[ role of adrenoceptors in the electrophysiological effects of hydroalcoholic extract of Citrus bigaradia in experimental model of atrial fibrilation of isolated atrioventricular node of rabbits]

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 supraventricuiar 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. 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 beta-adereceptor blocker [Nadolol 2 micro m]. 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. 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 micro m] prevented the whole effects of Citrus bigaradia on the nodal conduction time, refractoriness and concealed conduction. The above results indicate the potential pro-arrhythmic effects of Citrus bigaradia in worsing supraventricuiar 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 beta-adrenoceptores

Prolongation of AV nodal refractoriness by Ruta graveolens in isolated rat hearts. Potenial role as an anti-arrhythmic agent

To evaluate concentration-dependent effects of total extract of Ruta graveolens and its purified alkaloid fraction on the nodal basic and functional properties. In the present experimental study, we used the Langendorff model for perfusion of isolated rat hearts to determine the effects of various concentrations of methanolic extract of Rue 1.25x10-6% weight per volume percent [W/V]; 2.5x10-6% W/V; 3.75x10-6% W/V and total alkaloid of Rue 0.25x10-6% W/V; 0.5x10-6% W/V on electrophysiological properties of cardiac tissue. Selective stimulation protocols were used to independently quantify atrioventricular AV nodal recovery, facilitation, and fatigue. We used 3 groups N=24 of isolated perfused rat AV nodal preparations to assess the effect of Rue extracts. The study was carried out in October 2006 in the electrophysiology laboratory of the Cardiovascular Research Center of Golestan University of Medical Sciences, Golestan, Gorgan, Iran. Our results showed that both the total plant extract and the alkaloid fraction of Ruta graveolens had a similar trend of action on nodal conduction time and refractoriness. Furthermore, we observed increased atrioventricular conduction time 83 +/- 4 to 108 +/- 5 msec and functional refractory period 157.6 +/- 3 to 163.7 +/- 4 msec at a maximum concentration of 3.75x10-6% W/V. The above results indicated a potential antiarrhythmic effect of Ruta graveolens in treating supra ventricular tachyarrhythmia

[ effects of liquid extract of Allium sativum on the basic and speed-dependent electrophysiological properties of islolated atrioventicular nodal of rabbit]

Herbal treatments are suitable replacement for synthetic drugs due to their availability, minimal side effects and low price. Previous studies about pharmacologic and biochemical effects of Allium sativum [garlic] have shown antihypertensive, anti arrhythmic, negative inotropic and chronotropic activities. The aim of this study was to assess the effects of liquid extract of Allium sativum on the basic and rate-dependent electrophysiological properties of isolated atrioventricular [AV] nodal of rabbit. In the present study we used isolated perfused AV-Nodal rabbit [1.5-2 kg] preparation including right atrium, intra-atrial septum and His bundle of rabbit as an experimental model to determine the effects of various concentration of aqueous extract of Allium Sativum. Selective stimulation protocols [recovery, facilitation and fatigue] were used to independently assess AV nodal properties in 14 rabbits [two groups]. In the first group of experiment [n=8 rabbits], different concentrations [20, 30, 100, 850 mg/lit] of Allium Sativum and in the second group verapamil [0.1 m] [n=6 rabbits] was applied. Data were analyzed using ANOVA and Wilcaxon tests. The results of this research indicate a significant effect of various concentrations of Allium sativum on basic electrophysiological parameters of atrioventricular node [WBCL, recovery, facilitation, fatigue] and fatigue [P<0.05]. In the presence of garlic [20 mg/lit], AVCT [atrioventricular conduction time] increased from 41.3 +/- 5.3 to 45.6 +/- 5.1msec and FRP [functional refractory period] increased from 108.6 +/- 14.4 to 167 +/- 1.1 msec [P<0.05]. The Allium sativum extract has less inhibitory effect in comparison with verapamil on the basic parameters [P<0.05] of Node. The above results showed potential antiarrhythmic properties of Allium sativum by increasing fatigue and refractory period. Therefore, it may be considered for treatment of supraventricular arrhythmias

