RESUMO
We aimed to assess the influence of Melissa officinalis [lemon balm], a well-known herbal drug with numerous applications in traditional and modern medicine, on cardiac conduction and susceptibility to lethal ventricular arrhythmia. Forty-two male Wistar rats were divided into a control group [CTL], an M. officinalis group that received the aqueous extract of M. officinalis L. intraperitoneally [i.p.] at dosages of 50, 100, 200 and 400 mg/ml/kg, respectively, and an amiodarone group [Amio group] that received 30 mg/ml/kg i.p. of amiodarone. Heart ischemia/reperfusion was induced by the ligation and release of the left anterior descending branch of the left coronary artery. There were no statistical differences between the groups in the basal heart rate and blood pressure. PR, corrected QT [QTc] and QRS intervals increased in the M. officinalis and Amio groups. PR and QTc were statistically significant only in the Amio group and QRS was significant only in the group receiving 400 mg of M. officinalis [M400 group] in comparison with the CTL group. During the reperfusion period, the decrease in ventricular fibrillations was statistically significant in all groups [except the M400 group] when compared with the CTL group. The score of arrhythmia severity also decreased, but was statistically significant only in the Amio group [p < 0.05 vs. CTL group].Conclusions: Our findings suggest that M. offcinalis extract has a mild protective effect against reperfusion-induced lethal ventricular arrhythmias in rats