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C T Tai

Publications and source records attributed to C T Tai.

144 records · Page 8Linked to original sources
PubMed1996

Accessory atrioventricular pathway at the antero-medial mitral annulus--electrophysiologic characteristics and radiofrequency catheter ablation: a case report.

Accessory atrioventricular (AV) pathway located at or near the region of aorta-mitral continuity has rarely been mentioned. This report describes one such case with a concealed accessory AV pathway at the anteromedial mitral annulus adjacent to aorta-mitral continuity. The location of the accessory pathway was confirmed by successful radiofrequency catheter ablation. This patient was a 26-year-old male. His 12-lead surface ECG showed no evidence of ventricular preexcitation during sinus rhythm. The earliest retrograde atrial depolarization recorded from the routine catheters was at the His bundle area during ventricular pacing and orthrodromic AV reentrant tachycardia; paradoxically, the earliest left-sided atrial activation recorded from the coronary sinus catheters was at the distal coronary sinus area. The unique retrograde atrial activation sequence over the left atrium and His bundle area was not true for patients with left lateral or anterolateral accessory pathway. During tachycardia, the local electrogram from the successful ablation site showed local VA fusion in the anteromedial mitral annulus. After delivering one pulse of radiofrequency energy (30W), the accessory AV pathway was successfully eliminated without complication. This report presents a concealed left-sided accessory AV pathway at an unusual location. It is very important to describe special electrophysiologic characteristics and ablation technique in this unusual accessory pathway to improve knowledge in the era of interventional electrophysiology.

Adult↗
PubMed1996

Prevalence of dementia in an urban area in taiwan.

This two-stage epidemiologic study was to investigate the prevalence and types of dementia among elderly people in the Saa-Min district of Kaohsiung City in Taiwan. In stage one, the Chinese Mini-Mental Status Examination (CMMSE) and Blessed Dementia Rating Scale were employed. In stage two, a comprehensive neurobehavioral examination and neuropsychologic tests were administered by neurologists and neuropsychologists. Dementia was defined by DSM-III-R criteria. The National Institute of Neurological and Communication Disorders and Stroke-Alzheimer's Disease and Related Disorders Association guidelines for Alzheimer's disease (AD) and the National Institute of Neurological Disorder and Stroke-Association international pour la Recherche et l'Enseignement en Neurosciences criteria for vascular dementia (VaD) were applied. A total of 1,016 randomly selected elderly people participated in phase one: 131 people with CMMSE below cutoff values participated in phase two, of whom 45 were confirmed to have a form of dementia. The prevalence of dementia in this sample was 4.4% (3.2% in men and 5.8% in women): 2.0% for those 65 to 74 years old, 8.3% for those 75 to 84 and 24.4% for those > or = 85 years old; 6.0% for those who were illiterate, 3.3% for those who attended grade-school; and 2.8% for those who finished junior-high-school. AD (22 cases, 48.9%) was the most common cause of dementia, followed by VaD (11 cases, 24.4%) and mixed dementia (MIX: 5 cases, 11.1%). Old age and being female were significant high risk factors for AD. Medical history indicated that stroke and hypertension were significant risk factors for VaD. A relatively high prevalence of dementia was observed in this study, probably because we assessed neurobehavior in great detail. Although AD was the leading cause of dementia in the present population sample. VaD and MIX also comprised an important proportion, reflecting the high prevalence of stroke in Taiwan. Older women had high risk for AD, not for VaD; and those with a history of stroke and hypertension had high risk for VaD, not for AD.

Aged↗
PubMed1995

Effects of pregnancy on first onset and symptoms of paroxysmal supraventricular tachycardia.

