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Biomedical subjects

V Tsang

Publications and source records attributed to V Tsang.

At least 19 recordsLinked to original sources
PubMed2005

Sero-prevalence of Taenia solium cysticercosis and Taenia solium taeniasis in California, USA.

OBJECTIVES: Taenia solium Cysticercosis is a leading cause of epilepsy and neurological disability in the developing world. It is caused by ingestion of the eggs of the tapeworm, T. solium Taeniasis. The prevalence of either T. solium Cysticercosis or T. solium Taeniasis in the United States in populations at risk is poorly understood. The primary objectives of this study are to perform the first study of the sero-prevalence of T. solium Cysticercosis and T. solium Taeniasis in an at-risk community in the USA, specifically rural Southern California; identify T. solium Taeniasis positive individuals, and treat positive individuals for the tapeworm T. solium Taeniasis. METHODS: Community based sero-prevalence study of antibodies to T. solium Cysticercosis and T. solium Taeniasis in 449 subjects living in a federally funded, predominantly Hispanic residential community; and in two migrant farm worker camps in rural Ventura County, California, USA. For this study, fingerstick blood samples were obtained. Serum immunoblots for both T. solium Cysticercosis and T. solium Taeniasis were performed. RESULTS: The sero-prevalence of T. solium Cysticercosis was 1.8% and the sero-prevalence of T. solium Taeniasis by serum immunoblot was 1.1%. Taenia solium Cysticercosis and T. solium Taeniasis antibodies were not detected in children. The sero-prevalence of T. solium Taeniasis was highest in the migrant farm worker community. Handwashing frequency was correlated with T. solium Taeniasis sero-positivity. CONCLUSION: The sero-prevalence of T. solium Cysticercosis and T. solium Taeniasis in this population, as detected by serum immunoblot, approximates the prevalence in some endemic areas of Latin America. Importantly, most patients likely had prior exposure, not active infection. This study establishes for the first time, the relative sero-prevalence of T. solium Cysticercosis and T. solium Taeniasis in at-risk populations in the United States.

Adolescent↗
PubMed2004

Cardiac ECMO for biventricular hearts after paediatric open heart surgery.

OBJECTIVE: To delineate predictors of hospital survival in a large series of children with biventricular physiology supported with extracorporeal membrane oxygenation (ECMO) after open heart surgery. RESULTS: 81 children were placed on ECMO after open heart surgery. 58% (47 of 81) were transferred directly from cardiopulmonary bypass to ECMO. Hospital survival was 49% (40 of 81) but there were seven late deaths among these survivors (18%). Factors that improved the odds of survival were initiation of ECMO in theatre (64% survival (30 of 47)) rather than the cardiac intensive care unit (29% survival (10 of 34)) and initiation of ECMO for reactive pulmonary hypertension. Important adverse factors for hospital survival were serious mechanical ECMO circuit problems, renal support, residual lesions, and duration of ECMO. CONCLUSIONS: Hospital survival of children with biventricular physiology who require cardiac ECMO is similar to that found in series that include univentricular hearts, suggesting that successful cardiac ECMO is critically dependent on the identification of hearts with reversible ventricular dysfunction. In our experience of postoperative cardiac ECMO, the higher survival of patients cannulated in the operating room than in the cardiac intensive care unit is due to early effective support preventing prolonged hypoperfusion and the avoidance of a catastrophic cardiac arrest.

Cardiopulmonary Bypass↗
PubMed2002

Vacuum-assisted venous drainage in complex congenital cardiac surgery.

Here, we report on a case of temporary neurological damage following conduit replacement from the right ventricle to pulmonary artery during which vacuum-assisted venous drainage was used. We will discuss the benefits and risks of this technique with potential arterial air embolism despite the use of arterial line filters. We will also make recommendations for avoiding such complications.

Adult↗
PubMed2001

Reversible impairment of left and right ventricular systolic and diastolic function during short-lasting atrial fibrillation in patients with an implantable atrial defibrillator: a tissue Doppler imaging study.

