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Biomedical subjects

Y G Li

Publications and source records attributed to Y G Li.

At least 19 recordsLinked to original sources
PubMed2005

Study on changes of heme oxygenase-1 expression in patients with coronary heart disease.

BACKGROUND: Heme oxygenase (HO) is a rate-limiting enzyme of endogenetic carbon monoxide (CO) that degrades heme into carbon monoxide, bilirubin, and iron. These products have important physiologic effects: bilirubin is a potent antioxidant that can act against ischemia/reperfusion injury; there is a negative correlation between the content of HO-1 and the incidence of coronary heart disease (CHD). HYPOTHESIS: This study was undertaken to investigate the changes of HO-1 in patients with CHD. METHODS: Thirty-five patients with acute myocardial infarction (AMI), 40 patients with unstable angina pectoris (UAP, diagnosed by coronary angiography), and 30 patients with stable angina pectoris (AP, diagnosed by coronary angiography) were selected for the study; another 30 patients with normal coronary artery (diagnosed by coronary angiography) were selected as controls. The levels of HO-1 protein expression in monocyte and lymphocyte in the subjects were tested by immunohistochemistry and western blot. Computer picture analyzing systems were also used to measure the levels of HO-1 protein expression. RESULTS: Heme oxygenase-1 protein is located in cell plasma. The levels of HO-1 protein expression in patients with CHD were significantly higher than in those without CHD (p < 0.01). There were significant differences of HO-1 expression among the three groups of patients with CHD. The group with AMI was the highest, followed by the group with UAP and finally by the group with AP. CONCLUSIONS: There is a higher expression of HO-1 in patients with CHD. The levels of HO-1 protein are associated with the severity of CHD.

Biomarkers↗
PubMed2005

Acquired but reversible loss of erythrocyte complement receptor 1 (CR1, CD35) and its longitudinal alteration in patients with severe acute respiratory syndrome.

This longitudinal study investigates the change of erythrocyte complement receptor (E-CR1) expression in patients with severe acute respiratory syndrome (SARS). Circulating E-CR1 expression was semiquantified by flow cytometric analyses in 54 SARS patients and in 212 healthy individuals as a control. Since E-CR1 expression is influenced by the genetic polymorphisms in the CR1 gene, a major genetic polymorphism located within intron 27 of the CR1 gene was simultaneously analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The results showed that the expression level of E-CR1 (referred to as net fluorescence intensity values, NFI) was statistically correlated with the relevant genetic genotypes among the Chinese population including the healthy individuals (NFI: 5.14 +/- 0.82, 3.57 +/- 0.66 and 2.67 +/- 0.32 for HH, HL and LL genotypes, respectively) and SARS patients (NFI: 3.52 +/- 0.91 and 2.63 +/- 0.70 for HH and HL genotypes, respectively). Interestingly, the expression density of E-CR1 was found to fall significantly during the initiation and progressive phases (weeks 1 and 2 after the disease onset) and gradually returned close to normal through their whole convalescent phase (beginning from weeks 2 or 3 to weeks 7 or 8) in SARS patients irrespective CR1 genotype. In conclusion, our findings, at least, suggest that E-CR1 is likely involved in immune pathogenesis of SARS disease.

Adolescent↗
PubMed2001

[Lithotripsy for residual cholelithes by rigid choledochoscopy].

OBJECTIVE: To evaluate a new lithotomy for postoperatively residual cholelithes. METHOD: Using rigid choledochoscopy to extract the residual cholelithes which could hardly be extracted by fibrocholedochoscopy through the T-tube sinus in 31 cases. RESULT: The residual cholelithes were extracted in 30 cases, reoperation was avoided. CONCLUSION: The residual cholelithes can be effectively extracted by the rigid choledochoscopy plus mechanical lithotripsy through T-tube sinus.

Adolescent↗
PubMed2001

Effect of metoprolol and d,l-sotalol on microvolt-level T-wave alternans. Results of a prospective, double-blind, randomized study.

