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

The purpose of this study was to determine the effect of nitric oxide (NO) in the rostral ventrolateral medulla (RVLM) on the central integration of the cardiac sympathetic afferent reflex (CSAR) in normal rats and in rats with coronary ligation-induced chronic heart failure (CHF). Under alpha-chloralose and urethane anesthesia, mean arterial pressure, heart rate and renal sympathetic nerve activity (RSNA) were recorded at baseline and during elicitation of the CSAR evoked by electrical stimulation of the cardiac afferent sympathetic nerves in sino-aortic denervated and cervical vagotomized rats. A cannula was inserted into the left RVLM for microinjection of NO synthase inhibitor, S-methyl-L-thiocitruline (MeTC) or NO donor, S-nitroso-N-acetyl-penicillamine (SNAP). The CSAR was tested by electrical stimulation (5, 10, 20 and 30 Hz at 10 V for 1 ms) of the afferent cardiac sympathetic nerves. It was observed that (1) the responses of RSNA to stimulation were enhanced in rats with CHF; (2) MeTC (80 nmol) potentiated the responses of RSNA to stimulation in sham rats but not in rats with CHF; (3) SNAP (50 nmol) depressed the enhanced RSNA response to stimulation in CHF rats but had no effect in sham rats; and (4) MeTC increased the baseline RSNA and MAP only in sham rats, but SNAP inhibited the baseline RSNA and MAP in both sham and CHF rats. These results indicate that reductance of NO in the RVLM is involved in the augmentation of CSAR in CHF rats.
Afferent Pathways ; physiopathology ; Animals ; Heart Failure ; physiopathology ; Male ; Medulla Oblongata ; physiopathology ; Nitric Oxide ; metabolism ; physiology ; Rats ; Rats, Sprague-Dawley ; Reflex ; physiology ; Sympathetic Nervous System ; drug effects ; physiopathology

OBJECTIVE: To observe the immediate effect and safety of Shexiang Tongxin dropping pills (, STDP) on patients with coronary slow flow (CSF), and furthermore, to explore new evidence for the use of Chinese medicine in treating ischemic chest pain. METHODS: Coronary angiography (CAG) with corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) was applied (collected at 30 frames/s). The treatment group included 22 CSF patients, while the control group included 22 individuals with normal coronary flow. CSF patients were given 4 STDP through sublingual administration, and CAG was performed 5 min after the medication. The immediate blood flow frame count, blood pressure, and heart rate of patients before and after the use of STDP were compared. The liver and kidney functions of patients were examined before and after treatments. RESULTS: There was a significant difference in CTFC between groups (P<0.05). The average CTFC values of the vessels with slow blood flow in CSF patients were, respectively, 49.98 ± 10.01 and 40.42 ± 11.33 before and after the treatment with STDP, a 19.13% improvement. The CTFC values (frame/s) measured before and after treatment at the left anterior descending coronary artery, left circumflex artery, and right coronary artery were, respectively, 48.00 ± 13.32 and 41.80 ± 15.38, 59.00 ± 4.69 and 50.00 ± 9.04, and 51.90 ± 8.40 and 40.09 ± 10.46, giving 12.92%, 15.25%, and 22.76% improvements, respectively. The CTFC values of vessels with slow flow before treatment were significantly decreased after treatment (P<0.05). There were no apparent changes in the heart rate, blood pressure, or liver or kidney function of CSF patients after treatment with STDP (all P>0.05). CONCLUSIONS The immediate effect of STDP in treating CSF patients was apparent. This medication could significantly improve coronary flow without affecting blood pressure or heart rate. Our findings support the potential of Chinese medicine to treat ischemic chest pain.
Blood Pressure ; drug effects ; Coronary Circulation ; drug effects ; physiology ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Female ; Heart Rate ; drug effects ; Humans ; Kidney ; drug effects ; physiopathology ; Liver ; drug effects ; physiopathology ; Male ; Middle Aged ; No-Reflow Phenomenon ; drug therapy ; physiopathology

