Biomedical subjects

C T Tai

Publications and source records attributed to C T Tai.

At least 73 records · Page 4Linked to original sources

PubMed1999

Inducibility of atrial fibrillation during atrioventricular pacing with varying intervals: role of atrial electrophysiology and the autonomic nervous system.

INTRODUCTION: Patients receiving VVI pacemakers have a higher incidence of paroxysmal atrial fibrillation (AF) than those receiving DDD pacemakers. However, the mechanism behind the difference is not clear. The purpose of this study was to investigate whether atrial electrophysiology and the autonomic nervous system play a role in the occurrence of AF during AV pacing. METHODS AND RESULTS: The study population consisted of 28 patients who had (group I, n = 15) or did not have (group II, n = 13) AF induced by a single extrastimulus during pacing with different AV intervals. Atrial pressure, atrial size, atrial effective refractory periods, and atrial dispersion were evaluated during pacing with different AV intervals. Twenty-four-hour heart rate variability and baroreflex sensitivity also were examined. Atrial pressure, atrial size, effective refractory periods in the right posterolateral atrium and distal coronary sinus, and atrial dispersion increased as the AV interval shortened from 160 to 0 msec. During AV pacing, group I patients had greater minimal (52+/-17 vs 25+/-7 msec; P < 0.005) and maximal (76+/-16 vs 36+/-9 msec; P < 0.005) atrial dispersion than group II patients. The differences in atrial size and atrial dispersion among different AV intervals were greater in patients with AF than in those without AF. Baroreflex sensitivity (6.6+/-1.7 vs 3.9+/-1.0; P < 0.00005), but not heart rate variability, was higher in patients with AF than in those without AF. CONCLUSION: Abnormal atrial electrophysiology and higher vagal reflex activity can play important roles in the genesis of AF in patients receiving pacemakers.

Atrial Fibrillation↗

PubMed1999

Persistent atrial flutter in patients treated for atrial fibrillation with amiodarone and propafenone: electrophysiologic characteristics, radiofrequency catheter ablation, and risk prediction.

INTRODUCTION: Antiarrhythmic drugs have been reported to promote the conversion of atrial fibrillation to atrial flutter in patients with paroxysmal atrial fibrillation. However, information about the electrophysiologic mechanism and response to radiofrequency ablation of these drug-induced atrial flutters is limited. Furthermore, the determinants of the development of persistent atrial flutter in patients treated for atrial fibrillation with antiarrhythmic drugs are still unknown. METHODS AND RESULTS: Among the 136 patients treated for atrial fibrillation with amiodarone (n = 96) or propafenone (n = 40), 15 (11%, mean age 65.5 +/- 12.3 years) were identified to have subsequent development of persistent atrial flutter based on surface ECG characteristics during antiarrhythmic drug treatment. The mean interval between the beginning of drug treatment and the onset of atrial flutter was 5.0 +/- 5.5 months. Intracardiac mapping and entrainment studies revealed that 11 patients had counterclockwise typical atrial flutter, and 4 had clockwise typical atrial flutter. All 15 patients underwent successful ablation with creation of complete bidirectional isthmus conduction block. After a mean follow-up of 12.3 +/- 4.2 months, 14 (93%) of 15 patients who underwent successful ablation and continued taking antiarrhythmic drugs have remained in sinus rhythm. Univariate analysis of clinical variables demonstrated that only atrial enlargement was significantly related to the occurrence of persistent atrial flutter. CONCLUSION: In patients with atrial fibrillation, persistent typical atrial flutter might occur during antiarrhythmic drug treatment, and atrial enlargement was a risk factor for the development of such an arrhythmia. Radiofrequency ablation and continuation of pharmacologic therapy offered a safe and effective means of achieving and maintaining sinus rhythm.

Aged↗

PubMed1999

Bezold-Jarisch-like reflex during radiofrequency ablation of the pulmonary vein tissues in patients with paroxysmal focal atrial fibrillation.

