OBJECTIVEAlthough several reports documented the association of congenital hypothyroidism (CH) and left ventricular (LV) function in infants or neonates, right ventricular (RV) function in neonates with CH has not been previously studied. The aim of the present study was to assess RV function in neonates with CH before and after thyroxine substitution therapy by quantitative tissue velocity imaging (QTVI) and tissue tracking imaging (TTI).

METHODSFifty-two neonates aged 18-28 days (25 males and 27 females) with CH and 35 healthy neonates aged 18-28 days (16 males and 19 females) were studied by QTVI, TTI as well as conventional pulsed-wave Doppler echocardiography (PWD). The standard apical four-chamber view for long-axis motion of the right ventricle was used for echocardiographic evaluation. Peak systolic displacement (D), peak systolic velocity (Vs), peak early (Ve) and late (Va) diastolic velocity of tricuspid annule were measured, Ve/Va ratio was calculated as well. Transtricuspid flow velocity during early diastole (E) and late diastole (A) were also measured by pulsed-wave Doppler echocardiography. PWD and E/A ratio were calculated too. For each neonate, serum hormone levels of TSH, TT(3), TT(4), FT(3) and FT(4) were measured with a standard chemiluminescent immunoassay. After 1 month of levothyroxine (L-T(4)) substitution therapy in CH neonates, all the echocardiographic evaluations and biochemical tests were re-evaluated. Correlation analysis was also made between serum thyroid hormones levels and right ventricular function.

RESULTSThe indices of right ventricular diastolic function by PWD (E and E/A ratio) in CH group were (45 +/- 10) cm/s and (0.8 +/- 0.3), respectively. Compared with controls, E and E/A ratio in CH neonates were significantly lower (P < 0.001, respectively), while A did not differ between the two groups (P > 0.05). QTVI and TTI showed that right diastolic function (Ve and Ve/Va ratio) as well as right systolic function (Vs and D) in CH group were (3.69 +/- 1.38) cm/s, (0.74 +/- 0.19) cm/s, (4.38 +/- 0.63) cm/s and (0.52 +/- 0.12) cm, respectively. CH neonates had significantly lower Ve, Ve/Va ratio, Vs and D of tricuspid annular velocity (P < 0.001, respectively), whereas there was no significant difference in Va between the two groups (P > 0.05). After 1 month of substitutive therapy, CH neonates showed a significant increase of Ve, Ve/Va ratio, Vs, D, E, and E/A ratio, (6.92 +/- 1.86) cm/s, (1.13 +/- 0.22), (5.92 +/- 1.03) cm/s, (0.78 +/- 0.17) cm, (61 +/- 10) cm/s and (1.1 +/- 0.4), respectively (P < 0.001). Those parameters were positively correlated with serum TT(3), TT(4), FT(3) and FT(4) levels (P < 0.01, respectively), and were negatively correlated with serum TSH levels (P < 0.01, respectively).

CONCLUSIONSOur findings suggest that neonates with CH are associated with right ventricular subclinical systolic and diastolic dysfunction, which can be reversed by early L-T(4) substitution therapy. QTVI and TTI are valuable methods to evaluate right ventricular function in neonates. Systolic and diastolic velocities of the tricuspid annulus measured by QTVI and TTI are useful and accurate to assess RV function in neonates.

Adult ; Blood Flow Velocity ; Child, Preschool ; Congenital Hypothyroidism ; physiopathology ; Diastole ; drug effects ; physiology ; Echocardiography ; Echocardiography, Doppler, Pulsed ; Female ; Heart Ventricles ; drug effects ; physiopathology ; Humans ; Male ; Systole ; drug effects ; physiology ; Thyrotropin ; pharmacology ; Thyroxine ; blood ; pharmacology ; Tricuspid Valve ; physiopathology ; Ventricular Function, Left ; drug effects ; physiology ; radiation effects ; Ventricular Function, Right ; drug effects ; physiology

