1 Cardiology Section, Department of Internal Medicine,
National Taiwan University College of Medicine, National Taiwan
University Hospital, 600 Taipei; 2 College of Medicine, National
Cheng Kung ...University, Tainan; and 3 College of Public Health,
National Taiwan University and 4 Department of Surgery,
National Taiwan University Hospital, 600 Taipei, Taiwan
Distension of the
urinary bladder causes an increase in efferent sympathetic activity,
which can precipitate myocardial ischemia. Smoking has been shown to
modulate activities of afferent nerves from the distended urinary
bladder and to impair endothelial function in response to sympathetic
activation. To assess the effect of bladder distension on coronary
dynamics in smokers, we measured epicardial and microvascular responses
in 24 patients with early atherosclerosis (< 50% diameter stenosis).
Patients were classified into habitual smokers ( group 1 ,
n = 14) and nonsmokers ( group 2 ,
n = 10). Habitual smokers were randomized into two
subgroups on the basis of the use of doxazosin, as follows:
subgroup 1A ( n = 7), without administration
of doxazosin before catheterization; subgroup 1B
( n = 7), with dosing doxazosin. In response to bladder distension (mean intravesical pressure 21.5 mmHg), bladder distension significantly decreased coronary diameter at the stenotic segments, coronary blood flow, and increased coronary resistance compared with
baseline values, in subgroup 1A patients. In subgroup
1B patients during bladder distension, coronary diameter, coronary blood flow, and coronary resistance did not show significant changes compared with baseline values. There were significant differences of
coronary diameter at the stenotic segments, coronary blood flow, and of
changes of coronary vascular resistance between subgroup 1A
and group 2 during bladder distension, despite similar
changes in rate-pressure product. The present study showed that urinary bladder distension caused an abnormal vasomotor response of epicardial vasoconstriction and a concomitant increased coronary resistance, which
leads to reduction in coronary blood flow in patients with early
atherosclerosis. Smoking may further impair the response, implying that
smoking has exaggerated response to sympathetic stimulation of conduit
and resistance vessels. The abnormal response was abolished by
pretreated administration of doxazosin, suggesting that the involved
mechanisms are related to 1 -adrenoceptors.
intracoronary Doppler flow; urinary distension
Three hundred and two consecutive patients who had undergone cardiac operation for various cardiac lesions were studied prospectively to evaluate the incidence, risk factors, and the associated ...mortality of postoperative hyperbilirubinemia after cardiopulmonary bypass. Concentrations of the serum total (conjugated and unconjugated) bilirubin, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, albumin, globulin, and serum haptoglobin were measured before the operation and again on the first, second, and seventh postoperative days. Postoperative hyperbilirubinemia was defined as occurrence of a serum total bilirubin concentration of more than 3 mg/dl in any measurement during the postoperative period. Logistic regression was done to identify possible risk factors for postoperative hyperbilirubinemia. Overall incidence of postoperative hyperbilirubinemia was 35.1%; the incidence of postoperative hyperbilirubinemia was higher in patients whose valves were replaced with mechanical prostheses than in those without prostheses (p < 0.00001). In patients with postoperative hyperbilirubinemia, 70% of the increase of total bilirubin on the first postoperative day came about from an increase in unconjugated bilirubin. Serum haptoglobin decreased significantly at the same time (p < 0.01). Development of the postoperative hyperbilirubinemia was associated with a higher mortality (5.6% versus 0.5%, p < 0.01) and higher frequency of use of intraaortic balloon counterpulsation, especially for patients in whom the highest postoperative total bilirubin occurred after the first 2 days. The numbers of valves replaced, preoperative right atrial pressure, and preoperative total bilirubin concentration are the significant risk factors that, in combination, correctly predict the occurrence of postoperative hyperbilirubinemia in 80% of the patients. We concluded that postoperative hyperbilirubinemia results mainly from an increase in unconjugated bilirubin and is associated with higher mortality, especially for patients in whom highest postoperative total bilirubin occurred late after operation. Patients with the higher preoperative right atrial pressure and total bilirubin level who then underwent multiple valve replacement procedures are at greater risk for development of postoperative hyperbilirubinemia.
Off-pump coronary artery bypass grafting (CABG) OPCAB is preferred to conventional CABG with cardiopulmonary bypass (CPB) for many specific subgroups, such as elderly patients and high-risk patients. ...Whether OPCAB should be the first choice of surgical procedure for a wider range of coronary artery disease patient subgroups remains controversial. The purpose of this study was to compare the clinical results of OPCAB and CPB in our hospital.