INTRODUCTION: Information is lacking about the occurrence of ablation-related proarrhythmic events during application of radiofrequency (RF) energy at the pulmonary veins in patients with paroxysmal focal atrial fibrillation. The purpose of this study was to assess the theoretical risk of reflex bradycardia and hypotension response during RF ablation of these regions rich in endocardial nerve terminals. METHODS AND RESULTS: Among the 40 consecutive patients (29 men, 11 women; mean age 65+/-12 years) with clinically documented frequent attacks of paroxysmal atrial fibrillation who underwent superior pulmonary vein ablation for left focal atrial fibrillation, 6 patients (15%) developed bradycardia-hypotension syndrome during energy delivery. A single atrial fibrillation trigger focus in the left or right superior pulmonary vein was found in 3 and 1 patients, respectively. Two patients had two trigger foci originating from the orifice or proximal part of both superior pulmonary veins. After RF current was applied for a period of 14+/-10 seconds, 2 patients developed junctional rhythm and sinus bradycardia, another 2 patients had profound sinus bradycardia, 1 patient had two episodes of sudden onset of complete AV block with resultant 9.5-second asystole, and 1 patient showed profound sinus bradycardia, transient AV block, and an 8-second asystole due to sinus arrest. Blood pressure fell when any substantial bradyarrhythmias occurred. All 6 patients were free of rhythm disturbances during the postablation follow-up period (mean 8+/-2 months). CONCLUSION: RF catheter ablation of the pulmonary vein tissues could evoke a variety of profound bradycardia-hypotension responses. The Bezold-Jarisch-like reflex might be the underlying mechanism.

Adult↗

PubMed1999

Double multielectrode mapping catheters facilitate radiofrequency catheter ablation of focal atrial fibrillation originating from pulmonary veins.

INTRODUCTION: Several reports have demonstrated that focal atrial fibrillation (AF) may arise from pulmonary veins (PVs). The purpose of this study was to investigate the safety and efficacy of using double multielectrode mapping catheters in ablation of focal AF. METHODS AND RESULTS: Forty-two patients (30 men, 12 women, age 65+/-14 years) with frequent attacks of paroxysmal AF were referred for catheter ablation. After atrial transseptal procedure, two long sheaths were put into the left atrium. Two decapolar catheters were put into the right superior PV (RSPV) and left superior PV (LSPV), or inferior PVs if necessary, guided by pulmonary venography. All the patients had spontaneous initiation of AF either during baseline (2 patients), after isoproterenol infusion (8 patients) or high-dose adenosine (2 patients), after short duration burst pacing under isoproterenol (14 patients), or after cardioversion of pacing-induced AF (16 patients). The trigger points of AF were from the LSPV (12 patients), RSPV (8 patients), and both superior PVs (19 patients). The trigger points from PVs (total 61 points) were 18 (30%) in the ostium of PVs and 43 inside the PVs (9 to 40 mm). After 6+/-3 applications of radiofrequency energy, 57 of 61 triggers were completely eliminated, and the other 4 triggers were partially eliminated. During a follow-up period of 8+/-2 months, 37 patients (88%) were free of symptomatic AF without any antiarrhythmic drugs. Twenty patients received a transesophageal echocardiogram, and 19 showed small atrial septal defects (2.8+/-1.2 mm) with trivial shunt. Fifteen defects closed spontaneously 1 month later. CONCLUSION: The technique using double multielectrode mapping catheters is a relatively safe and highly effective method for mapping and ablation of focal AF originating from PVs.

Adult↗

PubMed1999

Right atrial focal atrial fibrillation: electrophysiologic characteristics and radiofrequency catheter ablation.

