Low-energy Internal Cardioversion Research Articles

Atrial fibrillation as a consequence of tuberculous pericardial effusion

in the current study for low-energy internal cardioversion of AF. Compared to the conventional lead configurations, the proposed electrode placement strategy achieves lower inter-electrode impedance and delivers more intense electric field thorough atrial myocardium while only having minimum amounts of myocardium subject to damage. We would like to thank Minnesota Supercomputing Institute for providing the computation resources. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [16].

A novel electrode placement strategy for low-energy internal cardioversion of atrial fibrillation: A simulation study

highlights the importance of implementing early general cardiovascular health monitoring. Monitoring and treatment of these risk factors may reduce the incidence of aortic dissection and its consequences, although diagnosis still relies on a high degree of clinical suspicion given the paucity of clinical signs and rapid progression to fatal outcomes. Further, post-menopausal women were noted to have the same risk as age matched males, highlighting the need for similar vigilance in cardiovascular monitoring in this population. Only 11.9% of the cases involved dissection associated with an area of aneurysmal dilatation. Previous clinical studies have demonstrated that aortic diameters are similar when comparing aneurysmal cases with and without dissection, further supporting the theory that aneurysm and dissection develop independently [1]. While current recommendations for aneurysm risk monitoring include annual imaging of the aorta of Marfan patients with an aortic diameter less than 4.5 cm, screening for aortic dissection in high risk demographics is not currently within the scope of published guidelines [3,5]. The diagnosis of aortic dissection remains clinically challenging and the outcomes from this disease are often fatal and in particular can apply to young men, where modifiable risk factors have been identified prematurely. Improved imaging of atherosclerotic changes within the thoracic aorta may have a role in improving diagnosis and management of aortic dissection in the future.

Successful low-energy cardioversion using a novel biodegradable gel pad: Feasibility of treating postoperative atrial fibrillation in animals

Postoperative atrial fibrillation is one of the most frequent complications of cardiac surgery. We developed a novel biodegradable gel pad consisting of biopolymers that directly attach to the myocardium by electrostatic interaction. The present study examines the feasibility and effectiveness of low-energy internal cardioversion using these pads. The hearts of 6 pigs were exposed through a median sternotomy under general anesthesia, and 2 monopolar pacing wires were placed on the left pulmonary veins (chest open group). Two biodegradable cardioversion gel pads were placed on the right appendage and the left atria without suturing. All wires were extruded through the skin and secured with a suture. Sustained atrial fibrillation was induced by burst-pacing from the pulmonary veins in continuous 20-ms cycles. Shock intensity started at 0.5 J, and the energy level was increased in 0.5-J increments until cardioversion occurred. This protocol was repeated 5 times per pig. In a second group of 6 pigs (chest closed group), the epicardial cardioversion electrode gel pads and pacing wire electrodes were positioned as described above. Shock intensity was started at 0.5 J. If the shock was unsuccessful, the energy level was increased in 0.5-J increments until 2 consecutive cardioversions were achieved at a single energy level. At postoperative days 1, 3, 5, and 7, the defibrillation threshold was determined with the chest closed. At postoperative day 10, the cardioversion wires were removed. At predetermined time intervals, the heart was reexposed and the extent of degradation in vivo was visually evaluated and histologically assessed after sacrifice. All pigs with induced atrial fibrillation were cardioverted to sinus rhythm on the determined postoperative day. The mean energy and lead impedance in the chest open group were 0.65 +/- 0.23 J and 97.6 +/- 5.52 Omega, respectively, and the overall values of mean energy and lead impedance in the chest closed group were 1.67 +/- 1.00 J and 75.9 +/- 13.3 Omega, respectively. No complications were observed after wire removal. The gel pads became degraded and decreased in thickness, and signs of mild inflammation were evident on the gel pad. However, the gel pads did not elicit significant severe inflammatory reactions according to both gross and histologic assessments at 1 month after the surgery. Atrial cardioversion using novel biodegradable gel pads that are easily affixed may afford a straightforward and effective treatment for atrial fibrillation after cardiac surgery.