We retrospectively analyzed the results for 404 patients who received OPCAB or CPB between March 2000 and December 2001. Surgical methods adopted were at the discretion of the attending surgeon. In addition, subgroups of patients were analyzed to assess whether or not OPCAB was more successful in patients with specific characteristics.
There were no significant differences in the demographic data between the 2 groups. The perioperative mortality rate was similar for the CPB and OPCAB groups (2.5% and 2.0%, respectively; p = 1.00.) OPCAB was superior with respect to inotropic use, postoperative bleeding amount, transfusion amount, and length of intensive care unit and hospital stay (p < 0.05 for all), and also had a lower incidence of re-entry due to bleeding (6.7% vs 13.6%, p = 0.04) and prolonged hospitalization > 30 days (1.5% vs 10.8%, p < 0.01). At 12 months' follow-up, the OPCAB group had a lower rate of mortality (1.5% vs 5.6%, p = 0.03) and a comparable rate of readmission for cardiac reasons (6.6% vs 9.6%, p = 0.28). The rate of poor in-hospital outcome was lower in the OPCAB than in the CPB group (3.0% vs 13.3%, p </= 0.01), while the percentage with poor results on follow-up was comparable between the 2 groups (7.1% vs 12.1%, p = 0.09). In addition, subgroups defined as: female, age > 65 years, age < 65 years, diabetes, peripheral arterial occlusive disease, end-stage renal disease, left ventricular ejection fraction < 50%, preoperative intra-aortic balloon pump use, and left-main disease had better in-hospital outcome in the OPCAB group compared with the CPB group, while no subgroups had worse in-hospital outcomes with OPCAB. The 12-month follow-up outcome was similar with the 2 techniques.
Use of OPCAB in CABG operation was associated with improved in-hospital outcome and similar follow-up outcome compared to CPB. No subgroup had a worse outcome with OPCAB.
A mathematical model was developed to simulate an optical fiber-forming process which is based on internal diffusion and surface evaporation (IDSE) of monomers in a liquid jet. The IDSE process ...requires that a polymer solution which consists mainly of one type of monomer and a different polymer be prepared and then extruded through a die to form a circular liquid jet, the monomers with diffuse to the jet surface and then evaporate. Once the concentration distribution of the monomers in the jet reaches a desired pattern, photopolymerization will commence and an optical fiber is generated. The model that describes the IDSE process involves momentum, heat and mass transfer with free-surface flows. Methods for evaluating the physical parameters in the model were proposed. An advanced numerical technique based on the finite-element method incorporated with schemes to treat free surfaces and high Peclet numbers was developed for the solution of the mathematical model. A test case was selected for illustration; the effects of several variables on the fiber forming were examined. It was found that only by balancing the internal diffusion and the evaporation at the jet surface could an optical fiber with a desirable pattern of the refractive index be generated.
We investigated the gene expression of calcium-handling genes including L-type calcium channel, sarcoplasmic reticular calcium adenosine triphosphatase (Ca(2+)-ATPase), ryanodine receptor, ...calsequestrin and phospholamban in human atrial fibrillation.
Recent studies have demonstrated that atrial electrical remodeling in atrial fibrillation is associated with intracellular calcium overload. However, the changes of calcium-handling proteins remain unclear.
A total of 34 patients undergoing open heart surgery were included. Atrial tissue was obtained from the right atrial free wall, right atrial appendage, left atrial free wall and left atrial appendage, respectively. The messenger ribonucleic acid (mRNA) amount of the genes was measured by reverse transcription-polymerase chain reaction and normalized to the mRNA levels of glyceraldehyde 3-phosphate dehydrogenase.
The mRNA of L-type calcium channel and of Ca(2+)-ATPase was significantly decreased in patients with persistent atrial fibrillation for more than 3 months (0.36+/-0.26 vs. 0.90+/-0.88 for L-type calcium channel; 0.69+/-0.42 vs. 1.21+/-0.68 for Ca(2+)-ATPase; both p < 0.05, all data in arbitrary unit). We further demonstrated that there was no spatial dispersion of the gene expression among the four atrial tissue sampling sites. Age, gender and underlying cardiac disease had no significant effects on the gene expression. In contrast, the mRNA levels of ryanodine receptor, calsequestrin and phospholamban showed no significant change in atrial fibrillation.
