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Showing 21 results for Khori

Vahid Khori, Mohsen Nayebpour,
Volume 10, Issue 4 (Winter 2007)
Abstract

Introduction: Treatment of supraventricular arrhythmia includes wide range of medical interventions. Herbal remedies are suitable alternatives for synthetic drugs due to their availability, minimal side effects and lower price. Pharmacological studies and traditional medical literature point to the cardiovascular effects of the Artemisia absinthium L. from Compositae family of plants. Methods: In the present study we used Langendorff model of isolated heart of rats as an experimental model to determine the effect of various concentrations of methanolic extract of A. absinthium (3×10 -11 %W/V to 4× 10 -8 %W/V) on electrophysiological properties of isolated hearts. Results: Our results showed depressant effect of A. absinthium extract on Wenchebach Cycle Length (WBCL), AV Conduction Time (AVCT), Effective and Functional Refractory Periods (ERP & FRP) of the isolated heart. Conclusion: The results indicated potential antiarrhythmic effect of A. absinthium extract in treating supraventricular tachyarrhythmia.
Vahid Khori, Mohsen Nayebpour, Jafar Golalipour, Smp Firouzabadi,
Volume 12, Issue 4 (Winter 2009)
Abstract

Introduction: The ablation technique is one of the important therapeutic interventions for treatment of AV Nodal tachyarrhythmia. Different animal models have been developed to study the effects of ablation on the functional interanodal structure. The aim of the present study was to develop a new model of computer analysis to produce lesions by using direct voltage in isolated perfused rabbit AV-Node. Methods: The model of Superfused-perfused isolated AV-Node of rabbit was used in our study. Posterior nodal extension (slow pathway) and anterior nodal approaches (fast pathway) were ablated by using direct voltage (100-110 V) in 30 sec. All stimulation protocols and computer analysis were performed by the custom made software that has been developed in the Electrophysiology laboratory of Golestan Cardiovascular Research Center. All protocols were applied to 2 groups (5 rabbits in each group). Results: His deflection was detected by software (AV-Node pack) and nodal recovery curved was constructed on line. By using specific electrophysiological criteria, we could precisely predict the place of nodal ablation. Slow pathway ablation caused significant ERP and AHmax prolongation and fast pathway ablation caused significant AHmin prolongation. Histology examination confirmed the ablation results. Conclusion: Computer analysis of nodal ablation is a new method to induce specific lesions in AV-nodal pathways. Changing dynamic electrophysiological behavior of AV-node after ablation is an important index for predication of outcome of ablations.
Vahid Khori, Mohsen Nayebpour, Abbas Mirabbasi, Mona Pourabouk,
Volume 13, Issue 1 (Spring 2009)
Abstract

  Introduction : The aim of this study is to obtain new insight into possible relation between functional properties of slow concealed pathway and rate-dependent properties of AV-node.

  Methods : Rate-dependent nodal properties of recovery, facilitation, and fatigue were characterized by stimulation protocols in one groups of (N=7) isolated superfused AV-Nodal rabbits. Small miniature lesions were made by delivering constant voltage (110 V-100 s) with unipolar silver electrode.

  Results : Fast pathway ablation significantly decreased facilitation and had no effect on fatigue and nodal refractoriness. The most important effect of fast pathway ablation was prolongation of minimum conduction time.

  Conclusion : The FP-ablation revealed the presence of the concealed SP. Rate-dependent property of node is dependent to dynamic interaction between concealed slow with slow pathway. Fast pathway involved in the mechanism of facilitation.

 


Aref Salehi, Vahid Khori, Mohsen Nayebpour, Elnaz Rakhshan,
Volume 13, Issue 2 (Summer 2009)
Abstract

