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Biomedical subjects

M S Chang

Publications and source records attributed to M S Chang.

At least 235 records · Page 13Linked to original sources
PubMed1996

Determination of a new antiulcer agent, YJA-20379-2, in human plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the determination of a new antiulcer agent, YJA-20379-2, in human plasma and urine. The sample preparation was simple: 2.5-volume of acetonitrile was added to the biological sample to deproteinize. A 50-microliter aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase employed was methanol-0.1M Sørensen phosphate buffer of pH 7.0-H2O (75:2:25, v/v/v), and was run at a flow-rate of 1.0 ml/min. The column effluent was monitored by ultraviolet detector at 295 nm. The retention time for YJA-20379-2 was approximately 7.0 min. The detection limits for YJA-20379-2 in human plasma and urine were both 100 ng/ml. The coefficients of variation of the assay (within-day and between-day) were generally low (below 9.16%) for both the human plasma and urine. No interference from endogenous substances was found.

Anti-Ulcer Agents↗
PubMed1995

Effects of pregnancy on first onset and symptoms of paroxysmal supraventricular tachycardia.

It is important for women to understand the risk of first onset and symptomatic exacerbation of paroxysmal supraventricular tachycardia (SVT) during pregnancy. Reports regarding the effects of pregnancy on first onset and symptomatic exacerbation of paroxysmal SVT have been controversial, and have not been conducted in a systematic fashion. Two hundred seven consecutive female patients diagnosed with symptomatic paroxysmal SVT were requested to respond to multiple questionnaires before electrophysiologic study and catheter ablation. A person-years data method was used to estimate risk of first onset of paroxysmal SVT during pregnancy. Exacerbation of paroxysmal SVT was assessed by a score scale including each of the following symptoms: palpitation, fatigue, rest dyspnea, effort dyspnea, dizziness, chest oppression, blurred vision, and syncope (total score change > 2 points). In the 107 patients with accessory pathway-mediated tachycardia, 7 patients had had a first onset of tachycardia during pregnancy (relative risk ratio 0.86, confidence interval 0.4 to 1.9, p = 0.35). In the 100 patients with atrioventricular nodal reentrant tachycardia, 1 patient had had the first onset of tachycardia during pregnancy (relative risk ratio 0.11, confidence interval 0.02 to 0.56, p = 0.004). Otherwise, 14 of the 63 patients (22%) with tachycardia in the pregnant and nonpregnant periods had exacerbation of symptoms during pregnancy. Thus, first onset of paroxysmal SVT during pregnancy was rare (3.9%), and pregnancy was associated with a low risk of first onset of paroxysmal SVT. However, symptoms of paroxysmal SVT were exacerbated during pregnancy in some patients.

Adolescent↗
PubMed1995

Population-based study of insulin, C-peptide, and blood pressure in Chinese with normal glucose tolerance.

Insulin resistance may play a role in the pathogenesis of essential hypertension. The purpose of the present study was to examine the relations of fasting serum insulin or C-peptide levels with hypertension and blood pressure (BP) in a stable homogeneous southern Chinese population with normal glucose tolerance. This community-based survey of adults aged > or = 30 years in Kin-Chen, Kinmen, was conducted by the Yang-Ming Crusade in 1992 and 1994. Data of fasting serum insulin and C-peptide from a total of 1,447 men and 1,800 women (mean age 46.7 years) were analyzed. Both continuous (by multiple regression) and categorical analyses (by analysis of covariance) were used. Fasting insulin concentrations (as independent variables) were significantly associated with log systolic BP (as outcome variables, coefficient = 0.000081, p = 0.0035) and log diastolic BP (as outcome variables, coefficient = 0.000098, p = 0.0006) after accounting for age, sex, body mass index, and waist-to-hip ratio. Similarly, fasting C-peptide concentrations were significantly associated with log systolic BP (coefficient = 0.023304, p = 0.0001) and log diastolic BP (coefficient = 0.032971, p = 0.0001). In categorical analyses, both fasting insulin and C-peptide concentrations were significantly different (insulin p = 0.01010, and C-peptide p = 0.0004) between hypertensive and normotensive subjects when the similar set of covariates were accounted for. In conclusion, both fasting serum insulin and C-peptide concentrations are significantly associated with BP in this homogeneous Chinese population with normal glucose tolerance.

