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Biomedical subjects

C M Yu

Publications and source records attributed to C M Yu.

At least 19 recordsLinked to original sources
PubMed2006

Use of silicone stents for the management of post-tuberculosis tracheobronchial stenosis.

The role of bronchoscopic management in post-tuberculosis tracheobronchial stenosis is not well defined. To investigate the role of bronchoscopic intervention, including silicone stenting, in the management of post-tuberculosis tracheobronchial stenosis, the current retrospective study was conducted at a tertiary referral hospital. Under rigid bronchoscopy, 80 patients underwent ballooning, neodymium-yttrium aluminium garnet laser resection and/or bougienation as first-line methods of airway dilatation between January 2000 and December 2003 inclusive, and were followed for a median of 41 months. Silicone stents were required in 75 out of 80 (94%) patients to maintain airway patency. Bronchoscopic intervention provided immediate symptomatic relief and improved lung function in 88% of the patients. After airway stabilisation, stents were removed successfully in 49 out of 75 (65%) patients at a median of 14 months post-insertion. Three patients out of 75 (4%) eventually underwent surgical management. Acute complications included: excessive bleeding (n = 1); pneumothorax (n = 5); and pneumomediastinum without mortality (n = 2). Stent-related late complications, such as migration (51%), granuloma formation (49%), mucostasis (19%) and re-stenosis (40%), were controllable during a median follow-up of 41 months. In conclusion, bronchoscopic intervention, including silicone stenting, could be a useful and safe method for treating post-tuberculosis tracheobronchial stenosis.

Adolescent↗
PubMed2006

Left ventricular diastolic function during normal pregnancy: assessment by spectral tissue Doppler imaging.

OBJECTIVE: Tissue Doppler imaging (TDI) is an echocardiographic technique for assessing the diastolic function that is relatively independent of preload. Since loading conditions change significantly during pregnancy, a load-independent technique will give a more accurate assessment of diastolic function in pregnant women. The aim of this study was to evaluate maternal diastolic function using tissue Doppler imaging. METHODS: This was a prospective observational study on 35 healthy pregnant women. M-mode, transmitral inflow (peak transmitral flow velocities during early diastole (E wave) and atrial contraction (A wave)) and TDI studies (peak myocardial velocities during early diastole (Em wave), during atrial contraction (Am wave) and peak systole in ejection phase (Sm)) were performed in each trimester and postpartum. The differences in variables between trimesters were analyzed. RESULTS: The peak transmitral inflow velocity during early diastole (E wave) was significantly decreased during the third trimester and postpartum. The peak flow velocity during atrial contraction (A wave) was increased in the second trimester, but decreased again in the third trimester and postpartum period. As a result, the E/A ratio progressively reduced as pregnancy advanced. TDI showed that peak myocardial velocities during early diastole (Em) tended to increase during the second trimester, and then decreased significantly in the third trimester or postpartum period. The peak myocardial velocities during atrial contraction (Am) increased significantly with advancing gestational age. As a consequence, both Em/Am and E/Em ratios decreased significantly throughout pregnancy. CONCLUSIONS: This study demonstrates the changes in myocardial relaxation velocity throughout pregnancy. Because of its advantage of being relatively load-independent, TDI may be a useful non-invasive technique for monitoring maternal cardiac function in high-risk pregnancies to detect the early signs of cardiac failure and to prevent further deterioration with prompt interventions.

Diastole↗
PubMed2006

A review of the management of patients after percutaneous coronary intervention.

The exponential increase in the numbers of percutaneous coronary interventions (PCIs) has led to many clinicians having to care for post-PCI patients. We review the management of early problems seen in post-PCI patients, such as vascular access site complications, contrast nephropathy, drug-induced thrombocytopaenia and chest pain. The management of possible restenosis and the use of stress testing are discussed. The complications from dual antiplatelet therapy are addressed. The prognosis of the post-PCI patient, the implications of co-existent heart failure and the newer technologies of implantable defibrillator and cardiac resynchronisation therapy are reviewed. We conclude by emphasising the importance of secondary prevention by risk factor modification as well as the communication between the clinician and the cardiologist.

