Biomedical subjects

Y K Chiang

Publications and source records attributed to Y K Chiang.

9 recordsLinked to original sources

PubMed1994

Double-blind efficacy and safety study of a novel anti-ischemic agent, ranolazine, versus placebo in patients with chronic stable angina pectoris. Ranolazine Study Group.

BACKGROUND: Ranolazine modulates the metabolism of ischemic myocardial cells and improves the efficiency of oxygen use. This study was conducted to evaluate the antianginal and anti-ischemic effects and safety of different doses of ranolazine administered three times daily (tid) compared with placebo in patients with stable angina pectoris. METHODS AND RESULTS: Patients with stable angina pectoris took part in the study. Previous antianginal drugs were discontinued under medical supervision. Three hundred nineteen patients received single-blind placebo for up to 18 days, and 318 stopped exercise because of angina of moderate severity, had evidence of myocardial ischemia (> or = 1-mm ST segment depression), and were randomized to one of four study groups in a double-blind manner: ranolazine 30 mg tid (n = 81), ranolazine 60 mg tid (n = 81), ranolazine 120 mg tid (n = 78), and placebo tid (n = 79). After the 4-week double-blind phase, symptom-limited exercise tests were repeated at 1 hour (peak test) and 8 hours (trough test) after the study medication was administered. In addition, patients kept an angina diary throughout the study and wore a Holter monitor for 48 hours. Total exercise duration at baseline (+/- SEM) was 5.9 +/- 0.2 minutes for the placebo group and 6.4 +/- 0.3, 5.9 +/- 0.3, and 6.6 +/- 0.2 minutes for the ranolazine 30-, 60-, and 120-mg groups, respectively (P = NS). After 4 weeks of double-blind therapy, compared with baseline values, at 1 hour after the study medication was administered (peak effect), total exercise duration (+/- SEM) increased by 0.45 +/- 0.2 minutes in the placebo group and by 0.3 +/- 0.2, 0.6 +/- 0.2, and 0.5 +/- 0.2 minutes in the ranolazine 30-, 60-, and 120-mg groups, respectively (placebo versus ranolazine, P = NS). Times to 1-mm ST segment depression at baseline were similar in the four groups and, after 4 weeks of therapy in each group, increased significantly by similar magnitudes at 1 hour after the administration of the medications. Similar changes were seen for the time to onset of angina. Eight hours after administration (trough effect), no differences in total exercise time or any other exercise variables were observed between the placebo and the ranolazine groups. Compared with the baseline values, the number of anginal attacks per week and the number and duration of ischemic episodes per 48 hours during Holter monitoring decreased significantly by similar magnitudes in the placebo and ranolazine groups. CONCLUSIONS: Therapy with ranolazine 30, 60, and 120 mg tid was not superior to placebo. Our study does not support the published beneficial effects of similar doses of ranolazine on either myocardial ischemia or exercise performance or on anginal attacks during daily life in patients with angina pectoris.

Acetanilides↗

PubMed1990

Combined low-dose medication and primary intervention over a 30-month period for sustained high blood pressure in childhood.

Studies of the pathobiologic consequences of high blood pressure in childhood, as well as those following blood pressure levels into young adulthood, indicate that early intervention in the natural history of essential hypertension is warranted. In an exploratory study of the concept, 95 children out of 1604 (aged 8 to 18 years), who persistently scored higher than the 90th percentile for blood pressure over a 4-month period, considering the race, sex, and height of the children, were studied. Five series of replicate measurements with 30 total observations were obtained. Children with evidence of secondary hypertension were excluded. The study children were randomly divided into treatment (n = 48) and high-comparison (n = 47) groups. Treatment consisted of low-dose combined drug therapy (propranolol and chlorthalidone) with an educational program directed towards hypertension and dietary and exercise modification. Monthly follow-up was continued for 30 months. Significant systolic (-3.59 mm Hg) and diastolic (-1.73 mm Hg) changes were noted up to 30 months (p less than 0.05) with minimal side effects. Furthermore, analyses suggested that the blood pressure change, at least in the first month, was mostly attributable to drug therapy. Moreover, the mechanism of blood pressure change appeared to be race-specific, with whites having pulse rate changes and blacks having significant weight changes, which were associated with blood pressure change. This trial shows further research is warranted to determine optimum approaches for early treatment of essential hypertension to prevent future hypertensive disease.