Adult↗
PubMed1995

Recurrent tachycardia after selective ablation of slow pathway in patients with atrioventricular nodal reentrant tachycardia.

Recurrence rate of atrioventricular (AV) nodal reentrant tachycardia after successful radiofrequency ablation varies widely, and the determinants of recurrent AV nodal reentrant tachycardia remain controversial. Furthermore, true or pseudorecurrence of tachycardia after successful ablation in patients with different forms of AV nodal reentrant tachycardia has not been evaluated systematically. Three hundred sixty-two patients (161 men and 201 women [mean age 52 +/- 16 years]), including 314 patients with typical-form, 10 patients with atypical-form, 4 patients with variant-form, and 34 patients with multiple-form AV nodal reentrant tachycardias, received selective radiofrequency ablation of the anterograde and/or retrograde slow AV nodal pathway. During a mean follow-up of 27 +/- 11 months, 9 patients (2.5%) experienced recurrent AV nodal reentrant tachycardia (true recurrence, group A), and 8 (2.2%) had inappropriate sinus tachycardia or paroxysmal atrial tachyarrhythmias (pseudorecurrence, group B). Neither the true nor pseudorecurrence rate was different among the 4 different forms of tachycardia. Factors including presence of residual slow pathway conduction, a single AV nodal reentrant echo beat, absence of an accelerated junctional rhythm during successful ablation, facilitating induction of tachycardia by isoproterenol, radiofrequency pulse number, and successful ablation site were not associated with an increased risk of recurrent AV nodal reentrant tachycardia. The onset time of recurrent tachycardia was significantly late in group B patients (30 +/- 21 vs 292 +/- 240 days, p = 0.04). Thus, this study demonstrated that both true and pseudorecurrence could occur after successful ablation.

Adolescent↗
PubMed1995

Relation between diurnal variation of blood pressure and left ventricular mass in a Chinese population.

In western populations, patients with hypertension who have a nocturnal decrease in blood pressure (BP) may have less left ventricular (LV) hypertrophy and cardiovascular morbidity than those without a diurnal variation in BP. To further examine this association between nocturnal BP reduction and LV mass index, we studied 720 normotensives (< 140/90 mm Hg), 380 borderline hypertensives (140 to 159/90 to 94 mm Hg), and 582 hypertensives (> or = 160/95 mm Hg) from Taiwan and Quemoy island by using 24-hour ambulatory BP monitoring and 2-dimensional echocardiography to obtain LV mass index during a community-based cardiovascular survey. After controlling for age, sex, height, weight, daytime BP, and daytime heart rate, the nocturnal reduction of systolic BP was found to associate weakly with LV mass index, for the whole population (partial correlation coefficient = -0.06, p < 0.05), as well as for the patients with hypertension (partial correlation coefficient = -0.09, p < 0.05), but these associations were eliminated when 24-hour BP and heart rate were accounted for. The average and percent nocturnal decrease of systolic BP (mean +/- SD; mm Hg, [%]) of 3.2 +/- 5.9 (2.7 +/- 4.8%); 3.3 +/- 7.3 (2.4 +/- 5.4%); and 4.6 +/- 9.0 (3.0 +/- 6.1%) in normotensives, borderline hypertensives, and hypertensives, respectively, was smaller than that found in previous studies. Hence, in this large Chinese population, a small nocturnal BP drop was found and it was only weakly associated with LV mass index. These results emphasize the general need for ambulatory BP reference values based on internal controls.