Prospective Randomized Trial of Transthoracic Versus Low-Energy Internal Cardioversion in Persistent Atrial Fibrillation Long Term Follow-up

Low energy internal cardioversion (ICV) is a relatively new method. This report describes the long-term follow-up results of a prospective randomized comparison of low energy ICV and transthoracic cardioversion (TT CV) in patients with persistent atrial fibrillation (AF). Fifty-two patients (mean age, 60.6 +/- 10.1 years, 23 males) with persistent AF were randomly assigned to either TT (n = 26) or ICV (n = 26). The baseline characteristics of the 2 groups were similar. Transthoracic CV was performed under sedation with hand-held electrodes in the apex-anterior position and high energy (100-360 J) monophasic shocks. ICV was performed by a dedicated balloon-directed catheter utilizing truncated, biphasic shocks of low energy (1-15 J). Sinus rhythm (SR) was restored in 24/26 (92%) patients in the ICV group and in 22/26 (85%) patients in the TT CV group (P > 0.05). Immediate recurrence of AF (IRAF), defined as reappearance of AF within 2 minutes of successful CV, occurred in 5 patients (21%) in the ICV group and in 1 patient (4.5%) in the TT group (P > 0.05). Successfully cardioverted patients in whom no IRAF occurred were followed-up for 18 months under both warfarin and Class 1 or 3 antiarrhythmic drugs, as guided by the current ACC/AHA/ESC Guidelines. The rate of SR at 1, 3, 6, 12, and 18 months of follow-up was not significantly different between the 2 groups, and in an intention-to-treat analysis at 18 months, SR was present in 6 patients (23%) in the ICV group and in 10 patients (38%) in the TT group (P > 0.05). The majority of AF recurrences occurred within a month of successful CV in both groups (8/12 [67%] in the TT group and 15/18 [83%] in the ICV group, P > 0.05). The mortality, thromboembolic, and bleeding complication rates were similar in the 2 groups. In this prospective randomized comparison of TT and low energy ICV in patients with persistent AF, the 18-month rates of SR and major adverse clinical events were found to be similar.

Prospective randomized trial of transthoracic versus low-energy transvenous internal cardioversion in persistent atrial fibrillation

Objective — Electrical cardioversion (CV) is used to restore sinus rhythm (SR) in patients with atrial fibrillation (AF). In this prospective randomized study, we compared two different methods of electrical CV, namely transthoracic (TT) and low-energy transvenous internal CV (ICV), in patients with persistent AF with respect to efficacy, safety and the magnitude of myocardial damage provoked by either method.Methods and results — Fifty-two patients with persistent AF were randomly assigned to either TT (n = 26) or ICV (n = 26). The baseline characteristics of the two treatment groups were similar. TT CV was performed under sedation with hand-held electrodes in the apex-anterior position and high-energy (100-360 J) monophasic shocks. ICV was performed by a single catheter approach utilizing a special balloon-directed catheter with proximal and distal arrays of shock electrodes that were positioned in the right atrium and left pulmonary artery under fluoroscopy. Truncated, biphasic shocks of low energy (1-15 joules) were used. Cardiac troponin T (cTpnT), creatine kinase (CK) and CK-MB levels were assessed before and 24 hours after each procedure.SR was restored in 24/26 (92%) patients in the ICV and 22/26 (85%) patients in the TT CV groups (p > 0.05). The mean energy to achieve SR was significantly higher with the TT method (9.8 ± 4.3 J vs. 246.4 ± 73.6 J, p < 0.05). CV with either method caused no elevation in cTpnT levels.Total CK and CK-MB levels remained unchanged with ICV. On the other hand, TT CV resulted in a significant increase in total CK (51.8 ± 30 vs. 156.5 ± 255.3, p < 0.05) and a nonsignificant rise in CK-MB levels (14.7 ± 7 vs. 17.3 ± 11.1, p > 0.05).Conclusions — In this prospective randomized comparison, TT and ICV were found to be equally effective to restore SR in patients with persistent AF. No evidence of myocardial damage was detected with either method.

