Biomedical subjects

C E Chiang

Publications and source records attributed to C E Chiang.

At least 37 records · Page 2Linked to original sources

PubMed1998

Intracardiac stimulation of human parasympathetic nerve fibers induces negative dromotropic effects: implication with the lesions of radiofrequency catheter ablation.

INTRODUCTION: The dromotropic effects of intracardiac parasympathetic nerve stimulation have not been well studied; furthermore, the effects of radiofrequency ablation lesions on parasympathetic nerve stimulation are not clear. METHODS AND RESULTS: Group I: intracardiac electrical stimulation in the right posteroseptal and anteroseptal areas under different stimulation strengths; group II: intracardiac electrical stimulation before and 10 minutes after intravenous propranolol; group III: intracardiac electrical stimulation before and 5 minutes after intravenous atropine. Among the 10 patients with AV nodal reentrant tachycardia (group IV) and the 10 patients with atrial flutter (group V), atrial fibrillation was induced before and after successful ablation, and intracardiac electrical stimulation in the right posteroseptal area was performed before and after successful ablation. The maximal response and complete decay of the response occurred within 2 to 6 seconds of initiation or termination of parasympathetic nerve stimulation. This negative dromotropic effect disappeared after atropine was administered, but not after propranolol. After successful ablation, parasympathetic stimulation still induced negative dromotropic effects. CONCLUSION: Electrical stimulation of parasympathetic nerve fibers near the posteroseptal and anteroseptal areas could induce a negative dromotropic effect, and this effect was preserved after successful radiofrequency ablation of slow pathway and isthmus conduction.

Adrenergic beta-Antagonists↗

PubMed1998

Focal atrial tachycardia: reanalysis of the clinical and electrophysiologic characteristics and prediction of successful radiofrequency ablation.

INTRODUCTION: Reports about the clinical and electrophysiologic characteristics of focal atrial tachycardia vary widely. Furthermore, the impact of age, gender, associated cardiac diseases, mechanism, location of atrial tachycardia, and the prediction of results of radiofrequency catheter ablation was not clear. The purpose of this study was to further understand the clinical and electrophysiologic characteristics of focal atrial tachycardia and the prediction of results of radiofrequency ablation. METHODS AND RESULTS: We searched the literature published between January 1969 and July 1997 using the key word "atrial tachycardia" from the MEDLINE and National Library of Medicine systems. The items analyzed were age, sex, cardiac disease, mechanism, attack pattern, cycle length, location, number of atrial tachycardias, results of ablation, and recurrence after ablation. Multivariate analysis showed that age and paroxysmal type of tachycardia were independent predictors of nonautomatic mechanism; age and presence of other cardiac diseases were independent predictors of multiple atrial tachycardias, and age also was the independent predictor of right-sided atrial tachycardia. Atrial tachycardia located in the right atrium was the only significant predictor of successful radiofrequency catheter ablation. Other cardiac diseases and multiple atrial tachycardias were the significant predictors of recurrence after initial successful radiofrequency catheter ablation. CONCLUSION: Patient age is closely related to the clinical and electrophysiologic characteristics of atrial tachycardia based on our reanalysis, which found that patient age is an independent predictor of nonautomatic mechanism, right atrial location, existence of multiple atrial tachycardias, and recurrence of atrial tachycardia after initial successful ablation.

Age Factors↗

PubMed1997

Idiopathic monomorphic ventricular tachycardia: clinical outcome, electrophysiologic characteristics and long-term results of catheter ablation.