OBJECTIVES: The study evaluated the effects of metoprolol, a pure beta-blocker, and d,l-sotalol, a beta-blocker with additional class III antiarrhythmic effects, on microvolt-level T-wave alternans (TWA). BACKGROUND: Assessment of TWA is increasingly used for purposes of risk stratification in patients prone to sudden death. There are only sparse data regarding the effects of beta-blockers and antiarrhythmic drugs on TWA. METHODS: Patients with a history of documented or suspected malignant ventricular tachyarrhythmias were eligible. All patients underwent invasive electrophysiologic (EP) testing including programmed ventricular stimulation and determination of TWA at increasing heart rates using atrial pacing. Reproducibility of TWA at two consecutive drug-free baseline measurements was tested in a random patient subset. Following baseline measurements, all patients were randomized either to double-blind intravenous infusion of sotalol (1.0 mg/kg) or metoprolol (0.1 mg/kg). Results of TWA assessment at baseline and after drug exposure were compared. RESULTS: Fifty-four consecutive patients were studied. In 12 patients, repetitive baseline measurement of TWA revealed stable alternans voltage (V(alt)) values (9.1 +/- 5.8 microV vs. 8.5 +/- 5.7 microV, p = NS). After drug administration, V(alt) decreased by 35% with metoprolol (7.9 +/- 6.0 microV to 4.9 +/- 4.2 microV; p < 0.001) and by 38% with sotalol (8.6 +/- 6.8 microV to 4.4 +/- 2.3 microV; p = 0.001). In eight patients with positive TWA at baseline, repeated measurement revealed negative test results. CONCLUSIONS: In patients prone to sudden cardiac death, there is a reduction in TWA amplitude following the administration of antiadrenergic drugs. This result indicates that TWA is responsive to the pharmacologic milieu and suggests that, to assess a patient's risk of spontaneous ventricular arrhythmia, the patient should be tested while maintaining the pharmacologic regimen under which the risk of arrhythmia is being assessed. This applies particularly for beta-blocker therapy.

Adrenergic beta-Antagonists↗
PubMed2001

Risk of development of delayed atrioventricular block after slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval.

AIMS: The objective of this prospective study was to assess risk factors for the development of atrioventricular block following slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval. METHODS AND RESULTS: Of 346 consecutive patients with atrioventricular nodal reentrant tachycardia undergoing slow pathway modification, 18 patients (62 +/- 7 years; five females) were found to have a prolonged PR interval prior to ablation. Total elimination of the functional slow pathway was assumed if the antegrade effective refractory period following slow pathway modification was longer than the cycle length of atrioventricular nodal reentrant tachycardia. To detect atrioventricular node conduction disturbances, 24-h Holter recordings were performed 1 day prior to slow pathway modification, and 1 day, 1 week, 1, 3 and 6 months after the procedure. Six patients developed late atrioventricular block. The incidence of delayed atrioventricular block following successful slow pathway modification was higher in patients with, compared to patients without, prolonged PR interval at baseline (6/18 vs 0/328, P < .001). In the former group, the antegrade effective refractory period was longer in patients with, compared to those without, a delayed atrioventricular block (492 +/- 150 ms vs 332 +/- 101 ms, P < 0.05). The incidence of delayed atrioventricular block was higher in patients with total elimination of the slow pathway compared to patients without (5/7 vs 1/11, P < 0.01). CONCLUSIONS: Slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a prolonged PR interval is highly effective. However, there is a significant risk of development of delayed atrioventricular block, particularly when the procedure results in total elimination of the slow pathway.

Case-Control Studies↗
PubMed2000

Association between atrial fibrillation and appropriate implantable cardioverter defibrillator therapy: results from a prospective study.

INTRODUCTION: Atrial fibrillation (AF) is associated with significant morbidity and mortality that may be related to hemodynamic impairment, thromboembolic events, or enhanced electrical instability of the ventricular myocardium. There is, however, a lack of data concerning the association of AF and ventricular tachyarrhythmias. METHODS AND RESULTS: Consecutive patients with indication for an implantable cardioverter defibrillator (ICD) were classified for the presence or absence of persistent AF at the time of device implantation. Incidence of device therapy, stored electrograms, and clinical events during follow-up were evaluated prospectively. Two hundred fifty patients were included. During follow-up (20+/-14 months), patients in AF experienced appropriate device therapy for recurrent ventricular arrhythmias more frequently compared with patients in sinus rhythm (SR) (63% vs 38%, P = 0.01). On multivariate analysis, AF was an independent predictor of appropriate ICD therapy (relative risk 1.8; 95% confidence interval [CI] 1.2 to 2.9) and inappropriate device therapy (relative risk 2.3; 95% CI 1.2 to 4.5). Predefined clinical events (cluster endpoint: death, syncope, and hospitalizations) were observed more frequently in AF than in SR patients (55% vs 31%, P = 0.01). Analysis of device-stored electrograms revealed a higher incidence of short-long-short cycles preceding ventricular arrhythmias in AF compared with SR patients (50% vs 16%, P = 0.002). Baseline heart rate preceding ventricular arrhythmias did not differ between the two groups. CONCLUSION: AF is an independent predictor of recurrent ventricular arrhythmias in ICD recipients. The underlying electrophysiologic mechanism seems to be irregular rather than rapid ventricular activation, with a high incidence of short-long-short sequences preceding ventricular tachyarrhythmias in AF patients.