The experiments were carried out on guinea pig isolated ventricular myocytes by using whole-cell patch clamp. The effects of angiotensin II (Ang II) on potassium ion channels of acute ischemic myocytes were observed. Whole-cell patch clamp recordings showed that physiological potassium current, including delayed rectifier potassium current and inward rectifier potassium current were inhibited under the condition of simulated ischemia, and then further inhibited by treatment with Ang II. ATP-sensitive potassium currents were increased under simulated ischemia and were further enhanced by Ang II treatment.
Angiotensin II ; pharmacology ; Animals ; Cells, Cultured ; Female ; Guinea Pigs ; Heart Ventricles ; cytology ; drug effects ; Male ; Myocardial Ischemia ; pathology ; physiopathology ; Myocytes, Cardiac ; drug effects ; Potassium Channels ; drug effects ; physiology

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

AIMTo observe the effect of stretching left ventricles in the end of action potential on rabbit cardiac activity, and to investigate its possible mechanisms.

METHODSStretch (120 mmHg, 50 ms) was applied in the end of action potential by the pressure-clamp technique to observe if there would be any changes in rabbit cardiac activity and streptomycin (500 micromol/L) was used to identify the mechanism.

RESULTSStretch in the end of action potential caused arrhythmia (P < 0.05) and streptomycin blocked the above effect (P < 0.05).

CONCLUSIONStreptomycin could block the effect of stretching left ventricles in the end of action potential on rabbit cardiac activity, which indicates that stretch-activated ion channels involve it.

Action Potentials ; physiology ; Animals ; Arrhythmias, Cardiac ; etiology ; physiopathology ; Female ; Heart Ventricles ; physiopathology ; In Vitro Techniques ; Ion Channels ; physiology ; Male ; Mechanoreceptors ; drug effects ; Proprioception ; Rabbits ; Streptomycin ; pharmacology

We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.
Adolescent ; Adrenergic beta-Agonists/pharmacology* ; Arrhythmia/physiopathology* ; Child ; Child, Preschool ; Comorbidity ; Electrocardiography ; Female ; Heart Rate/drug effects* ; Heart Rate/physiology* ; Human ; Isoproterenol/pharmacology* ; Male ; Syncope/physiopathology*

OBJECTIVETo study the effect of Shengmai injection (, SMI) on vascular endothelial and heart functions in coronary heart disease patients complicated with diabetes mellitus (CHD-DM).

METHODSOne hundred and twenty patients with CHD-DM, their diagnosis confirmed by coronary arteriography, were equally randomized into a control group treated with conventional treatment and a treated group treated with conventional treatment plus SMI. The changes in blood levels of nitric oxide (NO), endothelin-1 (ET-1) and angiotensin II (Ang II), as well as endothelium-dependent vascular dilating function and heart function in the patients were observed before treatment and after the 3-week treatment.

RESULTSAfter being treated with SMI for 3 weeks, in the treated group, blood level of NO was raised significantly from 69.8 + or - 33.1 micro mol/L to 120.1 + or - 50.8 micro mol/L, and ET-1 was lowered from 70.1 + or - 32.1 ng/L to 46.2 + or - 21.3 ng/L, respectively (P<0.01); that of Ang II was lowered from 81.3 + or - 24.3 ng/L to 50.2 + or - 27.3 ng/L (P<0.01); brachial arterial post-congestion blood flow increasing rate was raised from 389.4 + or - 26.3% to 459.3 + or - 27.8% (P<0.01); and the improvement in heart function as seen through the ejection fraction (EF) was increased from 44 + or - 5% to 68 + or - 6% (P<0.01), all the changes being more significant than those in the control group (all P<0.01).

CONCLUSIONSMI can improve not only the endothelial function in CHD-DM patients, but also heart contraction significantly.

Coronary Disease ; drug therapy ; physiopathology ; Diabetes Complications ; physiopathology ; Drug Combinations ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Endothelium, Vascular ; drug effects ; physiology ; Female ; Heart ; drug effects ; physiology ; Humans ; Male ; Middle Aged