Ventricular tachycardia (VT) without structural heart disease or any identifiable predisposing causes for arrhythmia is an uncommon but well-recognized clinical entity. The purpose of this study is to assess the results of catheter ablation therapy and the long-term outcome of patients with idiopathic monomorphic VT in a large patient group. Sixty-one consecutive patients (male/female=40/21; mean age 38+/-16 years) with idiopathic VT underwent electrophysiologic study and an attempt of catheter ablation therapy. The 'left VT' group included 31 patients with QRS morphology of right bundle branch block during VT suggestive of the VT originating from the left ventricle (LV), and the 'right VT' group consisted of 30 patients with QRS morphology of left bundle branch block with normal or right frontal axis deviation suggestive of VT arising from right ventricular outflow tract (RVOT). Idiopathic left VT has sustained VT during the clinical attacks, baseline electrophysiologic study or after isoproterenol infusion; it can be entrained by overdrive ventricular pacing, terminated by verapamil, but not by adenosine (except one case with VT focus at left ventricular free wall). Catheter ablation was successful in 22 (84%) of 26 patients, with recurrence rate of 9%. The successful ablation sites were located at LV inferior-apical septum (16 patients), mid-septum (three patients), high septum (two patients) and high anterior wall (one patient). In the right VT group, 20 (67%) of 30 patients presented clinically repetitive monomorphic VT. Most of the idiopathic right VT (22/30) required isoproterenol to facilitate induction of VT, and were sensitive to both verapamil and adenosine. Successful catheter ablation was achieved in 21 (84%) of 25 patients, with recurrence rate 19%. The successful ablation sites were located at RVOT-septum in 18 patients, and RVOT-free wall in three patients. During a mean follow-up period of 29.2+/-21.7 months (range 1-76 months) after hospital discharge, all patients were alive but one left VT case died of non-cardiovascular cause. We concluded that idiopathic left side and right side VTs have their distinct clinical, electrophysiologic and electropharmacological characteristics suggestive of different underlying mechanisms, and both have a benign prognosis. Furthermore, catheter ablation can be effective in eliminating idiopathic VT originating from the right ventricular outflow tract and left ventricle.

Adult↗

PubMed1997

Characterization of low right atrial isthmus as the slow conduction zone and pharmacological target in typical atrial flutter.

BACKGROUND: Previous electrophysiological studies in patients with typical atrial flutter suggested that the slow conduction zone might be located in the low right atrial isthmus, which is a path formed by orifice of inferior vena cava, eustachian valve/ridge, coronary sinus ostium, and tricuspid annulus. The conduction characteristics during atrial pacing and responses to antiarrhythmic drugs of this anatomic isthmus were unknown. METHODS AND RESULTS: Forty-four patients, 20 patients with paroxysmal supraventricular tachycardia (group 1) and 24 patients with clinically documented paroxysmal typical atrial flutter (group 2), were studied. A 20-pole halo catheter was situated around the tricuspid annulus. Incremental pacing from the low right atrium and coronary sinus ostium was performed to measure the conduction time and velocity along the isthmus and lateral wall in the baseline state and after intravenous infusion of procainamide or sotalol. In both groups, conduction velocity in the isthmus during incremental pacing was significantly lower than that in the lateral wall before and after infusion of antiarrhythmic drugs. Furthermore, gradual conduction delay with unidirectional block in the isthmus was relevant to initiation of typical atrial flutter. Compared with group 1, group 2 had a lower conduction velocity in the isthmus and shorter right atrial refractory period. Procainamide significantly decreased the conduction velocity, but sotalol did not change it. In contrast, sotalol significantly prolonged the atrial refractory period with a higher extent than procainamide. After infusion of procainamide, the increase of conduction time in the isthmus accounted for 52+/-19% of the increase in flutter cycle length, and 5 of 12 patients (42%) had spontaneous termination of typical flutter. After infusion of sotalol, typical flutter was induced in only 6 of 12 patients (50%) without significant prolongation of flutter cycle length. CONCLUSIONS: The low right atrial isthmus with rate-dependent slow conduction properties is critical to initiation of typical human atrial flutter. It may be the potentially pharmacological target of antiarrhythmic drugs in the future.

Adolescent↗

PubMed1997

Influence of beta-adrenergic and vagal activity on the effect of exogenous adenosine on supraventricular tachycardia termination.