Objectives: Dual pathways have a determinant role in the occurrence of atrio nodal tachyarrhythmia (AVNRT). The aim of present study is to determine the role of slow pathway (SP) in the concealment zone and protective role of AV node during atrial fibrillation (AF). Material &Methods: In 7 isolated nodal rabbit preparation zone of concealment and concealed conduction is quantified by Specific pacing protocols. The differences between effective refractory period of atrial and AV node in the basic cycle length and after introducing concealed beat was considered as Zone of concealment. AَF was simulated by high-rate atrial pacing with random coupling intervals. Small miniature lesions were made in superior compact node by delivering constant voltage100-110 v. Results: FP ablation resulted in longer minimum nodal conduction time, but without change of nodal effective and functional refractory period. Zone of concealment was determined as 10±4.8 ms. After fast pathway modification nodal characteristics during AF did not change significantly (average H–H intervals, number of concealed beats and zone of concealment). Conclusion: Fast pathway has not a determinant role in the mechanism of concealed conduction and zone of concealment. During AF, the wave fronts did not used fast pathway to conduct to ventricles.
Vahid Khori, Ali Davarian, Mohsen Nayebpour, Saeed Saleki, Aref Salehi, Ahmadali Shirafkan, Fakhri Badaghabadi, Mona Pourabouk, Alimohammad Alizadeh, Shima Changizi,
Volume 14, Issue 1 (Spring 2010)
Abstract

Introduction: Recent studies showed that nitrergic system have specific modulatory effects on electrophysiological properties of atrioventricular (AV) node. The aim of this study was to determine the effects of nitric oxide (NO) on the electrophysiological properties of isolated rabbit AV node and to investigate the role of adrenergic and cholinergic receptors in the mechanism of its action. Methods: In our laboratory, an experimental model of isolated double-perfused AV-node of rabbits weighing 1.5-2 kg was used. Specific experimental protocols of recovery, Facilitation, Fatigue and Wenckbach were applied in both control and in the presence of the drug. A total number of 35 rabbits were divided randomly into the following groups (n=7): 1) L-Arg (NO donor) (250, 750 and 1000 μmol), 2) L- NAME, a NO synthesis inhibitor (25, 50 and 100 μmol), 3) L-Arg + L- NAME, 4) Nadolol (1 μmol), 5) Atropine (3 μmol). All data were shown as mean ± SE. The level of statistical significance was set at p<0.05. Results: Our results revealed the depressant effect of L-Arg on the basic and rate-dependent electrophysiological properties of AV-node. L- NAME did not deteriorate the effects of L-Arg on the basic and rate-dependent properties, nevertheless, at high concentration (100 μmol) it had a direct inhibitory effect on the AV-node. Nadolol and atropine could prevent the effects of NO on the basic nodal characteristics and the fatigue phenomenon, respectively. Conclusion: Nitergic system can affect basic and rate-dependent electrophysiological properties of the AV-node through adrenergic and cholinergic receptors.
Vahid Khori, Fatemeh Alizadeh, Sorosh Aminosariyeh, Mona Pourabouk, Mohsen Nayebpour, Aref Salehi, Ahmadali Shirafkan, Saeid Saleki, Fakhri Badaghabadi, Ali Davariyan,
Volume 14, Issue 2 (Summer 2010)
Abstract

Introduction: Recent evidence has indicated that statins can reduce the incidence of both supraventricular and ventricular arrhythmias with various mechanisms. The primary goal of the present study was to determine direct protective role of simvastatin in modifying concealed conduction and the zone of concealment in a simulated model of atrial fibrillation (AF) in an isolated atrioventricular (AV) node in rabbits. Methods: Male Newsland rabbits (1.5-2 kg) were used in all experiments. Stimulating protocols (recovery, AF, zone of concealment) were used to study electrophysiological properties of the node in one group (N=8). All of the stimulated protocols were repeated in the presence and absence of different doses of simvastatin (0.5-10 μm). Results were shown as mean ± S.E. Results: Significant inhibition of the basic properties of the AV node was observed after the addition of simvastatin. Significant prolongation of Wenkebakh index (wbcl) from 138.7±5.6 to 182.1±6.9 and functional refractory period (FRP) from 157.7±5.9 to 182.1±6 msec at the concentration of 10 μM was observed. Maximum efficacy of simvastatin in atrial fibrillation (AF) protocol was observed at the concentration of 3.10 μM, that was accompanied with prolonged HH interval and increased number of concealed beats. Zone of concealment significantly increased at the concentrations of 1.3 and 10 μM. Conclusion: This study shows the protective effect of simvastatin in the prolongation of ventricular beats during atrial fibrillation. The effect of simvastatin in increasing AV-nodal refractory period and zone of concealment are probably the anti-arrhythmic mechanisms of this drug.
Vahid Khori, Saed Saleki, Aref Salehi, Alimohammad Alizadeh, Mona Pourabouk, Fakhri Badaghabadi, Shima Changizi, Mohsen Nayebpour,
Volume 14, Issue 3 (Fall 2010)
Abstract