INTRODUCTION: Information about focal atrial fibrillation (AF) originating from the right atrium has not been well described. The purposes of this study were to demonstrate the electrophysiologic characteristics and radiofrequency catheter ablation in patients who had right atrial focal AF. METHODS AND RESULTS: From January 1996 to September 1998, 172 patients with clinically documented attacks of paroxysmal AF were referred to this institution for electrophysiologic study and/or radiofrequency catheter ablation. Anterior free wall, crista terminalis, and right and left superior pulmonary veins were mapped simultaneously. Eight patients (4.7%) had right atrial focal AF, consistent activation sequence, irregular fibrillation interval (mean fibrillation interval: 164 +/- 11 msec), and episodes of exit block from the initiating foci observed. The presumed ablation site was chosen on the basis of the earliest bipolar activity relative to an atrial electrogram reference during the initiation of AF. After application of 2 +/- 1 radiofrequency pulses, AF was eliminated without recurrence during the follow-up period (mean: 14 +/- 8 months; range: 3 to 25). Twenty-four-hour Holter monitoring showed that the number of atrial premature beats decreased significantly at the 3-month follow-up (4,216 +/- 411 vs 135 +/- 14 beats/day). CONCLUSION: Right atrial focal AF is one subgroup of focal AF, and it can be cured by radiofrequency catheter ablation.

Atrial Fibrillation↗

PubMed1998

Electrophysiological mechanisms and determinants of vagal maneuvers for termination of paroxysmal supraventricular tachycardia.

BACKGROUND: The vagal maneuvers used for termination of paroxysmal supraventricular reentrant tachycardia (PSVT) appear to involve more complex mechanisms than we have known, and further study should be done to explore the possible mechanisms. METHODS AND RESULTS: In this study, 133 patients with PSVT and 30 age- and sex-matched control subjects were included. We assessed the effects of different vagal maneuvers on termination of PSVT and compared baroreflex sensitivity and beta-adrenergic sensitivity between the patients with PSVT and control subjects. Out of 85 patients with atrioventricular reciprocating tachycardia (AVRT), vagal maneuvers terminated in 45 (53%). Of these, 28 (33%) terminated in the antegrade limb and 17 (20%) terminated in the retrograde limb. Out of 48 patients with atrioventricular nodal reentrant tachycardia (AVNRT), vagal maneuvers terminated the tachycardia in the antegrade slow pathway (14%) or in the retrograde fast pathway (19%). Baroreflex sensitivity was poorer but isoproterenol sensitivity test better in patients with AVNRT. Poorer antegrade atrioventricular node conduction properties and better vagal response determined successful antegrade termination of AVRT by vagal maneuvers. Poorer retrograde accessory pathway conduction property but better vagal response determined successful retrograde termination of AVRT. Better sympathetic and vagal response associated with poorer retrograde atrioventricular node conduction determined retrograde termination of AVNRT by the Valsalva maneuver. CONCLUSIONS: Both the vagal response and conduction properties of the reentrant circuit determine the tachycardia termination by vagal maneuvers. Improved understanding of the interaction of autonomic and electrophysiological mechanisms in maintaining or terminating PSVT may provide important insight into the pathophysiology of these two tachycardias.

Adolescent↗

PubMed1998

Absence of junctional rhythm during successful slow-pathway ablation in patients with atrioventricular nodal reentrant tachycardia.

BACKGROUND: The presence of junctional rhythm has been considered to be a sensitive marker of successful slow-pathway ablation. However, in rare cases, junctional rhythm was absent despite multiple radiofrequency applications delivered over a large area in the Koch's triangle, and successful ablation was achieved in the absence of a junctional rhythm. METHODS AND RESULTS: This study included 353 patients with AV nodal reentrant tachycardia (143 men and 210 women; mean age, 50+/-17 years) who underwent catheter ablation of the slow pathway. Combined anatomic and electrogram approaches were used to guide ablation. Inducibility of AV nodal reentrant tachycardia was assessed after each application of radiofrequency energy. Successful sites were located in the posterior area in 18 (90%) of 20 patients without junctional rhythm during slow-pathway ablation compared with 200 (60%) of 333 patients with junctional rhythm (P<0.001). The fast-slow form of tachycardia was more common in patients without than in those with junctional rhythm (30% versus 3%; P=0.001). At the successful ablation sites, patients with junctional rhythm had a higher incidence of a multicomponent or slow-pathway potential (51% versus 10%; P<0.001), a longer duration of the atrial electrogram (64+/-8 versus 50+/-9 ms; P=0.04), and a smaller atrial/ventricular electrogram amplitude ratio (0.29+/-0.18 versus 0.65+/-0.27; P<0. 001) than those without junctional rhythm. Mean temperatures at successful sites (56+/-6 degreesC versus 58+/-9 degreesC; P=0.57) and incidence of transient AV block (2% versus 0%; P=0.86) were similar between patients with and without junctional rhythms. By multivariate analysis, location of ablation sites, atrial/ventricular electrogram amplitude ratio, absence of a multicomponent or slow-pathway potential, and occurrence of the fast-slow form of tachycardia were independent predictors of the absence of a junctional rhythm during successful slow-pathway ablation. CONCLUSIONS: In some rare cases, successful slow-pathway ablation is possible in the absence of a junctional rhythm.

