Angiotensin II ; pharmacology ; Animals ; Heart Rate ; drug effects ; physiology ; Rabbits

OBJECTIVEAlthough after pacing animal and human studies have demonstrated a rate-dependent effect of sotalol on ventricular repolarization, there is little information on the effects of sotalol on ventricular repolarization during exercise. This study attempted to show the effects of sotalol on ventricular repolarization during physiological exercise.

METHODSThirty-one healthy volunteers (18 males, 13 females) were enrolled in the study. Each performed a maximal treadmill exercise test according to the Bruce protocol after random treatment with sotalol, propranolol and placebo.

RESULTSSotalol significantly prolonged QTc (corrected QT) and JTc (corrected JT) intervals at rest compared with propranolol (QTc 324.86 ms vs 305.21 ms, P<0.001; JTc 245.04 ms vs 224.17 ms, P<0.001) and placebo (QTc 324.86 ms vs 314.06 ms, P<0.01; JTc 245.04 ms vs. 232.69 ms, P<0.001). The JTc percent reduction increased progressively with each stage of exercise and correlated positively with exercise heart rate (r=0.148, P<0.01). The JTc percent reduction correlation with exercise heart rate did not exist with either propranolol or placebo.

CONCLUSIONSThese results imply that with sotalol ventricular repolarization is progressively shortened after exercise. Thus the specific class III antiarrhythmic activity of sotalol, present as delay of ventricular repolarization, may be attenuated during exercise. Such findings may imply the need to consider other antiarrythmic therapy during periods of stress-induced tachycardia.

Adult ; Exercise ; physiology ; Exercise Test ; Female ; Heart ; drug effects ; physiopathology ; Heart Rate ; drug effects ; physiology ; Humans ; Male ; Sotalol ; pharmacology

BACKGROUNDShen song Yang xin (SSYX) is a compound of Chinese medicine with the effect of increasing heart rate (HR). This study aimed to evaluate its electrophysiological properties at heart and cellular levels.

METHODSThe Chinese miniature swines were randomly assigned to two groups, administered with SSYX or placebo for 4 weeks (n = 8 per group). Cardiac electrophysiological study (EPS) was performed before and after drug administration. The guinea pig ventricular myocytes were enzymatically isolated and whole cell voltage-clamp technique was used to evaluate the effect of SSYX on cardiac action potential (AP).

RESULTSSSYX treatment accelerated the HR from (141.8 +/- 36.0) beats per minute to (163.0 +/- 38.0) beats per minute (P = 0.013) without changing the other parameters in surface electrocardiogram. After blockage of the autonomic nervous system with metoprolol and atropin, SSYX had no effect on intrinsic HR (IHR), but decreased corrected sinus node recovery time (CSNRT) and sinus atrium conducting time (SACT). Intra cardiac EPS showed that SSYX significantly decreased the A-H and A-V intervals as well as shortened the atrial (A), atrioventricular node (AVN) and ventricular (V) effective refractory period (ERP). In isolated guinea pig ventricular myocytes, the most obvious effect of SSYX on action potential was a shortening of the action potential duration (APD) without change in shape of action potential. The shortening rates of APD(30), APD(50) and APD(90) were 19.5%, 17.8% and 15.3%, respectively. The resting potential (Em) and the interval between the end of APD(30) and APD(90) did not significantly change.

CONCLUSIONSThe present study demonstrates that SSYX increases the HR and enhances the conducting capacity of the heart in the condition of the intact autonomic nervous system. SSYX homogenously decreases the ERP of the heart and shortens the APD of the myocytes, suggesting its antiarrhythmic effect without proarrhythmia.

Action Potentials ; drug effects ; Animals ; Drugs, Chinese Herbal ; pharmacology ; Female ; Guinea Pigs ; Heart ; drug effects ; physiology ; Heart Rate ; drug effects ; Heart Ventricles ; In Vitro Techniques ; Male ; Myocytes, Cardiac ; drug effects ; physiology ; Sinoatrial Node ; drug effects ; physiology ; Swine ; Swine, Miniature

AIMTo investigate the role of intracerebroventricular (icv) injection substance P(SP) in cardiovascular regulation and the relationship with noradrenergic system.

METHODSRabbits anesthetized with urethane were intracerebroventricularly given SP in presence or absence of phentolamine, prazosin, yohimbine. Cardiovascular responses including heart rate (HR), mean arterial blood pressure (MAP), left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), the maximum velocity of ascending or descending in intraventricular pressure (+/- dp/dt(max)) and the maximum shortening velocity(Vpm) of myocardial contractile element were recorded, and changes of NA content in cerebrospinal fluid (CSF) were determined in rabbits with icy injection of SP.

