Mauro Villani

Local Capture by Atrial Pacing in Spontaneous Chronic Atrial Fibrillation

BACKGROUND Atrial fibrillation (AF) is considered to be maintained by multiple reentrant circuits without or with a very short excitable gap. However, the possibility of local atrial capture has been shown recently in experimental AF or induced AF in humans. METHODS AND RESULTS This study was undertaken to evaluate the feasibility of atrial capture-suggestive of an excitable gap-in spontaneous chronic AF. Decremental pacing was performed in 47 right atrial sites in 14 patients with chronic AF, not taking antiarrhythmic drugs. A Franz catheter (for pacing and monophasic action potential recording) and a recording quadripolar catheter positioned about 10 mm apart were used. Local capture was achieved in 41 (87.2%) sites for a total of 100 captures. In 71 episodes the capture was lost within 15 seconds, while in the remaining 29, pacing was stopped after 15 seconds of stable capture. AF types immediately before capture were type 1 in 83 and type 2 in 17 episodes. Type 3 AF was never captured. Pacing cycle at capture was 175.7 +/- 20.9 ms. The baseline atrial interval (FF) was 185.4 +/- 24.5, significantly longer than the FF recorded during pacing immediately before capture (176.0 +/- 19.8 ms) (P < .02). CONCLUSIONS During spontaneous chronic AF in humans, (1) local capture by atrial pacing is possible up to at least 15 mm from the pacing site, (2) regional entrainment is possible during type 1 and type 2 AF but not type 3 AF, and (3) pacing before capture accelerates AF, probably by transient or local capture. These findings suggest that an excitable gap is present in chronic AF, therefore supporting the hypothesis that leading circle reentry is not the unique electrophysiological mechanism maintaining the arrhythmia.

Single shock endocavitary low energy intracardiac cardioversion of chronic atrial fibrillation.

Background.Discomfort related to low-energy internal cardioversion (LEIC) represents a real problem in patients (pts) with atrial fibrillation (AF). The aim of our study was to verify if a single shock could restore sinus rhythm (SR) with a lower discomfort for the pt.Methods. Thirty pts with chronic AF were randomized to receive a single 350 V shock (15 pts) or multiple shocks of increasing energy (15 pts). Three leads were positioned, respectively, in the coronary sinus and in the lateral right wall for shock delivery, and in the right ventricular apex for R wave synchronization. Truncated, biphasic shocks were used. In the first group a single 350 V shock was directly delivered and a second 400 V shock was given only if SR has not been restored. In the second group, beginning at 50 volts the voltage was increased in steps of 50 volts until SR restoration. No patient was sedated. After each shock the pts were asked to rate their discomfort on a scale of 1 to 5 (1 = not perceived, 5 = severe discomfort)Results. SR was restored in all the subjects. In group 1 SR was obtained in 12/15 (80%) pts with the first 350 V (8.1±0.8 joules) shock, while the remaining 3 patients required the second 400 V (10.2±10.3 joules) shock. In group 2 the mean atrial defibrillation threshold was 346.7±29.7 volts (8.0±1.5 joules). Then discomfort score was 2.5±0.6 in group 1 and 3.3±0.6 in group 2 (p < 0.01).Conclusions. A single shock of 350 V restores SR in the majority of pts with chronic AF; by use this new approach, LEIC is tolerated better than the multiple shocks step-up protocol.

Low Energy Intracardiac Cardioversion of Persistent Atrial Fibrillation

The aims of the study were to verify the efficacy and safety of low energy internal Cardioversion (LEIC) in patients with persistent at rial fibrillation (AF) and to identify the factors affecting the at rial defihrillation threshold (ADT). Forty‐nine patients with persistent (lasting ≥ 10 days) AF underwent LEIC. In each patient, two 6 Fr custom‐made catheters with large active surface areas were positioned in the coronary sinus (cathode) and the lateral right wall (anode), respectively, for shock delivery, and a tetrapolar lead was placed in the fight ventricular apex for R wave synchronization. Truncated, biphasic (3 ms+3 ms). exponential shocks were used, beginning at 50 V and increasing in steps of 50 V until sinus rhythm had been restored. Mild sedation (diazepam 5 mg IV) was administered to 12 patients. Sinus rhythm was restored in all the subjects with mean voltage and energy levels of 352.0 ± 80.3 V and 8.2 ± 3.4 J, respectively. The ADT in patients pretreated with amiodarone (6.4 ± 1.8 J) was lower than that of patients who had not received any antiarrhythmic drugs (9.2 ± 3.7) (P = 0.04). No ventricular arrhythmias were induced by any of the atrial shocks, and no other complications were observed. During a mean follow‐up of 162.9 ± 58.7 days, AF recurred in 21 (43%) patients; 71% of these occurred in the first week after Cardioversion. LEIC is effective in restoring sinus rhythm in patients with persistent AF. The technique seems to be safe and does not require general anesthesia or, in most cases, sedation. Patients pretreated with amiodarone have lower ADTs.