Adult↗
PubMed1995

A population-based epidemiological study on cardiovascular risk factors in Kin-Chen, Kinmen.

We conducted a population survey of cardiovascular risk factors in Kin-Chen, Kinmen (Quemoy), an island under military control for 40 years and the focal point of confrontation between mainland China and Taiwan. During the period 1992-1994, all residents > or = 30 years of age in Kin-Chen, the largest township in Kinmen, were invited to participate. The response rate was 60.3% (3826/6346). The prevalence of hypertension (> or = 160/95 mmHg and/or under treatment) was 25.2% in men and 17.6% in women. The rate for smoking was 41.5% in men and 2.9% in women. The prevalence of diabetes was 6.7% in men and 6.4% in women. Mean values for systolic blood pressure, diastolic blood pressure, total cholesterol, triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were 135.3 mmHg, 85.5 mmHg, 5.3 mmol/l, 1.1 mmol/l, 3.5 mmol/l and 1.4 mmol/l in men; and 128.0 mmHg, 79.5 mmHg, 5.2 mmol/l, 1.0 mmol/l, 3.3 mmol/l and 1.5 mmol/l in women, respectively. The unexpectedly high prevalence of hypertension in Kin-Chen male may reflect the effect of more than 40 years of military control and discipline. The high serum cholesterol level in Kin-Chen relative to mainland China and the low triglyceride level relative to Taiwan and Beijing, suggest further study of the contributions of diet and other psychosocial or environmental factors.

Adult↗
PubMed1995

Cloning and characterization of the human megakaryocyte growth and development factor (MGDF) gene.

The megakaryocyte growth and development factor (MGDF) is a cytokine that regulates megakaryocyte development and is a ligand for the MPL receptor. In this study, we describe the genomic structure of the human MGDF gene. The MGDF gene was found to consist of seven exons and six introns spanning 8 kilobases. The protein is encoded by exons 3 through 7. The human MGDF gene has been mapped to chromosome 3q26.3. In addition to the previously described full-length cDNA, two cDNA variants were isolated from human fetal liver. Comparison of these two cDNA sequences with the genomic sequence indicates that they arise by differential splicing.

Amino Acid Sequence↗
PubMed1995

Epidemiology of hypertension in Kin-Hu, Kinmen.

Data on the prevalence and predictors of hypertension in Kinmen, an island very close to southern mainland China but under Republic of China administration, would be very helpful to understand the effect of environmental and psychosocial factors on hypertension in a specific ethnic group. In 1991, Kin-Hu residents > or = 30 years of age, living in the second largest township of Kinmen, were invited to participate in this survey incorporating face-to-face interviews with a structured questionnaire, collection of fasting blood samples and oral glucose tolerance test. The response rate for subjects with complete data was 80.3% (3289 of 4097). The prevalence rates for definite hypertension (> or = 160/95 mm Hg and/or under antihypertensive treatment) were 20.1, 14.0, and 16.9% for men, women, and the total population, respectively. Overall awareness, treatment, and control rates of definite hypertension were 46.9, 25.0, and 4.7%, respectively. According to the final logistic regression model, after controlling for all other covariates, the significant predictors for current-definite hypertension were old age, male sex, nonsmoking, obesity, alcohol intake, high waist-to-hip ratio, high serum triglyceride and high serum uric acid levels. In comparison with Chinese in Taiwan and mainland China, the unexpectedly high prevalence of hypertension and distinct set of its predictors in Kin-Hu form the basis for future study.

Adult↗
PubMed1995

Acute treatment of recent-onset atrial fibrillation and flutter with a tailored dosing regimen of intravenous amiodarone. A randomized, digoxin-controlled study.

