Biomedical subjects

Lexin Wang

Publications and source records attributed to Lexin Wang.

At least 19 recordsLinked to original sources

PubMed2006

Thrombolytic therapy with urokinase for pulmonary embolism in patients with stable hemodynamics.

BACKGROUND: Thrombolytic agents such as urokinase have been used in the treatment of patients with massive pulmonary embolism and hypotension, but their effect in patients with submassive pulmonary embolism and normal blood pressure has been controversial. MATERIAL/METHODS: Urokinase (20,000 IU /kg) was intravenously administered to 36 patients who had pulmonary embolism and a normal blood pressure. This was followed by subcutaneous injection of a low-molecular-weight heparin for a week. RESULTS: Improvement in clinical symptoms and reduction in pulmonary pressure was observed in 28 (77.8%) patients within the first week of the thrombolytic therapy. The improvement rate in patients with embolic symptoms of less than 14 days, and in those who had symptoms between 14 and 30 days before the thrombolytic therapy was 86% and 50%, respectively (p<0.01). Non-life threatening bleeding complications were observed in 10 (22.2%) patients. CONCLUSIONS: Thrombolytic therapy with urokinase followed by low-molecular-weight heparin is an effective therapeutic strategy for patients with pulmonary embolism and stable haemodynamics. However, the long-term benefits of this strategy remain to be seen and further studies are warranted.

Adult↗

PubMed2006

Autologous endothelial progenitor cells transplantation for the therapy of primary pulmonary hypertension.

Primary pulmonary hypertension (PPH) is a fatal cardiovascular disease characterized by increased pulmonary vascular resistance and progressive right heart failure. It is associated with a very high morbidity and mortality rate. The therapeutic effects of current pharmacological management of PPH are limited. Recent studies have demonstrated that endothelial dysfunction and cell loss play a critical role in the pathogenesis of PPH. Emerging evidence also shows that circulating endothelial progenitor cells instigate new vessel formation via vasculogenesis and revascularization, and provide ongoing endothelial repair by homing to site of endothelial damage. We hypothesized that autologous endothelial progenitor cells transplantation may be a feasible adjunctive therapeutic option for PPH.

Endothelium, Vascular↗

PubMed2006

Erythrocyte oxidative damage in chronic fatigue syndrome.

BACKGROUND: It has been hypothesized that a link exists between erythrocyte metabolism (particularly redox metabolism) and erythrocyte shape and that both are related to erythrocyte deformability. The aim of this research is to confirm the results of earlier studies and to investigate a correlation between erythrocyte morphology and erythrocyte oxidative damage in chronic fatigue syndrome (CFS). METHODS: Reduced glutathione (GSH), malondialdehyde (MDA), methemoglobin (metHb) and 2,3-diphosphoglyceric acid (2,3-DPG) were measured in 31 patients suffering from CFS and 41 healthy control subjects. Scanning electron microscopic studies of the erythrocytes from both groups were also carried out. RESULTS: There was evidence of oxidative damage in CFS with statistically significant increases in 2,3-DPG (p < 0.05), metHb (p < 0.005) and MDA (p < 0.01). The CFS patients in this study also had significantly more stomatocytes in their blood than the normal subjects (p < 0.005). CONCLUSIONS: There is a strong likelihood that the increase in erythrocyte antioxidant activity is associated with the presence of stomatocytes. The results of this study provide further evidence for the role of free radicals in the pathogenesis of CFS and a link between erythrocyte metabolism and erythrocyte shape.

2,3-Diphosphoglycerate↗

PubMed2006

Increased coronary flow may prolong transmural ventricular repolarisation.

An increase in spatial dispersion of ventricular refractory periods reflects inhomogeneity of ventricular refractoriness and is associated with an increased risk of life-threatening ventricular arrhythmias. Spatial dispersion in ventricular refractoriness is determined by the differences in refractory periods of myocytes in epicardium, mid-myocardium and endocardium. Prolongation of ventricular repolarisation with drugs or physical means may reduce the spatial dispersion and the risk of arrhythmia. An increase in coronary flow has been shown to prolong the duration of ventricular repolarisation measured from epicardium in the intact animal heart. We hypothesised that an increase in coronary flow may also prolong ventricular repolarisation cross the three layers of ventricular myocardium through the release of nitric oxide. The simultaneously prolongation of transmural repolarisation may reduce the spatial dispersion of ventricular repolarisation and hence, the risk of life-threatening ventricular arrhythmias.