AF with a fast ventricular response may cause ventricular mechanical impairment, though whether short-lasting AF with satisfactory rate control may affect ventricular function is unknown. This study investigated if prompt cardioversion by an implantable atrial defibrillator (IAD) may prevent left (LV) and right ventricular (RV) systolic and diastolic dysfunction. Ten patients (mean age 61 +/- 9 years, 8 men) with paroxysmal AF without structural heart disease who received an IAD were studied by echocardiography and tissue Doppler imaging (TDI) for both ventricles. Measurements were made during baseline sinus rhythm and at 1-minute, 20-minute, 4-hour, and 1-week postcardioversion of an episode of spontaneous AF. The occurrence of AF and the ventricular rate were monitored at 2-hour intervals by the device. There were 50 episodes of AF with a mean duration of 8.8 +/- 8.9 days (2 hours to 37 days). There was no difference in M-mode measured LV fractional shortening and ejection fraction between baseline sinus rhythm and after cardioversion. However, the TDI derived myocardial systolic velocity (TDI-S) was significantly lower at 1-minute postcardioversion and was normalized at 1 week in both LVs (baseline: 5.7 +/- 1.8, 1 minute: 4.2 +/- 1.0, 20 minutes: 4.3 +/- 0.9, 4 hours: 4.8 +/- 1.0, 1 week: 5.5 +/- 1.8 cm/s; P < 0.005 when comparing 1 minute and 20 minutes to baseline; P < 0.05 when comparing 4 hour to baseline) and RV (baseline: 10.4 +/- 2.1, 1 minute: 7.8 +/- 1.4, 20 minutes: 8.1 +/- 1.2, 4 hours: 9.2 +/- 1.5, 1 week: 10.0 +/- 2.0 cm/s; P < 0.005 when comparing 1 minute, 20 minutes, and 4 hours to baseline). For diastolic function, transmitral Doppler study showed a decrease in early filling velocity at 1 minute (P < 0.05) and 20 minutes (P < 0.005), which was normalized at 4 hours. There was no change in transtricuspid Doppler flow. However, TDI derived myocardial early filling velocity was decreased in the LV (baseline: 6.0 +/- 2.8, 1 minute: 5.4 +/- 2.3, 20 minutes: 5.4 +/- 2.1, 4 hours: 6.1 +/- 2.2, 1 week: 5.8 +/- 1.7 cm/s; P < 0.05 when comparing 1 minute and 20 minutes to baseline) and RV (baseline: 8.9 +/- 3.5, 1 minute: 7.9 +/- 3.3, 20 minutes: 8.1 +/- 3.3, 4 hours: 8.5 +/- 2.9, 1 week: 8.4 +/- 3.5 cm/s; P < 0.05 when comparing 1 minute to baseline). AF of a longer duration (> 48 hours) resulted in a more depressed TDI-S in LV (> 48 hours: 4.2 +/- 1.0, < or = 48 hours: 5.3 +/- 1.3 cm/s; P < 0.01). Shocks in sinus rhythm did not affect any of the above echocardiographic parameters. Therefore, despite adequate rate control, short-lasting AF impairs systolic and diastolic function in both ventricles, which improves gradually after cardioversion. Early restoration of sinus rhythm by an IAD minimizes ventricular dysfunction. TDI is a sensitive tool to assess early systolic and diastolic dysfunction.

Atrial Fibrillation↗
PubMed2000

Efficacy and tolerability of continuous overdrive atrial pacing in atrial fibrillation.

Overdrive right atrial pacing has been used to prevent atrial fibrillation, but its efficacy in atrial fibrillation prevention and the patient tolerability and quality of life during high rate pacing remain uncertain. The objective of this study was to test the effects of a consistent atrial pacing algorithm that automatically paced the atrium at 30 ms shorter than the sinus P-P interval for atrial fibrillation prevention. Fifteen patients with sick sinus syndrome implanted with a Thera DR (model 7940 or 7960, Medtronic Inc.) were randomly programmed to rate adaptive dual chamber pacing (DDDR) or DDDR + consistent atrial pacing mode, each for an 8-week study period. The efficacy of consistent atrial pacing was assessed by the number of automatic mode switching and the number of premature atrial complexes. Symptoms and quality of life were assessed by the SF-36 quality of life questionnaire and an atrial fibrillation symptom checklist. The percentage of atrial pacing increased from 57 +/- 32% to 86 +/- 28%. Overall, there was no significant difference in the number of automatic mode switching episodes between DDDR and DDDR + consistent atrial pacing (47 +/- 90 vs 42 +/- 87, P > 0.05), but a significant reduction in premature atrial complexes by 74.7% (P < 0.001). There was no undue increase in atrial rate by the DDDR + consistent atrial pacing mode versus DDDR (63 +/- 13 vs 70 +/- 7 bpm). There was no significant difference in quality of life scores and symptom severity on frequency between the two modes of pacing, but a trend towards a lower frequency of symptoms in the DDDR + consistent atrial pacing mode compared with baseline (29.5 +/- 10.2 vs 25.1 +/- 9.7, P = 0.07). An algorithm that provides consistent atrial overdrive pacing can suppress atrial fibrillation triggering premature atrial complexes without the need to increase the overall atrial rate compared with conventional pacing. The algorithm appears to be well-tolerated, but further studies are needed to address the clinical impact of this atrial fibrillation prevention algorithm.