A 24 h intravenous dosing regimen of amiodarone was designed to reach a peak plasma concentration at 1 h and to maintain the concentration above a certain level during the infusion period. A randomized, open-label, digoxin-controlled study was undertaken to observe the efficacy and safety of the dosing regimen of amiodarone in treating recent-onset, persistent, atrial fibrillation and flutter with ventricular rates above 130 beats.min-1. Fifty patients with a mean age of 70 +/- 7 (SD) years were enrolled and randomly assigned to receive either amiodarone intravenously (n = 26) or digoxin (n = 24). Amiodarone HCl was infused over 24 h according to the following regimen: 5 mg.min-1, 3 mg.min-1, 1 mg.min-1 and 0.5 mg.min-1 for 1, 3, 6 and 14 h, respectively, for a 70-kg subject. Digoxin (0.013 mg.kg-1) was infused in three divided doses, each dose 2 h apart and infused over 30 min. The mean heart rates in the amiodarone group decreased significantly from 157 +/- 20 beats.min-1 to 122 +/- 25 beats.min-1 after 1 h (P < 0.05 vs baseline), and then decreased further to stabilize at 96 +/- 25 beats.min-1 after 6 h (P < 0.05). The digoxin group had fewer dramatic alterations in heart rates, compared to the amiodarone group, in the first 8 h (P < 0.05, respectively). Maximum reduction was reached only after 8 h. The amiodarone infusion was prematurely aborted in two patients due to severe bradycardia and death after conversion in one patient and aggravation of heart failure in the other.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Initial onset of accessory pathway-mediated and atrioventricular node reentrant tachycardia after age 65: clinical features, electrophysiologic characteristics, and possible facilitating factors.

OBJECTIVE: To evaluate the clinical features electrophysiologic characteristics, and possible facilitating factors in older patients (> or = 65 years) with initial onset of accessory pathway-mediated and atrioventricular (AV) node reentrant tachycardia. DESIGN: Of the patients undergoing electrophysiologic study and radiofrequency catheter ablation of accessory pathway-mediated and AV node reentrant tachycardia at this institution, patients with initial tachyarrhythmia after age 65 years were compared with those presenting initially before age 30. SETTING: A tertiary medical center for the general public. PARTICIPANTS: Sixty-six patients had their initial symptoms after age 65: Group I, 32 patients with accessory pathway-mediated tachycardia, and Group II, 34 patients with AV node reentrant tachycardia. Four-hundred forty patients had their initial symptoms before age 30: Group III, 283 with accessory pathway mediated tachyarrhythmia, and Group IV, 157 with AV node reentrant tachycardia. INTERVENTION: All patients underwent electrophysiological study to determine the mechanisms of tachyarrhythmia, and radiofrequency catheter ablation for treatment of tachycardia. RESULTS: (1) Older patients with initial arrhythmia had incidence of critical clinical manifestations, including tachyarrhythmia-related syncope and cardioversion, similar to those with initial arrhythmia at a younger age. (2) Patients in Group III, showed anterograde effective refractory period (ERP) of the AV node (P = .432), longer anterograde ERP of the accessory pathway (P = .004), and greater difference of the anterograde ERP between the AV node and the accessory pathway (D-ERP) (P = .003) similar to patients in group I. In Group II, the ERP and Wenckebach cycle length of the retrograde fast pathway was significantly longer than in Group IV (P = .037 and P < .001, respectively), and a greater percentage of patients in Group II than in Group IV AV node reentrant tachycardia needed isoproteronol to facilitate the induction of reentrant tachycardia (P = .034). (3) Patients in Group I and Group II had a higher incidence of supraventricular and ventricular ectopic activity than those in Group III (P = .002 and P = .005, respectively) and Group IV (P = .024 and P = .012, respectively) in 24-hour ambulatory electrocardiograms. CONCLUSION: The initial onset of accessory pathway-mediated tachycardia after age 65 may be caused by changes of electrophysiologic properties (greater D-ERP) as well as increased supraventricular and ventricular ectopic activity. Influence of the autonomic nervous system, rather than changes of conduction properties in the AV node, and increase in ectopic activity may contribute to the new onset of AV node reentrant tachycardia in older adults. The choice of antiarrhythmic drugs and radiofrequency ablation require attention to the clinical profile and facilitating factors of reentrant tachycardia in this group of patients.