Action Potentials↗

PubMed2006

B-type natriuretic peptide is an independent predictor for cardiovascular death in patients with no clinical signs of ventricular dysfunction after acute myocardial infarction.

B-type natriuretic peptide (BNP) is released from cardiac ventricles in response to increased wall tension in patients with heart failure. It has been used as a biochemical marker for the diagnosis of congestive heart failure. BNP is also increased in patients with acute myocardial infarction, and is associated with an increased risk of cardiovascular mortality in those with impaired left ventricular function after myocardial infarction. We hypothesized that an increase in BNP soon after acute myocardial infarction is an independent predictor for long-term prognosis in patients with no clinical signs of left ventricular function.

Cardiovascular Diseases↗

PubMed2006

Atrial vulnerability is a major mechanism of paroxysmal atrial fibrillation in patients with Wolff-Parkinson-White syndrome.

Atrioventricular re-entrant tachycardia is the most common form of tachycardia in patients with Wolff-Parkinson-White (WPW) syndrome where one or more accessory pathways are present between atria and ventricles. Paroxysmal atrial fibrillation (PAF) is also a relatively common form of tachycardia in these patients. The mechanisms of PAF in patients with WPW syndrome are not completely understood. Previous studies have mainly focused on the role of accessory pathways in the development of PAF. However, up to 24% of patients still experience PAF after successful ablation of accessory pathways by surgical incision or radiofrequency catheter ablation techniques. We hypothesized that there are two primary mechanisms involved in the pathogenesis of PAF in patients with WPW syndrome. One is related to the accessory pathways that predispose the atria to fibrillation; the other is increased atrial vulnerability that is independent of the accessory pathways. Clarification of these mechanisms is critical in developing more effective means for the prevention or treatment of PAF in patients with WPW syndrome.

Atrial Fibrillation↗

PubMed2006

B-type natriuretic peptide levels in patients with paroxysmal lone atrial fibrillation.

To investigate the levels of B-type natriuretic peptide (BNP) in patients with atrial fibrillation (AF) but without structural heart disease, we measured plasma BNP concentration in 61 consecutive AF patients and in 61 age- and sex-matched healthy subjects. Plasma BNP concentration in the AF group was significantly higher than in the control group (121+/-32 vs 41+/-12 pg/ml, P<0.001). Logistic regression analysis showed that age (r=0.66, P<0.001), left atrial diameter (r=0.59, P<0.01), and a history of AF (r=0.72, P<0.001) were independent predictors of elevated BNP. We concluded that BNP was elevated in patients with paroxysmal lone AF. The clinical significance of BNP elevation in these patients requires further investigation.

Adult↗

PubMed2006

Prolonged ventricular action potential duration due to nitric oxide release.

BACKGROUND: Our previous study has demonstrated that increased intracoronary perfusion leads to a flow-dependent inversion of T waves on body surface ECG. However, whether increased coronary flow influences ventricular action potential duration measured directly from myocardium is unknown. METHODS: In six pentobarbital-anesthetized sheep, fresh arterial blood was injected into the left circumflex coronary (LCX) artery at a rate of 6 and 10 mL/min, respectively, in the presence of normal coronary flow. Activation-recovery interval (ARI), an estimate of ventricular action potential duration, was measured from epicardial ECGs acquired from the LCX territory. RESULTS: The intracoronary injection prolonged ARI by an average of 21 +/- 9 and 33 +/- 14 msec, respectively. After pre-treatment with nitro-l-arginine, a nitric oxide synthase inhibitor, intracoronary injection at the rate of 6 and 10 mL/min lead to an ARI increase of 3 +/- 2 msec (p >0.05) and 11 +/- 6 msec (p <0.05) respectively. CONCLUSIONS: An increase in coronary flow prolongs ventricular action potential duration in the intact sheep heart. Nitric oxide mediates the injection-induced increase in action potential duration.

Animals↗

PubMed2006

Catheter ablation of atrial fibrillation originating from superior vena cava.