It is important for women to understand the risk of first onset and symptomatic exacerbation of paroxysmal supraventricular tachycardia (SVT) during pregnancy. Reports regarding the effects of pregnancy on first onset and symptomatic exacerbation of paroxysmal SVT have been controversial, and have not been conducted in a systematic fashion. Two hundred seven consecutive female patients diagnosed with symptomatic paroxysmal SVT were requested to respond to multiple questionnaires before electrophysiologic study and catheter ablation. A person-years data method was used to estimate risk of first onset of paroxysmal SVT during pregnancy. Exacerbation of paroxysmal SVT was assessed by a score scale including each of the following symptoms: palpitation, fatigue, rest dyspnea, effort dyspnea, dizziness, chest oppression, blurred vision, and syncope (total score change > 2 points). In the 107 patients with accessory pathway-mediated tachycardia, 7 patients had had a first onset of tachycardia during pregnancy (relative risk ratio 0.86, confidence interval 0.4 to 1.9, p = 0.35). In the 100 patients with atrioventricular nodal reentrant tachycardia, 1 patient had had the first onset of tachycardia during pregnancy (relative risk ratio 0.11, confidence interval 0.02 to 0.56, p = 0.004). Otherwise, 14 of the 63 patients (22%) with tachycardia in the pregnant and nonpregnant periods had exacerbation of symptoms during pregnancy. Thus, first onset of paroxysmal SVT during pregnancy was rare (3.9%), and pregnancy was associated with a low risk of first onset of paroxysmal SVT. However, symptoms of paroxysmal SVT were exacerbated during pregnancy in some patients.

Adolescent↗
PubMed1995

Recurrent tachycardia after selective ablation of slow pathway in patients with atrioventricular nodal reentrant tachycardia.

Recurrence rate of atrioventricular (AV) nodal reentrant tachycardia after successful radiofrequency ablation varies widely, and the determinants of recurrent AV nodal reentrant tachycardia remain controversial. Furthermore, true or pseudorecurrence of tachycardia after successful ablation in patients with different forms of AV nodal reentrant tachycardia has not been evaluated systematically. Three hundred sixty-two patients (161 men and 201 women [mean age 52 +/- 16 years]), including 314 patients with typical-form, 10 patients with atypical-form, 4 patients with variant-form, and 34 patients with multiple-form AV nodal reentrant tachycardias, received selective radiofrequency ablation of the anterograde and/or retrograde slow AV nodal pathway. During a mean follow-up of 27 +/- 11 months, 9 patients (2.5%) experienced recurrent AV nodal reentrant tachycardia (true recurrence, group A), and 8 (2.2%) had inappropriate sinus tachycardia or paroxysmal atrial tachyarrhythmias (pseudorecurrence, group B). Neither the true nor pseudorecurrence rate was different among the 4 different forms of tachycardia. Factors including presence of residual slow pathway conduction, a single AV nodal reentrant echo beat, absence of an accelerated junctional rhythm during successful ablation, facilitating induction of tachycardia by isoproterenol, radiofrequency pulse number, and successful ablation site were not associated with an increased risk of recurrent AV nodal reentrant tachycardia. The onset time of recurrent tachycardia was significantly late in group B patients (30 +/- 21 vs 292 +/- 240 days, p = 0.04). Thus, this study demonstrated that both true and pseudorecurrence could occur after successful ablation.

Adolescent↗
PubMed1995

An accurate stepwise electrocardiographic algorithm for localization of accessory pathways in patients with Wolff-Parkinson-White syndrome from a comprehensive analysis of delta waves and R/S ratio during sinus rhythm.