Adolescent↗

PubMed1990

A controlled clinical trial to assess the effect of a calcium channel blocker on the progression of coronary atherosclerosis.

To determine whether calcium channel blockers influence the progression of coronary atherosclerosis, 383 patients age 65 years or less with 5-75% stenoses in at least four coronary artery segments were selected at random within 1 month of coronary arteriography to participate in double-blind therapy with a placebo or nicardipine 30 mg three times daily. Coronary events (5 deaths, 22 myocardial infarctions, and 28 unstable anginas) occurred in 28 of 192 nicardipine patients and 23 of 191 placebo patients (p = NS). At 24 months coronary arteriography was repeated in 335 patients. Progression, defined as a 10% or more worsening in diameter stenosis, measured quantitatively, was found in 147 of 1,153 lesions (12.7%) in 168 nicardipine patients and in 170 of 1,170 lesions (14.5%) in 167 placebo patients (p = NS). Ninety-two nicardipine patients (55%) and 95 placebo patients (57%) had progression at one or more sites (p = NS). Regression, that is, an improvement by 10% or more in diameter stenosis, was seen in 140 of 2,323 lesions (6.0%) overall, with no significant intergroup difference. Among the 217 patients with 411 stenoses of 20% or less in the first study, such minimal lesions progressed in only 15 of 99 nicardipine patients compared with 32 of 118 placebo patients (15% versus 27%, p = 0.046). In this subgroup, 16 of 178 minimal lesions in nicardipine patients and 38 of 233 minimal lesions in placebo patients progressed (p = 0.038). By stepwise logistic-regression analysis, baseline systolic blood pressure (p = 0.04) and the change in systolic blood pressure between baseline and 6 months (p = 0.002) correlated with progression of minimal lesions. This suggested blood pressure reduction may account for the beneficial action of nicardipine. These results suggested nicardipine has no effect on advanced coronary atherosclerosis but may retard the progression of minimal lesions.

Adult↗

PubMed1989

Relationship between change in height and changes in serum lipid and lipoprotein levels in adolescent males: the Bogalusa Heart Study.

The relationship between increase in height and changes in levels of serum lipids and lipoproteins in adolescent males were examined through a biracial sample of 397 individuals, ages 8-12 years, who were reexamined 5 years after the initial screening. Significant negative correlations were observed between height change and changes in levels of serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) after controlling for age, initial cholesterol level, height, weight, Tanner stage, and changes in Tanner stage and weight. There was significant inverse association between height change and change in the level of HDL-C in black males, while there was significant inverse association between height change and change in the level of LDL-C in white males. These associations were independent of age, sexual maturation, and weight. Thus, changes in levels of serum lipids and lipoproteins in males during adolescence are partly associated with the growth spurt in height.

Adolescent↗

PubMed1989

An illness-death process with time-dependent covariates.

A general model for the illness-death stochastic process with covariates has been developed for the analysis of survival data. This model incorporates important baseline and time-dependent covariates in order to make an appropriate adjustment for the transition and survival probabilities. The follow-up period is subdivided into small intervals and a constant hazard is assumed for each interval. An approximation formula is derived to estimate the transition parameters when the exact transition time is unknown. The method developed is illustrated with data from a study on the prevention of the recurrence of a myocardial infarction and subsequent mortality, the Beta-Blocker Heart Attack Trial (BHAT). This method provides an analytical approach with which the effectiveness of the treatment can be compared between the placebo and propranolol treatment groups with respect to fatal and nonfatal events simultaneously.

Biometry↗

PubMed1988

Influence of partial replacement of starch by sucrose in high fat-cholesterol diet on serum lipoprotein responses of cynomolgus monkeys.