Angioplasty, Balloon, Coronary↗
PubMed2006

Pulmonary TB and NTM lung disease: comparison of characteristics in patients with AFB smear-positive sputum.

OBJECTIVE: To compare the clinical and radiographic features of pulmonary tuberculosis (PTB) and non-tuberculous mycobacteria (NTM) lung disease in patients with acid-fast bacilli (AFB) positive sputum specimens. DESIGN: The initial clinical and radiographic features of 229 PTB patients were compared with those of 70 patients with NTM lung disease. The most commonly involved organisms in the NTM lung disease cases were Mycobacterium avium complex (n = 38, 54%) and M. abscessus (n = 26, 37%). RESULTS: Clinical and radiographic findings that were more common in patients with NTM lung disease than in PTB patients were: older age (P < 0.001), non-smoker (P < 0.001), history of previous TB treatment (P < 0.001), absence of pleural effusion (P = 0.017), involvement of middle and/or lower lung zones (P = 0.007), and bilateral disease (P = 0.005). Multivariate analysis showed that older age (> or = 40 years), non-smoker, previous TB treatment, absence of pleural effusion and involvement of middle and/or lower lung zones were significant independent predictors for NTM lung disease. CONCLUSIONS: There is considerable overlap in the clinical and radiographic appearances of PTB and NTM lung disease. The isolation and identification of causative organisms are mandatory for a correct diagnosis in patients with AFB-positive sputum specimens.

Coloring Agents↗
PubMed2005

Enhanced fusion of myoblasts with myofibers for efficient gene delivery induced by a partially purified protein fraction from rat muscle extract.

The biggest challenge to gene therapy is how to efficiently deliver the desired therapeutic gene into a sufficient number of recipient cells to achieve significant clinical efficacy. Here, we identified a partially purified extract from rat muscle probably containing myoblast specific fusion factor(s) (MSF), which significantly enhanced fusion of donor myoblast with host muscle fibers. Once incorporated, the introduced genetic construct could instruct the machinery of the hybrid cells to express the desired protein(s). Rat satellite cells containing a plasmid carrying a marker bone morphogenetic protein-4 (BMP-4) coding sequence were used as foreign gene delivery vehicle. BrdU labeling of the MSF-pretreated satellite cells allowed tracing the fate of the genetically modified satellite cells in the host muscles. Immunohistochemistry using anti-BMP-4 antibody demonstrated the translation of the introduced gene construct. It was demonstrated that in the presence of MSF, numerous BrdU positive nuclei and the expression of BMP-4 polypeptides could be observed in host hybrid fibers, while in the control group using rat serum to replace MSF containing fraction, only a few BrdU positive signals were detected. The expression of osteocalcin and the elevated alkaline phosphatase activity detected in the hybrid fibers indicated the proper folding, secretion and, post-translational modification of the expressed foreign protein. This strategy of enhanced myoblast-mediated gene transfer would break the major barrier in current practice of normal or engineered myoblast transplantation in the management of genetic muscle diseases or systemic genetic disorders.

Animals↗
PubMed2005

Do metoprolol and carvedilol have equivalent effects on diurnal heart rate in patients with chronic heart failure?