Aged↗
PubMed2000

Initial clinical experience with a new self-retaining left ventricular lead for permanent left ventricular pacing.

This study evaluated the performance of a new lead for permanent left ventricular (LV) pacing via the coronary sinus (CS) in four men and nine women (mean age = 71 +/- 13 years) with sick sinus syndrome. It consists of a 75-cm-long, 4.8-Fr, unipolar ventricular lead with a distal portion preshaped in an S curve to provide steerability and stability within the CS. Its efficacy and stability for permanent LV pacing were tested at implant, predischarge, and at 1, 3 and 6 months of follow-up. The lead was successfully implanted in 11/13 patients (85%) within a mean fluoroscopy time of 35 +/- 22 minutes. The final positions of the electrodes at the tip of the lead within venous tributaries of the CS were: (1) anterior (n = 2, 18%); (2) posterolateral (n = 5, 45%); and (3) the lateral (n = 4, 36%). Unsuccessful implants were due to unstable lead position (n = 1), or high pacing threshold (n = 1). There was no postprocedural lead dislodgment or significant changes in the R wave amplitude, LV pacing threshold and lead impedance up to 6 months of follow-up. In summary, this initial experience suggests that this new lead offers safe and reliable permanent LV pacing via the CS in the majority of patients and may be used in isolation or in conjunction with right ventricular pacing for biventricular synchronization.

Aged↗
PubMed2000

Mitral valve replacement in children: mortality, morbidity, and haemodynamic status up to medium term follow up.

OBJECTIVE: To investigate the outcome of mechanical mitral valve replacement in children after up to 11 years of follow up. DESIGN: Retrospective analysis of case records. Operative survivors underwent echocardiographic studies to define current haemodynamic status and prosthetic valve function. SETTING: Tertiary referral centre. PATIENTS: All 54 children who underwent mitral valve replacement between January 1987 and December 1997. RESULTS: 30 day mortality was 20.3% and was associated with small valve size and supra-annular position. The actuarial freedom from the following events at five years (70% confidence interval (CI)) was: death, including 30 day mortality and transplantation, 68% (70% CI 62% to 75%); bleeding, 89% (70% CI 84% to 94%); non-structural valve dysfunction and reoperation, 92% (70% CI 87% to 97%). The incidence of endocarditis and thromboembolism was low and there was no structural valve failure. Event-free survival was 52% (70% CI 45% to 60%). Low weight, young age, and small valve size increased the chance of death or reoperation. On echocardiography, left ventricular dilatation and wall motion abnormalities were often observed. A high mean gradient over the prosthesis was associated with small valve size but not with length of follow up. CONCLUSIONS: With the use of mechanical prostheses for mitral valve replacement in children, the problem of structural valve failure is no longer an issue. However, the procedure is still associated with a high complication rate, both at surgery and during follow up, and should therefore be reserved for patients in whom valve repair is not technically feasible.

Adolescent↗
PubMed1999

A comparison in individual murine tumors of techniques for measuring oxygen levels.

PURPOSE: To investigate the relationship between different techniques for measuring oxygen levels in a murine tumor model. METHODS AND MATERIALS: Using the murine fibrosarcoma line KHT-C, five techniques of measuring oxygen levels-the Eppendorf pO2 Histograph, EF5 binding, the comet assay, a paired survival assay, and an in vivo growth delay assay-were assessed. In these experiments, three or more techniques were applied in different combinations to measure the oxygen levels in individual tumors. RESULTS: Statistically significant correlations were observed between the hypoxic proportions calculated from the paired survival assay with those from EF5 binding. The comet assay was found to have a statistically significant correlation with the paired survival analysis and the growth delay analysis. No statistically significant correlation was found between the Eppendorf pO2 Histograph measurements and those from the other techniques, although there were weak correlations with the paired survival assay and EF5 binding. For technical reasons, a comparison was not made between EF5 binding and the growth delay assay. CONCLUSIONS: The correlations found between EF5 binding and the comet assay with the radiobiological assays suggest that these techniques have potential for predicting outcome following radiation treatment. The lack of correlation seen between the pO2 Histograph data and the radiobiological assays is in contrast to results from early clinical trials.