The influence of partial replacement of starch by sucrose on dietary cholesterol-induced serum lipoprotein responses was examined in 10 male cynomolgus monkeys (Macaca fascicularis). In a crossover design two semipurified diets provided either starch or starch and sucrose (1:1) as carbohydrate (49% by calories) with 0.4 mg cholesterol/kcal. Six weeks of starch + sucrose diet resulted in significantly reduced levels (mean +/- SE, mg/dl) of serum total cholesterol (264 +/- 9 vs 244 +/- 8) and apo B (110 +/- 6 vs 96 +/- 6) when compared with starch diet, whereas serum triglyceride levels remained similar between diets. With respect to changes in lipids and apolipoproteins (A-I or B) of very low (VLDL), low (LDL), intermediate (IDL), and high (HDL) density lipoproteins, starch + sucrose diet significantly increased VLDL-apo B (+34%), and decreased LDL-cholesterol (-18%) and LDL-apo B (-15%) as compared with starch alone; no differences were found in IDL and HDL between diets. The relative proportion of starch to sucrose in a diet appears to influence the magnitude of response of lipoproteins to dietary cholesterol.

Animals↗

PubMed1987

Blood pressure and echocardiographic measures in children: the Bogalusa Heart Study.

M mode echocardiograms were obtained from 654 healthy subjects, 7 to 22 years of age, whose diastolic blood pressure levels remained in the same height-, race-, and sex-specific decile during two biannual examinations. Echocardiographic measures of heart size, obtained according to the recommendations of the American Society for Echocardiography, were compared across the entire systolic and diastolic blood pressure distributions. Echocardiographic indexes of left heart size varied as a function of both blood pressure levels and body size. Significant positive correlations were present between systolic blood pressure and different measures of left ventricular size. Left ventricular wall thickness in systole correlated with systolic blood pressure (r = .42, p less than .0001), and persistence of this relationship was noted after adjustment for body size. Left ventricular wall thickness in diastole correlated with blood pressure before adjustment (r = .31, p less than .0001), but the relationship was not significant after adjustment for body size. The ratio of left ventricular thickness to chamber size (systole) correlated with systolic blood pressure levels both before and after adjustment for body size (r = .20 and r = .22, p less than .001). Male subjects of both races demonstrated significantly higher adjusted left ventricular mass, left ventricular wall thickness, and left ventricular chamber size. Adjusted left ventricular wall stress was significantly related to both systolic (r = .14) and diastolic blood pressure levels (r = .14, p less than .001). Measures of left ventricular wall thickness increased throughout the entire blood pressure distribution, indicating a consistent trend rather than a threshold effect seen only in the highest blood pressure groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1985

A computer program for an illness-death process with time-dependent covariates.

This paper presents a computer program for estimating transition probabilities between states in a stochastic model for an illness-death process which incorporates time-dependent covariates. Parameters are estimated by the method of maximum likelihood using the Newton-Raphson iterative procedure. The program provides the standard normal deviate statistics as well as the value of the maximum of the likelihood function which can be used on repeated applications to test hypotheses concerning coefficients associated with covariates. Although this program is demonstrated by using a model with two 'illness' states and two 'death' states, it is also suitable for analyzing data with models involving fewer states, such as the analysis of survival time with covariates assuming a proportional hazard model.

Computers↗

PubMedDate not supplied

Correlates of high density lipoprotein cholesterol and apolipoprotein A-I levels in children. The Bogalusa Heart Study.

Levels of high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (apo A-I) may provide independent information concerning cardiovascular disease risk. Therefore, possible correlates of HDL-C and apo A-I levels were studied in 2827 5- to 17-year-olds from a biracial community, and the possible differences in these relationships were assessed. The characteristics examined included sexual maturation, plasma levels of glucose and insulin, obesity, reported oral contraceptive use, alcohol consumption, and cigarette smoking. In addition, levels of endogenous sex hormones (testosterone, estrogen, and progesterone) were measured in 515 adolescent males. HDL-C and apo A-I levels showed different (p less than 0.001) relationships with both obesity and oral contraceptive use. Increases in subscapular skinfold thickness corresponded more closely to decreases in HDL-C, rather than apo A-I, levels; the relationship with HDL-C was probably mediated by triglyceride levels. In contrast, oral contraceptive use was associated with increases in mean levels of apo A-I (8 mg/dl, whites; 16 mg/dl, blacks), but with only very small changes in HDL-C. (High-estrogen oral contraceptives were related most closely to increases in levels of both HDL-C and apo A-I). Levels of both HDL-C and apo A-I were similarly related to sexual maturation and levels of testosterone (negatively in boys), cigarette smoking (negatively), and alcohol intake (positively). Since levels of apo A-I independently of HDL-C may indicate an increased risk of cardiovascular disease, characteristics related to apo A-I levels should be further examined.

Adolescent↗