Aged↗
PubMed2000

Efficacy and safety of transvenous atrial cardioversion in patients with mitral valve disease and long-standing atrial fibrillation.

BACKGROUND: Transvenous internal cardioversion (ICV) of atrial fibrillation (AF) may be successful after unsuccessful external CV. However, the safety and efficacy of ICV in patients with significant mitral valve disease and AF of long duration have not been evaluated prospectively. METHODS: This study included 22 consecutive patients (mean age = 59 +/- 14 years, 12 women) with mitral regurgitation grade = II (n = 14) or after mitral valve replacement (n = 8), who underwent ICV with 3/3 ms biphasic shocks delivered via two defibrillation catheters placed in the right atrium and the coronary sinus, respectively. The mean left atrial diameter was 53 +/- 7 mm (range 45-68), and AF had been diagnosed for a median of 24 months. All patients received oral amiodarone pretreatment followed by a maintenance dose of 200 mg/day. RESULTS: Sinus rhythm (SR) was restored by ICV in 15/20 patients (75%), and returned spontaneously in two patients during amiodarone pretreatment. The mean threshold for ICV was 6.2 +/- 3.5 J. Sinus node disease was present in one patient after ICV, and two patients developed amiodarone-induced hyperthyroidism. During a follow-up of 11 +/- 5 months, 8 patients had recurrent AF. The remaining 11 patients who were successfully cardioverted remained in stable SR. CONCLUSION: SR can be safely and successfully restored by ICV in patients with MVD and long-standing AF. During intermediate-term follow-up, a significant proportion of patients remained in SR with oral amiodarone therapy.

Administration, Oral↗
PubMed2000

Ablation of atypical atrial flutter guided by the use of concealed entrainment in patients without prior cardiac surgery.

INTRODUCTION: Mapping techniques have not been systematically evaluated with respect to atypical atrial flutter (AF) not involving the inferior vena cava isthmus. The purpose of this study was to assess prospectively the use of concealed entrainment (CE) in mapping of AF and to assess the clinical benefit of ablation of clinically relevant atypical AF. METHODS AND RESULTS: In seven consecutive patients without prior cardiac surgery presenting with atypical AF, mapping was performed in the right and, if necessary, left atrium. At sites with CE, radiofrequency energy was delivered. In a posthoc analysis, the endocardial activation time, stimulus-flutter wave (F) interval, presence of split potentials and diastolic potentials, and postpacing interval were assessed, and effective sites were compared to ineffective sites. A total of 22 forms of atypical AF either could be induced or were present at the time of the study. Eleven of the 13 targeted atypical AFs (85%) were successfully ablated. The positive predictive value of CE increased from 45% to 75% in the presence of matching electrogram-F and stimulus-F intervals or if flutter terminated during entrainment pacing, and to 88% in the presence of split atrial electrograms or diastolic potentials. During short-term clinical follow-up, none of the patients had recurrence of the ablated AF. However, the majority of patients required either medication for atrial fibrillation or repeated interventions for new forms of AF. CONCLUSION: Mapping and ablation of atypical AF is feasible if sites with CE can be identified. However, the clinical benefit of successful ablations in patients with atypical flutter appears to be limited.

Adult↗
PubMed2000

Location of the lower turnaround point in typical AV nodal reentrant tachycardia: a quantitative model.