This study was designed to explore the innervation of autonomic nervous system and the distribution of receptors on pacemaker cell membrane in guinea pig left ventricular outflow tract (aortic vestibule). By using conventional intracellular microelectrode technique to record action potentials, autonomic neurotransmitters and antagonists were used to investigate the electrophysiological features and regularities of spontaneous activity of left ventricular outflow tract cells. Electrophysiological parameters examined were: maximal diastolic potential (MDP), amplitude of action potential (APA), maximal rate of depolarization (V(max)), velocity of diastolic depolarization (VDD), rate of pacemaker firing (RPF), 50% and 90% of duration of action potential (APD(50) and APD(90)). The results are listed below: (1) Perfusion with 100 mumol/L isoprenaline (Iso) resulted in a significant increase in V(max) (P <0.05), VDD, RPF, and APA (P <0.01), a notable decrease in MDP (P<0.05), and also a marked shortening in APD(50) (P<0.01). Pretreatment with Iso (100 mumol/L), propranolol (5 mumol/L) significantly decreased RPF and VDD (P<0.01), decreased APA, MDP and V(max) (P<0.01) notably, prolonged APD(50) (P<0.01) and APD(90) (P<0.05) markedly. (2) Application of 100 mumol/L epinephrine (E) resulted in a significant increase in VDD (P<0.05), RPF (P<0.001), V(max) (P<0.05) and APA (P<0.001), and a notable shortening in APD(50) and APD(90) (P<0.05). (3) Perfusion with 100 mumol/L norepinephrine (NE) led to a significant increase in VDD, RPF, APA and V(max) (P<0.05), and a marked shortening in APD(50) (P<0.05). Pretreatment with NE (100 mumol/L), phentolamine (100 mumol/L) significantly decreased RPF and VDD, MDP and APA (P<0.01), decreased V(max) notably (P<0.05), prolonged APD(50) and APD(90) markedly (P<0.01). (4) During perfusion with 10 mmol/L acetylcholine (ACh), VDD and RPF slowed down notably (P<0.05), APA decreased significantly (P<0.001), V(max) slowed down notably (P<0.01), APD50 shortened markedly (P<0.05), Atropine (10 mmol/L) antagonized the effects of ACh (10 mumol/L) on APD(50) (P<0.05). These results suggest that there are probably alpha-adrenergic receptor (alpha-AR), beta-adrenergic receptor (beta-AR) and muscarinic receptor (MR) on pacemaker cell membrane of left ventricular outflow tract in guinea pig. The spontaneous activities of left ventricular outflow tract cells are likely regulated by sympathetic and parasympathetic nerves.
Action Potentials ; drug effects ; Animals ; Aorta, Thoracic ; cytology ; physiology ; Electrophysiological Phenomena ; Female ; Guinea Pigs ; Heart Ventricles ; cytology ; Male ; Microelectrodes ; Neurotransmitter Agents ; physiology ; Receptors, Adrenergic, alpha ; physiology ; Receptors, Adrenergic, beta ; physiology ; Receptors, Muscarinic ; physiology ; Ventricular Function, Left ; physiology

OBJECTIVETo evaluate the effects of erythropoietin (EPO) combined with granulocyte-colony stimulating factor (G-CSF) on left ventricular function and ventricular remodeling after acute myocardial infarction (AMI) and investigate the possible mechanism.

METHODSThe experimental design consisted of 5 groups of rats, namely the sham, myocardial infarction (MI) model, MI with EPO treatment, MI with G-CSF treatment, and MI with EPO plus G-CSF treatment groups. Apoptosis of the cardiomyocytes was detected by TUNEL staining, and HE staining, Masson trichrome staining, scarlatinum staining, and VIII agent staining were used to evaluate the survival, scar collagen deposition, and angiogenic effects. The cardiac structure and function of the rats after the treatments were assessed by echocardiography and hemodynamic examination.

RESULTSEchocardiography indicated that LVEF and FS were improved in all the intervention groups 7 days after MI, and the rats in EPO plus G-CSF treatment group showed the most obvious reduction of LVESD and LVESV (P<0.01). On day 28 after MI, all the intervention groups showed improvements in LVEF, FS, LVESD, LVEDD, LVESV and LVEDV, which were especially obvious in the combined treatment group; the interventions, especially the combined treatment, also resulted in decreased LVEDP and increased LVSP and +dP/dtmax. On day 1 after MI, the number of apoptotic cells was significantly greater in the MI model group than in EPO and G-CSF groups, and was the fewest in the combined treatment group (P<0.01). On day 28, the number of new vessels increased and the scar and collagen deposition reduced in the EPO and G-CSF groups, and these changes were more obvious in the combined treatment group.

CONCLUSIONSEPO combined with G-CSF can prevent left ventricular remodeling and improve cardiac systolic and diastolic functions by inhibiting cardiomyocyte apoptosis, reducing tissue collagen deposition and inducing neovascularisation.

