Biomedical subjects

William Hsu

Publications and source records attributed to William Hsu.

4 recordsLinked to original sources

PubMed2003

Exercise and vitamin E intake are independently associated with metabolic abnormalities in human immunodeficiency virus-positive subjects: a cross-sectional study.

We investigated the relationship among habitual exercise, diet, and the presence of metabolic abnormalities (body fat redistribution, dyslipidemia, and insulin resistance) in a cross-sectional study of 120 human immunodeficiency virus (HIV)-infected subjects with use of bivariate and multivariate regression-analysis models. Total and aerobic exercise were significantly and negatively associated with fasting plasma triglyceride levels in the entire sample and in the fat redistribution group. Inverse associations between total or aerobic exercise and insulin resistance were suggestive but did not achieve statistical significance. Diastolic blood pressure was significantly and inversely associated with supplemental or total but not habitual dietary intake of vitamin E. In conclusion, exercise and vitamin E intake were independently and negatively associated with several phenotypic manifestations of HIV-associated metabolic syndrome, whereas other macro- or micronutrients did not have comparable significance.

Antioxidants↗

PubMed2002

Effects of verapamil and ibutilide on atrial fibrillation and postfibrillation atrial refractoriness.

INTRODUCTION: Early recurrence of atrial fibrillation (AF) after cardioversion may be related to shortening of the atrial effective refractory period (ERP). This study compared the effects of verapamil and ibutilide on AF cycle length (AFCL), atrial ERP, and susceptibility to recurrent AF. METHODS AND RESULTS: In 33 adults, the atrial ERP was measured at basic drive CLs of 350 and 500 msec before and after a brief episode of pacing-induced AF. During AF, verapamil, ibutilide, or saline was infused in 11 patients each. Shortening of the post-AF atrial ERP was attenuated by verapamil and prevented by ibutilide. AFCL shortened by 32+/-21 msec in the verapamil group (P < 0.01), prolonged by 44+/-14 msec in the ibutilide group (P < 0.001), and did not change in the control group. AF converted to sinus rhythm within 10 minutes less often after verapamil (0%) than after ibutilide (82%) or than in the control group (73%). Post-AF, AF lasting > 10 minutes was induced more often in the verapamil group than in the ibutilide group (26% vs 0%; P = 0.01). Another 10 patients received verapamil or ibutilide in the absence of AF. Atrial ERP was unchanged after verapamil and prolonged after ibutilide. CONCLUSION: Verapamil shortens AFCL and impedes the conversion of induced AF, whereas ibutilide prolongs AFCL and does not impede the early conversion of induced AF. Ibutilide is more effective than verapamil in preventing pos

Adult↗

PubMed2002

Advanced rhythm discrimination for implantable cardioverter defibrillators using electrogram vector timing and correlation.

INTRODUCTION: Discrimination of ventricular and supraventricular arrhythmias remains one of the major challenges for appropriate implantable defibrillator (ICD) therapy delivery. The electrogram vector timing and correlation (VTC) algorithm was developed for such rhythm discrimination. The VTC algorithm differentiates normally conducted supraventricular beats from abnormally conducted ventricular beats by comparing the timing and correlation of rate and shock channel electrograms. METHODS AND RESULTS: Rate and shock channel electrograms of sinus rhythm and induced arrhythmias were collected from 93 patients during ICD placement. The algorithm was developed using data from 50 patients and prospectively tested in a software model with the remaining 43 patients. A sinus rhythm reference was formed by averaging complexes of the shock channel signal aligned by the peak amplitude of the rate channel. Eight features measuring the amplitude and timing of shock channel signal characteristics were extracted from the reference for comparison. When a high-rate rhythm was detected, the VTC algorithm computed the correlation of the arrhythmia complex features with the reference. Rhythms with a sufficient number of uncorrelated beats were classified as ventricular tachycardia (VT). In a dual-chamber implementation, the VTC algorithm is integrated with ventricular and atrial rate comparison (V>A) and stability above an atrial fibrillation rate threshold. The test set consisted of 117 arrhythmias. Dual-chamber sensitivity was 100% (81/81 VT) and specificity was 97% (35/36 supraventricular tachycardia). Single-chamber analysis demonstrated 99% sensitivity and 97% specificity. CONCLUSION: The VTC algorithm demonstrated high sensitivity and specificity in discriminating between ventricular and supraventricular arrhythmias.

Aged↗

PubMed2002

Effects of diltiazem and esmolol on cycle length and spontaneous conversion of atrial fibrillation.

BACKGROUND: Calcium channel blocking agents have been shown to prolong the duration of atrial fibrillation. This study compared the effects of intravenous diltiazem and esmolol on the cycle length and conversion rate of pacing-induced atrial fibrillation. METHODS AND RESULTS: In 41 adults without structural heart disease, atrial fibrillation was induced by rapid atrial pacing. After 3 minutes, either diltiazem (n = 13), esmolol (n = 15), or saline (n = 13) was infused. In the diltiazem group, the atrial fibrillation cycle length shortened by a mean of 43 milliseconds and became significantly shorter than in the control group, while the atrial fibrillation cycle length in the esmolol group did not change. Spontaneous termination of atrial fibrillation occurred significantly less often in the diltiazem group (23%) than in the esmolol (67%, P < 0.05) or placebo groups (77%, P = 0.01). CONCLUSIONS: Intravenous diltiazem shortens the atrial fibrillation cycle length and lowers the probability of spontaneous conversion of recent-onset atrial fibrillation to sinus rhythm. These results suggest that the use of diltiazem for acute rate control may unwittingly prolong the duration of recent-onset atrial fibrillation.

Adult↗