Under conditions of Na+ channel hyperactivation with aconitine, the changes in action potential duration (APD) and the restitution characteristics have not been well defined in the context of aconitine-induced arrhythmogenesis. Optical mapping of voltage using RH237 was performed with eight extracted rabbit hearts that were perfused using the Langendorff system. The characteristics of APD restitution were assessed using the steady-state pacing protocol at baseline and 0.1 microM aconitine concentration. In addition, pseudo-ECG was analyzed at baseline, and with 0.1 and 1.0 microM of aconitine infusion respectively. Triggered activity was not shown in dose of 0.1 microM aconitine but overtly presented in 1.0 microM of aconitine. The slopes of the dynamic APD restitution curves were significantly steeper with 0.1 microM of aconitine than at baseline. With aconitine administration, the cycle length of initiation of APD alternans was significantly longer than at baseline (287.5 +/- 9.6 vs 247.5 +/- 15.0 msec, P = 0.016). The functional reentry following regional conduction block appears with the progression of APD alternans. Ventricular fibrillation is induced reproducibly at pacing cycle length showing a 2:1 conduction block. Low-dose aconitine produces arrhythmogenesis at an increasing restitution slope with APD alternans as well as regional conduction block that proceeds to functional reentry.
Aconitine/*pharmacology ; Action Potentials/*drug effects ; Animals ; Arrhythmias, Cardiac/*chemically induced/*physiopathology ; Cardiac Pacing, Artificial ; Electrocardiography ; Heart/physiopathology ; Heart Conduction System/physiology ; Myocardium/*pathology ; Rabbits ; Sodium Channels/drug effects/metabolism ; Ventricular Fibrillation/physiopathology

BACKGROUNDEffect of percutaneous transluminal septal ablation (PTSA) with ethanol injection on electromechanical remodeling of left ventricule still remains unknown. This study was conducted to assess the potential significance of cardiac electromechanical mapping (CEMM) in analyzing the left ventricular remodeling before and immediately after percutaneous transseptal myocardial ablation (PTSMA) in patients with hypertrophic obstructive cardiomyopathy (HOCM).

METHODSEight patients with drug-refractory HOCM and 6 patients with hypertrophic cardiopathy (HM) without increased left ventricular outtract gradien (LVOTG) were enrolled into the present study. CEMM was undergone in patients with HOCM before and immediately after PTSA procedure, and in patients with HM.

RESULTSPTSA was successful in all patients with HOCM, LVOTG significantly decreased from (62.87 +/- 21.16) mmHg to (12.73 +/- 3.05) mmHg immediately after ablation procedure. Value of UVP in septal-base segment in HM group was higher than that in HOCM group [(22.79 +/- 2.34) mV vs (18.54 +/- 1.76) mV]. In patients with HOCM, lateral-middle and -base segments had lowest value of UVP [(15.93 +/- 1.11) mV and (15.83 +/- 1.07) mV] before PTSA. Value of UVP at posterior-middle segment decreased from (23.58 +/- 2.21) mV pre-PTSA to (18.89 +/- 1.91) mV post-procedure, PTSA led to significant increase of UVP at lateral-middle segment. Septal region in patients with HM and septal-middle, septal-base, posterior-base segments in HOCM had lower value of local linear shortening (LLS) among all patients in both HOCM and HM groups. PTSA resulted in significant reduction of LLS in anterior region and at septal-apex segment. Anterior-base and septal-middle segments in patients with HM had lowest value of local active time (LAT), and significantly differentiated from that in patients with HOCM [(-8.57 +/- 0.68) ms vs (-18.61 +/- 1.02) ms, (-6.75 +/- 0.37)ms vs (-21.90 +/- 0.96) ms, respectively]. LAT at septal-middle and -base segments in patients with HOCM was decreased significantly [(-21.90 +/- 0.96) ms vs (-13.80 +/- 1.04) ms, P < 0.002; and (-15.20 +/- 1.06) ms vs (-6.33 +/- 0.52) ms, respectively] immediately after PTSA.

CONCLUSIONSPosterior-lateral and anterior region probably played important roles in electromechanical remodeling. Significant electromechanical remodeling disassociation (uncoupling) was detected in most left ventricular regions, which would be important in differentiating of HOCM from HM, and in predicting the prognosis in patients with HOCM after PTSA procedure.

Body Surface Potential Mapping ; Cardiomyopathy, Hypertrophic ; physiopathology ; therapy ; Ethanol ; therapeutic use ; Heart Septum ; drug effects ; Humans ; Ventricular Remodeling ; physiology