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Background and Purpose: Previous studies have demonstrated the cardiovascular effects of Urtica dioica (Nettle) such as anti-hypertensive, and negative inotropic effects on heart . The effects of plant on atrioventricular node has not been explored yet.Inhibitory Na+-K+-ATPas pump has been shown ny U. dioica . The aims of the present study were: 1) to determine concentration-dependent effects of ethanolic extract of nettle on the nodal basic and functional properties. 2) to campare mechanism of action nettel with ouabaine and verapamil.
Materials and Methods: This was an experimental study. Male New Zealand rabbits (1-1.3 kg) were used in all of the experiments Various experimental stimulating protocols (Wbcl Recovery, Facilitation, Fatigue) were applied to assess electrophysiological properties of Node. We used isolated perfused AV-nodal preparation (n=18). All protocols were repeated in the presence and absence (control) of different concentration (0.2-0.4 g/l) of Nettle, verapamil (0.1μM) and ouabaine (0.25μM). Results were shown as Mean ± SE and a probability of 5% was used to indicate statistical significance.
Results: In the presence of Nettel, significant increases in WBCL (150.7± 4.3 to 180 ±15.2msec), AVCT (44±2.5 to 54±1.7msec), ERP (125±13 to 149 ±20.6msec) and magnitude of fatigue (ΔAH) 6 ± 0.9 msec were observed. The nettel has less inhibitory activity than verapamil, such as ERP of Nettel was 40% of verapamil. Also, Nettel had similar electrophysiological effects in regard to ouabain.
Conclusion: In the present study, negative dormotropic effect of extract, Citrus bigaradia of Nettel, was observed on the isolated AV-nodal preparation. The same electrophsiological trend of ouabain and Nettel, may indicate the role of Na+-K+-ATPas pump in the deppresant effect of Nettel.

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Background and purpose: Preliminary studies have been established to examine the cardiotonic effect of Citrus bigaradia extract, by implenenting various mechanisms. The functional protective role of this plant against supraventricular tachyarrhythmia remains to be determined.The present study is designed to assess the role of hydroalcoholic extract of Citrus bigaradia by modifing the electrophysiological properties of atrioventricular node, during simulated experimental atrial fibrillation in rabbits and also, to determine the role of adrenoceptores regarding effects of Citrus bigaradia on the AV node.
Materials and methods: In this present study, Newsland male rabbits(1.5-2 kg) was used. Programmed stimulation protocols (Recovery, Wenckbach, Atrial fibrilation and Zone of concealment) were applied in two groups (N=23) to assess electrophysiological properties of isolated rabbit AV node. In the first group (N=10), different concentrations of hydroalcoholic extract of Citrus bigaradia were added to thyrods to detect nodal concealed conduction. In the second group (N=13), the effects of extracts (54-108 mg/L) were analysied in the presence of β-adereceptor blocker(Nadolol 2 µm). AF protocol was simulated by high-rate atrial pacing with random coupling intervals (range 75-125 ms). All data have been shown as Mean±SE.
Results: Citrus bigaradia, had biphasic concentration-effect pattern, such as in low and intermediate concentrations (0.8-3.2 mg/L), shortened nodal functional refractory period and Wenckebach. We observed a non-significant decrease in the average H-H intervals and numbers of concealed beats in all concentrations of Citrus bigaradia. Zone of concealment was shortened by this plant. Nadolol (2 µm) prevented the whole effects of Citrus bigaradia on the nodal conduction time, refractoriness and concealed conduction.
Conclusion: The above results indicate the potential pro-arrhythmic effects of Citrus bigaradia in worsing supraventricular tachyarrhythmia. The effects of plant to decrease the AV-nodal refractory period and concealment zone may be considered the major mechanism of this plant.At least some parts of effects of Citrus is mediated through β-adrenoceptores.

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Background and purpose: Many studies have investigated the cardioprotective effects of olive leaf extract (OLE). None, however, has reported its antiarrhythmic role for in vivo model arrhythmia. This study aimed at investigating the antiarrhythmic effect of OLE andassessing the duration of its use inanesthetized rats. Materials and methods: Forty eight male Wistar rats were divided into six groups of eight. All groups-except group one (the control group)- received OLE (200 mg/kg/day, orally) for 1, 3, 7, 14 and 28 days, respectively. Then, their left anterior descending coronary artery (LAD) was occluded for 30 min under general anesthesia and artificial respiratory support. Direct blood pressure and electrocardiogram (ECG) were continuously monitored before and during the ischemia. Results: The data showed that severity of arrhythmia including ventricular ectopic beats, incidence of ventricular tachycardia (VT), and ventricular fibrillation (VF) reduced significantly in groups that received OLE for at least 14 days. Also, the number and duration of VT and VF episodes decreased significantly in groups five and six, especially the group that received OLE for 28 days. Conclusion: These results show that oral administration of OLE could induce antiarrhythmic effect, if used for more than seven days. Further studies are required to determine the effects of different doses and durations and cellular mechanisms of OLE.

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Background and purpose: Fluctuations in the heart rate can be affected by many factors such as breathing. The amplitude of heart rate variability during inhalation and exhalation provides a quantitative measure that puts the estimate of cardiac vagal function which is considered. The aim of this study was to investigate the effect of a single dose of hyoscine-N-butylbromide (hyoscine) on the amplitude of heart rate variability, namely cardiac vagal activity. Material and methods: 15 healthy young male subjects participated in the study. Each subject came to the laboratory twice with one week interval. Before and one hour after intramuscular injection of hyoscine or placebo, normal and deep breathing tests were performed every 10 minutes. The amplitude of respiratory sinus arrhythmia (RSA) associated with cardiac vagal activity between periods before and after administration of the drug/ or placebo were analyzed by RM_ANOVA. Results: Comparing with normal breathing, deep breathing increases the amplitude of the RSA. The One way ANOVA of RSA showed that hyoscine reduced the RSA amplitude that at 50 min after injection returned to basal level. Similar results were also observed during normal breathing test except that RSA amplitude at 40 min after injection of hyoscine returned to baseline. Conclusion: Overall, the findings of this study showed that intramuscular injection of 20 mghyoscine reduces cardiac vagal activity that returned to base line 40-50 minutes after the injection.

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Background and purpose: Cardiac magnetic resonance imaging (MRI) is a costly method to assess cardiac iron overload. The presence of fragmented QRS (fQRS) indicates changes due to iron overload in cardiac tissue. The aim of this study was to evaluate the correlation between fQRS and cardiac iron overload using cardiac MRI in patients with β-thalassemia major (β-TM).
Materials and methods: This analytical cross-sectional study was conducted in 40 β-TM patients admitted to Arak Amir-Kabir Hospital, Iran 2018-2019. Cardiac T2* MRI was performed and values of less than 20 ms were considered as cardiac iron overload. The patients were divided into two groups (<20 and >20 ms). The presence of fQRS was assessed on 12-lead surface electrocardiogram (ECG) and compared between two groups.
Results: There was a positive correlation between T2*MRI and serum ferritin (r= 0.041, P=0.657) and hemoglobin levels (r=0.057, P=0.540). The mean T2*MRI in patients with fQRS (18.43±7.24) was significantly lower than patients without fQRS (26.47±6.15) (P=0.001). We found a negative correlation between T2*MRI and fQRS (r= -0.048, P=0.001).
Conclusion: The presence of fQRS on ECGs could be a good predictor of cardiac iron overload in β-TM patients. It is believed that fQRS can indicate this change in electrocardiography and shows the need for more accurate monitoring for cardiac overload and aggressive chelation therapy.