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Biomedical subjects

W C Yu

Publications and source records attributed to W C Yu.

At least 55 records · Page 3Linked to original sources
PubMed2000

Pulmonary vein electrogram characteristics in patients with focal sources of paroxysmal atrial fibrillation.

INTRODUCTION: The major source of ectopic beats initiating paroxysmal atrial fibrillation (AF) is from pulmonary veins (PVs). However, the electrogram characteristics of PVs are not well defined. METHODS AND RESULTS: Group I consisted of 129 patients with paroxysmal AF. Group II consisted of 10 patients with a concealed left-sided free-wall accessory pathway. All group I patients had spontaneous AF initiated by ectopic beats, including 169 ectopic foci originating from the PVs. We analyzed PV electrograms from the 169 ectopic foci during sinus beats and ectopic beats. During AF initiation, most (70%) ectopic beats showed PV spike potential followed by atrial potential; 16% of ectopic beats showed PV fragmented potential followed by atrial potential; and 14% showed fusion potentials. The coupling interval between the sinus beat and the ectopic beat was significantly shorter in the inferior PVs than in the superior PVs (171 +/- 48 msec vs 222 +/- 63 msec, P = 0.001) and was significantly shorter in the distal foci than in the ostial foci of PVs (206 +/- 52 msec vs 230 +/- 56 msec, P = 0.01). The incidence of conduction block in the PVs during AF initiation was significantly higher in the inferior PVs than in the superior PVs (12/24 vs 37/145, P = 0.03) and was significantly higher in the distal foci than in the ostial foci of PVs (43/121 vs 6/48, P = 0.04). The maximal amplitude of PV potential was significantly larger in the left PVs than in the right PVs, and the maximal duration of PV potential was significantly longer in the superior PVs than in the inferior PVs during sinus beats in both group I and II patients. CONCLUSION: PV electrogram characteristics were different among the four PVs. Detailed mapping and careful interpretation are the most important steps in ablation of paroxysmal AF originating from PVs.

Adult↗
PubMed2000

Evaluation of quantitative PCR and branched-chain DNA assay for detection of hepatitis B virus DNA in sera from hepatocellular carcinoma and liver transplant patients.

This study evaluated the applicability of quantitative PCR (Q-PCR) and branched-chain DNA assays for detection of hepatitis B virus (HBV) DNA in sera. For 42 samples, the detection rates were 81 and 41%, respectively, with a correlation coefficient of 0.633. The Q-PCR is useful for early monitoring of HBV load in high-risk patients.

Adult↗
PubMed1999

Initiation of atrial fibrillation by ectopic beats originating from the pulmonary veins: electrophysiological characteristics, pharmacological responses, and effects of radiofrequency ablation.

BACKGROUND: Atrial fibrillation (AF) can be initiated by ectopic beats originating from the atrial or great venous tissues. This study investigated the anatomic characteristics and electrophysiological properties of pulmonary veins (PVs), as well as the possible mechanisms and response to drugs of ectopic foci, and assessed the effects of radiofrequency (RF) ablation on AF initiated by ectopic beats originating from PVs. METHODS AND RESULTS: Seventy-nine patients with frequent episodes of paroxysmal AF and 10 control patients were included. Distal PVs showed the shortest effective refractory periods (ERPs), and right superior PVs showed a higher incidence of intra-PV conduction block than left superior PVs. Superior and left PVs had longer myocardial sleeves than inferior and right PVs, respectively. These electrophysiological characteristics were similar between AF and control patients. Propranolol, verapamil, and procainamide suppressed ectopic beats that originated from the PVs. Of 116 ectopic foci that initiated AF, 103 (88.8%) originated from PVs. A mean of 7+/-3 RF applications completely eliminated 110 ectopic foci (94.8%). During the 6+/-2-month follow-up period, 68 patients (86. 1%) were free of AF without any antiarrhythmic drugs. Follow-up transesophageal echocardiogram showed 42.4% of ablated PVs had focal stenosis. One patient had mild exertional dyspnea after ablation, but it resolved 3 months later; 1 patient had onset of mild exertional dyspnea 5 months after ablation. CONCLUSIONS: Electrophysiological characteristics of PVs are different from those in the atria. Ectopic beats from PVs can initiate AF, and beta-adrenergic receptor blocker, calcium channel blockers, and sodium channel blockers can suppress these ectopic beats. Careful mapping and elimination of these ectopic foci can cure paroxysmal AF.

Adult↗
PubMed1999

Is 8-mm more effective than 4-mm tip electrode catheter for ablation of typical atrial flutter?