Atrial fibrillation originating from rapid firing foci in the superior vena cava is rare. Its electrophysiological features and catheter ablation techniques are described in this report. A decapolar catheter was positioned in the superior vena cava to map the origin of the atrial fibrillation in a 39-year-old female patient who had a 3-year history of symptomatic atrial tachycardia and fibrillation. Intracardiac mapping showed rapid firing foci in the anterior wall of the superior vena cava (SVC), 2.0 cm above the SVC-right atrium junction. During tachycardia, the focal electrogram from SVC was 55 msec earlier than the P waves on body surface ECG. Radiofrequency catheter ablation successfully abolished SVC potentials, resulting in a SVC-atrium conduction block. There was no recurrence of atrial arrhythmia after a 14-month follow-up. Rapid activities from the muscle sleeves in the SVC may cause atrial fibrillation. Such a focal atrial fibrillation can be eliminated by isolating the arrhythmogenic SVC with radiofrequency catheter ablation.

Adult↗

PubMed2006

Prognostic value of B-type natriuretic peptide in patients with acute coronary syndromes.

BACKGROUND: B-type natriuretic peptide (BNP) is released from the cardiac ventricles in response to increased wall tension in patients with heart failure. The significance of blood BNP in predicting cardiac death in patients with acute coronary syndromes (ACS) in Chinese patients is yet to be established. METHODS: Blood BNP concentration was measured in 106 ACS patients 1-3 days after onset of ischemic symptoms. Patients were followed-up for 6 months on mortality and other cardiovascular events. RESULTS: During the follow-up, cardiac death occurred in 13 patients (non-survival group). Another 12 patients were hospitalized due to recurrence of ACS or heart failure. The mean blood BNP concentration in the non-survival group was significantly higher than that of the survival group (median 1132 vs. 116 ng/L, p <0.001). Multivariate logistic regression analysis incorporating age, gender, history of hypertension, diabetes, left ventricular ejection fraction, troponin I and therapeutic regimens indicated that BNP was an independent predictor of cardiac death in these patients (odds ratio = 21.19, 95% confidence interval 4.53-99.06, p <0.001). CONCLUSIONS: BNP is a useful parameter in predicting cardiac death in Chinese patients with ACS.

Acute Disease↗

PubMed2006

Blood pressure control in patients with hypertension: a community-based study.

The objective of own study was to investigate the quality of hypertension management in a rural Chinese population. A prospective cross-sectional study was conducted in 922 hypertensive patients in a regional community in southern China. The average systolic (SBP) and diastolic blood pressure (DBP) was 167.8 +/- 22.5 mmHg and 94.3 +/- 14.2 mmHg respectively. A total of 823 patients (89.3%) patients had a SBP of greater than or equal to 140 mmHg, and 596 (64.6%) had a DBP of greater than or equal to 90 mmHg. Fully 568 patients (69.7%) were treated with one or two antihypertensive drugs, mostly with calcium channel blockers. In patients treated with antihypertensive drugs, the average SBP and DBP were 170.3 +/- 23.1 mmHg and 96.2 +/- 14.8 mmHg, respectively. Blood pressure was poorly controlled in these hypertensive patients. Further studies are required to identify the barriers to the effective management of uncontrolled hypertension in a rural setting.

Aged↗

PubMed2006

Brief airway occlusion produces prolonged reflex inhibition of inspiratory muscles in obstructive sleep apnea.

STUDY OBJECTIVES: The human inspiratory muscles respond to a brief occlusion of the upper airway during inspiration with a profound short-latency reflex inhibition. This inhibition contrasts with the excitatory stretch reflex of limb muscles and may protect the airway from aspiration. It was postulated that this reflex would be altered in subjects with obstructive sleep apnea (OSA) who have repetitive upper airway occlusion. DESIGN: Subjects underwent overnight polysomnography, as well as muscle reflex studies. For the reflex studies (performed during wakefulness), occlusions lasting 250 milliseconds were delivered during inspiration. Surface electromyogram was recorded over the scalenes, parasternal intercostals, and chest wall (overlying diaphragm). SETTING: Research and sleep laboratories. PARTICIPANTS: Nineteen subjects with untreated OSA (9 moderate and 10 severe) and 9 healthy control subjects. MEASUREMENTS AND RESULTS: In the subjects with severe OSA, the duration of the inhibition was prolonged by at least 25% compared with control subjects. The peak of the inhibitory response for scalenes occurred significantly later for subjects with severe OSA than for control subjects (by 76 +/- 5 ms vs 60 +/- 3 ms [mean +/- SEM], respectively). Onset latencies of the later excitatory response were delayed for scalenes, parasternal intercostals, and chest wall recordings (eg, scalenes: 105 +/- 9 ms for subjects with severe OSA vs 83 +/- 5 ms for control subjects). CONCLUSIONS: The latency of peak inhibition and duration of inhibition were positively correlated with the respiratory disturbance index for all muscle groups. These changes may reflect adaptation in central respiratory paths due to repetitive loading during sleep.