Animals ; Drug Therapy, Combination ; Erythropoietin ; therapeutic use ; Female ; Granulocyte Colony-Stimulating Factor ; therapeutic use ; Myocardial Infarction ; drug therapy ; physiopathology ; Rats ; Rats, Wistar ; Ventricular Function, Left ; physiology ; Ventricular Remodeling ; drug effects

To evaluate the effects of left ventricular contractility on the changes of average image intensity (AII) of the myocardial integrated backscatter (IB) and cyclic variation in IB (CVIB), 7 adult mongrel dogs were studied. The magnitude of AII and CVIB were measured from myocardial IB carves before and after dobatamine or propranolol infusion. Dobutamine or propranolol did not affect the magnitude of AII (13.8 +/- 0.7 vs 14.7 +/- 0.5, P > 0.05 or 14.3 +/- 0.5 vs 14.2 +/- 0.4, P > 0.05). However, dobutamine produced a significant increase in the magnitude of CVIB (6.8 +/- 0.3 vs 9.5 +/- 0.6, P < 0.001) and propranolol induced significant decrease in the magnitude of CVIB (7.1 +/- 0.2 vs 5.2 +/- 0.3, P < 0.001). The changes of the magnitude of AII and CVIB in the myocardium have been demonstrated to reflect different myocardial physiological and pathological changes respectively. The alteration of contractility did not affect the magnitude of AII but induced significant change in CVIB. The increase of left ventricular contractility resulted in a significant rise of the magnitude of CVIB and the decrease of left ventricular contractility resulted in a significant fall of the magnitude of CVIB.
Adrenergic beta-Agonists ; pharmacology ; Adrenergic beta-Antagonists ; pharmacology ; Animals ; Coronary Circulation ; Dobutamine ; pharmacology ; Dogs ; Echocardiography ; methods ; Hemodynamics ; drug effects ; Myocardial Contraction ; drug effects ; physiology ; Propranolol ; pharmacology ; Systole ; Ventricular Function, Left ; physiology

BACKGROUNDRecent studies in adult hearts have indicated that KATP channels in the inner mitochondrial membrane are responsible for the protection. And we investigated whether opening of mitochondrial KATP channels (mKATP) could provide myocardial protection for immature rabbits and determined its role in cardioprotection.

METHODSThirty-four 3-4-week-old rabbits, weighing 300 - 350 g, were divided randomly into five groups: Group I (control group, n = 8); Group II [diazoxide preconditioning group; n = 8; the hearts were pretreated with 100 micromol/L diazoxide for 5 minutes followed by 10-minute wash out with Krebs-Henseleit buffer (KHB)]; Group III [diazoxide + 5-hydroxydeconate (5-HD) preconditioning group; n = 5; the hearts were pretreated with 100 micromol/L diazoxide and 100 micromol/L 5-HD); Group IV (diazoxide + cardioplegia group; n = 8; cardioplegia containing 100 micromol/L diazoxide perfused the hearts for 5 minutes before ischemia); Group V (diazoxide + 5-HD + cardioplegia group; n = 5; the cardioplegia contained 100 micromol/L diazoxide and 100 micro mol/L 5-HD). All hearts were excised and connected to langendrff perfusion system and passively perfused with KHB at 38 degrees C under a pressure of 70 cmH(2)O. After reperfusion, the recovery rate of left ventricular diastolic pressure (LVDP), +/-dp/dtmax, coronary flow (CF), the creatinine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) in coronary sinus venous effluent and the tissue ATP were measured. Mitochondria were evaluated semiquantitatively by morphology.

RESULTSAfter ischemia and reperfusion (I/R), the two groups that were treated by diazoxide only (Groups II and IV) had a significant improvement in LVDP, +/-dp/dtmax, and CF recovery. AST, LDH, and CK were decreased, and the levels of tissue ATP in the two groups were higher. Mitochondria was protected better in Group IV than in other groups.

CONCLUSIONSActivating mKATP channels before and during ischemia can similarly protect immature rabbit hearts, and the mechanism is related to the direct protective effect on mitochondria. Opening of mKATP channel during ischemia provides a better protection for mitochondria than it does before ischemia.

Adenosine Triphosphate ; metabolism ; Animals ; Diazoxide ; pharmacology ; Female ; Ischemic Preconditioning, Myocardial ; Male ; Membrane Proteins ; physiology ; Mitochondria, Heart ; physiology ; ultrastructure ; Myocardial Ischemia ; physiopathology ; Potassium Channels ; Rabbits ; Time Factors ; Ventricular Function, Left ; drug effects

OBJECTIVETo explore the effects of Astragalus on cardiac function and serum tumor necrosis factor-alpha (TNF-alpha) level in patients with chronic heart failure (CHF).