BACKGROUND: The prospective, randomized study comparing 4- with 8-mm tip electrodes for radiofrequency linear ablation of typical atrial flutter is not available. METHODS AND RESULTS: A total of 104 consecutive patients with typical atrial flutter were randomly assigned to undergo radiofrequency linear ablation using a 4- (Group I, n=54) or 8-mm tip electrode (Group II, n=50) catheter (temperature-control model, preset 70 degrees C). If complete bidirectional isthmus block could not be achieved after 5 pulses, the ablation catheter was changed to the other type; the maximal radiofrequency pulse number was limited to <10 pulses. Complete or incomplete isthmus conduction block was assessed by activation sequence in a multielectrode Halo catheter during low lateral right atrial and proximal coronary sinus pacing. Before shifting to the other catheter type, the 8-mm electrode catheter achieved higher complete isthmus block rate (92% versus 67%, P<0.05) with fewer pulses (2+/-1 versus 3+/-1, P<0.05), shorter procedure time (24+/-15 versus 31+/-12 minutes, P<0.05), and shorter fluoroscopic time (14+/-10 versus 23+/-15 minutes, P<0.05). After 5 failed ablation pulses, 12 (67%) of 18 patients in group I attained complete isthmus block by using an 8-mm tip catheter, but none of 4 patients in group II achieved complete block by changing to a 4-mm tip catheter. CONCLUSIONS: The 8-mm tip electrodes are more effective than the standard 4-mm length electrodes in linear ablation for typical atrial flutter. This clinical benefit may be of particular value for some patients with broad and/or thick isthmus.

Aged↗
PubMed1999

Effects of radiofrequency catheter ablation on quality of life in patients with atrial flutter.

The long-term effects of radiofrequency catheter ablation on quality of life in patients with typical atrial flutter are still unknown. This study included 100 consecutive patients with clinically documented typical atrial flutter. Subjective perception of quality of life was assessed by a semiquantitative questionnaire before, and 1 and 6 months after ablation. Ablation of typical atrial flutter was associated with a significant improvement in the general quality of life, frequency of significant symptoms, and symptoms during attacks. The frequency of hospital admission and emergency room visits, and number of antiarrhythmic drugs significantly decreased after ablation. Activity capacity significantly improved after ablation in patients with depressed left ventricular function. All improvements after ablation were maintained over 6-month follow-up. However, patients with atrial fibrillation compared with those without atrial fibrillation before ablation had less improvement in the general quality of life, frequency of significant symptoms, and symptoms during attacks (including palpitation, asthenia, effort, dyspnea, rest dyspnea, and dizziness). Furthermore, patients with atrial fibrillation before ablation needed more antiarrhythmic drugs, and had a higher frequency of hospital admission and emergent room visits at 6-month follow-up (all variables p <0.01). Multivariate analysis demonstrated that only the presence of atrial fibrillation before ablation could independently predict improvement in general quality of life (p = 0.03), frequency of significant symptoms (p = 0.03), symptoms during attacks (p = 0.04), and decrease in the consumption of health care resources including antiarrhythmic drugs (p = 0.01), hospital admission (p = 0.02), and emergency room visits (p = 0.02). Ablation of typical atrial flutter could significantly improve quality of life, but patients who had atrial flutter associated with atrial fibrillation before ablation had less improvement than those without atrial fibrillation.

Activities of Daily Living↗
PubMed1999

Regional differences in the recovery course of tachycardia-induced changes of atrial electrophysiological properties.

BACKGROUND: Regional differences in recovery of tachycardia-induced changes of atrial electrophysiological properties have not been well studied. METHODS AND RESULTS: In the control group (5 dogs), atrial effective refractory period (AERP) and inducibility of atrial fibrillation (AF) were assessed before and every 4 hours for 48 hours after complete atrioventricular junction (AVJ) ablation with 8-week VVI pacing. In experimental group 1 (15 dogs), AERP and inducibility of AF were assessed before and after complete AVJ ablation with 8-week rapid right atrial (RA) pacing (780 bpm) and VVI pacing. In experimental group 2 (7 dogs), AERP and inducibility of AF were assessed before and after 8-week rapid left atrial (LA) pacing and VVI pacing. AERP and inducibility and duration of AF were obtained from 7 epicardial sites. In the control group, atrial electrophysiological properties obtained immediately and during 48-hour measurements after pacing did not show any change. In the 2 experimental groups, recovery of atrial electrophysiological properties included a progressive recovery of AERP shortening, recovery of AERP maladaptation, and decrease of duration and episodes of reinduced AF. However, recovery of shortening and maladaptation of AERP and inducibility of AF was slower at the LA than at the RA and Bachmann's bundle. CONCLUSIONS: The LA had a slower recovery of tachycardia-induced changes of atrial electrophysiological properties, and this might play a critical role in initiation of AF.

Animals↗
PubMed1999

Tolerance of the liver to intermittent pringle maneuver in hepatectomy for liver tumors.