BACKGROUND: Carvedilol exerted a greater reduction in mortality than metoprolol tartrate in the Carvedilol or Metoprolol European Trial (COMET). However, it is unclear if the degree and time course of beta1-blockade during a 24-h period was similar with each agent at the doses used. Therefore we analyzed 24-h ECG Holter recordings from a study which compared the long-term clinical efficacy of metoprolol tartrate to carvedilol in chronic heart failure patients using the same dosing regimen as in COMET. METHODS AND RESULTS: Fifty-one patients with chronic heart failure with a mean LVEF 26+/-1.8% were randomized in a double-blind fashion to receive metoprolol tartrate 50 mg bid or carvedilol 25 mg bid. 24-h ECG monitoring (Holter) was performed at baseline, 12 weeks and 1 year. Adequate quality recordings for analysis were obtained from 43 subjects at baseline, 42 at 12 weeks and 29 subjects at 1 year. Both drugs produced a fall in average 24-h heart rate from baseline at 12 weeks and at 1 year: metoprolol 88+/-3 to 71+/-2 and 69+/-3 bpm; carvedilol 83+/-3 to 70+/-2 and 70+/-3 bpm respectively (all p<0.001). The pattern of suppression of heart rate during the 24-h period was similar for both drugs. CONCLUSION: Metoprolol tartrate 50 mg bid and carvedilol 25 mg bid had similar effects on 24-h heart rate. This result suggests that the degree of beta1-blockade produced by these two drugs in these doses is comparable and the superior survival effect of carvedilol compared to metoprolol seen in COMET is likely to be due to actions of carvedilol other than beta1-blockade.

Adrenergic beta-Antagonists↗
PubMed2005

Management of diastolic heart failure--a practical review of pathophysiology and treatment trial data.

The lack of large randomised controlled trials to guide therapy in diastolic heart failure causes some difficulties for evidence-based medicine practising clinicians. Traditionally, treatments for systolic heart failure have been highjacked for diastolic heart failure without much proof of benefit. However, recent studies have began to provide some evidence base for our practice. Betablockers and angiotensin receptor antagonists have recently been shown to reduce hospitalisation in large randomised controlled trials. Diuretic based antihypertensive regimes have been shown to reduce heart failure by 50%. Left ventricular hypertrophy regression is likely to be a good surrogate endpoint for diastolic heart failure, although definitive proof for this is not yet available. Angiotensin receptor antagonists, ACEI, calcium channel blockers, diuretics and aldosterone blockers have all been shown to cause left ventricular hypertrophy regression. We recommend these drugs to achieve strict blood pressure control together with dietary and lifestyle modification for the treatment of diastolic heart failure. We emphasise the importance of rate control, as diastolic heart-failure patients tolerate tachycardia poorly. We further argue that the pathophysiology of diastolic heart failure is part of systolic heart failure and the two should not be thought of as separate entities. Therefore, our traditional practice of using systolic heart failure treatments for diastolic heart failure is theoretically sound and should not cause us undue anxiety.

Adrenergic beta-Antagonists↗
PubMed2004

Tissue Doppler imaging for predicting outcome in patients with cardiovascular disease.

PURPOSE OF REVIEW: Tissue Doppler imaging is being increasingly used for assessing global ventricular function in systole and diastole, and for quantifying regional wall motion abnormalities both in systolic heart failure with mechanical dyssynchrony and ischemic heart disease. Its use as a predictive tool is recent and the authors review publications relating to this aspect. RECENT FINDINGS: Peak early diastolic mitral annular velocity is a powerful predictor of outcome in a variety of cardiovascular conditions and adds incremental value to clinical parameters and standard mitral Doppler inflow velocities. Tissue Doppler imaging can also predict the development of hypertrophic cardiomyopathy in asymptomatic individuals carrying the genetic mutation even before the onset of overt left ventricular hypertrophy. In addition, the standard deviation of the time to peak systolic velocity is a good marker of mechanical asynchrony and can predict reverse remodeling. It may also be useful in identifying individuals with ischemic heart disease and regional wall motion abnormalities who have an adverse outcome. SUMMARY: Tissue Doppler imaging is a powerful new echocardiographic tool that is now becoming the standard for assessing ventricular function in a variety of situations and diseases.

Cardiac Pacing, Artificial↗
PubMed2004

Breast milk substitutes in Hong Kong.