Adult↗

PubMed2005

Surgical left cardiac sympathetic denervation for long QT syndrome: effects on QT interval and heart rate.

The primary aim of the present study was to investigate the short-term effects of surgical left cardiac sympathetic denervation (LCSD) on the QT interval and heart rate in patients with congenital long QT syndrome (LQTS). Left cardiac sympathetic denervation was performed in five LQTS patients who had a history of syncope. The patients' 12-lead and 24-h Holter monitoring ECG was recorded 24 h before and 24 h after LCSD. Treadmill exercise tests were also performed before and 6 days after surgery to assess changes in heart rate and the QT interval after surgery. Left cardiac sympathetic denervation was successful in all patients. The mean value of the corrected QT interval (QTc) in the five patients decreased from 0.59+/-0.05 to 0.48+/-0.04 s (P=0.006) immediately after the procedure and remained short (0.47+/-0.04, P<0.05) after a 21-month follow-up. The mean value of QTc on the 24-h Holter monitoring ECG also decreased in all patients (0.67+/-0.07 vs 0.60+/-0.05 s, P<0.01). The mean, maximum, and minimum heart rate on the 24-h ECG remained unchanged (P>0.05). The maximum heart rate during the exercise tests decreased from 162+/-4 beats/min before surgery to 129+/-10 beats/min (P<0.01). The exercise-induced increase in QTc remained unchanged after the surgery (P>0.05). Although four of the five patients were syncope-free until 21 months postoperatively, the remaining patient had a recurrence of syncope, requiring an increased dose of beta blocker. These findings indicate that LCSD shortens QTc and diminishes the exercise-induced increase in heart rate whereas the resting heart rate and exercise-induced increase in QTc remain unchanged. These results may have implications for the effectiveness and limitations of LCSD.

Adolescent↗

PubMed2005

Bedside tests of B-type natriuretic peptide in the diagnosis of left ventricular diastolic dysfunction in hypertensive patients.

AIMS: To investigate the value of B-type natriuretic peptide (BNP) in diagnosing left ventricular diastolic dysfunction in patients with hypertension. METHODS: The left ventricular diastolic function and plasma BNP levels were assessed prospectively in 135 hypertensive patients. RESULTS: The plasma BNP in patients with (n=61) and without (n=74) diastolic dysfunction was 122+/-105 and 18+/-16 pg/ml, respectively (p<0.001). Increased BNP levels were associated with systolic blood pressure (p<0.05), left ventricular mass index (p<0.001), the E/A ratio of transmitral flow (p<0.01) and the isovolumic relaxation time (p<0.01). A receiver-operator characteristic curve showing the sensitivity and specificity of BNP against the echocardiography diagnosis of diastolic dysfunction revealed an area under the curve (accuracy) of 0.904 (p<0.01). Using a cut-off value of >40 pg/ml, the sensitivity and specificity of plasma BNP in diagnosing left ventricular diastolic dysfunction were 79% and 92%, respectively. CONCLUSIONS: The plasma BNP levels in patients with hypertension are closely related to left ventricular hypertrophy and filling impairment. Plasma BNP may be used to facilitate the diagnosis of left ventricular diastolic dysfunction.

Adult↗

PubMed2005

Digoxin may reduce the mortality rates in patients with congestive heart failure.

Digoxin has been used to treat congestive heart failure (CHF) for more than two centuries. It's clinical efficacy, however, has been under question in recent years because recent clinical trials showed that digoxin therapy in CHF patients was associated with no beneficial effects in mortality, but only a modest reduction in clinical symptoms and the frequency of heart failure related hospitalisation. Digoxin's effect on mortality seems closely related to its serum concentrations; high serum concentrations (e.g. >or=1.2 ng/ml) have been found to increase the risk of all-cause mortality in heart failure patients. Digoxin-associated risk in mortality may be due to an increases in myocardial oxygen consumption and arrhythmogenesis at higher serum concentrations. We hypothesized that the serum concentration of digoxin is a major determinant factor of its efficacy on mortality rates in patients with congestive heart failure. The maintenance of digoxin's serum concentration at the lower end of the reference range, i.e., between 0.5 and 0.8 ng/ml, may reduce mortality rates as well as improve clinical symptoms.