Adolescent↗

PubMed1998

Prevalence and subtypes of dementia in southern Taiwan: impact of age, sex, education, and urbanization.

To determine the prevalence and subtypes of dementia in southern Taiwan, a two-phase study consisting of a phase I screening survey using the Mini-Mental Status Examination (MMSE) and a phase II diagnostic examination using the CERAD neuropsychological battery and the neurobehavioral examination was conducted. According to the household records, stratified random sampling by the degree of urbanization of the community was used, and 2915 inhabitants aged 65 and over participated in this study. The ICD-10NA criteria for dementia, NINCDS-ADRDA guidelines for Alzheimer's disease (AD), and NINDS-AIREN criteria for vascular dementia (VaD) were employed. Three hundred and ninety-eight persons who had MMSE scores below the cutoff values were recruited into the phase II study, of whom 108 had dementia. The prevalence rate (PR) of dementia was 3.7%, increasing from 1.3% in people 65-69 years old to 16.5% in people 85 years old and older. The age-standardized PR (ASPR) was 4.0%. AD (58 cases, 53.7%, PR=2.0%, ASPR=2.3%) was the most common cause of dementia, followed by VaD (25 cases, 23.1%, PR=0.9%, ASPR=0.9%), and mixed dementia (eight cases, 7.4%). After adjusting for age, sex and education using logistic regression analysis, aging was a significant risk factor for AD, VaD and total dementia. Female sex and illiteracy were significant risk factors for AD only. We concluded that the prevalence of dementia in Taiwan is lower than in the developed countries, which could be due to a relatively young elderly population and a high mortality from dementia in Taiwan. AD is the leading cause of dementia in Taiwan. Considering the high stroke prevalence, the relatively lower prevalence of VaD in Taiwan deserves further investigation.

Age Distribution↗

PubMed1998

Tachycardia-induced change of atrial refractory period in humans: rate dependency and effects of antiarrhythmic drugs.

BACKGROUND: Atrial fibrillation (AF) has been shown to shorten the atrial effective refractory period (ERP) and make the atrium more vulnerable to AF. This study investigated the effect of atrial rate and antiarrhythmic drugs on ERP shortening induced by tachycardia. METHODS AND RESULTS: Seventy adult patients without structural heart disease were included. For the first part of the study, right atrial ERP was measured with a drive cycle length of 500 ms before and after 10 minutes of rapid atrial pacing using five pacing cycle lengths (450, 400, 350, 300, and 250 ms) in 10 patients. For the second part of the study, the remaining 60 patients were included to study the effects of antiarrhythmic drugs on changes in atrial ERP induced by AF. Atrial ERP was measured with a drive cycle of 500 ms before and after an episode of pacing-induced AF. After the patients were randomized to receive one of six antiarrhythmic drugs (procainamide, propafenone, propranolol, dl-sotalol, amiodarone, and verapamil), atrial ERP was measured before and after another episode of pacing-induced AF. In the first part of the study, atrial ERP shortened significantly after 10 minutes of rapid atrial pacing, and the degree of shortening was correlated with pacing cycle length. The second part of the study showed that atrial ERP shortened after conversion of AF (172+/-15 versus 202+/-14 ms, P<0.0001) and that ERP shortening was attenuated after verapamil infusion (-4.6+/-1.2% versus -15.1+/-3.4%, P<0.001) but was unchanged after infusion of the other antiarrhythmic drugs. Furthermore, all of these antiarrhythmic drugs could decrease the incidence and duration of secondary AF. CONCLUSIONS: The atrial ERP shortening induced by tachycardia was a rate-dependent response. Verapamil, but not other antiarrhythmic drugs, could markedly attenuate this effect. However, verapamil and the other drugs could decrease the incidence and duration of secondary AF.

