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Biomedical subjects

Chih-Tai Ting

Publications and source records attributed to Chih-Tai Ting.

At least 37 records · Page 2Linked to original sources
PubMed2005

Delicate percutaneous renal artery stenting minimizes postoperative renal injury and protects kidney in patients with severe atherosclerotic renal artery stenosis and impaired renal function.

Percutaneous transluminal renal artery stenting (PTRAS) is associated with declining renal function in a non-negligible portion of patients and is inflicted by different mechanisms, including atheroembolism. This study investigated whether delicate PTRAS to reduce atheroembolism might minimize postoperative renal injury and better preserve renal function. Patients undergoing PTRAS performed by experienced interventional cardiologists, applying coronary intervention concepts, techniques, devices and delicacy principles whenever possible, were prospectively studied. A total of 34 patients (29 M/5 F) with impaired renal function (group A, creatinine 2.4 +/- 0.1 mg/dL) and another 20 patients (16 M/4 F) with normal serum creatinine (group B, baseline creatinine 1.2 +/- 0.0 mg/dL) were studied. PTRAS was successfully performed in all but one group A patient. During a 6-month follow-up, systolic and diastolic blood pressure (130 +/- 2 versus 148 +/- 4 mmHg, P = 0.001 and 70 +/- 2 versus 78 +/- 3 mmHg, P = 0.006) and serum creatinine (2.1 +/- 0.1 versus 2.4 +/- 0.1 mg/dL, P < 0.001) were all significantly lowered in group A patients. Using a 20% change cut-off value, renal function improved in eight (24%), remained unchanged in 24 patients (73%), and deteriorated in only one patient (3%). The corresponding alterations in blood pressure and renal function were insignificant in group B patients. Patients with bilateral involvement (eleven patients) also had significantly lowered serum creatinine on follow-up. In conclusion, delicately practiced PTRAS can reduce the rate of postprocedural renal deterioration in patients with impaired renal function, and should be adopted in every renal intervention.

Aged↗
PubMed2005

Relationship between several surrogate estimates of insulin sensitivity in non-diabetic patients with coronary artery disease.

BACKGROUND AND PURPOSE: Insulin resistance plays an important role in the pathogenesis of coronary artery disease (CAD). Thus, there is a need for accurate and accessible tools for measurement of insulin sensitivity in patients with this disease. This study explored the relationship between several surrogate estimates of insulin sensitivity in non-diabetic patients with angiographic evidence of CAD. METHODS: The study population consisted of 1363 non-diabetic subjects with angiography results which revealed evidence of CAD in 660 and no evidence of CAD in 703 subjects. After overnight fasting, blood samples were drawn for determination of glucose and insulin concentrations in order to determine the homeostasis model assessment for insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI). In addition, steady-state plasma glucose (SSPG) concentrations obtained from insulin suppression tests were carried out in 54 subjects with and 194 subjects without CAD. The correlation of QUICKI with other surrogate estimates of insulin sensitivity in obese and non-obese subjects was also evaluated. RESULTS: The QUICKI correlated significantly with other methods for estimating insulin sensitivity in the CAD and non-CAD groups. The QUICKI also had a closer correlation with SSPG and log fasting plasma insulin (log FPI) in subjects with CAD (r = -0.573 and -0.869, respectively) than HOMA-IR (r = 0.508 and 0.777, respectively). QUICKI had a closer correlation with SSPG in the obese subjects than in the non-obese subjects, irrespective of the presence of CAD. CONCLUSIONS: The QUICKI was more closely related with SSPG, insulin area, and log FPI than other measurements of insulin sensitivity. These findings suggest that the QUICKI may provide a convenient, efficient method to measure insulin sensitivity in non-diabetic patients with CAD.

Aged↗
PubMed2004

Mother rotors and the mechanisms of D600-induced type 2 ventricular fibrillation.

