A technique for the rapid diagnosis of atrial tachycardia in the electrophysiology laboratory.
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OBJECTIVE: The purpose of this study was to determine if the atrial response upon cessation of ventricular pacing associated with 1:1 ventriculoatrial conduction during paroxysmal supraventricular tachycardia is a useful diagnostic maneuver in the electrophysiology laboratory. BACKGROUND: Despite various maneuvers, it can be difficult to differentiate atrial tachycardia from other forms of paroxysmal supraventricular tachycardia. METHODS: The response upon cessation of ventricular pacing associated with 1:1 ventriculoatrial conduction was studied during four types of tachycardia: 1) atrioventricular nodal reentry (n = 102), 2) orthodromic reciprocating tachycardia (n = 43), 3) atrial tachycardia (n = 19) and 4) atrial tachycardia simulated by demand atrial pacing in patients with inducible atrioventricular nodal reentry or orthodromic reciprocating tachycardia (n = 32). The electrogram sequence upon cessation of ventricular pacing was, categorized as "atrial-ventricular" (A-V) or "atrial-atrial-ventricular" (A-A-V). RESULTS: The A-V response was observed in all cases of atrioventricular nodal reentrant and orthodromic reciprocating tachycardia. In contrast, the A-A-V response was observed in all cases of atrial tachycardia and simulated atrial tachycardia, even in the presence of dual atrioventricular nodal pathways or a concealed accessory atrioventricular pathway. CONCLUSIONS: In conclusion, an A-A-V response upon cessation of ventricular pacing associated with 1:1 ventriculoatrial conduction is highly sensitive and specific for the identification of atrial tachycardia in the electrophysiology laboratory. (+info)
Dispersion of signal-averaged P wave duration on precordial body surface in patients with paroxysmal atrial fibrillation.
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AIMS: This study sought to investigate whether the spatial dispersion of signal-averaged P wave duration would be increased in patients with paroxysmal atrial fibrillation, by use of precordial mapping of the P wave signal-averaged ECG. METHODS AND RESULTS: The P wave signal-averaged ECG was recorded by the P wave-triggering method from 16 precordial leads in 55 patients with paroxysmal atrial fibrillation and 57 control subjects. As an index of the dispersion of signal-averaged P wave duration, we obtained the difference between the maximum and minimum in 16 recording sites. The dispersion was significantly greater in the patients with paroxysmal atrial fibrillation than the controls (26.6 +/- 9.5 vs 14.8 +/- 6.7 ms, P<0.0001). In 25 patients with symptomatic attacks of paroxysmal atrial fibrillation, the signal-averaged ECG was repeated 1 h after a single dose of orally administered pilsicainide, a new class Ic drug. These patients were prospectively followed-up for 10 +/- 11 months with pilsicainide. The rate of freedom from recurrence of paroxysmal atrial fibrillation attacks was significantly (P<0.0001) higher in patients with whom dispersion was decreased by the single dose (54%[7/13]) than in those in whom dispersion increased (8%[1/12]). CONCLUSION: Increased dispersion of signal-averaged P wave duration would play an important role in generating paroxysmal atrial fibrillation and would be useful in the prediction of drug efficacy to evaluate the change in dispersion by a single administration of pilsicainide. (+info)
Double-blind placebo-controlled trial of digoxin in symptomatic paroxysmal atrial fibrillation.