OBJECTIVE: In 1981 the World Health Assembly (WHA) adopted the International Code of Marketing of Breast Milk Substitutes (the Code) to support breastfeeding. Despite improving trends, Hong Kong has low rates of breastfeeding compared to other developed countries. METHODS: We surveyed companies marketing breast milk substitutes in Hong Kong to determine self-reported adherence to the Code. Companies were informed that individual responses would not be published and seven of nine companies responded to the questionnaire. RESULTS: The majority of respondents promoted infant and follow-on formula in hospitals and provided free supplies of infant formula to hospitals. Follow-on formula and weaning foods were promoted in shops and to the general public and free samples were given to mothers reflecting a belief that, despite WHA resolutions, follow-on formula is not a breast milk substitute. CONCLUSIONS: Transnational companies should follow the Code and subsequent WHA resolutions equally in all countries.

Hong Kong↗
PubMed2004

Echocardiographic evaluation of cardiac dyssynchrony for predicting a favourable response to cardiac resynchronisation therapy.

Cardiac resynchronisation therapy (CRT) is an established therapy for patients with heart failure with wide QRS duration. Recent studies observed that assessment of systolic dyssynchrony is an important diagnostic tool as the treatment involves the re-coordination of regional wall contraction within the left ventricle. Therefore, the effectiveness of CRT depends heavily on whether systolic dyssynchrony is present before the treatment. Echocardiography is a useful tool for quantitative measurement of the severity of dyssynchrony in these patients before and after CRT. A number of echocardiographic tools have been developed during the past three years for such purpose, include M mode measurement of septal-to-posterior wall delay, tissue Doppler imaging for septal-to-lateral wall delay, the measurement of standard deviation of peak contraction time over 12 left ventricular segments, delayed longitudinal contraction, and potentially three dimensional echocardiography. This review discusses the potential role of various echocardiographic techniques in the assessment of systolic dyssynchrony and their clinical applications.

Cardiac Pacing, Artificial↗
PubMed2003

Consensus statement on iodine deficiency disorders in Hong Kong.

This article reviews the available data on the study of iodine deficiency disorders in Hong Kong and to discuss the approach towards preventing such disorders in Hong Kong. The importance of iodine and iodine deficiency disorders is described, and the available data on the dietary iodine intake and urinary iodine concentration in different populations of Hong Kong are summarised and discussed. Dietary iodine insufficiency among pregnant women in Hong Kong is associated with maternal goitrogenesis and hypothyroxinaemia as well as neonatal hypothyroidism. Borderline iodine deficiency exists in the expectant mothers in Hong Kong. Women of reproductive age, and pregnant and lactating women should be made aware and educated to have an adequate iodine intake, such as iodised salt, as an interim measure. A steering group involving all stakeholders should be formed to advise on the strategy of ensuring adequate iodine intake, including universal iodisation of salt in Hong Kong. Continuous surveillance of iodine status in the Hong Kong population is necessary.

Deficiency Diseases↗
PubMed2001

Plasma nitric oxide level in heart failure secondary to left ventricular diastolic dysfunction.

Nitric oxide (NO) is a free radical that is elevated in the plasma of patients with systolic heart failure. However, its relation to diastolic function is unknown. This study investigated the relation between the level of stable end-products of plasma NO (NOx level) and diastolic function in patients with heart failure. We performed echocardiographic Doppler studies in 76 patients (mean age of 66 +/- 10 years, 75% men) with congestive heart failure. Left ventricular (LV) diastolic dysfunction was classified as either a restrictive (RFP) or nonrestrictive filling pattern (non-RFP). Same day venous total nitrite plus nitrate levels were measured by chemiluminscence. Both patients with isolated diastolic heart failure (ejection fraction >50%) (77 +/- 9 micromol/L, n = 33) and systolic failure (ejection fraction < or = 50%) (115 +/- 17 micromol/L, n = 43) had significantly higher plasma NOx levels than controls (37 +/- 2 micromol/L, both p <0.001). RFP coexists mostly in patients with systolic heart failure (15 of 18), and these patients had a higher NOx level than patients with systolic failure and a non-RFP (n = 28) (163 +/- 35 vs 88 +/- 16 micromol/L, p <0.05). Patients who were not on oral nitrate drugs had insignificant lower plasma NOx levels than those on regular nitrate therapy, although it was still higher than controls. Plasma NOx level did not correlate with LV ejection fraction. Stepwise multiple regression analysis confirmed that the presence of RFP was the only independent predictor of NOx, and hence NO production. Plasma NOx level is elevated in patients with isolated diastolic heart failure. In addition, in patients with LV systolic failure, the severity of LV diastolic dysfunction determines the amount of NO production.