BACKGROUND: Two types of ventricular fibrillation (VF) have been demonstrated in isolated rabbit hearts during D600 infusion. Type 1 VF is characterized by the presence of multiple, wandering wavelets, whereas type 2 VF shows local spatiotemporal periodicity. We hypothesized that a single mother rotor underlies type 2 VF. METHODS AND RESULTS: One (protocol I) or 2 (protocol II) cameras were used to map the epicardial ventricular activations in Langendorff-perfused rabbit hearts. Multiple episodes of type 2 VF were induced in 22 hearts by high-concentration (> or =2.5 mg/L) D600 (protocol I). During type 2 VF, a single spiral wave (n=19) and/or an epicardial breakthrough pattern (n=11) was present in 14 hearts. These spiral waves either slowly drifted or intermittently anchored on the papillary muscle (PM) of the left ventricle. Dominant-frequency (DF) analyses showed that the highest local DF was near the PM (12.5+/-1.1 Hz). There was an excellent correlation between the highest local DF of these spiral waves and breakthroughs (11.8+/-1.7 Hz) and the DF of simultaneously obtained global pseudo-ECG (11.2+/-1.8 Hz, r=0.97, P<0.0001) during type 2 VF. We also successfully reproduced the major features of type 2 VF by using the Luo-Rudy action-potential model in a simulated, 3-dimensional tissue slab, under conditions of reduced excitability and flat action-potential duration restitution. CONCLUSIONS: Either a stationary or a slowly drifting mother rotor can result in type 2 VF. Colocalization of the stationary mother rotors with the PM suggests the importance of underlying anatomic structures in mother rotor formation.

Action Potentials↗
PubMed2004

Single nucleotide polymorphisms in protein tyrosine phosphatase 1beta (PTPN1) are associated with essential hypertension and obesity.

Protein tyrosine phosphatase 1beta (PTP-1beta) is involved in the regulation of several important physiological pathways. It regulates both insulin and leptin signaling, and interacts with the epidermal- and platelet-derived growth factor receptors. The gene is located on human chromosome 20q13, and several rare single nucleotide polymorphisms (SNPs) have been shown to be associated with insulin resistance and diabetes in different populations. As part of our ongoing investigations into the genetic basis of hypertension, we examined common sequence variants in the gene for association with hypertension, obesity and altered lipid profile in two populations of Japanese and Chinese descent. We re-sequenced all exons, selected intronic sequences and the promoter region in 24 individuals from our cohort. Fourteen SNPs were discovered, and six of these spanning 78 kb were genotyped in 1553 individuals from 672 families. All six SNPs were in linkage disequilibrium, and we found strong association of common risk haplotypes with hypertension in Chinese and Japanese (P<0.0001). In addition, individual SNPs showed association to total plasma cholesterol, LDL-cholesterol and VLDL-cholesterol levels, as well as obesity measures (body mass index). This analysis supports that PTP-1beta affects plasma lipid levels, and may lead to obesity and hypertension in Japanese and Chinese. Given similar associations found in other populations to insulin resistance and diabetes, this gene may play a crucial role in the development of the characteristic metabolic changes seen in patients with the metabolic syndrome.

Adult↗
PubMed2004

Characteristics of virtual unipolar electrograms for detecting isthmus block during radiofrequency ablation of typical atrial flutter.