Adenosine, which binds to cell surface receptors and couples with guanosine triphosphate-binding inhibitory proteins (G(i)), is potent in terminating supraventricular tachycardia (SVT). However, whether the differences in autonomic tone will influence this effect remains unknown. This study was designed to investigate the role of beta-adrenergic and vagal activity on the action of adenosine. Forty patients with clinically documented SVT (22 with atrioventricular node reentrant tachycardia and 18 with atrioventricular reciprocating tachycardia) were divided into 4 groups with 10 patients in each group. In groups 1 and 2, adenosine was intravenously injected during the baseline state and during infusion of isoproterenol (2 and 4 microg/min, respectively). Group 2 patients received atropine (0.04 mg/kg) injection before isoproterenol infusion. In groups 3 and 4, intravenous injection of adenosine was given during the baseline state and after injection of atropine (0.02 and 0.04 mg/kg, respectively). Group 4 patients received propranolol (0.2 mg/kg) before atropine injection. The minimal dose of adenosine to terminate tachycardia during isoproterenol infusion of 2 microg/min was greater than that during the baseline state in both groups 1 and 2. The minimal dose of adenosine during isoproterenol infusion with 4 microg/min was higher than that with 2 microg/min in group 2, but not in group 1 patients. In both groups 3 and 4, the minimal dose of adenosine required to terminate tachycardia during atropine injection with 0.02 mg/kg was greater than that during the baseline state. The minimal effective dose of adenosine during atropine injection with 0.04 mg/kg was higher than that with 0.02 mg/kg in group 4, but not in group 3 patients. In conclusion, either limb of the autonomic nervous system may modulate the adenosine dosage required for termination of SVT. Patients taking drugs such as beta blockers or vagolytic agents may need alterations in the dose of adenosine for therapy.

Adenosine↗

PubMed1997

Genistein directly induces cardiac CFTR chloride current by a tyrosine kinase-independent and protein kinase A-independent pathway in guinea pig ventricular myocytes.

With one-suction electrode voltage-clamp technique, we demonstrated that genistein, a tyrosine kinase (TK) inhibitor, could directly activate cystic fibrosis transmembrane regulator (CFTR) chloride current in guinea pig ventricular myocytes. The activation showed concentration-dependent effect with the estimated IC50 of 39.7 microM. Tyrphostin 51, another TK inhibitor, had no effect, suggesting that genistein's effect might be unrelated to TK inhibition. After the chloride current had been activated by the maximally elevated intracellular cAMP content by saturating concentration of isoproterenol, forskolin and IBMX, genistein could further enhance the current. Pre-treatment with saturating concentration of a specific protein kinase A (PKA) inhibitor, H-89, or other protein kinase inhibitors H-8 and H-9 in the perfusate or intracellularly could not prevent the activation of the current by genistein, suggesting a PKA-independent activity. Furthermore, saturating concentration of calyculin A, a specific inhibitor of phosphotase 1 and 2A, in the perfusate or intracellularly could not block genistein's action. It is possible that genistein opens the channels directly or inhibits the dephosphorylation process of CFTR, which is not sensitive calyculin A.

Adrenergic beta-Agonists↗

PubMed1997

Complex electrophysiological characteristics in atrioventricular nodal reentrant tachycardia with continuous atrioventricular node function curves.