Animals↗
PubMed1999

Relation between direct detection of Chlamydia pneumoniae DNA in human coronary arteries at postmortem examination and histological severity (Stary grading) of associated atherosclerotic plaque.

BACKGROUND: Numerous studies have suggested a link between Chlamydia pneumoniae infection, atherosclerosis, and coronary artery disease. However, it is still unclear whether C pneumoniae plays a causal role in the pathogenesis of these conditions. Accordingly, we have performed a systematic dissection of the 3 coronary arteries on 33 postmortem subjects and studied the relationship in individual artery segments between the presence of C pneumoniae DNA and the severity of associated atherosclerosis. METHODS AND RESULTS: The prevalence of C pneumoniae DNA in arterial segments was determined by polymerase chain reaction (PCR) after controlling for the presence of PCR inhibitors. Atherosclerosis in each arterial segment was graded histologically with the Stary classification. C pneumoniae was detected by PCR in 78.8% of subjects, but there was no association between the presence of this DNA and cause of death or grade of atherosclerosis. When paired mild and severe atherosclerotic lesions within subjects were compared, mild lesions were as likely to be positive for C pneumoniae as severe lesions. CONCLUSIONS: This study demonstrates that C pneumoniae can frequently be detected in atheromatous plaques in coronary arteries. However, its distribution did not correlate with severity or extent of disease.

Aged↗
PubMed1999

The prevalence of Chlamydia pneumoniae in atherosclerotic and nonatherosclerotic blood vessels of patients attending for redo and first time coronary artery bypass graft surgery.

OBJECTIVES: To determine if Chlamydia pneumoniae (C. pneumoniae) is more prevalent in atherosclerotic compared with normal blood vessels of patients requiring redo and first time coronary artery bypass graft surgery (CABG). BACKGROUND: Serological and pathological studies have associated atherosclerosis with C. pneumoniae infection. As atherosclerosis is one of the causes of graft failure following CABG, then it may be expected that the prevalence of the organism in failed grafts and diseased native vessels should be greater than in the new grafts. METHODS: Endarterectomy specimens and failed and new grafts were collected from 49 patients with late graft failure. Endarterectomy specimens and new grafts were also collected from nine patients having first time CABG. The presence of C. pneumoniae DNA was then checked for using a nested polymerase chain reaction. RESULTS: The prevalence of C. pneumoniae DNA in failed venous grafts (38.2%) was similar to that in endarterectomy specimens from native coronary arteries (38.5%) and greater than that in new saphenous vein grafts (11.8%). However, it was similar to that in new internal mammary artery grafts (30.0%). Also, the interval between surgery in redo patients was the same regardless of whether C. pneumoniae was present or not. CONCLUSIONS: Cross sectional studies cannot determine whether C. pneumoniae is a cause of atherosclerosis since they do not show whether infection precedes or follows its development. However, our results suggest that the organism is not an important factor in graft failure or atherosclerosis.

Aged↗
PubMed1998

New combination of the old drugs for elderly patients with small-cell lung cancer: a phase II study of the PAVE regimen.