OBJECTIVES: The purpose of this study was to investigate the characteristics of the second component of local virtual unipolar electrograms recorded at the ablation line during coronary sinus (CS) pacing after radiofrequency ablation (RFA) of the cavotricuspid isthmus (CTI) for typical atrial flutter (AFL). BACKGROUND: Radiofrequency ablation of the CTI can produce local double potentials at the ablation line. The second component of unipolar electrograms represents the approaching wavefront in the right atrium opposite the pacing site. We hypothesized that the morphologic characteristics of the second component of double potentials would be useful in detecting complete CTI block. METHODS: Radiofrequency ablation of the CTI was performed in 52 patients (males = 37, females = 15, 62 +/- 12 years) with typical AFL. The noncontact mapping system (Ensite 3000, Endocardial Solutions, St. Paul, Minnesota) was used to guide RFA. Virtual unipolar electrograms along the ablation line during CS pacing after RFA were analyzed. Complete or incomplete CTI block was confirmed by the activation sequence on the halo catheter and noncontact mapping. RESULTS: Three groups were classified after ablation. Group I (n = 37) had complete bidirectional CTI block. During CS pacing, the second component of unipolar electrograms showed an R or Rs pattern. Group II (n = 12) had incomplete CTI block. The second component of unipolar electrograms showed an rS pattern. Group III (n = 3) had complete CTI block with transcristal conduction. The second component of unipolar electrograms showed an rSR pattern. CONCLUSIONS: A predominant R-wave pattern in the second component of unipolar double potentials at the ablation line indicates complete CTI block, even in the presence of transcristal conduction.

Action Potentials↗
PubMed2004

The short-/intermediate-term changes in novel vascular inflammatory markers after angioplasty plus stenting in patients with symptomatic advanced systemic arterial diseases.

Studies on cell adhesion molecules and high-sensitivity C-reactive protein (hs-CRP) in systemic arterial diseases are limited in numbers and some results not consistent. It also remains undefined whether, for how long and to what extent these markers are perturbed after angioplasty. Patients with systemic arterial diseases admitted for percutaneous transluminal angioplasty (PTA) by standard procedures and techniques were prospectively studied. Fasting morning blood samples were collected to determine general biochemistry and relevant molecules by commercially available methods at baseline, 2 weeks and 3 months post-PTA/stenting. A group of equally numbered sex- and age-matched asymptomatic subjects without illness were selected as control. A total of 33 patients (28 M/5 F, aged 72 +/- 2 years) were recruited. Patients with systemic arterial disease had significantly higher baseline serum creatinine, circulating VCAM-1, ICAM-1, and hs-CRP, but lower p-selectin and HDL-C than control subjects. Except ICAM-1, cell adhesion molecules and hs-CRP levels were aroused significantly for at least 2 weeks after PTA/stenting, returned to baseline by 3 months, but p-selectin remained elevated beyond 3 months. ICAM-1 only showed a modest rise after PTA but the overall change was insignificant. In conclusion, cell adhesion molecules and hs-CRP did play a significant role in patients with advanced systemic arterial diseases who underwent PTA/stenting.

Aged↗
PubMed2004

Physical inactivity is an important lifestyle determinant of insulin resistance in hypertensive patients.

The purpose of the study is to assess the relative impact of lifestyle factors including physical inactivity, cigarette smoking, and alcohol intake on insulin resistance in hypertensive patients. In total, 872 hypertensive patients, of Chinese and Japanese origin, from the Stanford Asia and Pacific Program for Hypertension and Insulin Resistance were included for the current analysis. Homeostasis model assessment for insulin resistance (HOMA-IR) and the insulin sensitivity index ISI0,120 were chosen as surrogate measures of insulin resistance. Standardized interview-administered questionnaires were used to obtain information on demographic and lifestyle characteristics. The sedentary hypertensive patients were more insulin resistant than the non-sedentary hypertensive. There were significant differences in Log (HOMA-IR) (0.06-unit increases, p < 0.01) and Log (ISI0,120) (0.05-unit decreases, p < 0.01) between sedentary and non-sedentary hypertensive patients after controlling demographic variables. There were no differences in insulin sensitivity in subjects with different smoking status. Neither smoking nor alcohol intake was persistently associated with insulin resistance in the analysis. Our results suggest that physical inactivity is an important lifestyle determinant of insulin resistance in hypertensive patients. The influences of smoking and alcohol intake on insulin resistance are less significant than physical inactivity in hypertensive subjects.

Adult↗
PubMed2003

Insulin-like growth factor-1 prevents loss of electrochemical gradient in cardiac muscle mitochondria via activation of PI 3 kinase/Akt pathway.