Cardiotonic Agents↗

PubMed2005

Effect of radiofrequency catheter ablation on plasma B-type natriuretic peptide.

The study was designed to investigate the impact of radiofrequency catheter ablation on the plasma level of B-type natriuretic peptide (BNP). In 36 patients who underwent catheter ablation of paroxysmal supraventricular tachycardia, the plasma level of BNP was analyzed before and after the ablation procedures. The plasma BNP at baseline, 30 minutes after the ablation, 3 and 24 hours after the ablation was 12.78 +/- 2.47, 18.45 +/- 4.02 (P = 0.446), 43.54 +/- 8.12 (P = 0.0001), and 17.88 +/- 4.71 (P = 0.493) pg/mL, respectively. Plasma troponin I was also increased 3 and 24 hours after the ablation (n = 10, P < 0.05). Multivariate regression analysis showed a significant correlation between the levels of BNP 3 hours after ablation and the preablation BNP and the total radiofrequency energy used for the ablation. We conclude that radiofrequency catheter ablation of supraventricular tachycardia increases the plasma level of BNP. The clinical significance of the ablation-induced increase in BNP needs to be further investigated.

Adolescent↗

PubMed2005

Plasma BNP levels are determined by the severity of left ventricular systolic dysfunction but not the types of underlying heart disease.

OBJECTIVES: The primary aim of the study was to investigate whether there is a difference in plasma B-type natriuretic peptide (BNP) levels among the left ventricular systolic dysfunction caused by different types of heart disease. METHODS AND RESULTS: Plasma BNP was measured in patients with left ventricular systolic dysfunction as a result of mitral valve regurgitation (n=26), hypertension (n=36), coronary heart disease (n=37) and dilated cardiomyopathy (n=32). The left ventricular end-diastolic diameter and ejection fraction were assessed with echocardiography. The valvular heart disease group had more women and was younger (p < 0.05). There was no significant difference in the New York Heart Association functional class, left ventricular end-diastolic diameter and ejection fraction among the four groups (p < 0.05). The average plasma BNP was also similar among the four groups of patients. In each group, a significant correlation between the levels of BNP and the left ventricular end-diastolic diameter or ejection fraction was identified (p < 0.001). CONCLUSION: Plasma BNP concentrations during left ventricular systolic dysfunction are associated with left ventricular diameter and function, but they are not determined by the causes of the heart failure.

Adult↗

PubMed2005

The antimicrobial effect of nitric oxide on the bacteria that cause nosocomial pneumonia in mechanically ventilated patients in the intensive care unit.

BACKGROUND: Nosocomial pneumonia is the second most frequent nosocomial infection and the leading cause of death from hospital-acquired infection. Endogenously produced nitric oxide is an important component of the body's natural defense mechanism. Recent studies have demonstrated that exogenous gaseous nitric oxide (gNO) is bactericidal and that inhaled gNO is beneficial to bacterial clearance. OBJECTIVE: Determine the antimicrobial effect of exogenous gNO in vitro against organisms from culture collections and pathogens derived from tracheal aspirates of mechanically ventilated patients with pneumonia in an intensive care unit. METHODS: Using bacterial isolates in pure culture, a 0.5 McFarland standard (10(8) colony-forming-units [cfu] per mL) was prepared and further diluted to 1:1,000 with saline, to 10(5) cfu/mL. For each isolate tested, 3 mL was pipetted into each well of a 6-well plate, and placed in a specially designed incubator with compartments for both a treatment arm and a control arm. Both chambers received a continuous flow of heated, humidified gas. The treatment chamber had 200 ppm of gNO in the gas flow, which is higher than the clinically accepted concentration for gNO. Samples were drawn off at time intervals, plated onto Columbia agar base with 5% sheep blood, and placed in a traditional incubator at 35 degrees C for a minimum of 24 h. All tests were performed in duplicate. The colony-forming units were visually counted to determine percentage kill. RESULTS: There was total kill (100% of all colony-forming units) of each bacterial strain subjected to the test conditions at between 2 and 6 h of exposure to 200 ppm gNO. CONCLUSION: gNO is bactericidal against various strains of bacteria suspended in saline, including both Gram-positive and Gram-negative organisms, and those that commonly cause nosocomial pneumonia in mechanically ventilated patients. Future work should focus on developing strategies that maximize the antimicrobial effect while minimizing the effect of these same interventions on host cells.

Administration, Inhalation↗