Introduction: Electrophysiological studies have demonstrated a relationship between aging and atrioventricular (AV) nodal conduction and refractoriness. The aim of the present study was to determine the effects of nodal aging on dynamic AV nodal field potential recording during atrial fibrillation (AF) in rabbit. Methods: Two groups of male New Zealand rabbits (neonatal 2-week-olds and adult 12-week-olds, n=14 each group) were used in this study. Field potential recordings were executed by silver electrodes with a diameter of 100 M. Pre-defined stimulation protocols of AF, zone of concealment (ZOC) and concealed conduction for determination of the electrophysiological properties of the AV-node were separately applied in each group. Results: Results of the study showed that mean ventricular rate (HH) during atrial fibrillation was smaller in the neonatal compared to the adult group (229.1 ± 8.3 versus 198.6 ± 13.1 msec, respectively). Also ventricular distribution conduction pattern showed two peaks in the adult and one peak in the neonatal group. Analyzing the zone of concealment in different rates and after concealed beat indicated that the zone of concealment in neonates were significantly smaller compared with adult rabbits and increasing zone of concealment, which is accompanied with increasing ventricular rate is abrogated in the neonatal group (5 ± 3.3, 12.2 ± 6.3 msec). Conclusion: The results of this study showed that the electrophysiological protective dynamic behavior of the AV node during atrial fibrillation is smaller in neonates compared to adults. Narrower zone of concealment, abrogation rate dependent trend of the zone of concealment and shorter nodal refractoriness can account for the specific nodal electrophysiological properties of neonatal rabbits.
Vahid Khori, Mohammad Azadbakht, Mohsen Nayebpour, Amirhosean Jamshidi, Mona Pourabouk, Alimohammad Alizadeh, Fakhri Badaghabadi, Shima Changizi, Maryam Rajaei,
Volume 15, Issue 1 (Spring 2011)
Abstract

Introduction: Despite extensive studies about effects of Crataegus monogyna on cardiovascular diseases yet, a few study has been undertaken antiarrhythmic property of this plant. Aims of the present study were: 1) To determine the protective role of methanolic extract of C.monogyna on the rate-dependent model and the concealed conduction . 2) To explore the role of Na+-K+ A TPase in the protective role of C.monogyna.

 

Methods: In all experiments were used of male New Zealand rabbits (1.5-2kg). Stimulation protocols were used to measure basic and rate-dependent ( recovery, atrial fibrilation and zone of concealment ) AV nodal properties in two groups(N=14) . In the first group all the stimulation protocols before and after different concentrations of C.monogyna extract were repeated (n=7) in the second group (n=7) in the presence of all stimulation protocols Ouabaine(0.05 m M) and extract were repeated. All results have been shown as Mean±SE.

 

Results: Basic and rate-dependent properties of node were inhibited after addition of plant extract of C.monogyna to KerebsHenselite solution . At the maximum concentration of cratagus.m(30 mg/l),WBCL cycle longth is increased significantly from 156.5±3.4 to 173±5.8 ms and nodal functional refractory is prolonged from 164.4±4.1 to 182.7±3.8 ms(P < 0.05).Was recorded Significant decreases of ventricular rhythm in both selective concentrations of plant. The depressent electrophysiologic effect of C.monogyna on the AV node did abolish inhibt by ouabaine.(Selective inhibitore Na+-K+ A TPase Enzyme ).

 

Conclusion: All results are indicating the potential anti-arrhythmic and protective effects of C.monogyna . The effect of plant in increasing nodal refractory period and widen concealment zone might be the major mechanism of this plant. The protective role of cratagus.m does not related to the Na+-K+ A TPase activity.