Adult↗

PubMed1998

Electropharmacologic effects of class I and class III antiarrhythmia drugs on typical atrial flutter: insights into the mechanism of termination.

BACKGROUND: Acute effects of class I and class III antiarrhythmia drugs on the reentrant circuit of typical atrial flutter are not fully studied. Furthermore, the critical electrophysiologic determinants of flutter termination by antiarrhythmia drugs are not clear. METHODS AND RESULTS: The study population consisted of 36 patients (mean age, 53+/-17 years) with clinically documented typical atrial flutter. A 20-pole "halo" catheter was positioned around the tricuspid annulus. Incremental pacing was performed to measure the conduction velocity along the isthmus and lateral wall, and extrastimulation was performed to evaluate atrial refractory period in the baseline state and after intravenous infusion of ibutilide, propafenone, and amiodarone. Efficacy of these drugs in conversion of typical atrial flutter and patterns of termination were also determined. Ibutilide significantly increased the atrial refractory period and decreased conduction velocity in the isthmus at short pacing cycle length. It terminated atrial flutter in 8 (67%) of 12 patients after prolongation of flutter cycle length due to increase (86+/-19%) of conduction time in the isthmus. Propafenone predominantly decreased conduction velocity with use dependency and significantly increased atrial refractory period, but it only converted atrial flutter in 4 (33%) of 12 patients. Amiodarone had fewer effects on atrial refractory period and conduction velocity than did ibutilide and propafenone, and it terminated atrial flutter in only 4 (33%) of 12 patients. Termination of typical atrial flutter was due to failure of wave front propagation through the isthmus, which occurred with cycle length oscillation, abruptly without variability of cycle length, or after premature activation of the reentrant circuit. CONCLUSIONS: Ibutilide, with a unique increase in atrial refractoriness, was more effective in conversion of atrial flutter than were propafenone and amiodarone.

Adult↗

PubMed1998

Effects of antiarrhythmic drugs on variability of ventricular rate and exercise performance in chronic atrial fibrillation complicated with ventricular arrhythmias.

For conversion of atrial fibrillation to sinus rhythm and management of ventricular arrhythmias, antiarrhythmic drugs were frequently used. However, the effects of antiarrhythmic drugs on exercise performance and on the variability of ventricular rate were not available. This study included 37 patients who had chronic atrial fibrillation complicated with symptomatic ventricular arrhythmias. The patients were divided into three groups and received sotalol, propafenone, and procainamide, respectively. Before and after taking the drugs for 14 days, these patients received treadmill exercise test, 24 h Holter electrocardiogram, and tilt table test for evaluation of the exercise performance and the variability of ventricular rate (including the mean RR intervals, mRR, the standard deviation of RR intervals, SDRR, and the root mean square of the difference in successive RR intervals, rMSSD). All these antiarrhythmic drugs could suppress ventricular arrhythmia but only sotalol could significantly increase the exercise duration (374+/-50 to 476+/-55 s, P=0.02), and reduce the maximal heart rate (186+/-23 to 136+/-16 beats/min, P=0.01) during exercise test. Furthermore, only sotalol increased the mRR (777+/-60 to 885+/-66 ms, P=0.02), SDRR (190+/-40 to 216+/-48 ms, P=0.04) and rMSSD (223+/-48 to 253+/-40 ms, P=0.03) during 24 h Holter electrocardiogram. With head-up tilt, the mRR, SDRR and rMSSD all decreased significantly before drug therapy, and these changes were still present only after propafenone therapy. Therefore, comparisons among sotalol, propafenone and procainamide showed that sotalol increased the exercise performance and the variability of ventricular rate in patients who had chronic atrial fibrillation complicated with symptomatic ventricular arrhythmias.