Insulin-like growth factor-1 (IGF 1) suppresses myocardial apoptosis and improves myocardial function in experimental models of cardiomyopathy. Apoptosis is triggered by mitochondria dysfunction and subsequent activation of caspases. We had previously shown that IGF 1 inhibited cardiomyocyte apoptosis via suppression of caspase, however, how IGF 1 and its signaling pathway modulates mitochondria function in cardiac muscle is not yet known. In this study we investigated how IGF 1 signaling modulates mitochondria membrane depolarization in the cardiomyocytes treated with doxorubicin. Doxorubicin rapidly induced loss of mitochondria electrochemical gradient and triggered mitochondria depolarization in primary cardiomyocytes, whereas addition of IGF 1 restored mitochondria electrochemical gradient. The effects of IGF 1 was blocked by a chemical inhibitor of PI 3 kinase and a dominant negative Akt, suggesting that IGF 1 signaling to mitochondria involves the PI 3 kinase-Akt pathway. Transducing cardiomyocytes with constitutive active PI 3 kinase partially restored the mitochondria electrochemical gradient in doxorubicin-treated cells. These findings provide direct evidence that IGF 1 modulation of mitochondria function is mediated through activation of PI 3 kinase and Akt. Additional experiments using agonist and antagonist of mitochondria K(ATP) channel suggest that IGF 1 signaling to mitochondria membrane does not directly involve K(ATP) channel. These findings suggest that cytosolic signaling to mitochondria may play a fundamental role in the cardiotoxic actions of doxorubicin and cardioprotective actions of IGF 1.

Adenoviridae↗
PubMed2003

Effect of atrial dilatation on electrophysiologic properties and inducibility of atrial fibrillation.

INTRODUCTION: Atrial dilatation may play an important role in the occurrence of atrial fibrillation (AF) in clinical situations. However, the electrophysiologic characteristics of dilated atria are still unclear. METHODS AND RESULTS: In 18 isolated Langendorff-perfused canine hearts (14.6 +/- 2.2 kg), we measured atrial effective refractory periods (ERPs) at four different sites, conduction velocity and percentage of slow conduction on the right atrium (using a high-density electrode plaque), and assessed the inducibility of AF at the baseline (0 cm H(2)O) and high (15 cm H(2)O) atrial pressure. The atrial ERPs did not change significantly, but the dispersion of ERP increased significantly (40 +/- 18 vs 25 +/- 9 vs ms, p = 0.01) during high atrial pressure. The percentage of slow conduction (< 25 cm/s) over the mapping area, and the inducibility of AF increased during high atrial pressure (23.7 +/- 10.2 % vs 32.1 +/- 12.5 %, p = 0.02). The AF inducibility significantly correlated with the ERP dispersion (R = 0.75, p < 0.001) and maximal percentage of slow conduction (R = 0.88, p < 0.001). Furthermore, ERPs were significantly shorter in the induced AF group than those without induced AF (68 +/- 17 vs 84 +/- 16 ms, P < 0.05). CONCLUSIONS: The increased inhomogenity in atrial electrophysiological properties during atrial dilatation contributed to the inducibility of AF.

Animals↗
PubMed2003

Percutaneous coronary revascularization improves the prognosis of patients with cardiogenic shock in acute coronary syndrome: a chronological study.