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BACKGROUND: Digoxin is commonly prescribed in symptomatic paroxysmal atrial fibrillation (AF) but has never been evaluated in this condition. METHODS AND RESULTS: From a multicenter registry, 43 representative patients with frequent symptomatic AF episodes were recruited into a randomized, double-blind crossover comparison of digoxin (serum concentration, 1.29+/-0.35 nmol/L) and placebo. The study end point was the occurrence of 2 AF episodes (documented by patient-activated monitors), censored at 61 days. The median time to 2 episodes was 13.5 days on placebo and 18.7 days on digoxin (P<0. 05). The relative risk (95% CI) of 2 episodes (placebo:digoxin) was 2.19 (1.07 to 4.50). A similar effect was seen on the median time to 1 episode: increased from 3.5 to 5.4 days (P<0.05), relative risk 1. 69 (0.88 to 3.24). The mean+/-SD ventricular rates during AF recordings during placebo and digoxin treatment were 138+/-32 and 125+/-35 bpm, respectively (P<0.01). Twenty-four-hour ambulatory ECG recordings did not show significant differences in the frequency or duration of AF or in ventricular rate. CONCLUSIONS: Digoxin reduces the frequency of symptomatic AF episodes. However, the estimated effect is small and may be due to a reduction in the ventricular rate or irregularity rather than an antiarrhythmic action. (+info)
Local slow potential preceding the surface QRS complex detected at the subvalvular mitral annulus in patients with a left-sided concealed accessory pathway. Incidence, electrophysiological characteristics and the possible mechanism, with demonstration of anterograde concealed conduction through the pathway.
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AIM: We sought to evaluate the incidence and electrophysiological features of the local slow potential preceding the surface QRS complex (pre-QRS potential) which was detected more frequently at successful sites of catheter ablation of left parietal concealed accessory pathways, than at unsuccessful sites. METHODS AND RESULTS: Thirty eight consecutive patients with a single left sided concealed accessory pathway underwent radiofrequency catheter ablation exclusively from the subvalvular mitral annulus. The local bipolar electrograms during sinus rhythm from the target sites were carefully analysed and the incidence of pre-QRS potentials was compared between successful and unsuccessful ablation sites. All ablation sessions attained a successful outcome with a total of 84 radiofrequency current applications (38 at successful sites, 46 at unsuccessful sites). The incidence of pre-QRS potentials (preceding by 10 ms or more) was 12/38 at successful sites (32%) and 1/46 at unsuccessful sites (2%) (P<0.001). The QV interval, defined as the interval between the upstroke of the QRS complex and the ventricular electrogram, including the pre-QRS potential, was -5.6+/-9.1 ms at successful sites, while it was 1.2+/-6.1 ms at unsuccessful sites (P<0.001). The pre-QRS potential disappeared during atrioventricular reciprocating tachycardia and right ventricular pacing, and was eliminated by successful ablation. CONCLUSIONS: Detection of the pre-QRS potential was clinically relevant and could be distinguished from artifact. This potential may be caused by anterograde concealed conduction through the accessory pathways. (+info)
Conversion of recent onset paroxysmal atrial fibrillation to normal sinus rhythm: the effect of no treatment and high-dose amiodarone. A randomized, placebo-controlled study.
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BACKGROUND: Spontaneous conversion of recent onset paroxysmal atrial fibrillation to normal sinus rhythm occurs commonly and is not affected by low-dose amiodarone treatment. METHODS: In a randomized, placebo-controlled trial of 100 patients with paroxysmal atrial fibrillation of recent onset (<48 h) we compared the effects of treatment with continuous intravenous amiodarone 125 mg per hour (total 3 g) and intravenous placebo. Patients in the placebo group who did not convert to normal sinus rhythm within 24 h were started on amiodarone therapy. RESULTS: Conversion to normal sinus rhythm occurred within 24 h in 32 of 50 patients (64%) in the placebo group, most of whom converted within 8 h. Lower conversion rates were observed in patients with hypertension, ischaemic heart disease or congestive heart failure and in patients with echocardiographic findings of left atrial diameter above 45 mm, ejection fraction below 45% or significant mitral regurgitation. However, in most patients these clinical or echocardiographic risk factors of decreases in conversion rate were not present. In such patients the spontaneous conversion rate was approximately 90%. The conversion rate during 24 h of treatment in the amiodarone group was 92% (P=0.0017, compared to the placebo group). In this group, the conversion rate was largely unaffected by baseline characteristics. Of the 18 patients who did not convert with placebo, 15 (85%) converted after being crossed over to amiodarone. All patients not responding to high-dose amiodarone were in chronic atrial fibrillation within 1 month. In patients still in atrial fibrillation after 8 h of treatment, the pulse rate decreased significantly more in the amiodarone as compared to the placebo group (83+/-15 vs 114+/-20 beats. min(-1), P=0.0014). CONCLUSION: The spontaneous conversion of recent onset paroxysmal atrial fibrillation is high and approaches 90% in specific clinical and echocardiographically defined subgroups. Intravenous high-dose amiodarone safely facilitates conversion of paroxysmal atrial fibrillation. However, such treatment should be reserved for patients with unfavourable risk factor profiles, not converting during 8 h of observation or requiring rate control. (+info)
Radiofrequency ablation of a right atriofascicular Mahaim fiber and two contralateral left free-wall accessory pathways.