Aged↗
PubMed2001

Dual-site atrial pacing for atrial fibrillation in patients without bradycardia.

Atrial pacing has been shown to delay the onset of atrial fibrillation (AF) when compared with ventricular pacing in patients with sick sinus syndrome. The role for pacing in the control of AF in patients without bradycardia is uncertain. We performed a randomized, crossover, single-blinded study in 22 patients (14 women, aged 63 +/- 10 years) with paroxysmal AF refractory to treatment with oral sotalol (202 +/- 68 mg/day) and no bradycardic indication for pacing. All patients received a dual-chamber pacemaker with 2 atrial pacing leads positioned at the high right atrium and coronary sinus ostium, respectively. Patients were randomized in a crossover fashion to be paced for 12 weeks, either with high right atrial (RA) pacing at 30 beats/min ("Off") or dual-site RA pacing with an overdrive algorithm that maintained atrial pacing at a rate slightly above the sinus rate ("On"). Treatment on resulted in a significantly higher percentage of atrial pacing and a reduction in atrial ectopic frequency than the treatment off period. The time to the first clinical AF recurrence was prolonged (15 +/- 17 to 50 +/- 35 days, p = 0.006), and total AF burden was reduced (45 +/- 34% vs 22 +/- 29%, p = 0.04) in the on-treatment phase. However, there was no difference in AF checklist symptom scores or overall quality-of-life measures. Dual-site RA pacing with continued sinus overdrive prolonged the time to AF recurrence and decreased AF burden in patients with paroxysmal AF. The absence of a major impact on symptom control suggests that pacing should be used as an adjunctive therapy with other treatment modalities for AF.

Adolescent↗
PubMed2001

Effect of verapamil on prevention of atrial fibrillation in patients implanted with an implantable atrial defibrillator.

BACKGROUND: The role of verapamil in the prevention of atrial fibrillation (AF) in patients with recurrent AF is unknown. HYPOTHESIS: The aim of this study was to evaluate the effect of verapamil on the prevention of AF in patients implanted with an implantable atrial defibrillator (IAD). METHODS: The effects of verapamil (240 mg/day) on the total duration of AF, number of AF recurrences, and number of cardioversions were prospectively evaluated in a randomized, crossover fashion over an 8-week period in 11 patients (9 men, 2 women; mean age: 60 +/- 6 years) implanted with an IAD. RESULTS: Implantable atrial defibrillators successfully converted 13 of 14 (93%) spontaneous episodes of AF. There was no significant difference in the efficacy of cardioversion (86 vs. 100%, p = 0.8), the total duration of AF (173 +/- 198 vs. 270 +/- 241 h, p = 0.5), the number of AF episodes (8.5 +/- 9.0 vs. 9.3 +/- 10.2, p = 0.3), and the number of cardioversions (1.7 +/- 2.4 vs. 1.8 +/- 2.1 p = 0.7) with or without treatment with verapamil. CONCLUSIONS: The results of the present study suggest that treatment with verapamil has no significant effect on the prevention of AF in patients treated with an LAD.

Anti-Arrhythmia Agents↗