Changes in Intracardiac Atrial Cardioversion Threshold at Rest and During Exercise

OBJECTIVES We sought to analyze in patients with chronic atrial fibrillation (AF) the change in the intracardiac atrial defibrillation threshold (ADT) at rest and during exercise, to quantify the effective risk of low energy endocavitary cardioversion during the effort and to compare the ADT of chronic and reinduced AF. BACKGROUND Low energy endocavitary cardioversion is a new alternative to transthoracic shock in patients with chronic AF. Nevertheless, patient discomfort and possible induction of ventricular arrhythmias should be further evaluated. METHODS Sixteen patients with chronic AF were included in the study. Two 6F custom-made catheters (Electro-Catheter, Inc.) were used for shock delivery and one tetrapolar lead for ventricular synchronization. Without sedation and in a random order, patients underwent two sequences of shocks to determine the ADT at rest and during exercise. Exercise was performed isometrically by the superior limbs. Atrial fibrillation was reinduced by atrial pacing. After each shock, the patients were requested to grade their discomfort with a score from 1 to 5. The power of the study was > 90% in detecting a 25% difference in the ADT between groups. RESULTS Patients were classified into two groups: Nine patients (group A) underwent the first cardioversion during exercise; seven patients (group B) underwent the first cardioversion at rest. In total, the mean (+/-SD) ADT was 6.70 +/- 1.54 J during exercise and 7.02 +/- 1.82 J at rest (p = 0.59). A significantly lower ADT was observed in the second shock sequence than the first one (6.32 +/- 2.09 J vs. 7.40 +/- 0.87 J, p < 0.05). The discomfort score was 3.25 +/- 0.86 at rest and 2.94 +/- 0.77 during exercise (p = 0.09). No complications occurred. CONCLUSIONS Low energy endocavitary cardioversion is a safe and effective procedure in patients with chronic AF. Discomfort is not generally severe enough to result in procedure termination. The ADT is not influenced by exercise and is higher in chronic than in reinduced AF.

Analysis of high-resolution atrial activation: Report on 403 cases

The findings of a study carried out on a sample of 403 P waves, selected over the 50 to 300 Hz frequency range, by a portable microcomputer system capable of averaging 512 P waves, are reported. Detailed analysis of P waves was attempted in healthy subjects and in patients affected by pathologic processes where atrial involvement had been observed. An attempt was made to individualize P wave parameters which may be associated with these pathologic conditions. On each atrial signal a 512-point fast Fourier transform was used. The original sample was divided into 18 classes, and the mean values of some parameters of each class were computed. The results of fast Fourier transform computing and of the mean values of parameters for both patients and healthy subjects show two different behaviors with respect to the amplitude-frequency relationships and mean peak-to-peak amplitude, respectively. The present results indicate that this technique may be useful for further detailed analysis of P waves.

Automatic analysis of high resolution atrial activation in mitral valve stenosis

High resolution P-waves of 28 patients having a mean age of 45 years and affected by isolated mitral valve stenosis (nine of whom showed paroxysmal atrial fibrillation) have been compared with those obtained from 30 healthy subjects about 35 years old. Our primary aim was to characterize the signal-averaged P-wave in mitral valve stenosis. Parameters which differed between the two groups in time domain analysis were the P-wave duration, the abscissa of the maximum positive voltage amplitude, the peak-to-peak amplitude and the integrated voltage-time product, which turned out to be greater in the patient class than in the healthy set; furthermore, in the frequency domain analysis, amplitudes in the range from 37 to 60 Hz were greater in healthy subjects than in patients. A successive analysis carried out to predict those patients with mitral valve stenosis who are at risk of developing paroxysmal atrial fibrillation showed that the P-wave duration and the amplitudes (in the range 60-106 Hz) were the most distinctive parameters, but, unfortunately, without any significant difference with respect to those of patients with mitral valve stenosis alone. Finally, some correlations between the age, the P-wave duration and the left atrial diameter of patients, were revealed to exist only in patients affected by episodes of atrial fibrillation.