BACKGROUND: Cardiogenic shock complicating acute coronary syndrome (ACS) implies grim prognosis with conventional management. Previous studies of coronary intervention yielded controversial results and were rarely analyzed chronologically. This study was to determine the impact of percutaneous coronary revascularization on outcome by studying two time periods 5 years apart in which the revascularization was more frequent and techniques more refined in the later period. METHODS AND MATERIALS: All patients admitted to the intensive or coronary care unit for ACS in two 1.5-year study periods (Period I: Jan 1994-Jun 1995, Period II: Oct 1999-Apr 2000) were retrospectively screened. Patients who met strict criteria of cardiogenic shock within 24 h of ACS were enrolled. The demographics, management and in-hospital/3-month outcomes were analyzed. RESULTS: Thirty-seven patients (33M/4F, aged 65+/-8 years) were enrolled in Period I and 32 patients (25M/7F, aged 68+/-13 years) in Period II. The incidence of cardiogenic shock was 11.8 and 9.3%, respectively. The demographics were similar except patients in Period II were older. Significantly more coronary angiography and interventions were done in the later period. The in-hospital (68 vs. 44%, P=0.047) and 3-month mortalities (70 vs. 44%, P=0.03) were significantly reduced in Period II. The in-hospital survivors in two study periods differed only in use of coronary angiography (94 vs. 50%, P=0.005) and interventions (83 vs. 33%, P=0.005) but not others. CONCLUSIONS: Percutaneous coronary revascularization does improve the clinical outcome of cardiogenic shock when analyzed chronologically. This treatment is warranted in every such patient in the interventional era.

Aged↗
PubMed2003

Pedal Tc-99m phytate lymphoscintigraphy in primary chylopericardium.

This paper describes a case of 65-year-old woman with primary chylopericardium. She received Tc-99m phytate lymphoscintigraphy after pericardial drainage and was managed with medium-chain triglycerides without surgical intervention. This was the first reported case of primary chylopericardium diagnosed with Tc-99m phytate lymphoscintigraphy.

Aged↗
PubMed2003

Influence of ductal size on the results of transcatheter closure of patent ductus arteriosus with coils.

To assess the influence of ductal size on the results of transcatheter closure of patent ductus arteriosus (PDA) with coils, 154 consecutive patients were studied prospectively. Ductal size was defined as the narrowest diameter of ductus measured on aortography. All patients were divided into 5 groups according to ductal size: < 1 mm, 1-1.9 mm, 2-2.9 mm, 3-3.9 mm, and > or = 4 mm. The occlusion of PDA with coils was performed through a transarterial approach. The results were evaluated by angiography at 10 minutes and by color Doppler echocardiography at 1 day, 2 days, 1 week, 1 month, 3 months, 6 months, and 12 months after the procedure. The immediate occlusion rates for ductal sizes < 1 mm, 1-1.9 mm, 2-2.9 mm, 3-3.9 mm, and > or = 4 mm were 89.7%. 75.4%, 51.4%, 30.8%, and 40%, respectively; whereas the occlusion rates at 12-months follow-up were 100%, 98.5%, 97.3%, 69.2%, and 80%, respectively. There were no significant differences in occlusion rate at 12-months follow-up among the groups with ductal sizes < 3 mm or among the groups with ductal sizes > or = 3 mm. The occlusion rate for ductal size < 3 mm at each follow-up time was significantly higher than that for ductal size > or = 3 mm (10 minutes: 71.8% vs 34.8%. P = 0.001; 12-months: 98.5% vs 73.9%, P < 0.001). The occlusion rate of residual shuntings at 12-months follow-up for ductal size < 3 mm was also significantly higher than that for ductal size > or = 3 mm (94.6% vs 60%, P = 0.007). The results of the present study demonstrate that ductal size < 3 mm had a higher occlusion rate than that for a size > or = 3 mm. PDA with a size > or = 3 mm may need other treatment strategies or other devices to achieve better results.

Cardiac Catheterization↗
PubMed2003

Right coronary artery arising from the left main stem with dynamic compression by great vessels.

Anomalous origin of the right coronary artery from the left main stem is a very rare congenital anomaly. The entrapment of its course between the aorta and pulmonary artery can cause dynamic blood flow limitation. We report a 68-year-old female presenting with recurrent chest pain and a positive treadmill exercise test. The coronary angiography disclosed anomalous origin of the right coronary artery from the left main stem with dynamic compression between aortic root and pulmonary trunk during the systolic phase. With hesitation about surgical revascularization, the patient was maintained on oral medication uneventfully.

Aged↗
PubMed2003

Atrial demand pacemakers in sick sinus syndrome: an efficient and reliable approach in selected patients.