Aged↗

PubMed1998

Idiopathic ventricular fibrillation: clinical, electrophysiologic characteristics and long-term outcomes.

The long-term prognosis, including risks of arrhythmic recurrence of idiopathic ventricular fibrillation (VF), is uncertain; moreover, the role of electrophysiologic study in the diagnosis and guiding of antiarrhythmic drugs therapy for idiopathic VF remains controversial. The purpose of this study was to study the clinical features, electrophysiologic characteristics and long-term clinical outcomes of six consecutive patients (five males) who had at least one episode of aborted cardiac arrest (5 patients) or syncope (1 patients) with documentation of ventricular fibrillation (VF) in the absence of apparent heart disease. Idiopathic VF was diagnosed by exclusion. All patients underwent the electrophysiologic study including intravenous antiarrhythmic drug testing. Recurrences of VF after therapy and the long-term outcomes were assessed. The mean age at the first episode was 43+/-19 years (range from 16 to 63 years). All patients had sustained VF induced by double (3 patients) or triple (3 patients) ventricular extrastimuli at a paced cycle length of 400 or 500 ms from the right ventricular apex. Intravenous procainamide and/or mexiletine could suppress the reinduction of sustained VF in 4 (67%) of 6 patients. Recurrence of VF (documented VF attack, sudden cardiac arrest or syncope) was observed in 3 (100%) of 3 patients who received procainamide or mexiletine alone. Four patients (including 3 patients who experienced recurrence) received amiodarone alone or in combination with mexiletine, and these drugs could effectively prevent recurrence of VF. One patient with exercise-induced VF remained asymptomatic without any treatment during a follow-up period of 95 months. Another patient received an implantable cardioverter-defibrillator without concomitant antiarrhythmic drug therapy and had no discharge of electrical shock during 28 months of follow-up. During a mean follow-up period of 64+/-40 months (range from 28 to 128 months), all the patients were alive except patient No. 2 who died of acute hepatic failure. In conclusion, electrophysiologic study is a reliable diagnostic method, but it was of limited value in guiding antiarrhythmic drug therapy for preventing recurrence of idiopathic VF. Class I drug alone was associated with a high recurrence rate (100%) despite predictions that it would be effective by the electrophysiologic study. Amiodarone alone or in combination with mexiletine effectively prevented the recurrence of VF during the long-term follow-up along with a favourable outcome.

Administration, Oral↗

PubMed1998

Comparisons of quality of life and cardiac performance after complete atrioventricular junction ablation and atrioventricular junction modification in patients with medically refractory atrial fibrillation.

OBJECTIVES: This study compared the long-term effects of complete atrioventricular junction (AVJ) ablation with those of AVJ modification in patients with medically refractory atrial fibrillation (AF). BACKGROUND: Comparisons between the long-term effects of AVJ ablation with those of AVJ modification in patients with medically refractory AF have not been systematically studied. METHODS: Sixty patients with medically refractory AF were randomly assigned to receive complete AVJ ablation with permanent pacing or AVJ modification. Subjective perception of quality of life (QOL) was assessed by a semiquantitative questionnaire before and 1 and 6 months after ablation. Cardiac performance was evaluated by echocardiography and radionuclide angiography within 24 h (baseline) and at 1 and 6 months after ablation. RESULTS: Both methods were associated with significant improvement in general QOL and a significant reduction in the frequency of major symptoms and symptoms during attacks. The frequency of hospital admission and emergency room visits and antiarrhythmic drug trials significantly decreased after ablation in both groups. However, patients after complete AVJ ablation had a significantly greater improvement in general QOL and a significantly reduced frequency of major symptoms and symptoms during attacks (including palpitation, dizziness, chest oppression, blurred vision and syncope). Left ventricular (LV) systolic function and the ability to perform activities of daily life significantly improved after ablation in patients with depressed LV function in both groups. All improvements after ablation or modification were maintained over the 6-month follow-up period. CONCLUSIONS: AVJ ablation with permanent pacing, as compared with AVJ modification, had a significantly greater ability to decrease the frequency of attacks and the extent of symptoms of AF, and the patients who received this procedure were more satisfied with their general well-being.

