First human experience with pulmonary vein isolation using a through-the-balloon circumferential ultrasound ablation system for recurrent atrial fibrillation. (1/1050)

BACKGROUND: Standard mapping and ablation of focal sources of atrial fibrillation are associated with very long procedure times and low efficacy. An anatomic approach to complete pulmonary vein isolation could overcome these limitations. METHODS AND RESULTS: Fifteen patients with atrial fibrillation refractory to medication underwent circumferential isolation of the pulmonary veins by using a novel catheter, with an ultrasound transducer (8-MHz) mounted near the tip, in a saline-filled balloon. Twelve atrial foci and/or atrial fibrillation triggers were identified in 9 patients (pulmonary vein locations: left upper, 3; right upper, 6; right middle, 1; right lower, 1; and left inferior, 1). In 5 patients, lesions were placed in the absence of any mapped triggers. Irrespective of trigger mapping, circumferential isolation of both upper pulmonary veins was attempted in all patients. The lower pulmonary veins were ablated when sinus rhythm activation mapping revealed evidence of a sleeve of atrial muscle in the vein. The median number of lesions per patient required to isolate 1 pulmonary vein was 4 (range, 1 to 29). After ablation, no evidence of narrowing was seen with repeat venography or follow-up computed tomography scan. After a mean follow-up of 35+/-6 weeks, 5 patients had recurrence of atrial fibrillation. Three responded to drugs that were previously ineffective, and 2 remained in atrial fibrillation. CONCLUSIONS: This novel ultrasound ablation system can successfully isolate multiple pulmonary veins. At early follow-up, this approach seems to be effective in preventing recurrent atrial fibrillation in a significant number of patients.  (+info)

Radiofrequency ablation of haemodynamically unstable ventricular tachycardia after myocardial infarction. (2/1050)

OBJECTIVE: To determine whether radiofrequency (RF) ablation might have a role in haemodynamically unstable ventricular tachycardia. METHODS: 10 patients with a history of ventricular tachycardia producing haemodynamic collapse in whom drug treatment had failed and device therapy was rejected underwent RF ablation of ventricular tachycardia in sinus rhythm. The arrhythmogenic zone was defined on the basis of abnormal systolic movement, the presence of fragmentation (low amplitude, prolonged multiphasic electrograms), and pace mapping. RF lesions were delivered in power mode in linear fashion within the defined arrhythmogenic zone. RESULTS: Success (no ventricular tachycardia inducible postablation or at retest) was achieved in six patients, possible success (a different ventricular tachycardia inducible at more aggressive stimulation) in three. In one patient, the procedure was abandoned because of poor catheter stability. There were no clinical events during a mean (SD) follow up period of 23 (10) months in any of the nine patients defined as definite or possible successes. CONCLUSIONS: RF ablation for addressing haemodynamically unstable ventricular tachycardia opens the door for the wider use of catheter ablation for treating this arrhythmia.  (+info)

Anisotropic reentry in a perfused 2-dimensional layer of rabbit ventricular myocardium. (3/1050)

BACKGROUND: Anisotropy creates nonuniformity in electrical propagation and may contribute to the occurrence of unidirectional conduction block and reentry. We describe the characteristics of reentrant tachycardia in a 2D layer of anisotropic ventricular myocardium. METHODS AND RESULTS: A Langendorff-perfused epicardial sheet (1.0+/-0.4 mm, n=35) was created by freezing the intramural layers of the rabbit left ventricle. Epicardial activation maps were constructed by use of different high-resolution mapping arrays connected to a mapping system. In 5 experiments, monophasic action potentials were recorded. In the intact left ventricle, no arrhythmias except VF could be induced. After freezing, programmed electrical stimulation or rapid pacing led to the induction of sustained VT (cycle length 130+/-11 ms). VT was caused by reentry around a functional line of block oriented parallel to the epicardial fiber direction. Action potential recordings demonstrated that the central line of block was kept refractory by electrotonic currents generated by the depolarization waves propagating at either side of the line of block. At the pivot points of the line of block, the pronounced curvature of the turning wave and abrupt loading changes created an excitable gap of 30 ms in the reentrant pathway. CONCLUSIONS: In uniform anisotropic myocardium, reentry around a functional Z-shaped line of block may occur. The core of the circuit is kept refractory by electrotonic currents. The pronounced wave-front curvature and abrupt loading changes at the pivot points cause local conduction delay and create a small excitable gap.  (+info)

Reduction of atrial defibrillation threshold with an interatrial septal electrode. (4/1050)

BACKGROUND: The standard lead configuration for internal atrial defibrillation consists of a shock between electrodes in the right atrial appendage (RAA) and coronary sinus (CS). We tested the hypothesis that the atrial defibrillation threshold (ADFT) of this RAA-->CS configuration would be lowered with use of an additional electrode at the atrial septum (SP). METHODS AND RESULTS: Sustained atrial fibrillation was induced in 8 closed-chest sheep with burst pacing and continuous pericardial infusion of acetyl-ss-methylcholine. Defibrillation electrodes were situated in the RAA, CS, pulmonary artery (PA), low right atrium (LRA), and across the SP. ADFTs of RAA-->CS and 4 other lead configurations were determined in random order by use of a multiple-reversal protocol. Biphasic waveforms of 3/1-ms duration were used for all single and sequential shocks. The ADFT delivered energies for the single-shock configurations were 1.27+/-0.67 J for RAA-->CS and 0. 86+/-0.59 J for RAA+CS-->SP; the ADFTs for the sequential-shock configurations were 0.39+/-0.18 J for RAA-->SP/CS-->SP, 1.16+/-0.72 J for CS-->SP/RAA-->SP, and 0.68+/-0.46 J for RAA-->CS/LRA-->PA. Except for CS-->SP/RAA-->SP versus RAA-->CS and RAA-->CS/LRA-->PA versus RAA+CS-->SP, the ADFT delivered energies of all of the configurations were significantly different from each other (P:<0. 05). CONCLUSIONS: The ADFT of the standard RAA-->CS configuration is markedly reduced with an additional electrode at the atrial SP.  (+info)