Prediction of accessory pathway location before radio-frequency ablation has become increasingly important for patients with Wolff-Parkinson-White syndrome. However, existing electrocardiographic (ECG) criteria for localization of accessory pathways have several limitations, and the polarity of delta waves has not been well defined. In the present study, 369 patients with a single anterogradely conducting accessory pathway who underwent successful radiofrequency ablation were included. The polarity of delta waves was defined and categorized in detail, and various ECG characteristics of the most preexcited QRS complexes were examined and compared with QRS complexes after successful ablation in the initial 182 patients, which included morphology and polarity of delta waves, initial 20, 40, and 60 ms segments of the preexcited QRS complex, R/S ratio in the precordial leads, R/S ratio in the frontal leads, delta wave axis in the frontal plane, polarity of delta waves in the frontal leads, and polarity of delta waves in the precordial leads. The polarity of the initial 40 ms segment of the most preexcited QRS complexes in each of the frontal leads, and the polarity of the initial 60 ms segment of the most preexcited QRS complex in each of the precordial leads proved to be the best representatives of delta wave polarity in the respective leads.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1995

Radiofrequency catheter ablation of paroxysmal supraventricular tachycardia in patients with congenital heart disease.

Radiofrequency catheter ablation was performed in 21 patients who had congenital heart diseases associated with accessory pathway (AP)-mediated tachycardia (14 patients), with atrioventricular (AV) nodal reentrant tachycardia (4 patients), with intraatrial reentrant tachycardia (1 patient), with coexistent AP mediated tachycardia and AV nodal reentrant tachycardia (1 patient) and with coexistent AV nodal reentrant tachycardia and atrial tachycardia (1 patient). Congenital heart diseases diagnosed were seven with Ebstein's anomaly and six with septal defect; the others included patent ductus arteriosus, supravalvular aortic stenosis and left superior vena cava-coronary sinus fistula. Incidence of multiple APs (26.7 vs. 7.7%, P = 0.027), antidromic tachycardia (20.0 vs. 2.9%, P = 0.011), tachyarrhythmia-related syncope (26.7 vs. 7.2%, P = 0.022) and cardiac arrest (13.3 vs. 0%, P = 0.001) was higher in patients with AP and congenital heart diseases. Longer procedure (3.9 +/- 0.7 vs. 2.4 +/- 1.3 h for AP, P = 0.001; 3.0 +/- 0.7 vs. 2.5 +/- 0.8 h for AV nodal reentrant tachycardia, P = 0.001), and radiation exposure times (102 +/- 27 vs. 35 +/- 23 min for AP, P = 0.001; 62 +/- 23 vs. 20 +/- 11 min for AV nodal reentrant tachycardia, P = 0.001) were necessary to achieve a high success rate (95%) in patients with congenital heart disease.

Adolescent↗
PubMed1995

Both electrolytic and excitotoxic lesions of nucleus accumbens disrupt latent inhibition of learning in rats.

Evidence indicating a role for the nucleus accumbens in the development of latent inhibition of learning has accumulated. Two experiments were conducted using Wistar rats to investigate this role directly. Experiment 1 used a conditioned emotional response paradigm to assess the effects of discrete electrolytic lesions in the shell region of the nucleus accumbens. Latent inhibition was attenuated by this lesion. In order to determine the contribution made by damage to fibers en passage associated with electrolytic lesions, Experiment 2 assessed the effects of NMDA-induced lesions in the shell of the nucleus accumbens in the same task. Latent inhibition was again significantly attenuated. These findings support the proposition that an intact nucleus accumbens is necessary for the normal development of latent inhibition.

Animals↗
PubMed1995

Initial onset of accessory pathway-mediated and atrioventricular node reentrant tachycardia after age 65: clinical features, electrophysiologic characteristics, and possible facilitating factors.