Activities of Daily Living↗

PubMed1998

Role of autonomic tone in facilitating spontaneous onset of typical atrial flutter.

OBJECTIVES: This study sought to study the change in autonomic tone that precedes the initiation of paroxysmal atrial flutter. BACKGROUND: An abrupt change in the autonomic tone of the heart is an important initiating factor in the pathogenesis of ventricular tachyarrhythmias and paroxysmal atrial fibrillation. Whether the autonomic tone has a role in the initiation of paroxysmal atrial flutter has not been reported. METHODS: Holter electrocardiographic recording was used to investigate the changes in heart rate variability before the onset of paroxysmal atrial flutter. RESULTS: A total of 12 patients with paroxysmal atrial flutter were analyzed. An increase in the normalized value of the low frequency (LF) component and the LF/high frequency (HF) ratio and a decrease in the normalized value of the HF component began at 6 min before the onset of episodes of paroxysmal atrial flutter, which indicated that sympathovagal balance had shifted to more sympathetic predominance. CONCLUSIONS: An increase in sympathetic modulation or vagal withdrawal, or both, may facilitate the initiation of atrial flutter.

Aged↗

PubMed1998

Role of atrial electrophysiology and autonomic nervous system in patients with supraventricular tachycardia and paroxysmal atrial fibrillation.

OBJECTIVES: The purposes of this study were to evaluate the atrial electrophysiology and autonomic nervous system in patients who had paroxysmal supraventricular tachycardia (PSVT) associated with paroxysmal atrial fibrillation (PAF). BACKGROUND: PAF frequently appeared in patients with PSVT. However, the critical determinants for the occurrence of PAF were not clear. METHODS: This study population consisted of 50 patients who had PSVT with (n=23) and without (n=27) PAF. Atrial pressure, atrial size, atrial effective refractory periods (AERPs), and AERP dispersion were evaluated during baseline and PSVT, respectively. Twenty-four hour heart rate variability and baroreflex sensitivity (BRS) were also examined. RESULTS: There was greater baseline AERP dispersion in patients with PAF than in those without PAF. The atrial pressure, atrial size, AERPs in the right posterolateral atrium and distal coronary sinus, and AERP dispersion were increased during PSVT as compared with those during baseline. Patients with PAF had greater AERP dispersion than those without PAF during PSVT. The differences of atrial size, right posterolateral AERP, and AERP dispersion between baseline and PSVT were greater in patients with PAF than in those without PAF. BRS, but not heart rate variability, was higher in patients with PAF than in those without PAF. Univariate analysis showed that higher BRS (>4.5 ms/mm Hg, p=0.0002, odds ratio=16.1), AERP dispersion during PSVT (>40 ms, p=0.0008, odds ratio=9.7), and increase of right atrial area during PSVT (>2 cm2, p=0.016, odds ratio=10.7) were significantly correlated with the occurrence of PAF in patients with PSVT. CONCLUSIONS: Disturbed atrial electrophysiology and higher vagal reflex could play important roles in the genesis of PAF in patients with PSVT.

Adult↗

PubMed1998

Electrophysiologic characteristics of different ectopic rhythms during slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia.