BACKGROUND: Although typical atrioventricular nodal reentrant tachycardia (AVNRT) with discontinuous AV node function curves has been well studied, there has been a lack of any significant information about AVNRT without evidence of dual AV nodal pathway physiology during atrial extrastimulus testing or atrial pacing. METHODS AND RESULTS: Group 1 included 9 patients with continuous curves during atrial extrastimulus testing but without a jump (> or = 50 ms) of the atrial-His bundle (AH) interval during incremental atrial pacing. The maximal AH interval during atrial pacing (266 +/- 61 versus 168 +/- 27 ms, P = .007) or extrastimulus testing (290 +/- 60 versus 176 +/- 18 ms, P = .005) shortened significantly after ablation. Antegrade and retrograde AV node properties were similar before and after ablation. Group 2 included 14 patients with continuous curves and a jump of the AH interval during incremental atrial pacing. The atrial pacing cycle length with 1:1 AV conduction and effective refractory period (ERP) of the antegrade AV node increased significantly, whereas the maximal AH interval during atrial pacing (358 +/- 70 versus 203 +/- 28 ms, P = .001) or extrastimulus testing (338 +/- 75 versus 196 +/- 34 ms, P = .002) shortened significantly after ablation. Group 3 included 24 patients with discontinuous curves. The maximal AH interval during atrial pacing or extrastimulus testing and the ERP of the antegrade fast AV node shortened, whereas the ERP of the antegrade AV node increased significantly after ablation. The maximal AH interval before ablation, extent of decrease in maximal AH interval after ablation, ERP of the retrograde AV node before ablation, and tachycardia cycle length were significantly shorter in group 1 than groups 2 and 3. CONCLUSIONS: In AVNRT with continuous AV node function curves, dual AV nodal pathway physiology may or may not be demonstrated during atrial pacing. Significant shortening of the maximal AH interval during atrial pacing after radiofrequency ablation suggests successful elimination of AVNRT.

Catheter Ablation↗

PubMed1997

Comparisons of oral propafenone and sotalol as an initial treatment in patients with symptomatic paroxysmal atrial fibrillation.

The main goal of this study is to evaluate the safety and efficacy of propafenone versus sotalol as an initial choice of treatment in patients with symptomatic paroxysmal atrial fibrillation (AF), according to a double-blind randomized system. In the oral propafenone group (n = 41), 2 patients (5%) discontinued therapy because of gastrointestinal discomfort in 1 and dizziness in the other. Thirty-one (79%) of the 39 patients who continued the treatment had effective response to oral propafenone (>75% reduction of symptomatic arrhythmic attacks) on a mean dose of 663 +/- 99 mg/day with a decrease in attack frequency from 10 +/- 3 to 2 +/- 1 times per week. In the oral sotalol group (n = 38), 4 patients (11%) discontinued treatment because of dizziness in 2 and symptomatic bradycardia in 2. Twenty-six of the 34 patients (76%) who continued the treatment had effective response to oral sotalol on a mean dose of 200 +/- 57 mg/day with a decrease in attack frequency from 11 +/- 3 to 2 +/- 1 times per week. Comparisons of the results between propafenone and sotalol groups showed a similar incidence of intolerable (2 of 41 vs 4 of 38, p = 0.42) and tolerable side effects (10 of 39 vs 8 of 34, p = 1.0). The attack frequency at baseline (11 +/- 3 vs 10 +/- 4 times per week, p = 0.23) and after treatment (3 +/- 1 vs 3 +/- 2 times per week, p = 0.85) did not differ significantly between the 2 groups. The incidence of effective response to drugs was also similar (31 of 39 vs 26 of 34, p = 0.78). Furthermore, the decrease of symptom scores (-32 +/- 8% vs -29 +/- 7%, p = 0.18) and percentage decrease of ventricular rate (-15 +/- 4% vs -18 +/- 4%, p = 0.10) during AF were also similar between the 2 groups. In conclusion, oral propafenone and sotalol are equally effective and safe in preventing attacks and alleviating symptoms of paroxysmal AF.

Administration, Oral↗

PubMed1997

Results of radiofrequency ablation in patients with clinically documented, but noninducible, atrioventricular node reentrant tachycardia and orthodromic atrioventricular reciprocating tachycardia.

Among 1,281 patients with symptomatic supraventricular tachycardia, 34 patients (2.7%) with presumed diagnosis of atrioventricular node reentrant tachycardia and orthodromic atrioventricular reciprocating tachycardia did not have inducible tachycardia in the electrophysiologic laboratory. Application of radiofrequency energy to the presumed arrhythmogenic sites could achieve a high success rate, with a low recurrence rate in these patients.

Adult↗

PubMed1997

Electrophysiologic characteristics and radiofrequency catheter ablation of fast-slow form atrioventricular nodal reentrant tachycardia.