BACKGROUND: Hepatectomy can be performed with a low mortality rate, but massive hemorrhage during the operation remains a potentially lethal problem. The Pringle maneuver is traditionally used during hepatectomy to reduce blood loss, but the effect on the metabolic function of hepatocytes is potentially harmful. Although our randomized study showed that an intermittent Pringle maneuver is safe and effective during hepatectomy, the upper limit of the duration of the Pringle maneuver is not known. HYPOTHESIS: The liver can tolerate intermittent Pringle maneuver if the duration is not excessive. DESIGN: From July 20, 1995, to November 25, 1997, 112 patients underwent hepatectomy for liver tumors. The data of 50 patients who had hepatectomy without the Pringle maneuver were compared with those of 62 patients who had a liver transection using a Pringle maneuver for 20 minutes and a 5-minute clamp-free interval. The data were collected prospectively. MAIN OUTCOME MEASURES: The surface area of liver transection was measured, and blood loss during liver transection per centimeter square of transection area was calculated. Routine liver biochemical tests, arterial ketone body ratio (AKBR), and plasma cytokine-interleukin (IL) 1alpha, 1beta, 2, and 6, and tumor necrosis factor alpha--levels were measured before and after the operation. The morbidity and hospital mortality rates were also compared among the patients with different ischemic durations and those without an intermittent Pringle maneuver. SETTING: Tertiary referral center. RESULTS: The cutoff point of accumulated ischemic time that induced substantial liver damage, as shown by the postoperative recovery rate of the AKBR, was found to be 120 minutes. Compared with the control group, the patients whose accumulated ischemic time was shorter than 120 minutes had less blood loss related to transection area (10 mL/cm2 vs 22 mL/cm2; P<.001), less blood transfused (0 L vs 0.6 L; P = .004), a shorter transection time related to transection area (2.0 min/cm2 vs 2.8 min/ cm2; P = .002), a significantly higher AKBR in the first 2 hours after liver transection, an equal recovery rate of the AKBR, and a comparable increase of the plasma level of IL-6 postoperatively. For the patients whose accumulated ischemic time was longer than 120 minutes, blood loss from the transection area was less than for the control group (14 mL/cm2 vs 22 mL/cm2; P<.05), but the transection time related to the transection area and the blood transfusion volume did not differ from those of the control group. Furthermore, they had a significantly lower recovery rate of the AKBR and higher plasma levels of IL-6 postoperatively than the control group.

Adult↗
PubMed1999

Reversal of atrial electrical remodeling following cardioversion of long-standing atrial fibrillation in man.

BACKGROUND: In animal studies, atrial fibrillation has been shown to shorten the atrial refractory period and impair its rate adaptation. However, little is known about the effects of chronic atrial fibrillation on atrial electrophysiology and its recovery course in humans. METHODS AND RESULTS: Nineteen patients, mean age 64 +/- 14 years, with chronic atrial fibrillation of more than six months duration were included in this study. All of them were successfully converted to sinus rhythm with an external defibrillator. Atrial effective refractory periods at right atrial appendage and distal coronary sinus were determined with five pacing cycle lengths (300, 400, 500, 600 and 700 ms) at 30 min after cardioversion and once a day for four days. The atrial conduction properties, including P wave duration of surface ECG, and right and left atrial conduction times, were also measured at the same time interval. Twenty age-matched patients without a history of atrial tachyarrhythmia were evaluated as controls. In comparison with controls, chronic atrial fibrillation significantly shortened the atrial effective refractory period, impaired its rate adaptation response, especially at distal coronary sinus, and depressed the conduction properties of atria. The atrial conduction properties did not change during the four-day follow-up period; however, the atrial effective refractory period was gradually prolonged and its rate adaptation response improved after restoration of sinus rhythm. CONCLUSIONS: In humans, chronic atrial fibrillation significantly shortened the atrial effective refractory period, and impaired its rate adaptation response. Restoration and maintenance of sinus rhythm could reverse these electrophysiological changes.

Aged↗
PubMed1999

Early recurrence of atrial fibrillation after external cardioversion.