The presence of ectopic rhythm has been considered to be the most important marker for successful slow pathway ablation, but the details of different ectopic rhythms have not been well described. This study included 83 consecutive patients with typical AV node reentrant tachycardia who underwent slow pathway ablation. The interval between the atrial signals of the His bundle electrogram and the distal ablation catheter [A(H)-A(Ab)], and the interval between the atrial components of the distal ablation catheter and the ostium of coronary sinus catheter [A(Ab)-A(CSos)] were measured. One hundred episodes of ectopic rhythm occurred with 81 (81%) successful applications. There are two different origins and three activation sequences of ectopic rhythms, including HIS rhythm (78 applications, the earliest atrial activation in the His bundle electrogram), CSos rhythm (6 applications, the earliest atrial signal in the coronary sinus ostium electrogram) and CSos preceding HIS (CSos-->HIS) rhythm (16 applications, the atrial activation sequences changing from CSos to HIS rhythm). The CSos rhythm had a shorter mean cycle length (445 +/- 81 vs. 511 +/- 132 vs. 579 +/- 140 ms, p < 0.05), a shorter [A(Ab)-A(CSos)] interval (-2.5 +/- 9.8 vs. 14.1 +/- 11.2 vs. 12.8 +/- 8.4 ms, p < 0.05) and a lower success rate (33% vs. 84% vs. 94% p < 0.05) than HIS rhythm and CSos-->HIS rhythm. Otherwise, the mean cycle length of ectopic rhythm was significant shorter in successful than in failed ablation (506 +/- 135 vs. 559 +/- 118 ms, p = 0.04). In conclusion, we found two different origins and three activation sequences of ectopic rhythms. CSos rhythm had a lower success rate in ablation of slow pathway, thus it was a poor marker for successful ablation.

Adolescent↗

PubMed1998

Electrophysiologic characteristics of a dilated atrium in patients with paroxysmal atrial fibrillation and atrial flutter.

This study investigated the difference of atrial electrophysiologic characteristics between a normal and dilated atrium and compared them among patients with paroxysmal atrial fibrillation and flutter. Twenty-seven patients with paroxysmal atrial fibrillation and 28 patients with paroxysmal atrial flutter were divided into four subgroups, according to the presence of a normal atrium or bilateral atrial enlargement. Thirty patients without atrial arrhythmia (20 patients with normal atrium and 10 patients with bilateral atrial enlargement) were included in control group. The atrial refractoriness in patients with a dilated atrium was longer than those with normal atrial size. In patients with paroxysmal atrial fibrillation and patients of control group, the P-wave duration and interatrial conduction velocity with or without atrial enlargement were similar. However, in patients with paroxysmal atrial flutter, P-APCS (86 +/- 10 ms vs. 73 +/- 9 ms, p < 0.05) and P-ADCS (109 +/- 9 ms vs. 95 +/- 9 ms, p < 0.05) in patients with a dilated atrium were longer than in patients with a normal atrium. The patients with paroxysmal atrial fibrillation or atrial flutter all demonstrated longer P-wave duration and interatrial conduction time than control group. Among the groups with a normal atrium or a dilated atrium, atrial refractoriness in patients with paroxysmal atrial flutter was shorter than that in control group. Moreover, in the patients with a normal atrium, the potential minimal wavelength in control group (6.6 +/- 1.7) was longer than that of paroxysmal atrial fibrillation (5.3 +/- 1.1), or atrial flutter (5.0 +/- 1.2). These findings suggest that atrial electrophysiologic characteristics of a dilated atrium were different from those of normal atrium, and these changes were different between paroxysmal atrial fibrillation and flutter. Multiple factors are considered to be related to the genesis of atrial tachyarrhythmias.

Aged↗

PubMed1998

Radiofrequency ablation of idiopathic left ventricular tachycardia with changing ECG morphology.

Idiopathic left ventricular tachycardia is a distinct clinical entity with a typical ECG of right bundle branch block and left axis deviation. We presented a 39-year-old man with idiopathic left ventricular tachycardia, which demonstrated change in the configuration of QRS complex during successive radiofrequency catheter ablation. We proposed that this idiopathic left ventricular tachycardia may have alternative pathways within the reentrant circuit leading to different exits.

Adult↗