Increase in QT/QTc dispersion after low energy cardioversion of chronic persistent atrial fibrillation

Background: The effects of atrial internal cardioversion on QT interval and QT dispersion (parameters associated with increased risk of ventricular tachyarrhythmias) are unknown. We investigated changes in QT interval, QTc and QT dispersion immediately after shock delivery for internal cardioversion in patients with chronic persistent atrial fibrillation. Method: Twenty-two patients with chronic persistent atrial fibrillation (mean duration, 17±23 months) underwent transvenous low-energy internal atrial cardioversion with a step-up protocol of shocks delivered between catheters in the right atrium and coronary sinus. (successful shock, 7.2±4.2 J). RR interval, QT interval, QTc interval, QT dispersion, and QTc dispersion were all measured on three consecutive beats (at 75 mm/s on at least 9 of 12 leads) and then averaged both before and after (1) the last unsuccessful shock, and (2) sinus rhythm restoration. Results: All parameters remained similar in the minute before and after the last unsuccessful shock. At 1 min after the successful shock, abrupt increases in QT dispersion (+43.8% vs. pre-shock; P<0.001 at least significant difference analysis) and QTc dispersion (+30.0%; P<0.05) were observed, followed by a gradual return to pre-shock values at 15 min. Conclusions: These findings strongly suggest the likely existence of a brief period of increased electrical vulnerability immediately after restoration of sinus rhythm by internal cardioversion. Particular caution should therefore be applied whenever class III antiarrhythmic drugs are administered immediately after successful internal atrial cardioversion.

Effectiveness and safety of low-energy internal cardioversion of long-standing atrial fibrillation after unsuccessful external cardioversion

This study examines the efficacy, safety, and long-term follow-up of low-energy internal cardioversion as a day-stay procedure in patients with long-standing persistent atrial fibrillation (AF) who have had unsuccessful conventional external cardioversion.

Atrial Mechanical Performance After Internal and External Cardioversion of Atrial Fibrillation: An Echocardiographic Study

To compare the time course of resumption of mechanical performance of the left and right atrium after the novel method of internal low-energy cardioversion (CV) and conventional external CV of atrial fibrillation (AF). Right atrial performance has been shown to normalize before the left atrium after external CV. However, no data on atrial function after internal CV are available. Sixty-three patients with chronic AF were randomized to participate in either external or internal CV. Echocardiographic examinations were carried out before as well as immediately after CV (day 0), and at days 1, 7, and 28 thereafter for the determination of cardiac dimensions, volumes, and transvalvular flow patterns. After randomized internal CV or external CV, stable sinus rhythm was restored in 59 patients. Irrespective of the mode of CV, the right atrium resumed its mechanical function immediately after CV, whereas the left atrium was stunned beyond day 7. The mode of CV, internal or external, had no influence on the recovery of atrial mechanical function. The right atrium resumes its normal function immediately after internal as well as external CV, whereas left atrium function is delayed. In contrast to the assumption that low-energy internal CV would impact less on atrial mechanical recovery, the type of method of CV used has no effect on such recovery.

Low-energy internal cardioversion in patients with long-lasting atrial fibrillation refractory to external electrical cardioversion: results and long-term follow-up.

Low-energy internal cardioversion is a new electrical treatment for patients with persistent atrial fibrillation. This paper evaluates the efficacy and safety of low-energy internal cardioversion in patients with long-lasting atrial fibrillation refractory to external electrical cardioversion, and the clinical outcome of such patients. The study population consisted of 55 patients [32 male, mean age 65 +/- 10 years, 48 (87%) with underlying heart disease] with long-lasting (mean 18 +/- 34 months) atrial fibrillation in whom external cardioversion had failed to restore sinus rhythm. Two custom-made catheters were used: one positioned in the right atrium and one in the coronary sinus or the left pulmonary artery. A standard catheter was inserted into the right ventricular apex to provide R wave synchronization. Sinus rhythm was restored in 52 patients (95%) with a mean defibrillating energy of 6.9 +/- 2.6 J (320 +/- 60 V). No complications were observed. During follow-up (mean 18 +/- 9 months), 16 patients (31%) suffered early recurrence (< or = 1 week) of atrial fibrillation and 20 patients (38%) had late recurrence (> 1 week, mean 3.5 +/- 3.6 months) of atrial fibrillation. Six patients with a late recurrence again underwent cardioversion and five of these maintained sinus rhythm. Therefore, a total of 21/52 patients (40%) were in sinus rhythm at the end of follow-up. No clinical difference was found between patients with and without recurrences. Low-energy internal cardioversion is a useful means of restoring sinus rhythm in patients with long-lasting atrial fibrillation refractory to external electrical cardioversion. More than one-third of patients maintained sinus rhythm during long-term follow-up.

