect changes in antioxidant defense system. Furthermore, the specific dynamic is suggestive of close relation to the rhythm disorder. Future studies would allow for determination of the precise role of the antioxidant defense system in the disease pathogenesis as well as its significance for the disease prevention and treatment.