INTRODUCTION: Recent observations suggest that the circuit of AV nodal reentrant tachycardia (AVNRT) may extend down to the His bundle. The purpose of this study was to develop a quantitative model indicating the location of the lower turnaround point in AVNRT. METHODS AND RESULTS: Slow pathway modification was performed in 70 patients with typical AVNRT. During sinus rhythm, ventricular pacing was performed with the AVNRT cycle length. During AVNRT, the HinitAinit interval was measured from initial His to the initial atrial deflection recorded in the His-bundle lead. During ventricular pacing, the HendAinit interval was measured from end of the His to the beginning of the atrial deflection. It was hypothesized that x reflects conduction time from the lower turnaround point to Ainit, whereas y reflects conduction time from the lower turnaround point to Hinit. Anterograde conduction during AVNRT and retrograde conduction during ventricular pacing were assumed to be identical if there was 1:1 retrograde conduction at the AVNRT cycle length. The following formulas describe the relation of the measured parameters: x - y = HinitAinit; and x + y = HendAinit. Resolving both formulas yields the unknown x and y: y = (HendAinit - HinitAinit)/2, x = (HendAinit + HinitAinit)/2. These criteria were present in 52 of 70 patients. The mean cycle length of AVNRT was 355 +/- 42 msec, mean HinitAinit was 54 +/- 27 msec, and mean HendAinit was 60 +/- 29 msec. Accordingly, in 20 of 52 patients, the lower turnaround point was located within the His bundle (y = -15.4 +/- 16.1 msec), in 3 of 52 it was in the nodal-His junctional area (y = 0), and in 29 of 52 it was above the His bundle (y = +12.7 +/- 10.3 msec). The HinitAinit interval was significantly longer (66 +/- 32 msec vs 47 +/- 20 msec; P = 0.02) and the HendAinit interval was significantly shorter (45 +/- 30 msec vs 69 +/- 24 msec; P = 0.004) when the first group was compared with the others. CONCLUSION: In about 1 of 3 of patients with typical AVNRT, the lower turnaround point of the circuit is within the His bundle; in more than half of the patients it is above the His bundle. These data do not support the concept that all AVNRTs have an intranodal circuit, but are in accordance with the finding of longitudinal dissociation of the His bundle.

Adult↗
PubMed2000

Pharmacological management of atrial fibrillation: an update.

Therapy of atrial fibrillation remains difficult in many patients. There is increasing awareness that antiarrhythmic drug therapy instituted to maintain sinus rhythm after successful cardioversion of atrial fibrillation may pose a substantial risk to the patient. Therefore, results of prospective randomized trials are needed to allow a more evidence-based approach to the treatment of this common arrhythmia. Two recently published studies have shown superiority of amiodarone over conventional antiarrhythmic drugs in maintaining sinus rhythm. The largest such study published today, the Canadian Trial in Atrial Fibrillation (CTAF), has randomized 403 patients to amiodarone or to sotalol or propafenone. At the end of the observation period, amiodarone-treated patients were significantly more likely to remain in sinus rhythm than conventionally treated patients. A number of new antiarrhythmic drugs, mainly class III substances, are currently developed for the treatment of atrial fibrillation or atrial flutter. Ibutilide has recently been released for intravenous administration, attempting pharmacological cardioversion of atrial fibrillation/atrial flutter. It has been evaluated in a number of prospective trials, which showed a higher conversion rate in patients with atrial flutter. Dofetilide is another new compound developed mainly for maintenance of sinus rhythm after restoration of sinus rhythm. It has been evaluated in two prospective, randomized, placebo-controlled trials; moreover, analysis of the DIAMOND trials showed effectiveness of dofetilide in maintaining sinus rhythm in patients with depressed left ventricular function without increased mortality when compared with placebo. Finally, several ongoing studies compare the therapeutic strategy of controlling ventricular rate in atrial fibrillation compared with the strategy of maintaining sinus rhythm. These trials will help to optimize therapy in atrial fibrillation, the most commonly encountered arrhythmia.

Anti-Arrhythmia Agents↗
PubMed2000

[Microvolt level T wave alternans: a new marker for noninvasive risk stratification].

Prospective identification of patients with structural heart disease who could profit from prophylactic ICD therapy is hampered by the low predictive power of the currently available risk stratification parameters. Microvolt T wave alternans measured noninvasively is a new promising parameter to assess impaired ventricular repolarization which has been associated with an increased incidence of ventricular tachyarrhythmias. T wave alternans is rate-dependent; to induce alternans, heart rate may be increased by atrial stimulation during invasive EP testing or noninvasively by exercise stress testing. The first clinical validation with respect to prediction of inducibility of ventricular tachyarrhythmias and of arrhythmic events during follow-up in patients undergoing invasive EP testing was reported in 1994. Subsequently, a good concordance between the results of invasive and noninvasive assessment of T wave alternans was demonstrated by our group. The first prospective evaluation of the noninvasive alternans measurement using submaximal exercise testing was performed in patients surviving prehospital ventricular fibrillation or sustained ventricular tachycardia referred to our institution. The occurrence of T wave alternans in this patient population was predictive of future tachyarrhythmic events with subsequent appropriate ICD therapy. The results of the currently performed prospective trials in various patient populations will help to establish the utility of T wave alternans assessment as a risk stratifier in clinical practice.

Action Potentials↗
PubMed2000

[Study of the factors of Cr(III) bioaccumulation on Spirulina platensis].