Adult↗
PubMed1995

Future ablation concepts of tachyarrhythmias.

Application of radiofrequency energy to arrhythmogenic substrates after careful cardiac mapping could ensure a high success rate in eliminating certain types of tachyarrhythmias. Future studies of catheter ablation will focus on how to improve ablation efficacy and achieve a better result in various types of tachyarrhythmias. More information about the arrhythmogenic mechanisms will be provided to improve the knowledge of diagnostic and interventional electrophysiology.

Arrhythmias, Cardiac↗
PubMed1995

Different effects of fosinopril and atenolol on wave reflections in hypertensive patients.

We conducted this study to compare the effects of fosinopril versus atenolol on peripheral blood pressure, central arterial wave reflection, and left ventricular mass in a group of patients with essential hypertension. We conducted a double-blind, randomized trial of fosinopril and atenolol in 79 hypertensive patients (52 men, 27 women; mean age, 45.8 +/- 8.5 years; range, 30 to 68 years). Carotid pressure waveforms were recorded noninvasively by applanation tonometry with a Millar micromanometer-tipped probe. The extent of wave reflection was estimated by the augmentation index defined as the ratio of the amplitude of pressure wave above its systolic shoulder to the pulse pressure. The augmentation index, left ventricular mass index by two-dimensional echocardiography, and 24-hour ambulatory blood pressures were determined before and after 8 weeks of daily treatment with fosinopril (10 to 20 mg) or atenolol (50 to 100 mg) with or without diuretics and compared with those values in 79 normotensive control subjects. After 8 weeks of treatment, both drugs lowered 24-hour ambulatory peripheral systolic and diastolic pressures into the normal range to a similar extent (fosinopril, -18/-13 mm Hg; atenolol, -23/-17 mm Hg, both P = NS). On the other hand, whereas the elevated augmentation index in hypertensive patients compared with normotensive subjects (16 +/- 11% versus 10 +/- 8%) was completely normalized by fosinopril (-9.3 +/- 9.8%, P < or = .002), it was lowered by atenolol (-4.8 +/- 8.9%, P < .002) but to a significantly smaller extent (fosinopril versus atenolol effect, P = .04).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Arterial hemodynamics in human hypertension. Effects of the calcium channel antagonist nifedipine.

Previous studies have shown some distinct hemodynamic alterations in essential hypertension, including increased resistance, wave reflections, and pulse wave velocity and decreased arterial compliance. These abnormalities are completely normalized by nonspecific smooth muscle dilation with nitroprusside but not by combined alpha- and beta-adrenergic blockade or angiotensin-converting enzyme inhibition, suggesting an enhanced smooth muscle tone that cannot be attributed solely to the sympathetic nervous or renin-angiotensin systems. Since hypertensive patients have an enhanced calcium influx-dependent vasoconstriction, we performed the present study to examine the extent to which the dihydropyridine calcium channel antagonist nifedipine could normalize the hemodynamic abnormalities in essential hypertension. An essential hypertensive patient group was compared with a normotensive group similar in age, body size, and proportion of men and women. During diagnostic cardiac catheterization, ascending aortic micromanometer pressures and electromagnetic flows were measured at baseline and after sufficient sublingual nifedipine (mean, 24 mg) to normalize blood pressure. From the pressures and flows, aortic input impedance, wave reflection magnitude, and compliance were computed. In the hypertensive group, the hemodynamic alterations were indistinguishable from those summarized above. Nifedipine produced sufficient vasodilation to completely normalize all of these hemodynamic alterations, including wave reflections. From these results, together with those reported in our previous studies, it is clear that the various classes of antihypertensive agents affect hemodynamics differently. All are capable of decreasing blood pressure to normotensive levels, but only nitroprusside and nifedipine can also completely normalize all the other pulsatile hemodynamic alterations. Thus, these hemodynamic effects of the different classes of antihypertensive agents should be considered in choosing a therapeutic modality.

