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Biomedical subjects

R B Hsu

Publications and source records attributed to R B Hsu.

44 records · Page 3Linked to original sources
PubMed1995

Effect of triiodothyronine administration in experimental myocardial injury.

Twelve healthy pigs were subjected to a 20-min, period of regional myocardial ischemia by snaring the left anterior descending coronary artery (LAD) between its first and second diagonal branches. The resulting myocardial injury caused significant acute hemodynamic impairments. Cardiac index declined significantly during reperfusion interval and returned to preischemic level by postoperative day 7. Plasma total triiodothyronine (TT3), free triiodothyronine (FT3) and free fatty acid (FFA) decreased gradually and reached the nadir at 6 h after LAD occlusion. In contrast, plasma reverse triiodothyronine (rT3) increased progressively after LAD occlusion and reperfusion. To investigate the effect of T3 on ischemic myocardium, T3 (0.2 microgram/kg/dose; n = 5) or saline (placebo; n = 6) was administered immediately, 30 min, 60 min, 90 min, and 120 min after reperfusion. Plasma TT3 and FT3 increased dramatically after triiodothyronine supplement but declined to presichemic level at six h after LAD occlusion. The pigs treated with T3 demonstrated a rapid improvement in cardiac index over the reperfusion interval, whereas cardiac index in the placebo group remained depressed. Myocardial oxygen consumption estimated by rate pressure product showed no difference between placebo and T3-treated groups. Oxygen extraction as O2 saturation difference between aorta and coronary sinus was less in T3-treated group. Nine pigs (four in the T3-treated group and five in the placebo group) were subjected to euthanasia with hypertonic KCl solution on postoperative day 7. Myocardial infarct size determined by triphenyltetrazolium chloride (TTC) tissue enzyme staining technique was not significantly different between T3-treated and placebo groups. We concluded that this animal model is a useful model of myocardial injury simulating "euthyroid sick syndrome" as seen in patients with cardiopulmonary bypass, and T3 supplementation after reperfusion significantly enhanced postischemic left ventricular functional recovery but did not affect myocardial oxygen consumption and myocardial infarct size.

Animals↗
PubMed1993

Graft flow and reactive hyperemia immediately following coronary artery bypass surgery.

Graft flow rates and reactive hyperemia (RH) were measured in 166 patients undergoing coronary artery bypass graft surgery. A wide range of graft flow rates was found within 273 grafts: the left anterior descending (LAD) arterial graft flow rate was the highest; the left circumflex (LCX) arterial graft flow rate was the lowest; and the right coronary (RCA) arterial graft flow rate was in between. There was no relation between the severity of coronary stenosis and basal graft flow. In LAD and RCA grafts, there was a higher percentage of positive RH (> 10%) in vessels with severe obstruction (grades 4 and 5). No correlation was demonstrated between graft flow and RH in patients with or without myocardial infarction. In addition, RH increased in patients with good coronary arterial collateral circulation (p < 0.05). Our data support the theory that coronary collaterals do not provide sufficient blood flow to the myocardium supplied by a stenotic coronary artery.

Adult↗
PubMed1991

Thyroid hormone changes after cardiovascular surgery and clinical implications.

Alterations in serum concentrations of total triiodothyronine (TT3), total thyroxine (TT4), and thyroid-stimulating hormone (TSH) frequently occur in patients with nonthyroidal illnesses. These changes correlate with the severity of the illness and the prognosis. In this study, 44 patients undergoing a cardiovascular operation had significant declines in serum TT3 and TT4 levels during cardiopulmonary bypass and thereafter. Serum TT3 and TT4 concentrations reached their nadir at 30 minutes after the start of cardiopulmonary bypass with values (mean +/- standard error of the mean) of 0.77 +/- 0.12 nmol/L (50.4 +/- 7.6 ng/dL) and 68.2 +/- 10.2 nmol/L (5.30 +/- 0.79 micrograms/dL), respectively. The mean serum concentrations of TSH and TT4 returned to preoperative levels by the sixth day after operation, whereas TT3 levels remained low throughout the study period. The patients whose recovery was uneventful had higher serum TT3, TT4, and TSH levels than those who had complications or died. The trend toward recovery was initiated by a sharp increase in the serum TSH level and increases in serum TT3 and TT4 concentrations on the fourth day after operation. Patients with complications either did not show these changes or had only a transient increase in TT3 and TT4 levels. All of the patients had a normal serum free T4 level before anesthesia. Those with an uneventful recovery had a higher serum free T4 level on the sixth day after operation than those with complications. Two patients in the latter group had serum free T4 levels less than normal at that time.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1983

The relationship of transmembrane potential to surface morphology of human atrial muscle and cardiac hemodynamics.

A correlative study of transmembrane potential characteristics, surface morphological features of human atrial muscle, and cardiac hemodynamics was carried out in 41 patients, who were divided into 2 groups based on the level of the mean maximum diastolic potentials (MDP). Group A consisted of 19 patients with MDP values ranging from -60.0 to -82.0 mV (mean +/- S.D. = -65.70 +/- 6.63 mV). Group B included 22 patients who had abnormally low MDP (range -36.0- -58.5 mV, mean +/- S.D. = -48.14 +/- 6.72 mV). The differences in electrophysiological data were statistically significant. However, there were no significant differences in the hemodynamic data between the 2 groups. Furthermore, there was poor correlation between the electrophysiological and hemodynamic data in both groups. In group A, scanning and transmission electron microscopy revealed either no changes or only mild alterations in the surface morphology of the atrial myocardium. Various degrees of surface morphological changes, including a focal loss of the endothelium which was always associated with endocardial fibrosis, irregular thickening and lamination of the glycocalyx, disruption of the sarcolemma and complete destruction of the surface membrane structures were more often observed in group B. These results provide valuable evidence that sarcolemmal changes may underlie the electrophysiological alterations in diseased human atria. We suggest that the principal pathogenetic mechanisms leading to the transmembrane potential changes are the altered surface morphology of atrial myocardial cells, resulting from underlying disease processes.

Adolescent↗
PubMedDate not supplied

Creation of a one-way interatrial communication in the treatment of critical pulmonary stenosis with intact ventricular septum: a case report.

BACKGROUND: In biventricular repair of pulmonary outflow tract obstruction with intact ventricular septum, the right ventricle is loaded with total pulmonary blood flow acutely as the right-to-left shunt is abolished by closure of the atrial septal defect (ASD). METHODS: We designed a one-way interatrial communication by creation of an atrial septal flap to reduce the excessive volume load of the right ventricle. RESULTS: This procedure was successfully performed in a 3-year-old girl undergoing definitive biventricular repair for critical pulmonary stenosis associated with tricuspid stenosis and a small right ventricle. CONCLUSIONS: We believe that creation of a one-way interatrial communication might be a good alternative to adjustable ASD and/or bidirectional Glenn shunt in biventricular repair of critical pulmonary stenosis or pulmonary atresia with intact ventricular septum.

Child, Preschool↗