Some factors of Cr(III) bioaccumulation on Spirulina platensis were studied in detail. It was found that the bioaccumulation of Cr(III) on Spirulina platensis involved two steps: rapid adsorption and slow absorption. Chromic(III) compounds with weaker chemical bond had higher bioaccumulation efficiency. Under the same algal cell concentration, Cr(III) bioaccumulation rosed up with Cr(III) concentration. On the other hand, with Cr(III) concentration not changed, the total bioaccumulation of Cr(III) on Spirulina platensis increased with algal cell concentration, but the Cr(III) bioaccumulation on unit algae reduced. The study also showed that Spirulina platensis powder could bioaccumulate more Cr(III) than fresh Spirulina platensis, pH is a quite important factor and more suitable pH for Cr(III) bioaccumulation is 7. It was also proved that Cr(III) bioaccumulation benefited from the increase of temperature and light intensity. Cations had either stimulation or inhibition effects on the Cr(III) bioaccumulation on Spirulina platensis.

Bacterial Proteins↗
PubMed2000

[Mixotrophic cultivation of Synechocystis sp. 6803: influences of light intensity and glucose].

The growth characteristics and the effects of glucose and light on the growth of Synechocystis sp. PCC6803 under mixotrophic conditions have been investigated. An exponential growth phase had been observed before glucose was consumed. The results showed that both of light intensity and glucose concentration had obvious effects on the mixotrophic growth of Synechocystis sp. PCC6803: the specific growth are decreased with the increase of glucose concentration at light; the specific growth rate and biomass/glucose yield increased with light intensity, ranging from 15-55 microE.m-2.s-1; when light intensity was higher than 55 microE.m-2.s-1, light saturation appeared.

Carbon Dioxide↗
PubMed2000

[Improvement of nitrogen fixation efficiency and plasmid stability in Bradyrhizobium japonicum by the introduction of dctABD and parCBA/DE genes].

A recombinant plasmid pHN207 containing C4-dicarboxylic acid transport genes (dctABD) from Sinorhizobium meliloti, parCBA/DE genes from pTR102 and reporter genes luxAB from pDB30 was constructed by using pLAFR3 as the vector. The pHN207 was then introduced into the Bradyrhizobium japonicum TA11 and CB1809 by bi-parental mating. It was confirmed that parCBA/DE genes could increase the stability of pLAFR3 in the transconjugants under both free-living and symbiotic condition. The results of plant pot experiment indicated that the introduction of dctABD genes could significantly improve the symbiotic nitrogen fixation efficiency of TA11 and CB1809 with soybean varieties of Heilong 33, Ningzhen No. 1 and Yudou No. 1. Compared with the control, the shoot dry weight (biomass) and total nitrogen content of the plants tested were significantly increased.

Bacterial Proteins↗
PubMed1999

Septal Q waves in surface electrocardiographic lead V6 exclude minimal ventricular preexcitation.

Electrocardiograms of 37 consecutive patients with minimal preexcitation (i.e., PR >120 ms, QRS <120 ms) were compared before and after ablation with electrocardiograms of 37 age-matched patients with atrioventricular nodal reentrant tachycardia. The presence of a septal Q wave could be used to exclude minimal preexcitation with a high degree of reliability in both patients and controls before and after radiofrequency ablation.

Cardiac Pacing, Artificial↗
PubMed1999

[T-wave alternans in microwave frequency as a new indicator of disordered ventricular repolarization: pathophysiology, methodology, clinical results].

Primary prevention of sudden cardiac death is hampered by the inability to accurately identify high risk patients. Various noninvasive methods such as determination of left ventricular function or heart rate variability as well as invasive electrophysiologic testing are currently used for risk stratification. Noninvasive measurement of microvolt T wave alternans (TWA) is a promising new method to assess repolarization abnormalities; in experimental studies, TWA was associated with an increased incidence of ventricular tachyarrhythmias. Since the occurrence of TWA is heart rate-dependent, it is measured either during atrial pacing or during exercise stress testing. The first clinical validation of the method was performed in patients undergoing invasive EP testing to assess prediction of inducibility of ventricular tachyarrhythmias. A first prospective validation of the noninvasive method was performed in patients surviving out-of-hospital cardiac arrest fitted with an ICD. Further studies have shown a good concordance between invasive and noninvasive TWA determination. The occurrence of TWA in this population was of predictive value with respect to arrhythmia recurrence. Recently published data confirm the value of TWA assessment with respect to identification of patients with congestive heart failure at high risk of malignant ventricular tachyarrhythmias. The use of this method in post myocardial infarction risk stratification is currently under prospective evaluation.

Cardiac Pacing, Artificial↗