Postcardioversion atrial electrophysiologic changes induced by oral verapamil in patients with persistent atrial fibrillation. (5/1050)

OBJECTIVES: The aim of our study was to verify the effect of oral administration of verapamil on atrial electrophysiologic characteristics after cardioversion of persistent atrial fibrillation (AF) in humans. BACKGROUND: Discordant findings have been reported regarding the efficacy of verapamil in preventing the electrical remodeling induced by AF. METHODS: We determined the effective refractory periods (ERPs) at five pacing cycle lengths (300 to 700 ms) and in five right atrial sites after internal cardioversion of persistent AF (mean duration 238.1+/-305.9 days) in 19 patients. Nine patients received oral verapamil (240 mg/day) starting four weeks before the electrophysiologic study, whereas the other 10 patients were in pharmacologic washout. RESULTS: The mean ERPs were 202.0+/-22.7 ms in the washout group and 189.3+/-18.5 ms in the verapamil group (p < 0.0001). The degree of adaptation of refractoriness to rate was similar in the two groups (mean slope value in the washout group and verapamil group: 0.07+/-0.03 and 0.08+/-0.05, respectively), showing a normal or nearly normal adaptation to rate in the majority of the paced sites in both groups. The mean ERP was slightly longer in the septum than in the lateral wall and in the roof, both in the washout and verapamil groups. CONCLUSIONS: In patients with persistent AF, long-term administration of verapamil before internal cardioversion resulted in 1) shortening of atrial ERPs; 2) no change in refractoriness dispersion within the right atrium; and 3) no change in atrial ERP adaptation to rate.  (+info)

A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification. (6/1050)

OBJECTIVES: The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study. BACKGROUND: Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification. METHODS: This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality. RESULTS: Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0. CONCLUSIONS: T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.  (+info)

Targeting the slow pathway for atrioventricular nodal reentrant tachycardia: initial results and long-term follow-up in 379 consecutive patients. (7/1050)

OBJECTIVES: This study is designed to examine the immediate and short-term outcomes of patients who have undergone slow pathway ablation/modification for atrioventricular nodal reentrant tachycardia. BACKGROUND: Targeting the slow pathway has emerged as the superior form of treatment for atrioventricular nodal reentrant tachycardia. This technique has been found effective and is associated with a low complication rate. However, little is known of the long-term outcome of patients undergoing this procedure. METHODS: Over a 40-month period the slow pathway was targeted in 379 consecutive patients with proven atrioventricular nodal reentrant tachycardia. The case records of all patients were examined. Accurate follow-up data is available in 96% of patients a mean of 20.6 months after the procedure. RESULTS: The initial success rate was 97%. The incidence of complete heart block was 0.8% and the mean fluoroscopy duration was 27.3 min. The recurrence rate was 6.9%. Age, number of pulses and fluoroscopy time were positively associated with either initial failure or recurrence. A total of 11.3% of patients were still taking antiarrhythmic medication at follow-up. CONCLUSIONS: Targeting the slow pathway is an effective form of treatment for atrioventricular nodal reentrant tachycardia. The technique has a high initial success rate, a low complication rate and a low recurrence rate at long-term follow-up. Slow pathway modification is associated with similar success rates and recurrence rates as slow pathway ablation and may confer theoretical long-term benefits.  (+info)

Risk of development of delayed atrioventricular block after slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval. (8/1050)

AIMS: The objective of this prospective study was to assess risk factors for the development of atrioventricular block following slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval. METHODS AND RESULTS: Of 346 consecutive patients with atrioventricular nodal reentrant tachycardia undergoing slow pathway modification, 18 patients (62 +/- 7 years; five females) were found to have a prolonged PR interval prior to ablation. Total elimination of the functional slow pathway was assumed if the antegrade effective refractory period following slow pathway modification was longer than the cycle length of atrioventricular nodal reentrant tachycardia. To detect atrioventricular node conduction disturbances, 24-h Holter recordings were performed 1 day prior to slow pathway modification, and 1 day, 1 week, 1, 3 and 6 months after the procedure. Six patients developed late atrioventricular block. The incidence of delayed atrioventricular block following successful slow pathway modification was higher in patients with, compared to patients without, prolonged PR interval at baseline (6/18 vs 0/328, P < .001). In the former group, the antegrade effective refractory period was longer in patients with, compared to those without, a delayed atrioventricular block (492 +/- 150 ms vs 332 +/- 101 ms, P < 0.05). The incidence of delayed atrioventricular block was higher in patients with total elimination of the slow pathway compared to patients without (5/7 vs 1/11, P < 0.01). CONCLUSIONS: Slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a prolonged PR interval is highly effective. However, there is a significant risk of development of delayed atrioventricular block, particularly when the procedure results in total elimination of the slow pathway.  (+info)