UNLABELLED: Early recurrence of atrial fibrillation (AF) has been reported to occur in a significant number of patients after internal cardioversion. However, information about early recurrence of AF after external cardioversion has never been reported. The present study was conducted to investigate the clinical and electrophysiological characteristics of early recurrence of AF and its role in failure of cardioversion in patients with chronic AF. METHODS AND RESULTS: The study included 50 consecutive patients, age 69+/-9, with a history of chronic AF for more than 3 months duration and electrical cardioversion. They were divided into two groups according to the presence (group 1) or absence (group 2) of early recurrence of AF. There were 13 (26%) patients in group 1 and 37 (74%) patients in group 2. The age, gender, duration of AF, left ventricular function, left atrial dimension, and underlying heart disease were similar between group 1 and 2. Forty-five patients were successfully converted to sinus rhythm with a mean energy of 158+/-57 . Among those who failed to be converted to sinus rhythm, 4 (80%) belonged to group 1 and 1 (20%) belonged to group 2. The early recurrences of AF were initiated with consecutive APDs; but the numbers of APD in the first 30 seconds after cardioversion were similar between group 1 and 2. However, the coupling interval of the second APD was shorter in group 1 than group 2 (188+/-22 vs 324+/-59 ms, P = 0.003). Nine of the 13 early recurrences were prevented by an increase of shock energy (n = 3) or intravenous amiodarone infusion (n = 6). There were no differences in duration of follow-up, recurrence rate, and time interval to recurrence between group 1 and group 2. Early recurrence of AF occurred in 26% of chronic AF patients who underwent external electrical cardioversion and was a major cause of failure in cardioversion. Early recurrence of AF was initiated by APDs with decreasing coupling intervals and could be prevented with an increase of shock energy or amiodarone.

Aged↗
PubMed1999

Change of atrial refractory period after short duration of rapid atrial pacing: regional differences and possible mechanisms.

It is unknown whether there are regional differences in the change of atrial effective refractory period (ERP) after a short duration of rapid atrial pacing. Furthermore, the effects of calcium channel and potassium channel on this phenomenon have not been extensively investigated. In opened-chest dogs, the endocardial monophasic action potential duration at 90% repolarization (APD90) from the right atrial appendage, and ERP from seven atrial sites were measured before and after rapid atrial pacing at 800 beats/min for 30 minutes. Both atrial ERP and APD90 significantly shortened after rapid atrial pacing. The postpacing atrial ERP and APD90 shortening persisted for 119 +/- 3 and 123 +/- 4 seconds after cessation of pacing, respectively. There was no significant difference in the magnitude or recovery course of atrial ERP shortening after pacing among the seven atrial sites. Pretreatment with nicorandil and d-sotalol had no effects on the magnitude or recovery course of atrial ERP shortening after pacing. However, the degree of ERP and APD90 shortening after pacing was significantly attenuated in the verapamil and ryanodine groups; furthermore, the recovery of ERP and APD90 after cessation of pacing was faster in the two groups. In conclusion, shortening of atrial ERP induced by short-duration rapid atrial pacing was uniform in both atria. Both the adenosine triphosphatase (ATP) dependent potassium current and rapid component of the delayed rectifier did not significantly influence this phenomenon, but both the verapamil and ryanodine could significantly attenuate the degree of atrial ERP and APD90 shortening.

Adenosine Triphosphatases↗
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↗
PubMed1999

Effects of 17beta-estradiol on tachycardia-induced changes of atrial refractoriness and cisapride-induced ventricular arrhythmia.

INTRODUCTION: Gender difference is known to be associated with the occurrence of arrhythmia. However, the effects of female sex hormone on atrial electrophysiology, and on the occurrence of torsades de pointes (TdP) induced by cisapride have been unclear. METHODS AND RESULTS: Two experiments were included in this study. In experiment 1, effective refractory periods (ERPs) from five epicardial atrial sites were measured before and after rapid atrial pacing at 800 beats/min for 30 minutes in dogs with pretreatment of verapamil (n = 10), 17beta-estradiol (n = 10), or without pretreatment (n = 10, control group). In experiment 2, limb-lead ECG and monophasic action potentials in the left and right ventricles were recorded before and after each dose of cisapride (2 to 6 mg/kg) during different ventricular rates in dogs with (n = 9) and without (n = 14) concomitant administration of 17beta-estradiol (0.3 microg/kg). After 17beta-estradiol administration, there were greater atrial ERPs in the study dogs than in the control group. The atrial ERPs were shortened significantly after rapid atrial pacing, but the degree was greater in the control group than in the dogs pretreated with verapamil or 17beta-estradiol. Moreover, the recovery of atrial ERPs was faster in dogs pretreated with verapamil or 17beta-estradiol than in the control group. In experiment 2, cisapride prolonged the QT interval and biventricular APD90 and induced early afterdepolarizations (EADs) in a dose-dependent manner. However, dogs receiving cisapride combined with 17beta-estradiol had a greater increase of ventricular repolarization and a higher incidence of EADs than those receiving cisapride only. Moreover, dogs receiving cisapride combined with 17beta-estradiol (3/9, 33%) had a greater incidence of TdP than those receiving cisapride only (0/14, 0%, P < 0.05). CONCLUSIONS: 17beta-estradiol has a significant effect on atrial electrophysiology, which may be related to the prevention of atrial fibrillation. However, the high incidence of TdP in dogs receiving cisapride combined with 17beta-estradiol suggests that the female sex hormone is an important risk factor of cisapride-induced proarrhythmia.

Action Potentials↗
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

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↗