Adult↗
PubMed1995

Short- and long-term effects of antihypertensive drugs on arterial reflections, compliance, and impedance.

This article reviews our work on the effects of different classes of antihypertensive agents on the hemodynamic alterations in essential human hypertension. Short-term studies were done during cardiac catheterization in young normotensive subjects (mean age, 33 years; range, 19 to 40) and several different age-matched (range, 25 to 53 years) groups of patients with essential hypertension. Aortic impedance, resistance, wave reflections, and compliance were calculated from high-fidelity recordings of ascending aortic pressure and flow signals during baseline and after nitroprusside, propranolol followed by phentolamine, phentolamine, captopril, and nifedipine, respectively, at doses sufficient to normalize blood pressure in each hypertensive group. Propranolol exacerbated all the hemodynamic parameters; these effects were only partially overcome by phentolamine. Among the other agents only phentolamine did not completely normalize compliance, and only captopril did not completely normalize wave reflections. The long-term study was a randomized, double-blind comparison of fosinopril and atenolol in 79 normotensive subjects and 79 essential hypertensive patients. Baseline 24-hour ambulatory blood pressures and carotid artery tonometry to index wave reflections were performed in all subjects and in hypertensive patients after 8 weeks of therapy. Both fosinopril and atenolol normalized blood pressure and lowered the elevated augmentation index, but fosinopril had a significantly larger effect than atenolol. Both short- and long-term beta-blockade did not have as beneficial an effect as the other agents. Thus, the differing hemodynamic effects of the various classes of antihypertensive agents might be a consideration in the choice of therapy.

Adult↗
PubMed1995

Transvenous permanent left ventricular pacing. A case report.

This case report presents a patient who inadvertently received transvenous permanent left ventricular pacing through an unexpected atrial septal defect. This lead malpositioning was proved by two-dimensional and transesophageal echocardiography. The abnormal pattern of electric activation was demonstrated by radionuclide phase image analysis. He has been followed up for a total of forty-three months with antiplatelet therapy and has been free from systemic embolic phenomena. A simple and readily available method that could lead to early recognition of lead malpositioning is reiterated and the various causes, methods of detection, and prognosis of left ventricular pacing are discussed.

Aged↗
PubMed1995

Reappraisal of continuous positive airway pressure therapy in acute cardiogenic pulmonary edema. Short-term results and long-term follow-up.

To investigate whether serial incremental continuous positive airway pressure (CPAP) has any short-term or long-term advantages over face-mask oxygen therapy by way of intrapulmonary shunt reduction, 100 patients admitted to the coronary care unit for the treatment of acute cardiogenic pulmonary edema were studied. All patients received Swan-Ganz catheterization. Hemodynamic and pulmonary function parameters were recorded over the next 6 h, and the patients were followed until hospital discharge. All survivors received regular follow-up at 1-month intervals in the outpatient clinic. During the first-stage investigation period (3 h) PaO2 in the CPAP group showed a significant increase, whereas the intrapulmonary shunt and alveolar-arterial oxygen tension gradient (P[A-a]O2) was significantly reduced (p < 0.005). The CPAP group had significantly lower rate-pressure product and higher stroke volume index compared with the control group. The therapeutic failure rate over 6 h was 24% in the CPAP group and 50% in the control group (p < 0.01). The CPAP group had a significantly lower incidence of tracheal intubation and ventilator therapy than the control group; however, there was no significant difference in short-term mortality and hospital stay between the two groups. In conclusion, although study size was not large enough to demonstrate a difference in mortality, CPAP therapy resulted in physiologic cardiovascular and pulmonary function improvement and significantly reduced the need for intubation; however, it did not decrease mortality in patients with acute cardiogenic pulmonary edema, and a much larger study is needed to investigate this possibility.

Acute Disease↗