Vahid Khori, Alimohammad Alizadeh, Mahsa Niknam, Hamid Reza Moheimani, Hamid Yazdi, Mona Pourabouk, Fakhri Badaghabadi, Shima Changizi, Mryam Rajaei, Mohsen Nayebpour,
Volume 15, Issue 2 (Summer 2011)
Abstract

Introduction: Developmental changes in atrioventricular nodal conduction time and refractoriness have been shown in several studies. Prevalence of atrioventricular nodal reentrant tachycardia (AVNRT) is clearly age-dependent. The purpose of this study was to determine developmental changes of basic and frequency-dependent electrophysiological properties of the atrioventricular node (AV-node) in neonatal and adult rabbits. Methods: In this study, the effects of increasing age on the basic and rate-dependent properties of isolated perfused AV-node were analyzed in neonatal (2-week-old) and adult (12-week-old) New Zealand rabbits. Specific stimulation protocols of recovery, facilitation and fatigue were separately applied in each group (n=7). Unipolar extracellular field potential was recorded by a silver electrode (100 M). Results: The results showed that the basic nodal properties (ERP, FRP, WBCL and AHmax) were significantly shorter in neonates compared to the adult group. The magnitude of fatigue was also decreased in the neonatal group compared to control (18.9 ±3.3 vs. 11.1 ± 1.2 msec). Time constant of recovery of the adult group was significantly higher than the neonatal group (P<0.05). Conclusion: The results of this study showed that nodal basic and frequency-dependent properties are age-related and different developmental changes of slow and fast pathways are responsible for this behavior and may reveal the grater susceptibility of AVNRT in young adults compared to infants.
Vahid Khori, Sepideh Shariatnejad, Alimohammad Alizadeh, Hamidreza Yazdi, Mona Pourabouk, Fakhri Badaghabadi, Hamid Reza Moheimani, Shima Changizi, Maryam Rajee, Mohsen Nayebpour,
Volume 15, Issue 2 (Summer 2011)
Abstract

Introduction: Recent studies have shown acute cardioprotective effects of cyclosporine. The aim of the present study was to determine the protective role of cyclosporine on the model simulated the rotational nodal arrhythmia (AVNRT) by using extracellular field potential recordings of isolated atrioventricular-node (AV-node) of rabbit. Methods: This study was performed on isolated double-perfused AV-node of male New Zealand rabbits (1.5-2.5 kg) in one group (n=7). Basic and rate-dependent stimulation protocols (recovery, facilitation, fatigue) and arrhythmia threshold (index of refractoriness) and % Gap incidence were measured for assessment of electrophysiological properties of the AV- node. All stimulation protocols were repeated in control step and in the presence of various cumulative concentrations of cyclosporine (0.5 - 10 μm). Results: Cyclosporine prolonged the effective refractory period from 114.3±7.9 to 142±7.3 msec at the concentration of 10 μm. It also prolonged the functional refractory period from 162±3.3 to 178.6±5 msec and increased the time of Wenckebach at the concentrations of 5 - 10 μM. Various concentrations of cyclosporine increased fatigue and reached a significant level at 10 μm. Gap incidence was 82%, 16.6% and 20% in the control and treatments with 0.5 and 10 μm of cyclosporine, respectively. Conclusion: Block of MPTP by cyclosporine caused inhibition of basic and rate-dependent properties of atrioventricular node. Cyclosporine, by raising the threshold of arrhythmia, could be possibly considered as an anti- AVNRT drug.
Masoomeh Mazandarani, Fatemeh Hoseini, Akhtar Seifi, Hooman Bayat, Mona Pourabouk, Fakhri Badaghabadi, Maryam Rajaei, Hamidreza Moheimani, Vahid Khori,
Volume 15, Issue 3 (Fall 2011)
Abstract