BACKGROUND: Atrial demand pacemakers offer the advantages of lower cost and less cumbersome implantation in selected sick sinus syndrome patients with acceptable atrioventricular (AV) conduction. However, concerns about their long-term performance and AV conduction degeneration still worry certain implantation physicians. There were still limited long-term follow-up data of atrial demand pacemakers, especially in oriental people. Thus, we reviewed our long-term follow-up results. METHODS: From January 1996 to December 1998, all symptomatic sick sinus syndrome patients with atrial demand pacemaker (AAI, AAIR) treatment were retrospectively studied. They were all regularly followed up at our pacemaker clinic. The patients' clinical presentations, coronary angiography, electrophysiology results and their initial implantation parameters were collected. All outpatient follow-up histories, electrocardiogram (EKG) rhythm strips, and chronic threshold test data were also retrieved. RESULTS: There were 51 patients enrolled in this study, with a mean age of 68 +/- 7 years. The average follow-up duration was 44 +/- 17 months. The baseline His bundle-ventricular (HV) interval was 40 +/- 6 ms and AV 1:1 conduction cycle lengths were up to 388 +/- 65 ms. Two patients (2/51, 3.9%) had acute lead dislodgement within three days and needed reimplantation. During the long-term follow-up, all patients maintained good pacing function. Five patients (5/51, 9.8%) had occasions of sensing failure, as detected by 12-lead surface EKG or Holter monitor, which all resolved after reprogramming of the sensing threshold. Only 1 patient ( 1/51, 1.9%) developed Wenckebach AV block in the daytime as shown by EKG and was later upgraded to a DDDR pacemaker uneventfully. No patient became victim of chronic atrial fibrillation during the long-term follow-up. CONCLUSIONS: Our follow-up study again suggests that atrial demand pacemakers have good initial implantation and long-term results. The chance of developing AV conduction degeneration during follow-up is quite low (1.9%, average annual incidence 0.5%). AAI and AAIR pacemakers are a reliable and physiological approach to selected sick sinus syndrome patients and should be the pacemaker of choice in suitable cases.

Aged↗
PubMed2002

Two types of ventricular fibrillation in isolated rabbit hearts: importance of excitability and action potential duration restitution.

BACKGROUND: The combined effects of excitability and action potential duration (APD) restitution on wavefront dynamics remain unclear. METHODS AND RESULTS: We used optical mapping techniques to study Langendorff-perfused rabbit hearts. In protocol IA (n=10), D600 at increasing concentrations was infused during ventricular fibrillation (VF). With concentration increased to 0.5 mg/L, fast VF (dominant frequency, 19.1+/-1.8 Hz) was consistently converted to ventricular tachycardia (VT). However, increasing D600 further to 2.5 or 5.0 mg/L converted VT to slow VF (11.9+/-2.3 Hz, P=0.0011). In an additional 4 hearts (protocol IB), tetrodotoxin converted a preexisting VT to slow VF (11.0+/-1.4 Hz). Optical maps show wandering wavelets in fast VF, organized reentry in VT, and spatiotemporal periodicity in slow VF. In protocol II, we determined APD and conduction time(-1) (CT(-1)) restitutions during D600 infusion. CT(-1) was used as an estimate of excitability. At 0.1 mg/L, APD and CT(-1) restitutions were steep and flat, respectively. APD restitution became flattened when D600 increased to 0.5 mg/L, converting fast VF to VT. Further increasing D600 to 2.5 or 5.0 mg/L steepened CT(-1) restitution and widened the range of S(1) pacing cycle lengths over which CT(-1) decreased, converting VT to slow VF. CONCLUSIONS: Two types of VF exist in isolated rabbit hearts. Fast (type I) VF is associated with a steep APD restitution, a flat CT(-1) restitution, and wandering wavelets. Slow (type II) VF is associated with a flat APD restitution, a steep CT(-1) restitution, and spatiotemporal periodicity. Both excitability and APD restitution are important in VF maintenance.

Action Potentials↗