RESULTS(1) icv SP elicited significant increased of HR, MAP, LVSP, LVEDP, + dp/dt(max), -dp/dt(max), Vpm and the levels of NA in intracisternal CSF 30 min after injection. (2) Pretreatment with phentolamine, prazosin, but not yohimbine, attenuated icv SP-induced cardiovascular responses compared with controls (P < 0.05).

CONCLUSION(1) icv SP can produce positive inotropic and chronic response in myocardium and pressor response in intact rabbits. (2) alpha1 adrenoceptors may be involved in the cardiovascular responses to icy SP. (3) Central administration of SP can increase the release of NA or inhibit reuptake of NA, which may be responsible for an important mechanism of SP-potentiated cardiovascular responses in brain.

Animals ; Blood Pressure ; drug effects ; Heart ; drug effects ; Heart Rate ; drug effects ; Lateral Ventricles ; Myocardium ; Norepinephrine ; cerebrospinal fluid ; Rabbits ; Substance P ; pharmacology

AIMTo explore the effect and mechanism of interleukin-2 (IL-2) on the rhythm of isolated rat heart and neonatal myocytes.

METHODSCultured neonatal rat cardiomyocytes and isolated perfused rat heart were used.

RESULTS(1) IL-2 (2.5-200 u/ml) reduced the spontaneous beating rate of cultured neonatal rat cardiomyocytes in a dose-dependent manner. (2) IL-2 at 50 u/ml increased both the heart rate and the number of premature ventricular excitation in the isolated heart. (3) Pretreatment with propranolol abolished the effect of 50 u/ml IL-2 on the isolated heart. (4) Heat inactivated IL-2 had no significant effect on the cultured cardiomyocytes and isolated hearts.

CONCLUSIONIL-2 inhibited the auto rhythmic of cultured cardiomyocyte directly while the positive chronotropic and arrhythmogenic effects of IL-2 in the isolated rat heart may be mediated by endogenous catecholamine.

Animals ; Animals, Newborn ; Cells, Cultured ; Heart ; drug effects ; Heart Rate ; drug effects ; In Vitro Techniques ; Interleukin-2 ; pharmacology ; Myocytes, Cardiac ; drug effects ; physiology ; Propranolol ; pharmacology ; Rats ; Rats, Sprague-Dawley

Anti-Arrhythmia Agents ; therapeutic use ; Drugs, Chinese Herbal ; therapeutic use ; Echocardiography ; Heart Failure ; drug therapy ; Heart Rate ; drug effects ; Humans

OBJECTIVETo explore the effects of particulate matters less than 2.5 μm in aerodynamic diameter (PM2.5) on heart repolarization/depolarization and heart rate variability (HRV).

METHODSWe conducted a panel study for elderly subjects with heart disease in Beijing from 2007 to 2008. PM2.5 was measured at a fixed station for 20 h continuously each day while electrocardiogram (ECG) indexes of 42 subjects were also recorded repeatedly. Meteorological data was obtained from the China Meteorological Data Sharing Service System. A mixed linear regression model was used to estimate the associations between PM2.5 and the ECG indexes. The model was adjusted for age, body mass index, sex, day of the week and meteorology.

RESULTSSignificant adverse effects of PM2.5 on ECG indexes reflecting HRV were observed statistically and the strongest effect of PM2.5 on HRV was on lag 1 day in our study. However, there were no associations between PM2.5 and ECG indexes reflecting heart repolarization/depolarization. Additionally, the effects of PM2.5 on subjects with hypertension were larger than on the subjects without hypertension.

CONCLUSIONThis study showed ambient PM2.5 could affect cardiac autonomic function of the elderly people with heart disease, and subjects with hypertension appeared to be more susceptive to the autonomic dysfunction induced by PM2.5.