Introduction: Considering the long traditional history of anti-inflammatory and anti-spasmodic effects of Matricria spices on the gastrointestinal system, the present study aimed to investigate the role of calcium channels and Histamine receptors in the inhibitory effects of hydroalcoholic dry extract of German chamomile (Matricaria recutita L.) on the isolated rabbit jejunum. Methods: All experiments were done on the isolated jejunum of New Zealand rabbits (1.8-2.5 kg). Dry extract of aerial parts of M. recutita was obtained by the maceration technique. The study was performed on two groups (n=6 in each group). In the first group, the effects of cumulative concentrations of M. recutita (3×10-3-1×10-2 mg/ml) on normal and K+-induced contractions (50 mM) of isolated jejunum were studied. In the second group, the inhibitory role of M. recutita ( 3 – 13×10-3 mg/ml) was evaluated in the presence and absence of histamine and cetrizine. In the presence and absence of 10 μM certizine, a histamine H1-antagonist, a concentration-dependent inhibitory effect of M. recutita extract in the range of 3-13×10-3 mg/ml was recorded the rabbit jejunum. Results: Results showed that EC50 of M. recutita in the absence and presence of K+ was 6.3×10-3 and 6.5×10- 3mg/ml, respectively. IC50 values for two concentrations of M. recutita (8×10-3 , 1×10-2 ) to abrogated contractive phase of Histamine was 9.55 × 10-6 and 1.57 × 10-6 μM. Cetrizine (10 μM) abolished inhibitory effects of M. recutita (IC50=3.6×10-3), (p< 0.001). Conclusion: Dry extract of matricaria recutita had inhibitory effects on the contractions of isolated rabbit jejunum. Calcium channels and histamine were involved in these antispasmodic effects.
Vahid Khori, Alimohammad Alizadeh, Ameneh Navaiyan, Mohsen Nayebpour, Mona Porabouk, Fakhri Badaghabadi, Shima Changizi, Maryam Rajaei, Hamidreza Moheimani, Hamidreza Yazdi,
Volume 15, Issue 3 (Fall 2011)
Abstract

Introduction: The aim of the present study was to determine direct effects of NO modulation on protective electrophysiological properties of atrioventricular node (AV node) in the experimental model of AF in rabbit. Methods: Isolated perfused rabbit AV nodal preparations were used in two groups. In the first group (N=7), LNAME (50μM) was applied. In the second group (N=12), different concentrations of L - argenine (250 μM - 5000 μM) were added to the solution. Programmed stimulation protocols were used to quantify AV nodal conduction time, refractoriness and zone of concealment. AF protocol was executed by software with coupling intervals (ranging from 75 – 125 msec). Results: L-NAME had depressive effects on basic AV nodal properties. L-Arginine (250μM) had direct inhibitory effects on nodal conduction time, Wenckebach and refractoriness. Significant increases in the number of concealed beats were induced by L-Arginine (500 μM ). Number of concealed beats were increased from 700.7 ± 33.7 to 763 ±21 msec (P<0.05). Trend of zone of concealment prolongation in a frequency-dependent model was abrogated by Larginine (250, 5000 μM). Conclusion: NO at low concentration (in the presence of L-NAME) had facilitatory role on AV nodal properties, but at high concentration (in the presence of L-arginine) enhanced protective role of AV node during AF. Biphasic modulatory role of NO may affect protective behavior of AV node during AF.
Ali Mohammad Alizadeh, Mahdieh Faghihi, Vahid Khori, Maryam Mohsenikia,
Volume 15, Issue 4 (Winter 2012)
Abstract