This study demonstrates that the fast-slow form of atrioventricular nodal reentrant tachycardia is usually catecholamine-sensitive and its electrophysiologic characteristics are significantly different from those of the slow-fast form. However, radiofrequency catheter ablation is a safe and effective treatment for patients with the fast-slow form of atrioventricular nodal reentrant tachycardia.

Adrenergic beta-Agonists↗

PubMed1997

Atrioventricular node reentrant tachycardia in patients with a long fast pathway effective refractory period: clinical features, electrophysiologic characteristics, and results of radiofrequency ablation.

Twenty-two patients (group 1) with AV node reentrant tachycardia and a baseline fast pathway effective refractory period (ERP) > or = 500 msec were compared with 30 consecutive patients (group 2) with AV node reentrant tachycardia and a fast pathway ERP < 500 msec. Both groups underwent slow pathway ablation. In the patients with complete elimination of slow pathway, the fast pathway ERP and shortest 1:1 conduction cycle length shortened significantly after ablation but was greater in group 1 (n = 14) than in group 2 (n = 21) (125 +/- 78 msec vs 48 +/- 29 msec, p < 0.001 and 103 +/- 72 msec vs 52 +/- 30 msec, p < 0.001, respectively). In group 1, the shortening of fast pathway ERP was correlated to baseline difference between anterograde fast and anterograde slow ERP (r = 0.806, p < 0.001, slope = 1.08), and the shortening of fast pathway shortest 1:1 conduction cycle length was correlated to baseline difference between anterograde fast and anterograde slow shortest 1:1 conduction cycle length (r = 0.885, p < 0.001, slope = 1.47). During follow-up bradycardia did not develop in any patient and no one required pacing. This shortening of the fast pathway ERP and shortest 1:1 conduction cycle length after complete elimination of slow pathway reduced the concern of subsequent impairment of AV node conduction.

Adrenergic beta-Agonists↗

PubMed1997

Role of the surface electrocardiogram in the diagnosis of patients with supraventricular tachycardia.

In this era of interventional electrophysiology, the accuracy of the electrocardiogram in diagnosis of supraventricular tachycardia could be improved by detailed endocardial mapping and confirmed by results of radiofrequency catheter ablation. This article describes the electrocardiographic characteristics for different types of supraventricular tachycardia: atrial fibrillation, atrial flutter, atrial tachycardia, atrioventricular reciprocating tachycardia using an accessory pathway, and atrioventricular node reentrant tachycardia. Several limitations, including the identification of P wave morphologies and polarities and separation between the terminal part of T wave and P wave during tachycardia, should be resolved before an accurate algorithm of the 12-lead surface electrocardiogram is developed for the diagnosis of supraventricular tachycardia.

Atrial Fibrillation↗

PubMed1997

A new electrocardiographic algorithm using retrograde P waves for differentiating atrioventricular node reentrant tachycardia from atrioventricular reciprocating tachycardia mediated by concealed accessory pathway.

OBJECTIVES: The purpose of this study was to use an electrocardiographic (ECG) algorithm, derived from the results of radiofrequency ablation, to discriminate atrioventricular node reentrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) and to localize a concealed accessory pathway, prospectively. BACKGROUND: Information about ECG criteria for differentiating AVNRT from AVRT is limited and has not been confirmed by surgical or catheter ablation. METHODS: Four hundred six ECGs (obtained from 406 different patients) that demonstrated narrow QRS complex (< 0.12 s) supraventricular tachycardia with an RP' interval less than the P'R interval or pseudo r' wave in lead V1 or pseudo S wave in inferior leads, or both, were examined, and the results were confirmed by radiofrequency catheter ablation. The initial 226 ECGs were analyzed to develop a stepwise algorithm, and the subsequent 180 ECGs were prospectively evaluated by the new algorithm. RESULTS: The presence of a pseudo r' wave in lead V1 or a pseudo S wave in leads II, III, aVF indicated anterior-type AVNRT with an accuracy of 100%. With the difference of RP' intervals in leads V1 and III > 20 ms, posterior-type AVNRT could be differentiated from AVRT utilizing a posteroseptal pathway with a sensitivity of 71% (95% confidence interval [CI] 55% to 89%), a specificity of 87% (95% CI 67% to 97%) and a positive predictive value of 75% (95% CI 56% to 91%). According to the polarity of retrograde P waves in leads V1, II, III, aVF and I during AVRT, the concealed accessory pathway could be localized to one of the nine regions on the atrioventricular annuli with an accuracy of 75% (for a right midseptal pathway) to 93.8% (for a left posterior pathway). Overall, the new algorithm had an accuracy of 97.8% in discriminating AVNRT from AVRT and 88.1% in localizing a concealed accessory pathway, prospectively. Prediction was incorrect in only 15 patients (9.1%). CONCLUSIONS: The new ECG algorithm derived from the analysis of retrograde P waves during tachycardia could provide a criterion for differential diagnosis between AVNRT and AVRT and for predicting the location of concealed accessory pathways.