METHODSForty-five patients of Xin-qi deficiency or Xin-yang deficiency types were assigned to the Chinese medicine (CM) group and the Western medicine (WM) group by a randomizing digital table. Standard treatment for correcting heart failure, including digoxin, diuretics, etc. was administered to both groups, but to the CM group oral medication of Astragalus granule was given additionally at the dosage of 2.25 g twice a day, the treatment for both was continued for two weeks. NYHA cardiac functional grading, serum TNF-alpha level, left ventricular ejection fraction (LVEF) and walk distance in 6 min (WD) were measured before and after treatment, and a correlation analysis was carried out.

RESULTSAfter therapy, the level of TNF-alpha in the two groups decreased (P < 0.05) and it was lower in the CM group [(54.77 +/- 9.34) microg/L] than in the WM group [(62.10 +/- 9.94) microg/L] (P < 0.05); LVEF in the two groups increased (P < 0.05) and it was higher in the CM group [(64.45 +/- 12.47)%] than that in the WM group [(56.03 +/- 13.33)%] (P < 0.05); both groups' WD increased (P < 0.05) and it was longer in the CM group [(446.97 +/- 68.82) m] than in the WM group [(345.40 +/- 63.62) m] (P < 0.05); the improvement of cardiac functional grading in the CM group was outstriper than the WM group (P < 0.05). The improvement in cardiac function was negatively correlated with TNF-alpha level.

CONCLUSIONAstragalus can alleviate the calcium overload-induced myocardial damage and improve both systolic and diastolic functions of heart in patients with CHF.

Aged ; Astragalus membranaceus ; chemistry ; Chronic Disease ; Coronary Disease ; complications ; Drugs, Chinese Herbal ; therapeutic use ; Female ; Heart Failure ; drug therapy ; etiology ; Humans ; Male ; Middle Aged ; Phytotherapy ; Tumor Necrosis Factor-alpha ; blood ; Ventricular Function, Left ; drug effects ; physiology

OBJECTIVETo explore the dose-effect relationship of Astragalus granule (AG) on improving the quality of life (QOL) of the patients with chronic heart failure (CHF).

METHODSNinety CHF patients of Fei ()-qi-deficiency and/or Xin ()-Shen () yang-deficiency syndromes were equally randomized divided with a random number table into three groups; they received the high (7.5 g), moderate (4.5 g), and low dosage (2.25 g) of AG orally taken twice a day, respectively, and 4 mg of perindopril tablet once a day for 30 successive days. The heart function grade, patients' left ventricular ejection fraction (LVEF) and walking distance in 6 min (6mWD) were measured before and after treatment, and the patients' QOL was scored by the Minnesota Questionnaire for QOL evaluation in the patients with CHF at the same time.

RESULTSThe heart function grades of all the three groups after treatment were improved compared with those before treatment, but the improvements in high-dose group and moderate dose group were better than that in the low dose group (P<0.05). LVEFs were increased significantly in all the three groups, but the improvements in the high-dose group (59.42%±7.50%) and moderate dose group (61.98%±6.82%) were better than that in the low dose group (51.45%±6.80%, P<0.01); the 6mWDs in the all groups were also significantly increased (P<0.01), up to 419.80±36.23 m, 387.15±34.13 m, and 317.69±39.97 m, respectively; and Minnesota scores in them were lowered to 29.59±4.69 scores, 35.74±5.89 scores, and 42.78±6.06 scores, respectively; comparisons in aspects on 6mWD and Minnesota score showed that the effectiveness with high dose is the most effective, moderate dose as the second, and low dose as the lowest (P<0.01).

CONCLUSIONSAG was sufficient to display an optimal effect on improving heart contraction at the moderate dose. In aspects of improving the QOL of CHF patients, the effectiveness of AG showed a dose-dependent trend. It should be applied discriminatively depending on the actual condition of patients and the aim of treatment in clinic.