Aged ; Air Pollutants ; toxicity ; Electrocardiography ; Environmental Monitoring ; Female ; Heart Diseases ; physiopathology ; Heart Rate ; drug effects ; Heart Ventricles ; drug effects ; physiopathology ; Humans ; Male ; Middle Aged ; Particle Size

High salt intake increases blood pressure, and dietary salt intake has been clearly demonstrated to be associated with hypertension incidence. Japanese people consume higher amounts of salt than Westerners. It has been reported that miso soup was one of the major sources of daily salt intake in Japanese people. Adding salt is indispensable to make miso, and therefore, in some cases, refraining from miso soup is recommended to reduce dietary salt intake. However, recent studies using salt-sensitive hypertensive models have revealed that miso lessens the effects of salt on blood pressure. In other word, the intake of miso dose not increase the blood pressure compared to the equivalent intake of salt. In addition, many clinical observational studies have demonstrated the absence of a relationship between the frequency of miso soup intake and blood pressure levels or hypertension incidence. The mechanism of this phenomenon seen in the subjects with miso soup intake has not been fully elucidated yet. However, in basic studies, it was found that the ingredients of miso attenuate sympathetic nerve activity, resulting in lowered blood pressure and heart rate. Therefore, this review focused on the differences between the effects of miso intake and those of the equivalent salt intake on sympathetic nerve activity, blood pressure, and heart rate.
Blood Pressure ; drug effects ; physiology ; Heart Rate ; drug effects ; physiology ; Humans ; Soy Foods ; adverse effects ; Sympathetic Nervous System ; drug effects ; physiology

OBJECTIVETo study the effect of single administration of aqueous extracts from aconite on "dose-toxicity" relationship and "time-toxicity" relationship of mice hearts, through changes in electrocardiogram (ECG) and serum biochemical indexes.

METHODMice were grouped according to different drug doses and time points, and orally administered with water extracts from aconite for once to observe the changes of mice ECG before and after the administration, calculate visceral indexes heart, liver and kidney, and detect levels of CK, LDH, BNP and CTn-I in serum.

RESULTAccording to the "time-toxicity" relationship study, at 5 min after oral administration with aqueous extracts from aconite in mice, the heart rate of mice began rising, reached peak at 60 min and then slowly reduced; QRS, R amplitude, T duration and amplitude and QT interval declined at 5 min, reduced to the bottom at 60 min and then gradually elevated. The levels of CK, LDH, BNP and CTn-I in serum elevated at 5 min and reached the peak at 60 min, with no significant change in ratios of organs to body at different time points. On the basis of the "dose-toxicity" relationship, with the increase in single dose of aqueous extracts from aconite, the heart rate of mice. QRS, T duration and amplitude and QT interval declined gradually, and levels of CK, LDH, BNP and CTn-I in serum slowly elevated, with a certain dose dependence and no significant change in ratios of organs to body in mice.

CONCLUSIONSingle oral administration of different doses of aqueous extracts from aconite could cause different degrees of heart injury at different time points, with a certain dose dependence. Its peak time of toxicity is at 60 min after the administration of aqueous extracts from aconite.

Aconitum ; adverse effects ; chemistry ; Animals ; Dose-Response Relationship, Drug ; Drugs, Chinese Herbal ; administration & dosage ; isolation & purification ; toxicity ; Female ; Heart ; drug effects ; physiology ; Heart Rate ; drug effects ; Kidney ; drug effects ; Liver ; drug effects ; Male ; Mice

OBJECTIVETo observe the clinical efficacy of Xin'anning Nasal Drop (XAND) in treating coronary heart disease with unstable angina pectoris (CHD-UAP).

METHODSSixty patients with CHD-UAP were assigned, according to the randomizing number table, to two groups, the control group treated with conventional Western medicine, and the treated group treated with conventional Western medicine plus XAND. The clinical efficacy and the changes of S-T segment in resting EKG and total ischemia burden (TIB) in 24-h dynamic EKG were observed.

RESULTSThe clinical efficacy, including the effect of angina alleviation, its initiation, and the effect of TCM syndrome score reduction, were significantly superior in the treated group to those in the control group ( P<0.05 or P<0.01). The degree and extent of myocardial ischemia were significantly improved in both groups ( P<0.01), but the improvement in the treated group was better than that in the control group ( P<0.05). Moreover, it was worth mentioning that the immediate effect in the treated group was better than that in the control group, and the reduction of TIB, the improvement in heart rate and myocardial oxygen consumption (immediately after the first administration or by the end of the therapeutic course), and systolic blood pressure after treatment in the former were all superior to those in the latter, showing significant difference (P<0.05 or P<0.01).

CONCLUSIONXAND has a quick effect in alleviating angina in patients with CHD-UAP, and it is worthy of further studies and spreading in clinical practice. unstable angina pectoris, Xin'anning Nasal Drop, clinical study

Administration, Intranasal ; Adult ; Aged ; Angina, Unstable ; drug therapy ; physiopathology ; Electrocardiography ; drug effects ; Female ; Heart Rate ; drug effects ; Humans ; Male ; Medicine, Chinese Traditional ; Middle Aged ; Systole ; drug effects