Introduction: Cardiac preconditioning represents the most potent and consistently reproducible method of rescuing heart tissue from undergoing irreversible ischemic damage. The aim of the present study was to evaluate oxytocin (OT) induced cardioprotection and its signaling pathways on lactate dehydrogenase (LDH) and creatine kinase-MB isoenzyme (CK-MB) in the anesthetized rats. Methods: Eighty-four rats were divided into fourteen groups. Animal’s hearts were subjected to 25 min ischemia and 2 h reperfusion (I/R). Oxytocin (0.03 μg/kg) was used 25 min prior to ischemia. Atosiban, an OT receptor antagonist (1.5 μg/kg), 5-hydroxydecanoic acid, an inhibitor of mitochondrial ATP-dependent potassium channel (10 mg/kg), atractyloside, an opener of mitochondrial permeability transition pores (5 mg/kg), chelytraine, a protein kinase C inhibitor (5 mg/kg) and N-acetylcysteine, a reactive oxygen species scavenger (200 mg/kg) were used 10 min prior to OT administration. Then, LDH and CK-MB levels in plasma were measured. Results: OT administration significantly decreased CK-MB and LDH levels compared to I/R group. Administration of atosiban, 5-hydroxydecanoic, atractyloside, chelytraine and N-acetylcysteine abolished the cardiac preconditioning effect of OT. Conclusion: The present study demonstrates that oxytocin cardioprotective effects are complex and its signaling pathways may mediate through mKATP channels, mPTP, PKC activation and increase ROS.
Vahid Khori, Samaneh Naeimipour, Alimohammad Alizadeh, Ali Haeri Rouhani, Mona Pourabouk, Fakhri Badaghabadi, Maryam Rajaei, Sepideh Shariatnezhad, Hamidreza Moheimani, Saeed Saleki, Mohammad Ali Zeyghami, Mohsen Nayebpour,
Volume 15, Issue 4 (Winter 2012)
Abstract

Introduction: Previous studies have indicated a relationship between MPTP pore and AV nodal rate-dependent properties. The aim of present study was to determine acute direct effects of cyclosporine on extracellular field potential of isolated rabbit AV node during experimental atrial fibrillation. Methods: In one group of male New Zealand rabbits (1.5-2.5 kg) cumulative concentrations of cyclosporine (0.5 – 10 m) were applied on isolated perfused atrio-nodal preparation (n=7). Extracellular field potential recording was sampled during specific stimulation protocols (recovery, zone of concealment and atrial fibrillation) in the presence of drug on electrophysiological properties of AV-node. Results: Cyclosporine significantly decreased the ventricular rate (HH mean) from 231.8 ± 5.7 to 277.4 ± 14.6 msec and functional refractory period during AF (AF FRP) from 138.3 ± 7.5 to 161.2 ± 10.31 msec in control and treated groups, respectively. Effective refractory period during AF (AF ERP) was significantly decreased by cyclosporine 10 mM compared to control group (p<0.05). Conclusion: Cyclosporine-evoked slowing ventricular heart rate during AF was induced by increasing functional refractoy period and ZOC. A possible mechanism can be through blocking of MPT pores.
Vahid Khori, Samaneh Naeimipour, Ali-Mohammad Alizadeh, Mona Pourabouk, Fakhri Badaghabadi, Maryah Rajaei, Sepideh Shariatnezhad, Hamidreza Moheimani, Saeed Saleki, Mohammadali Zeyghami, Mohsen Nayebpour,
Volume 16, Issue 1 (Spring 2012)
Abstract

Introduction: Intranodal pathways of atrioventricular (AV) node play a vital role in the delay of conduction time in response to various atrial inputs. The present study was aimed to determine the frequency-dependent electrophysiological properties of concealed slow pathway according to a functional model of isolated rabbit atrioventricular node preparation after fast pathway ablation. Methods: Experiments were carried out in rabbit isolated heart AV-nodal preparations (N=8) by superfused/perfused mode. Extracellular recording was carried out from transitional cells of posterior and anterior extension of AV-node and upper part of atrium and its bundle. Unipolar silver electrode (100 μm) and direct voltage (100-110 V) was applied to create AV-nodal fast pathway ablation. Results: Minimum conduction time (AHmin) was significantly increased after fast pathway ablation (p<0.05). Fast pathway ablation had no significant impact on fatigue phenomenon but significantly reduced facilitation value (p<0.05). Rate-dependency properties of concealed slow pathway were explained according to functional nodal model. Conclusion: The mathematical functional model accurately simulated frequency-dependent electrophysiological properties of concealed slow pathway after fast pathway ablation, but some modifications are necessary for accurate prediction of nodal behavior in various cycle lengths and in arrhythmia. Concealed slow pathway may be considered as a potential electrophysiological substrate of fatigue and facilitation phenomenon
Mohsen Nasri, Ali Mohammad Alizadeh, Vahid Khori, Sohrab Hajizadeh, Saeed Khodayari,
Volume 16, Issue 4 (Winter 2013)
Abstract