Aged ; Astragalus Plant ; chemistry ; Chemistry, Pharmaceutical ; Chronic Disease ; Dose-Response Relationship, Drug ; Drugs, Chinese Herbal ; administration & dosage ; Female ; Heart ; drug effects ; physiology ; Heart Failure ; drug therapy ; psychology ; Heart Function Tests ; Humans ; Male ; Middle Aged ; Plant Preparations ; administration & dosage ; Quality of Life ; Treatment Outcome ; Ventricular Function, Left ; drug effects ; physiology

PURPOSE: Urapidil is putatively effective for patients with hypertension and acute heart failure, although randomized controlled trials thereon are lacking. We investigated the efficacy and safety of intravenous urapidil relative to that of nitroglycerin in older patients with hypertension and heart failure in a randomized controlled trial. MATERIALS AND METHODS: Patients (>60 y) with hypertension and heart failure were randomly assigned to receive intravenous urapidil (n=89) or nitroglycerin (n=91) for 7 days. Hemodynamic parameters, cardiac function, and safety outcomes were compared. RESULTS: Patients in the urapidil group had significantly lower mean systolic blood pressure (110.1±6.5 mm Hg) than those given nitroglycerin (126.4±8.1 mm Hg, p=0.022), without changes in heart rate. Urapidil was associated with improved cardiac function as reflected by lower N terminal-pro B type natriuretic peptide after 7 days (3311.4±546.1 ng/mL vs. 4879.1±325.7 ng/mL, p=0.027) and improved left ventricular ejection fraction (62.2±3.4% vs. 51.0±2.4%, p=0.032). Patients given urapidil had fewer associated adverse events, specifically headache (p=0.025) and tachycardia (p=0.004). The one-month rehospitalization and all-cause mortality rates were similar. CONCLUSION: Intravenous administration of urapidil, compared with nitroglycerin, was associated with better control of blood pressure and preserved cardiac function, as well as fewer adverse events, for elderly patients with hypertension and acute heart failure.
Acute Disease ; Aged ; Antihypertensive Agents/*administration & dosage ; Blood Pressure/drug effects ; Cause of Death ; Female ; Heart Failure/*drug therapy/physiopathology ; Heart Rate/drug effects/physiology ; Hemodynamics ; Humans ; Hypertension/*drug therapy/physiopathology ; Injections, Intravenous ; Male ; Middle Aged ; Natriuretic Peptide, Brain/blood ; Nitroglycerin/administration & dosage ; Peptide Fragments/blood ; Piperazines/*administration & dosage ; Ventricular Function, Left/drug effects/physiology

OBJECTIVETo evaluate the protective effects of Tongxinluo on myocardium and microvasculature after reperfusion in patients with acute myocardial infarction.

METHODSThe research was performed on the patients with AMI whose initial ECG showed ST segment elevation and the patients received PCI or thrombolysis immediately after onset. These patients were classified randomly into two groups: control group in which the patients were given routine drug treatment (52 cases) and treatment group in which the patients were given routine drug plus Tongxinluo capsule (60 cases). We observed the abnormal movement of the ventricle wall in 2DE, and the change in LVEDV or LVEF on the 1st day, 7th day, 13th day, 3rd month, and 6th month after onset, which were compared with the result of DISA and SPECT for myocardial image. At the same time we also examined the blood NO and MDA levels on the 1st day, the 7th day and 13th day.