L-type calcium channel and the sarcoplasmic reticular Ca(2+)-ATPase gene were down-regulated in atrial fibrillation. These changes may be a consequence of, as well as a contributory factor for, atrial fibrillation.
Background: Aortic valve replacement relieves mechanical outflow obstruction in patients with aortic stenosis. However, there is limited information on whether aortic valve replacement can provide ...regression of ventricular repolarisation inhomogeneity.
Objectives: To determine whether aortic valve replacement can provide regression of ventricular repolarisation inhomogeneity in patients with aortic stenosis after bileaflet aortic valve replacement.
Methods: We studied the changes of electrocardiographic QT or QTc intervals and QT or QTc dispersions of 71 patients with severe aortic stenosis and angiographically insignificant coronary lesions (<50% in diameter) before and after valve replacement (6±3 days after operation). Seventy-one healthy control subjects, matched for age and sex, served as control subjects. Twelve-lead electrocardiograms and echocardiographic examinations were measured before and after surgery. The QT interval was corrected for heart rate using the standard Bazett formula. QT dispersion was defined as the difference between maximal and minimal QT interval measurements occurring among any of the 12 leads on a standard electrocardiogram. QTc dispersion was calculated in a manner similar to QT dispersion. No subject had fewer than nine measurable leads.
Results: Left ventricular systolic blood pressure, pressure gradient across aortic valve, left ventricular mass index, and systolic wall stress were significantly reduced after valve replacement compared with before valve replacement. The QT interval significantly decreased from 425±38 ms to 398±32 ms after replacement (
P<0.0001). The QTc dispersion significantly decreased from 62±25 ms to 32±13 ms after replacement (
P<0.0001). The value of QT or QTc dispersion after replacement was similar to that in controls. Univariate analysis revealed that QTc dispersion was significantly only correlated with left ventricular mass index (
r=0.236,
P=0.05). Multivariate analysis revealed that the best predictor of QTc dispersion was sex and left ventricular mass index (
P=0.008 and 0.005, respectively).
Conclusions: Our study demonstrated a favorable consequence of aortic valve replacement distinct from hemodynamic improvement. Patients with aortic stenosis before valve replacement have abnormal prolonged QT or QTc intervals and increased QT or QTc dispersions. After successful valve replacement left ventricular mass index regressed and QT or QTc intervals and QT or QTc dispersions were normalized. These findings warrant further investigation in a large trial and long-term follow-up for clinical implications.
The interlead variation in QT interval (QT dispersion) can be used to assess regional inhomogeneity of ventricular repolarization under a variety of conditions, including stress. Patients with ...syndrome X may have increased sympathetic activity that could change QT interval regionally and give rise to an increase in QT dispersion under exercise testing. To test the hypothesis, 26 consecutive patients with syndrome X (group 1) were studied. Two additional groups matched in terms of age, sex, and left ventricular mass index consisting of 26 nonconsecutive patients with coronary artery disease (group 2) and 20 normal subjects (group 3) were studied for comparison. Standing induced a significantly higher increase of heart rate in group 1 than in groups 2 and 3 (7.5 ± 6.0 vs 4.0 ± 6.3 and 1.1 ± 3.6 beats/min; p = 0.05 and 0.003, respectively). There were significant differences in QT dispersion between groups 1 and 2 on upright standing (48 ± 12 vs 34 ± 14 ms, p = 0.0003), but not at baseline (33 ± 14 vs 38 ± 11 ms, p = NS) or at peak exercise (38 ± 9 vs 38 ± 9 ms, p = NS). Results did not change when QT
c dispersion was substituted for QT dispersion. From a conditional multivariate logistic regression analysis, the only independent predictor of occurrence of syndrome X on upright standing was QT
c dispersion (odds ratio = 1.255, p = 0.01). Electrocardiographic QT
c dispersion provides important clinical information. Patients with syndrome X had a higher increase of heart rate and QT
c dispersion in response to standing from the supine position compared with patients with coronary artery disease and normal subjects.
This paper studies an iterative multiuser detection for nonbinary LDPC coded multicarrier MFSK multiple access system to increase system performance under specific signal-to-noise ratio and data ...rate. When multiuser detection process is carried out, we test the soft outputs of channel decoder. When the soft output exceeds a threshold, the user is declared as a reliable user. For each signal, we count the number of reliable users on it. The reliable information iteratively updates the soft output calculation in the iterative demodulation and decoding process. Numerical results show that system performances are improved after multiuser detection over Rayleigh fading channel.
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