Adolescent↗

PubMed1997

Effect of high intensity drive train stimulation on dispersion of atrial refractoriness: role of autonomic nervous system.

OBJECTIVES: This study evaluated the effect of high intensity drive train (S1) stimulation on the atrial effective refractory period (ERP) and its relation to the autonomic nervous system. BACKGROUND: High intensity S1 stimulation was demonstrated to shorten the ventricular ERP and to increase dispersion of refractoriness. These effects may be due to local release of neurotransmitters. The response of the atrium and ventricle to neurotransmitters was different. The effects of high intensity S1 stimulation at the atrial tissue were evaluated. METHODS: Forty patients without structural heart disease were studied. In group 1, 20 patients, the atrial ERP was measured at 0, 7, 14, 21 and 28 mm away from the S1 site under both twice diastolic threshold and high intensity (10 mA) S1 stimulation. The same protocol was repeated after sequential administration of propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg). In group 2, the other 20 patients, the atrial ERP was studied at three atrial sites (high lateral right atrium [HLRA], right posterior interatrial septum [RPS] and distal coronary sinus [DCS] with twice diastolic threshold and high intensity S1 stimulation at baseline and after sequential autonomic blockade. The three atrial sites were randomly assigned as the S1 location. RESULTS: In group 1, high intensity S1 stimulation shortened the atrial effective refractory period most prominently at the site of S1: (mean +/- SD) 13.3 +/- 6.4% (p < 0.001), 8.1 +/- 3.8% (p < 0.001), 4.8 +/- 4.3% (p < 0.001), 3.7 +/- 4.7% (p < 0.001) and 0.5 +/- 2.6% at 0, 7, 14, 21 and 28 mm from the S1 site, respectively. The effect of high intensity S1 stimulation was blunted with propranolol and autonomic blockade but persisted after atropine alone. High intensity S1 stimulation also increased dispersion of refractoriness (from 23 +/- 11 ms to 31 +/- 12 ms, p = 0.01), which was eliminated with autonomic blockade. In group 2, high intensity S1 stimulation had similar effects at different locations (ERP shortening of 10.8 +/- 2.7%, 10.8 +/- 2.2% and 12.2 +/- 4.6% at the HLRA, RPS and DCS, respectively). The responses to sequential autonomic blockade were similar to those in group 1. However, high intensity S1 stimulation at HLRA increased dispersion of refractoriness, but at DCS it reduced dispersion of refractoriness. CONCLUSIONS: High intensity S1 stimulation led to local shortening of the atrial ERP and increased dispersion of refractoriness. These effects were blunted with propranolol and autonomic blockade. High intensity S1 stimulation at the HLRA increased dispersion of atrial refractoriness, whereas the same stimulation at the DCS decreased dispersion of atrial refractoriness.

Adolescent↗

PubMed1997

Identification of fiber orientation in left free-wall accessory pathways: implication for radiofrequency ablation.