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We report a rare combination of a right atriofascicular Mahaim fiber and two left-sided atrioventricular accessory pathways in a 57-year-old female presenting with an antidromic atrioventricular reciprocating tachycardia. Radiofrequency ablation was first targeted at the left lateral accessory pathway that served as the retrograde limb of the tachycardia. After elimination of the left lateral pathway, a bystander left posterolateral pathway was detected, and it too was successfully ablated. Although no tachycardia was reinducible, the Mahaim pathway was ablated because of its short effective refractory period. A discrete Mahaim potential recorded at the right atrial free-wall successfully guided the ablation. (+info)
Prediction of paroxysmal atrial fibrillation in patients with congestive heart failure: a prospective study.
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OBJECTIVES: We sought to prospectively determine whether patients with congestive heart failure (CHF) at risk for paroxysmal atrial fibrillation (PAF) could be identified by clinical and study variables including the P-wave signal-averaged electrocardiogram (P-SAECG). BACKGROUND: Although it is important to assess the risk of developing PAF in patients with CHF, it still remains difficult to predict the PAF appearance in patients with CHF clinically. METHODS: The study group consisted of 75 patients in sinus rhythm without a history of PAF, whose left ventricular ejection fraction, as measured by radionuclide angiography, was <40%. These patients underwent P-SAECG, echocardiography and 24-h Holter monitoring; in addition, the plasma concentration of atrial natriuretic peptide (ANP) was measured at study entry. RESULTS: An abnormal P-SAECG was found at study entry in 29 of 75 patients. In the follow-up period of 21 +/- 9 months, the PAF attacks documented on the ECG significantly more frequently occurred in patients with (32%) rather than without an abnormal P-SAECG (2%) (p = 0.0002). The plasma ANP level was significantly higher in patients with rather than without PAF attacks (75 +/- 41 vs. 54 +/- 60 pg/ml, p = 0.01), although there were no significant differences in age, left atrial dimension or high grade atrial premature beats between the groups. The multivariate Cox analysis identified that the variables significantly associated with PAF development were an abnormal P-SAECG (hazard ratio 19.1, p = 0.0069) and elevated ANP level > or =60 pg/ml (hazard ratio 8.6, p = 0.018). CONCLUSIONS: An abnormal P-SAECG and elevated ANP level could be predictors of PAF development in patients with CHF. (+info)
Shortening of conduction time over arborized atrioventricular accessory pathway with Mahaim fibers physiology just before interruption during radiofrequency ablation.
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A 21-year-old woman had paroxysmal wide QRS tachycardia with a left bundle branch block configuration and a retrograde conducted P wave just behind the QRS complex. An electrophysiological study revealed antidromic atrioventricular tachycardia involving an atrioventricular connection with decremental conduction as the anterograde limb and normal atrioventricular node as the retrograde limb. During constant pacing from the high right atrium (HRA) at the cycle length (CL) of 600 ms, the QRS configurations were not identical to those during the wide QRS tachycardia or constant pacing at the CL of less than 500 ms. The process by which this arborized atrioventricular accessory pathway with the Mahaim fibers physiology was interrupted by radiofrequency catheter ablation is described. Radiofrequency energy was delivered to the site recording a Mahaim potential at the tricuspid annulus during constant pacing from the HRA at the CL of 429 ms. The stimulus-QRS interval gradually shortened as it reached the power plateau without changing the preexcited QRS configuration. Shortening of the conduction time over the Mahiam pathway might have resulted in changing of the propagation from a slow to fast conduction zone or acceleration in response to thermal effect in a node-like structure on the atrial insertion site. (+info)