OBJECTIVE: To evaluate the clinical features electrophysiologic characteristics, and possible facilitating factors in older patients (> or = 65 years) with initial onset of accessory pathway-mediated and atrioventricular (AV) node reentrant tachycardia. DESIGN: Of the patients undergoing electrophysiologic study and radiofrequency catheter ablation of accessory pathway-mediated and AV node reentrant tachycardia at this institution, patients with initial tachyarrhythmia after age 65 years were compared with those presenting initially before age 30. SETTING: A tertiary medical center for the general public. PARTICIPANTS: Sixty-six patients had their initial symptoms after age 65: Group I, 32 patients with accessory pathway-mediated tachycardia, and Group II, 34 patients with AV node reentrant tachycardia. Four-hundred forty patients had their initial symptoms before age 30: Group III, 283 with accessory pathway mediated tachyarrhythmia, and Group IV, 157 with AV node reentrant tachycardia. INTERVENTION: All patients underwent electrophysiological study to determine the mechanisms of tachyarrhythmia, and radiofrequency catheter ablation for treatment of tachycardia. RESULTS: (1) Older patients with initial arrhythmia had incidence of critical clinical manifestations, including tachyarrhythmia-related syncope and cardioversion, similar to those with initial arrhythmia at a younger age. (2) Patients in Group III, showed anterograde effective refractory period (ERP) of the AV node (P = .432), longer anterograde ERP of the accessory pathway (P = .004), and greater difference of the anterograde ERP between the AV node and the accessory pathway (D-ERP) (P = .003) similar to patients in group I. In Group II, the ERP and Wenckebach cycle length of the retrograde fast pathway was significantly longer than in Group IV (P = .037 and P < .001, respectively), and a greater percentage of patients in Group II than in Group IV AV node reentrant tachycardia needed isoproteronol to facilitate the induction of reentrant tachycardia (P = .034). (3) Patients in Group I and Group II had a higher incidence of supraventricular and ventricular ectopic activity than those in Group III (P = .002 and P = .005, respectively) and Group IV (P = .024 and P = .012, respectively) in 24-hour ambulatory electrocardiograms. CONCLUSION: The initial onset of accessory pathway-mediated tachycardia after age 65 may be caused by changes of electrophysiologic properties (greater D-ERP) as well as increased supraventricular and ventricular ectopic activity. Influence of the autonomic nervous system, rather than changes of conduction properties in the AV node, and increase in ectopic activity may contribute to the new onset of AV node reentrant tachycardia in older adults. The choice of antiarrhythmic drugs and radiofrequency ablation require attention to the clinical profile and facilitating factors of reentrant tachycardia in this group of patients.

Adult↗
PubMed1995

Future ablation concepts of tachyarrhythmias.

Application of radiofrequency energy to arrhythmogenic substrates after careful cardiac mapping could ensure a high success rate in eliminating certain types of tachyarrhythmias. Future studies of catheter ablation will focus on how to improve ablation efficacy and achieve a better result in various types of tachyarrhythmias. More information about the arrhythmogenic mechanisms will be provided to improve the knowledge of diagnostic and interventional electrophysiology.

Arrhythmias, Cardiac↗
PubMed1995

Accessory atrioventricular pathways and atrioventricular nodal reentrant tachycardia in teenagers. Electrophysiologic characteristics and radiofrequency catheter ablation.

UNLABELLED: Accessory pathway-mediated tachyarrhythmias and AV nodal reentrant tachycardia represent a large portion of supraventricular tachycardia in younger patients. Reports comparing electrophysiologic characteristics and results of radiofrequency ablation between teenagers and adults from the same electrophysiology laboratory are rare, and these deserve further study. This study included 49 teenage patients (mean age 17 +/- 3 years, range from 10 to 20) and 1008 adult patients (mean age 50 +/- 13 years, range from 21 to 92) referred for electrophysiologic study and radiofrequency ablation for treatment of accessory pathway-mediated and AV nodal reentrant tachycardia. The results showed that: (1) mean duration of tachyarrhythmia was shorter in teenagers, but incidences of syncope, cardioversion for hemodynamic compromise and associated cardiovascular diseases were similar in both groups; (2) teenagers had a higher incidence of right-sided free wall accessory pathways (34.1% vs 14.9%, p = 0.048) and better conduction properties of accessory pathways and AV nodal pathways; (3) fast-slow and multiple forms of AV nodal reentrant tachycardia were significantly less frequent (p = 0.026) in teenagers, whereas atrial fibrillation with ventricular preexcitation was common in adults; (4) success rate, incidence of recurrent tachycardia, total procedure time, radiation exposure time and number of radiofrequency pulses for successful ablation did not differ significantly between teenagers and adults. IN CONCLUSION: (1) different electrophysiologic characteristics were found between teenagers and adults; and (2) radiofrequency ablation was effective and safe in teenagers with paroxysmal supraventricular tachycardia.