Plasma catecholamines during low energy internal atrial cardioversion and during electrophysiological study for induction of ventricular tachyarrhythmias Giuseppe Boriani, Mauro Biffi, Francesco Pergolini, Cristian Martignani, Alberto Bargossi, Romano Zannoli, Angelo Branzi. Institute of Cardiology-University of Bologna, Bologna, Italy

Plasma catecholamines during low energy internal atrial cardioversion and during electrophysiological study for induction of ventricular tachyarrhythmias Giuseppe Boriani, Mauro Biffi, Francesco Pergolini, Cristian Martignani, Alberto Bargossi, Romano Zannoli, Angelo Branzi. Institute of Cardiology-University of Bologna, Bologna, Italy

Transvenous low energy internal cardioversion for atrial fibrillation: a review of clinical applications and future developments.

Low energy internal atrial cardioversion can be performed by delivering biphasic shocks between transvenous catheters positioned within the cardiac chambers or great vessels. Delivery of shocks results in effective cardioversion at energies < 6-10 J and the procedure can be effective even when external cardioversion has failed. Shock induced discomfort varies from patient to patient, but the procedure can be usually performed without general anesthesia and eventually under mild sedation. Nevertheless, tolerability has to be improved by obtaining a substantial reduction in defibrillating thresholds. With regard to safety, delivery of shocks for defibrillating the atria implies a potential risk of inducing ventricular fibrillation; to minimize this risk, shock delivery must be synchronous to the QRS and should be avoided during rapid RR cycles (< 300 ms). Presently, transvenous low energy cardioversion is an investigational procedure, but a widening of indications is expected in the near future. The cost of the procedure, which remains invasive and requires a brief hospital stay, must be balanced with the benefit of restoring sinus rhythm and the possibility of maintaining sinus rhythm for the medium- to long-term. Experimental and clinical investigations of low energy internal cardioversion have resulted in the development of devices for atrial defibrillation whose clinical role and cost-benefit ratio is currently under evaluation.

Internal Low Energy Atrial Cardioversion: Efficacy and Safety in Older Patients with Chronic Persistent Atrial Fibrillation

Low-energy internal atrial cardioversion is a relatively new technique based on delivery of intracardiac shocks through transvenous catheters placed into the atria or the vessels. The aim of this study was to assess in older and younger patients with chronic persistent atrial fibrillation (AF) the efficacy and safety of transvenous low-energy internal atrial cardioversion performed without routine administration of sedatives or anesthetics. A prospective longitudinal study. A cardiological university hospital. 82 patients, divided into older (> or = 60 years) (n = 49) and younger (n = 33) subjects. Atrial defibrillation threshold for internal cardioversion, measured as leading edge voltage (V) and delivered energy (J) of effective shocks, percentage of patients maintaining sinus rhythm at short-term (within 3 days) and at long-term follow-up. Patients with chronic persistent AF, treated with oral anticoagulants for at least 3 to 4 weeks, were admitted to hospital. Following a clinical work-up, patients were subjected to low-energy internal atrial cardioversion with shock delivery according to a step-up protocol. Internal cardioversion was effective in restoring sinus rhythm in 90% (44/49) of the older patients and in 94% (31/33) of the younger patients. Shocks were effective at a mean energy between 6 and 8 joules (range 0.9-23) and administration of sedatives or anesthetics was required during the procedure in 22% (11/49) of older and in 48% (16/33) of younger patients (P = .026 at chi-square). No major complications occurred during the procedure. Pharmacological prophylaxis of AF recurrences was instituted immediately following the procedure. During inhospital stay and during the follow-up (mean 12 +/- 9 months for older patients and 15 +/- 10 months for younger patients), AF recurred in 39% (17/44) of older patients and in 16% (5/31) of younger subjects (P = .064 at chi-square). Internal low energy cardioversion is a very effective procedure for restoring sinus rhythm in patients with AF; it can be performed in older patients, and administration of sedatives or anesthetics can be avoided or minimized in a substantial proportion of subjects. Recurrences of AF in the long term tend to be higher in older subjects and intensive prophylaxis with antiarrhythmic drugs is required.