[ effect of essence of Citrus aurantium on the electrophysiological properties of isolated perfused rabbit AV-node]

Pharmacological studies and traditional medical literature point to the cardiovascular effects of the Citrus aurantium L. [Rutaceae] in many instances. In the present study, we used isolated perfused AV-node of rabbit as an experimental model to determine the effect of various concentrations of essence of Citrus aurantium [0.1-0.3 v/v] on electrophysiological properties of isolated heart. The second goal of the present study was to assess the protective role of essence of Citrus aurantium on arrhythmogenic effects of ouabain. This was a semi-experimental study. We used isolated perfused rabbit AV-nodal preparation, in three groups. In the first group, the effect of various concentration of the Citrus aurantium [0.1, 0.2, 0.3 ml/l] was assesed on the AV-node. In the second and third groups, the effect of Citrus aurantium was tested in the presence of ouabain [0.1 micro molar] and verapamil [0.1 micro molar]. We used 6 rabbit in each group. Statistical analysis was preformed by SPSS Mean +/- SE was used in the all results. Our results showed depressant effects of extract of Citrus aurantium on Wenchebach Cycle Length [WBCL], AV Conduction Time [AVCT], Effective and Functional Refractory Periods [ERP and FRP]. Rate-dependent properties such as Facilitation and fatigue significantly increased by Citrus.a [0.3ml/l]. We had significant increase in the AVCT [32.6 +/- 3.6 to 40 /- 6.08 msec] and FRP [147 +/- 5.1 to 166.6 +/- 3.6 msec] by Citrus.a. We had a protective role of Citrus aurantium on ouabain induced AV-nodal depression. The magnitude of facilitation and fatigue in the concentration of 0.3 C.aurantium was 7.5 +/- 0.3 and 6.5 +/- 0.5, respectively. The above results indicated potential inhibitory and antiarrhythmic effect of Citrus aurantium in treating supraventricular tachyarrhythmia

Comparative clinical and electrophysiologic effects of adenosine and verapamil on termination of paroxysmal supraventricular tachycardia.

The efficacy and electrophysiologic effects of adenosine and verapamil in termination of paroxysmal supraventricular tachycardia (SVT) were compared in 18 patients (age 18-48 years, mean 33 +/- 9 years) with recurrent sustained and inducible SVT. Ten patients had atrioventricular nodal reentrant tachycardia (AVNRT) and 8 had atrioventricular reentrant tachycardia involving a retrograde accessory pathway (cycle length of SVT 280-360 msec; mean 315 +/- 20 msec). Each patient served as his own control. After induction of SVT, adenosine was administered first (6 mg i.v. bolus). If the tachycardia was not terminated, a bolus of 12 mg was given. Ten minutes later, verapamil (5 mg i.v. over 30 sec) was administered after reinduction of SVT. If the tachycardia was not terminated, a 5 mg dose was repeated every 5 minutes upto 20 mg. Adenosine terminated the SVT in 16 cases (6 mg - 7 patients, 12 mg - 9 patients). Verapamil was effective in 11 patients (5 mg - 6 patients, 10 mg - 4 patients, 15 mg - 1 patient, 20 mg - nil). The overall efficacy of adenosine (89%) was significantly greater than that of verapamil (61%; p < 0.05). Adenosine terminated the tachycardia more quickly than verapamil (mean 24 +/- 11 sec versus 142 +/- 40 sec; p < 0.01). Termination of tachycardia by both drugs was related to antegrade block of the atrioventricular node in all patients except one with AVNRT in whom adenosine blocked the retrograde fast pathway. Ventricular premature beats were seen transiently in 5 patients following adenosine. Transient side effects such as flushing, burning and chest pain were frequently observed with adenosine and correlated with the termination of tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)