Adolescent↗
PubMed1995

The effects of accumulated experience on radiofrequency ablation of accessory pathways.

Increasing experience in radiofrequency ablation for accessory pathways appears to reduce the procedure time, radiation time and radiofrequency pulse number, and results in a higher success rate. However, the effect of a learning curve on this procedure from the perspective of location and conduction direction of accessory pathways has not been reported before. The purpose of this study was to determine the effect of accumulated experience on the outcomes of radiofrequency ablation for accessory pathways and on the duration of the procedure parameters by analyzing the results of a dedicated ablation team. The first 512 patients with a single accessory pathway treated in this laboratory were included for analysis of the procedure parameters with respect to locations and conduction directions of accessory pathways. The results showed that the average procedure time, radiation time, and radiofrequency pulse number differed significantly among the different subgroups (left free wall, right free wall, posteroseptal and anteromidseptal location; manifest or concealed conduction). All subgroups except the anteromidseptal pathways showed a significant improvement of the procedure parameters with increased ablation experience. Although the initial rate of improvement was similar among the different subgroups, the rate of improvement in left free wall pathways nearly reached a plateau after 120 ablation procedures. Thus it was concluded that a certain number of ablation procedures was necessary before achievement of a high success rate with shorter procedure and radiation times and a lower radiofrequency pulse number.

Catheter Ablation↗
PubMed1995

Set-shifting aptitude in Parkinson's disease: external versus internal cues.

A modified version of the odd-man-out test was used to investigate set-shifting aptitude in 12 patients with Parkinson's disease. We asked subjects to execute in alternation two different sorting rules over successive items. External and internal cueing conditions were employed. Patients with Parkinson's disease were impaired on the tasks with internal cues but were normal on the tasks with external cues. Moreover, the shift costs were consistently larger for the shift to the easier task than the shift to the more difficult task. These findings indicated that the model of 'Supervisory Attentional System' may not be sufficient to explain the data as Brown and Marsden (1988) originally suggested.

Aged↗
PubMed1995

[The changes of central and peripheral nerve conduction and the effect of thyroxine replacement in thyroidectomized rats].

The aim of this study is to make serial BAEPs and PNCS in hypothyroid rats in order to provide objective and quantitative methods of detecting dysfunction of the central and peripheral nervous system in hypothyroid status and elucidating the relationship between the recovery potential and the duration of hypothyroid status. Thyroidectomy was performed in eighteen naive 5-month-old Sprague-Dawley rats in order to induce hypothyroid status, which was confirmed by RIA study 1-2 months after the surgery. Initial BAEP and PNCS were performed in two groups of the hypothyroid animals 1 and 3 months after thyroidectomy. Following the initial examination, thyroxin replacement therapy was given to each hypothyroid group, and then followed by BAEPs and PNCS at two month intervals, up to twice normal studies or six months after the initiation of therapy. In the BAEP study, the prolonged I-V inter-peak latency was the most consistent abnormal finding in all hypothyroid rats. Delayed peak latencies as well as prolonged I-III and III-V inter-peak intervals occurred when the hypothyroid status was longer than one month. We noted that the longer the hypothyroid status, the more severe the central conduction dysfunction. Nonetheless, these abnormalities always returned to normal after the replacement therapy if the hypothyroid state was shorter than 3 months in duration. For the PNCS study, all groups of thyroidectomized rats showed the normal results. We think the peripheral nervous system of rats may be more resistant to damage by hypothyroidism than the central nervous system.