Plasma catecholamines levels during low energy internal cardioversion for persistent atrial fibrillation and during electrophysiological study for ventricular tachyarrhythmias

Plasma catecholamines levels during low energy internal cardioversion for persistent atrial fibrillation and during electrophysiological study for ventricular tachyarrhythmias

Plasma catecholamines levels during low energy internal cardioversion for persistent atrial fibrillation and during electrophysiological study for ventricular tachyarrhythmias

Plasma catecholamines levels during low energy internal cardioversion for persistent atrial fibrillation and during electrophysiological study for ventricular tachyarrhythmias

Transoesophageal low-energy cardioversion of atrial fibrillation. Results with the oesophageal-right atrial lead configuration.

Low energy internal cardioversion is a safe and effective procedure to restore sinus rhythm in patients with atrial fibrillation refractory to external cardioversion. However the procedure is invasive and fluoroscopy is mandatory. Aim of the study To assess the efficacy, safety and tolerability of a new simplified procedure of low energy internal cardioversion. Twenty-five consecutive patients (19 males and 6 females) with persistent atrial fibrillation were submitted to low energy internal cardioversion using a step-up protocol (in steps of 50 V, starting from 300 V). A large surface area lead (cathode) was positioned in the oesophagus, 45 cm from the nasal orifice. A second large surface area lead (anode) was positioned in the right atrium. A quadripolar lead was positioned at the right ventricular apex to achieve ventricular synchronization and back-up pacing. Oesophageal endoscopy was performed within 24 h of the end of the procedure and repeated after 48 h, if injury to the oesophageal mucosa had occurred. Sinus rhythm was restored in 23 patients (92%) with a mean delivered energy of 15.74 J (range 5-27) and a mean impedance of 48 Omega. In two patients, endoscopy revealed that small burns had occurred in the oesophageal mucosa. Such lesions spontaneously healed after 48 h. This new technique of performing low energy internal cardioversion is effective and safe and avoids the positioning of a lead in the coronary sinus or in the left pulmonary artery, thereby simplifying the procedure.

Cardioversión eléctrica interna con baja energía y curva bifásica en fibrilación auricular inducida durante el estudio electrofisiológico

Atrial fibrillation is observed in 10% of electrophysiological studies. Previous studies have shown the efficacy of biphasic low energy internal cardioversion to restore sinus rhythm. We studied the efficacy and safety of low-energy internal cardioversion and the biphasic curve, in sustained atrial fibrillation (>15 min) during electrophysiologic procedures. From January 1997 to August 1998, 320 patients underwent an electrophysiological study. An internal cardioversion was done on those patients who developed sustained atrial fibrillation. We delivered biphasic shocks between electrodes-catheters positioned in the right atrium and the coronary sinus. Increasing energy was applied until restoration of sinus rhythm or a maximum of 10 joules were achieved with no result. A right ventricle electrode was used to synchronize the V wave and for temporary pacing. Thirty one episodes of sustained atrial fibrillation were observed in 26 patients (1,23 episodes/patient) and a mean of 2,58 internal cardioversions were applied per every patient. Sinus rhythm was restored in twenty three patients. The mean energy delivered was 4.1 joules. The mean time for the recovery was 3,200 ms. Temporary pacing was used in 16% of the patients for up to 1 minute. No AV blocks were observed. Internal cardioversion successfully restored sinus rhythm in 88.5% of the patients who presented sustained atrial fibrillation (88.5%). Temporary pacing was necessary for the treatment of postsinus shock pauses.

Clinical feasibility of low energy internal atrial cardioversion with a three-electrode configuration in patients with unsuccessful conventional configurations.