Abstract Introduction: Isolated perfused heart models such as perfusion and superfusion are commonly used for mammalian heart research. However, there are several fundamental limitations in the current techniques. In perfusion model, a suitable cannula is connected to the aorta and the perfusion is retrogradely performed. But, electrode displacement is a potential unwanted event resulted from heart contractions. In superfusion model, atrioventricular node (AV) node area is completely visible and fixed in the tissue bath after appropriate preparation, but tissue ischemia is inevitable due to the absence of cell to cell nutrition. The aim of the present study was to create a novel isolated dual perfusion/superfusion model to be used in heart physiological and pharmacological studies. Methods: The rabbit hearts (n=10) were excised. After preparation of proper sections, the electrodes were attached till the steady state appeared. The stimulation protocols consisting Wenckebach and recovery were then carried out during the isolated dual perfusion/superfusion as well as perfusion and superfusion models. Results: The AV node conduction time was increased from 33±4 ms in the isolated dual perfusion/superfusion heart model to 43±5 and 52±5 ms in perfusion and superfusion models, respectively (P<0.05). In addition, Wenckebach cycle length, effective and functional refractory periods were increased in perfusion and superfusion models compared to the isolated dual perfusion/superfusion model (P<0.05). Conclusion: This study shows the superiority of the isolated dual perfusion/superfusion heart model in tissue nutrition compared to the other common methods of mammalian heart studies.
Mahdih Faghihi , Ali Mohammad Alizadeh, Vahid Khori, Vahid Khodayari , Saeed Moradi ,
Volume 16, Issue 4 (Winter 2013)
Abstract

Abstract Introduction: Occurrence of cardiac arrhythmias and myocardial infarction are two main deleterious events that are caused by ischemia-reperfusion (IR) injury in the heart. Cardiac preconditioning represents the most potent method of rescuing heart tissue from undergoing irreversible ischemic damage. The aim of the present study was to evaluate oxytocin (OT) cardioprotective effects and its signaling pathways in cardiac arrhythmias including ventricular tachycardia (VT) and ventricular fibrillation (VF) in anesthetized rats. Methods: Fifty-four rats were divided into nine groups. Animals’ hearts were subjected to 25 min ischemia and 2 h reperfusion. Oxytocin was used 25 min prior to ischemia. In certain groups, atosiban (an oxytocin receptor antagonist), atractyloside (an opener of mitochondrial permeability transition pore, mPTP) and N-acetylcysteine (a reactive oxygen species scavenger) were used 10 min prior to OT administration. Then, the severity and incidence of cardiac arrhythmias including VT and VF were measured. Results: OT administration significantly decreased the severity and incidence of cardiac arrhythmias compared to the IR group (P<0.05). Administration of atosiban, atractyloside and N-acetylcysteine abolished the cardiac preconditioning effect of OT in cardiac arrhythmia (P<0.05). Conclusion: The present study demonstrates that preconditioning with oxytocin reduced ischemia-reperfusioninduced ventricular arrhythmias and its signaling pathways are probably mediated through mitochondrial permeability transition pore and reactive oxygen species.
Vahid Khori , Ali Mohammad Alizadeh, Bagher Nikyar , Ardeshir Banikarimi, Fakhri Badaghabadi, Ahmad Soltani , Mohsen Nayebpour,
Volume 17, Issue 1 (Spring 2013)
Abstract