PURPOSE: A regimen of cisplatin, doxorubicin, vincristine, and etoposide (PAVE) was designed for patients with small-cell lung cancer (SCLC) who were older than 65 years, with the following objectives compared with standard chemotherapy regimens: maintain efficacy, diminish toxicity, enhance compliance, and improve chemotherapy administration convenience at an acceptable cost. PATIENTS AND METHODS: The PAVE regimen consisted of cisplatin 30 mg/m2 intravenously (i.v.) day 1; doxorubicin 40 mg/m2 i.v. day 1; vincristine 1.0 mg/m2 i.v. day 1; and etoposide 100 mg/m2 i.v. day 1 and orally days 3 and 5. Cycles were repeated every 3 weeks for four cycles. Patients with limited-stage disease and selected patients with extensive-stage disease received thoracic irradiation delivered concurrently with etoposide-cisplatin (EP) at the time of the second chemotherapy cycle. RESULTS: Sixty-six eligible patients were treated, which included 25 patients with limited-stage disease and 41 patients with extensive-stage disease. Median survival was 70 weeks and 5-year survival was 25% for limited-stage disease. Median survival was 46 weeks for extensive-stage disease. Only one treatment-related death occurred and severe toxicity was infrequent. The median delivered dose-intensity was according to protocol and the mean delivered total dose was 80% of intended. CONCLUSION: The treatment outcome achieved with PAVE in a phase II study of elderly patients compared favorably with published results of standard regimens in patient populations with better prognostic factors. Because the PAVE regimen can be delivered with good compliance, has acceptable toxicity, and is associated with logistic advantages compared with standard regimens, this protocol is suitable for further investigative trials in elderly patients with SCLC.

Age Factors↗
PubMed1998

Carotid artery stenosis in patients who have undergone radiation therapy for head and neck malignancy.

Although it is established that small and medium sized arteries undergo extensive radiation damage, the effect on large vessels such as the carotid arteries is less well understood. We sought to determine if an increased severity of carotid artery stenosis is present in patients who have undergone radiotherapy for head and neck tumours. 45 patients aged 43-90 years (average 67) with head and neck malignancies treated with radiotherapy underwent colour Doppler ultrasonographic scanning of the carotid arteries. These patients were compared with a population of asymptomatic historical controls. 60% of patients demonstrated stenosis ranging from 21 to 86%. 38% of patients demonstrated a stenosis greater than or equal to 50%. Carotid artery stenosis appears to be increased in patients who have previously undergone treatment with radiotherapy to the head and neck regions compared with controls (p < 0.001). These findings suggest that radiation has an adverse effect on large vessels. Colour Doppler follow-up may be indicated for patients receiving head and neck radiation therapy.

Adult↗
PubMed1997

Clinical use of asymmetric collimators.

PURPOSE: To illustrate some of the radiation treatment techniques with asymmetric collimators in one field dimension. METHODS AND MATERIALS: Treatment planning for various sites is done with an in-house developed treatment planning system. Dose distributions in the central plane are illustrated. RESULTS: The use of asymmetric collimation, in addition to being a replacement for cerrobend and lead blocks, can facilitate treatment setup with boost fields and with half-beam asymmetric fields as in matching two adjacent fields, in avoiding nearby critical organ or tissue, and in tangential breast treatment. The use of asymmetric collimators would alter the dose distribution across the radiation field and should be accounted for during treatment planning. In conjunction with arc rotation or multiple asymmetric fields, two-dimensional conformal radiotherapy is possible. CONCLUSION: The full potential of asymmetric collimation requires the use of a proper treatment planning algorithm. Some of the treatment techniques with asymmetric collimation in one field dimension are shown here.

Breast Neoplasms↗
PubMed1997

[Prevalence of neurocysticercosis in individuals affected by epilepsy].

INTRODUCTION: In this investigations, was carried out a neurocysticercosis (NC) prevalence study during seven months in the Instituto Neurológico de Antioquia with the purpose of known neurocysticercosis frequency as cause of epilepsy in patients older than ten years that we attended in our institute. MATERIAL AND METHODS: Computerized tomographies (CT) were made to 503 patients, with epilepsy, 24.7% of them were CT positive for NC. Cysticercosis enzyme linked immunoelectrotransfer blot (EITB) and enzyme linked immunoabsorbent assay (ELISA) test were made to 178 patients, 19.6% were EITB positive for NC and 5% ELISA positive for NC. Results. From this result it is possible to infer that about 8% of the 503 patients with epilepsy had cysticercosis, according to EITB that is the golden assay for NC. The CT and ELISA test had 94.3% and 27.7% sensitivity, respectively, according to EITB. The specificity of the CT for NC was 49.2% and specificity for ELISA test was 100% as compared to EITB. The multivariate analysis with logistic regression allowed to establish association of positive EITB with factors such as male sex, eating pork, headaches and multiple lesions in CT. CONCLUSIONS: Prevention and education actions are necessary for the interruption of the neurocysticercosis transmission chain in order to diminish the high prevalence of epilepsy in the country and its complication and consequences.

Adult↗