RESULTS(1) The recover rate for the abnormal movement of the ventricle segments in the treatment group were 11.86%, 18.12% and 18.79% respectively, which were higher than that of the control group (4.13%, 8.27% and 11.11% respectively) on the 1st week, the 2nd week, and the 1st month. At the 6th month the total recover rate for the abnormal movement of the ventricle segments of Tongxinluo group was 70.03%, which was significantly higher than that of the control group (51.68%). The WMSI was also decreased more than that of the control group. (2) The LVEDV in Tongxinluo group increased by 9.42% one week after onset, which was close to that of the control group (9.59%). There was no significant change (9.40% and 9.42% respectively) after two weeks and one month in Tongxinluo group, whereas it was increased continuously in the control group (11.84% and 12.33%). LVEDV in Tongxinluo group was decrease obviously after three and six months (3.62% and 5.07% respectively), which was close to the original level, whereas the result of the control group remained on a higher level (13.70% and 11.72% respectively). (3) LVEF of the Tongxinluo group was 53.32% before treatment, which was comparable with that of the control group (P = 0.45). There was no significant difference between the two groups after treatment for 1 week, 2 week and 1 month (P = 0.11, P = 0.13, P = 0.18, respectively). LVEF for the two groups was 58.27% and 53.40% respectively after three months and there was a statistical significance (P < 0.01). LVEF for the two groups was 58.33% and 53.82% respectively after 6 months and the difference remained statistically significant (P < 0.05). (4) The 2DE WMSI for the Tongxinluo group was 1.7552 after 12 hours to 24 hours of the CVR and there was no significant difference compared with that of the control group (WMSI = 1.5380, P = 0.6945). After 6 months, the WMSI decreased to 1.3767 in the Tongxinluo group, which was statistically different from that of the control group (WMSI = 1.5380, P < 0.01). The myocardium acquire isotope score index of the Tongxinluo group was 0.6075 at 6 months, which was significantly different from that of the control group (0.8781). (5) Ultrasonic humerus artery examination in static status showed that there was no significant difference on the diameter of blood vessel and the speed of blood stream between Tongxinluo group and control group with. The diameter of the blood vessel after artery pressure in Tongxinluo group was expanded, which was significantly different from that in the static status (P < 0.001) and that in control group (P < 0.001). The diameter of blood vessel after administration of nitroglycerin in both groups was expanded, which was significantly different from that in the static status (P < 0.001 and P < 0.05). However, Tongxinluo group was expand more obviously than that of the control group (P < 0.05). (6) The MDA level of the Tongxinluo group was decreased (all P < 0.05) and the NO level was increased (all P < 0.05) gradually from the 1st week to the 4th week; however, the MDA level of the control group was not decreased until the 4th week (P < 0.05), and the NO level of the control group was increased evidently at the 2nd week (P < 0.05).

CONCLUSIONS(1) After reperfusion in AMI patients, administration of routine drug combined with Tongxinluo is more effective than routine drug alone in the reduction of infarction size. (2) In Tongxinluo group, the recover time and the total recover rate of the abnormal movement of the ventricle segments were higher than the control group, and the WMSI were significantly decreased than the control group. (3) The improvement degree and the recover time on LVEDV in Tongxinluo group was superior to control group. (4) The improvement of LVEF in time and in degree was superior to control group. (5) The blood concentration of the MDA was decreased significantly in Tongxinluo group, while the NO level was increased significantly, and the time was superior to control group significantly.

Diastole ; drug effects ; Echocardiography ; Female ; Heart ; drug effects ; Humans ; Male ; Malondialdehyde ; blood ; Medicine, Chinese Traditional ; Microcirculation ; drug effects ; physiology ; Myocardial Infarction ; diagnostic imaging ; drug therapy ; physiopathology ; Myocardial Reperfusion Injury ; prevention & control ; Nitric Oxide ; biosynthesis ; Stroke Volume ; drug effects ; Ventricular Function, Left

OBJECTIVETo investigate the changes of guinea pig heart electrophysiological properties caused by increasing left ventricular preload, and to assess the effects of tetradrine on these changes.

METHODWorking model preparation of guinea pig hearts in vitro was used, and the preload of left ventricle was increased by adjusting the prefusion pressure of left atria. The changes of heart electrophysiologic parameters including monophasic action potential duration (MAPD90), monophasic action potential amplitude (MAPA), effective refractory period (ERP) and ventricular fibrillation threshold (VFT) were observed before and after altering the preload of left ventricle, and compared in the absence and presence of tetradrine, streptomycin or verapamil.

RESULTThe rising of left ventricular preload led to shortening of MAPD90, ERP, and to descent of MAPA, VFT (all P<0.01). Both Tetradrine and streptomycin inhibited these changes of heart electrophysiologic parameters caused by elevation of left ventricular afterload (all P<0.01). In contrast, verapamil had no effects on the preload-related electrophysiological changes (all P>0.05).

CONCLUSIONElectrophysiologic changes caused by increasing left ventricular preload may be inhibited by tetrandrine, through inhibition of stretch-activated ion channels.

Action Potentials ; drug effects ; Alkaloids ; isolation & purification ; pharmacology ; Animals ; Anti-Arrhythmia Agents ; isolation & purification ; pharmacology ; Benzylisoquinolines ; isolation & purification ; pharmacology ; Calcium Channel Blockers ; pharmacology ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Female ; Guinea Pigs ; Heart ; physiology ; In Vitro Techniques ; Male ; Plants, Medicinal ; chemistry ; Refractory Period, Electrophysiological ; drug effects ; Stephania tetrandra ; chemistry ; Streptomycin ; pharmacology ; Ventricular Function, Left ; drug effects ; Verapamil ; pharmacology