Introduction: Endorphins are produced by cardiomyocytes, and exert different effects on the heart. The aim of the present study is to assess morphine effects on extracellular atrioventricular (AV) node field potential pattern and ventricular rhythm of isolated rabbit heart during experimental atrial fibrillation (AF). Methods: Effects of different concentrations of morphine (10, 20, 50 and 100 μM) were assessed by applying basic stimuli protocols involving Wenckebach, recovery, zone of concealment and concealed conduction parameters during experimental atrial fibrillation in isolated rabbit heart. Two-way ANOVA was used to compare the groups. Results: Morphine significantly suppressed basic parameters of AV node. Morphine (100 μM) significantly increased wenckebach index (153.6±3.9 to 169.8±2.9 ms) and functional refractory period (156.9±3.0 to 176.4±3.5 ms) (P<0.05). During experimental atrial fibrillation, morphine nonsignificantly increased mean His–His interval, concealed conduction and zone of concealment (P > 0.05). Conclusion: The present results showed that morphine has concentration-dependent effects on AV node electrophysiological properties. Morphine at low concentrations can decrease nodal conduction and refractoriness of AV node, but in high concentrations causes increased nodal conduction without concealed conduction changes. Dual effects of morphine can explain the unpredictable behavior of heart in cardiac tachyarrhythmias.
Vahid Khori, Ali Mohammad Alizadeh, Hamidreza Moheimani, Delaram Shakiba, Soroosh Soroosh Aminolsharieh Najafi, Shahryar Alizadeh, Taghi Amiriyani, Ardeshir Banikarimi, Mahdi Zahedi, Mohamad Hadi Molseghi, Ahmadreza Dehpour,
Volume 17, Issue 1 (Spring 2013)
Abstract

Introduction: The present study is aimed to evaluate electrophysiological remodeling of atrioventricular (AV) node and ventricular conduction during experimental atrial fibrillation (AF) model in isolated heart of cirrhotic rats. Methods: Cirrhosis-induced electrophysiological remodeling was evaluated in 24 isolated retrogradely perfused rat hearts in 2 groups (control and cirrhotic). Cirrhosis was induced after 6 weeks of common bile duct ligation in rats. Extracellular filed potential was recorded from upper atrium and right ventricle. The conduction time, refractoriness and frequency-dependent properties of AV node were characterized by specific stimulation protocols. Experimental AF was simulated by high-rate atrial pacing with random coupling intervals (range 75–125 ms). Results: Nodal conduction time and ventricular responsiveness were significantly increased in the cirrhotic rats compared to the control (95.8 ± 4.2 ms vs. 78.8 ± 3.3 ms) (P< 0.05). Nodal protective function during AF was potentiated with increased R-R interval, concealed beats, ventricular refractoriness and zone of concealment in the cirrhotic group. Cirrhosis evoked rate–dependent ventricular conduction time shortening with different patterns during arrhythmia. Conclusion: Cirrhosis-induced electrophysiological remodeling was shown by increased AV nodal conduction and shortened ventricular conduction. This electrophysiological remodeling may be considered as a new manifestation of cirrhotic cardiomyopathy in the heart, which can change ventricular rhythm during arrhythmia.
Vahid Khori, Habibeh Shirmohammali , Ali Mohammad Alizadeh, Maryam Rajaii, Ardeshir Banikarimi, Mohammadhadi Molseghi,
Volume 17, Issue 2 (Summer 2013)
Abstract

Introduction: Cardiac preconditioning is an important method to reduce the damage caused by prolonged ischemia. Previous studies have shown that corticosteroids have protective effects on the heart, however at high concentrations this effect may be reduced with unknown mechanisms. We hypothesize that the contradictory effects of hydrocortisone at high concentration may be mediated via mineralocorticoid receptors. Therefore, this study was designed to determine the protective effects of various concentrations of hydrocortisone on the heart and its relationship with the mineralocorticoid receptor. Methods: In an experimental study, ninety-six male rats were divided into eight groups treated with different doses of hydrocortisone (1, 5, 10 and 20 μM). Spirinolactone was used as a mineralocorticoid receptor antagonist to investigate its role in the hydrocortisone acute effects on the heart. The hearts were excised first, and transferred and connected to the Langendorff system, and then subjected to 30 min ischemia and 90 min reperfusion. The infarct size and ventricular arrhythmias were measured. Two-way ANOVA was used to compare the groups. Results: The results showed that hydrocortisone at various concentrations could reduce the infarct size and protect cardiomyocytes. The protective effects were lower at high concentrations (P<0.05). Spironolactone, a mineralocorticoid receptor antagonist amplified these protective effects (P<0.05). Hydrocortisone and spironolactone administration not significantly decreased severity and incidence of ventricular arrhythmia in comparison with IR group (P>0.05). Conclusion: The results showed the hydrocortisone cardioprotective effects as a pharmacological preconditioning agent. Opposing effects of hydrocortisone at medium and high concentrations can at least be partially reversed by mineralocorticoid receptors.

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