Previous reports on the anatomic discordance between atrial and ventricular insertion sites of left free-wall accessory pathways were limited and their findings were controversial. The purpose of this study was to explore the fiber orientation and related electrophysiologic characteristics of left free-wall accessory pathways. The study population comprised 96 consecutive patients with a single left free-wall accessory pathway (33 manifest and 63 concealed pathways), who underwent electrophysiologic study and radiofrequency catheter ablation using the retrograde ventricular approach. The atrial insertion site of the accessory pathway was defined from the cinefilms as the site with the earliest retrograde atrial activation bracketed on the coronary sinus catheter during tachycardia, and the ventricular insertion site was defined as the site where successful ablation of the pathway was achieved. Forty-two patients (44%) had their atrial insertion sites 5-20 mm (10 +/- 3 mm) distal to the ventricular insertion sites (proximal excursion), 30 (31%) patients had their atrial insertion sites 5-20 mm (12 +/- 3 mm) proximal to the ventricular insertion sites (distal excursion), and 24 (25%) patients had directly aligned atrial and ventricular insertion sites. Retrograde conduction properties, including 1:1 VA conduction and effective refractory period, were significantly poorer in the pathways with proximal excursion (302 +/- 67, 285 +/- 61 ms respectively) than in those with distal excursion (264 +/- 56, 250 +/- 48 ms respectively) or direct alignment (272 +/- 61, 258 +/- 73 ms respectively). Accessory pathways at the more posterior location had a significantly higher incidence of proximal excursion (P = 0.006), and those at the more anterior location had a higher incidence of distal excursion (P = 0.012). In conclusion, a wide variation in fiber orientations and related electrophysiologic characteristics was found in left free-wall accessory pathways. This may have important clinical implications for radiofrequency ablation.

Adult↗

PubMed1997

Atrioventricular node reentrant tachycardia in patients with a prolonged AH interval during sinus rhythm: clinical features, electrophysiologic characteristics and results of radiofrequency ablation.

Among a consecutive series of 600 patients who underwent radiofrequency catheter ablation for AV node reentrant tachycardia, 14 patients (age 29-76 years) had a prolonged AH interval during sinus rhythm (172 +/- 18 ms, range 140 to 200). Seven of them had unsuccessful ablation during the previous ablation sessions. Eight patients with anterograde dual AV node pathway physiology received anterograde slow pathway ablation, and the other 6 patients without dual-pathway physiology received retrograde fast pathway ablation. All patients had successful elimination of AV nodal reentrant tachycardia after a mean of 4 +/- 4 radiofrequency applications, power level 36 +/- 6 watts and a pulse duration of 42 +/- 4 seconds. The postablation AH interval remained unchanged. During a follow-up period of 25 +/- 13 months, one patient who received slow pathway ablation developed 2:1 AV block with syncope. As compared with the other 586 patients without a prolonged AH interval, these 14 patients had significantly poorer anterograde AV nodal function and lower incidence of anterograde dual AV node physiology (P < 0.01). We concluded that slow pathway ablation in patients with dual pathway physiology, and retrograde fast pathway ablation in patients without dual pathway physiology were effective and safe in patients with a prolonged AH interval. However, delayed onset of symptomatic AV block is possible and careful follow-up is necessary.

Adult↗

PubMed1997

Accessory atrioventricular pathways with only antegrade conduction in patients with symptomatic Wolff-Parkinson-White syndrome. Clinical features, electrophysiological characteristics and response to radiofrequency catheter ablation.