Animals↗
PubMed1991

Electrolytic lesions of the nucleus accumbens in rats which abolish the PREE enhance the locomotor response to amphetamine.

The partial reinforcement extinction effect (PREE) refers to the increased resistance to extinction observed in animals trained on a partial reinforcement (PR) schedule compared with those trained on a schedule of continuous reinforcement (CR). It has been suggested that the PREE is dependent upon the integrity of the septo-hippocampal system, but recent evidence has indicated that the role originally proposed for the lateral septal nucleus may in fact be subserved by the nucleus accumbens. Experiment I therefore tested the effects of electrolytic lesions of the nucleus accumbens on the PREE. These lesions abolished the PREE, the abolition resulting from a decreased rate of extinction in the lesion CR rats coupled with an increased rate of extinction in the PR rats. These results clearly implicate the nucleus accumbens in the development of the PREE, and suggest that theoretical models of the PREE based simply upon consideration of septohippocampal interactions need radical revision. The lesion also enhanced running speeds in acquisition in both the CR and the PR groups. Experiment II therefore assessed spontaneous locomotor activity and the locomotor response to amphetamine challenge at two doses. The lesion produced no increase in spontaneous locomotion; an enhanced increase in response to 1 mg/kg amphetamine; and no changes in the stereotyped behaviours induced by 10 mg/kg amphetamine.

Amphetamine↗
PubMedDate not supplied

Clinical and electrophysiological characteristics in children with atrioventricular nodal reentrant tachycardia.

Atrioventricular (AV) nodal reentrant tachycardia is one of the most common supraventricular tachycardias in childhood. However, information about AV nodal reentrant tachycardia in childhood is limited, especially about the variant and multiple forms. The purpose of this retrospective study was to investigate the clinical and electrophysiological characteristics in pediatric patients with AV nodal reentrant tachycardia. Forty-eight pediatric patients with AV nodal reentrant tachycardia were included (ages 11-18 years; 25 males and 23 females). The age of onset and duration of symptoms were significantly younger and shorter in pediatric patients, respectively. A higher incidence of antegrade dual AV nodal pathways was found in adult patients than pediatric patients (72.9 vs 52.1% p = 0.003). Both antegrade and retrograde slow pathway functions were better in pediatric than adult patients. There was no significant difference between children and adults in the occurrence of variant and multiple forms of AV nodal reentrant tachycardia. This study demonstrated that pediatric patients have different electrophysiologic characteristics from those of adult patients.

Abnormalities, Multiple↗
PubMedDate not supplied

Electropharmacologic characteristics and radiofrequency catheter ablation of sustained ventricular tachycardia in patients without structural heart disease.

Twenty-six patients (mean age 39 +/- 17 years) with idiopathic sustained ventricular tachycardia (VT) were included for study. The patients were divided into two groups: group I: 14 patients with VT originating from the right ventricular outflow tract (wide QRS tachycardia with complete left bundle branch block pattern), and group II: 12 patients with VT originating from the left ventricle (wide QRS tachycardia with complete right bundle branch block pattern). Most of the group I patients (11/14) needed isoproterenol to facilitate induction of VT, and were sensitive to both verapamil and adenosine. Eight patients had successful radio-frequency (RF) ablation and were free of VT without any antiarrhythmic drugs. In group II, sustained VT was induced by programmed ventricular stimulation in all the patients (only 3 patients needed isoproterenol for facilitation); verapamil could terminate all the VT but none of the patients responded to adenosine. Eight patients received RF ablation and 6 patients had successful ablation without recurrent tachycardia on a long-term basis. Different sensitivity to adenosine and isoproterenol between right and left ventricular idiopathic VT suggested different underlying mechanisms for both types of VT. The patients who did not receive catheter ablation still had attacks of VT despite antiarrhythmic drug treatment; however, none of these patients had sudden death since the first attack of VT (mean 95 +/- 51 months), suggesting a benign prognosis in idiopathic VT.

Adolescent↗