Information about accessory pathways conducting only in the antegrade direction is limited. The purposes of the present study were to prospectively investigate the clinical features, electrophysiological characteristics, effects of radiofrequency catheter ablation and recurrent atrial fibrillation after successful ablation in patients with accessory pathways conducting only in the antegrade direction, and to compare them with those who had pathways capable of bidirectional conduction in a consecutive series of 759 patients. Electrophysiological studies and radiofrequency catheter ablation were performed in 33 study patients with antegrade-only accessory pathways and in 377 patients with bidirectional accessory pathways for comparison. The patients with accessory pathways conducting only in the antegrade direction were older (47 +/- 16 vs 40 +/- 16 years, P = 0.037) and had a higher incidence of atrial fibrillation (100% vs 27.1%, P < 0.001) as well as related syncope (33.3% vs 10.1%, P = 0.001). The study patients also had more accessory pathways located in the posterior septum and a higher incidence of retrograde atrioventricular nodal conduction. The biophysical variables, success and complication rates of radiofrequency ablation were similar in both groups. During the follow-up period of 32 +/- 12 months, symptomatic atrial fibrillation after successful ablation did not recur in 79% and 81% of patients with unidirectional and bidirectional accessory pathways, respectively. Furthermore, old age and cardiovascular diseases were independent predictors of recurrent atrial fibrillation after radiofrequency ablation. In conclusion, this study showed that atrial fibrillation with preexcitation was the usual presentation in patients who had symptomatic Wolff-Parkinson White syndrome with an antegrade-only accessory pathway, and might be related to antegrade conduction of the accessory pathway. Therefore elimination of antegrade-only and bidirectional pathways by radiofrequency ablation could prevent the recurrence of symptomatic atrial fibrillation in younger patients without cardiac disease.

Adult↗

PubMed1997

Electrophysiologic characteristics and radiofrequency catheter ablation in patients with clockwise atrial flutter.

INTRODUCTION: Although the mechanism and radiofrequency catheter ablation of counterclockwise (typical) atrial flutter have been studied extensively, information about the electrocardiographic and electrophysiologic characteristics and effects of radiofrequency ablation in patients with clockwise atrial flutter is limited. METHODS AND RESULTS: Thirty consecutive patients with clinically documented paroxysmal clockwise atrial flutter were studied. Endocardial recordings and entrainment study using a "halo" catheter with 10 electrode pairs in the right atrium were performed. Radiofrequency energy was applied to the inferior vena cava-tricuspid annulus (IVC-TA) and/or coronary sinus ostium-tricuspid annulus (CSO-TA) isthmus to evaluate the effects of linear catheter ablation. Eighteen patients had both counterclockwise and clockwise atrial flutters, and 12 patients had only clockwise atrial flutter. Both forms of atrial flutter had similar flutter cycle lengths (232 +/- 30 vs 226 +/- 25 msec, P = 0.526) but reverse activation sequences. Right atrial pacing at a cycle length 20 msec shorter than the flutter cycle length from the CSO-TA isthmus, IVC-TA isthmus, and the area between the two isthmuses revealed concealed entrainment with stimulus-to-P wave intervals of 32 +/- 19, 95 +/- 14, and 50 +/- 17 msec (P = 0.022) in the counterclockwise form, and 110 +/- 12, 40 +/- 20, and 60 +/- 15 msec (P = 0.018) in the clockwise form. In clockwise atrial flutter, 20 patients with biphasic P waves in the inferior leads had the presumed exit site of slow conduction area located at the low posterolateral right atrium; 10 patients with positive P waves in the inferior leads had the presumed exit site located at the mid-high posterolateral right atrium. Among the 18 patients with both forms of atrial flutter, linear ablation lesions directed at the IVC-TA isthmus eliminated both forms of atrial flutter in 14 patients; in the remaining 4 patients, CSO-TA linear lesions eliminated the counterclockwise form and IVC-TA lesions eliminated the clockwise form. Among the 12 patients with the clockwise form only, CSO-TA linear lesions eliminated flutter in 2 and IVC-TA linear lesions eliminated flutter in 10 patients. Successful ablation was confirmed by creation of bidirectional conduction block in the IVC-TA and/or CSO-TA isthmus during pacing from the proximal coronary sinus and right posterolateral atrium sandwiching the linear lesions. During the follow-up period of 17 +/- 8 months, 2 patients had recurrence of clockwise atrial flutter, 1 patient had new onset of atypical atrial flutter, and 2 patients had new onset of atrial fibrillation. CONCLUSIONS: Counterclockwise and clockwise atrial flutters may have overlapping slow conduction areas with different exit sites. Radiofrequency catheter ablation using the linear method directed at the IVC-TA and CSO-TA isthmuses was feasible and effective in treating both forms of atrial flutter.

Adult↗