Low energy internal cardioversion is a safe and highly effective method for atrial fibrillation termination. We will describe 6 patients in whom the conventional 2-electrode systems with the defibrillation leads positioned in the right atrium and in the coronary sinus or left pulmonary artery failed to terminate the arrhythmia despite the use of maximal available energies. A 3-electrode configuration including right atrium, coronary sinus and left pulmonary artery was used in order to encompass as much atrial mass as possible between the cathode and the anode. The atrial fibrillation was successfully interrupted in 4 out of 6 patients. The creation of a 3-electrode configuration may be a further technical expedient in order to increase the success rate of internal cardioversion when usual manoeuvres like lead repositioning, reversion of polarity, or addition of antiarrhythmic drugs are ineffective.

Transvenous internal cardioversion for atrial fibrillation: a randomized study on defibrillation threshold and tolerability of asymmetrical compared with symmetrical shocks

The aim of the study was to compare, according to a randomized cross-over design, two different biphasic waveforms (6.5/2.5 ms and 3.0/3.0 ms phases duration, respectively) for low energy internal atrial cardioversion with regard to energy requirements for cardioversion and shock induced discomfort. Methods: Nineteen patients with chronic persistent atrial fibrillation (AF)(mean duration 16±20 months) were submitted to internal atrial cardioversion (shock delivery between catheters in right atrium and coronary sinus, respectively) and were randomly allocated to baseline cardioversion with an asymmetrical biphasic shock (6.5/2.5 ms) or with a symmetrical biphasic shock (3.0/3.0 ms), according to a step up protocol. After baseline cardioversion, a sustained AF was reinduced and the patients crossed to the alternative waveform. The procedure was performed without routine administration of sedatives and shock induced discomfort was monitored by a subjective score (1 to 5). Sedatives or anesthetics were administered at patient’s request. Results: The procedure was effective in all the patients and was performed without need for sedatives/anesthetics in 17/19 patients (89%). Leading edge voltage of effective shocks resulted lower for asymmetrical shocks compared to symmetrical shocks (290±76 vs. 337±104 V, P<0.001) with no statistically significant differences in delivered energy (7.74±4.25 vs. 8.65±5.94 J). Moreover shock induced discomfort resulted lower for asymmetrical shocks compared to symmetrical (pain score=4.18±0.73 vs. 4.59±0.62, P<0.02). Shock impedence of effective shocks was 59±10 ohms for both waveforms. No significant complications occurred during the procedure and no ventricular arrhythmia was observed after atrial cardioversion. Transient bradycardia requiring support ventricular pacing was observed in one patient. Conclusions: Delivery of biphasic asymmetrical shocks (6.5/2.5 ms) results in lower leading edge voltage of effective shocks and better patients tolerability compared with conventional biphasic symmetrical shocks (3.0/3.0 ms). These findings are of interest both for transvenous internal cardioversion of chronic persistent AF and for implantable atrial defibrillators.

Internal low-energy cardioversion: a therapeutic option for restoring sinus rhythm in chronic atrial fibrillation after failure of external cardioversion.

Conventional external cardioversion remains the technique of choice for restoration of sinus rhythm in patients with chronic atrial fibrillation (AF). Recent reports have suggested that internal low-energy cardioversion is efficient and safe in terminating AF in patients with failed external cardioversion. In 20 of 118 consecutive patients with spontaneous chronic AF (>7/days), who underwent low-energy cardioversion, one or more attempts at restoring sinus rhythm with external cardioversion had failed. Low-energy internal cardioversion was performed under light sedation. Shocks were delivered (using an external custom defibrillator) between two nonapolar catheters positioned in the right atrium (cathode) and in the coronary sinus (anode). Heart disease was present in 12 and absent in eight patients ('lone' atrial fibrillation). Atrial fibrillation was established for a period ranging from 12 days to 53 months. Low-energy internal cardioversion restored sinus rhythm in 15 of the 20 patients (75%) with a mean energy of 4.5+/-1.2 J, a mean conversion voltage of 355+/-53 V and a mean impedance of 63+/-8 ohms. No complications were observed. With a mean follow-up of 6+/-7 months, 11 patients (73%) were in stable sinus rhythm. This study provides evidence in support of low-energy internal cardioversion as a valuable therapeutic option in patients in whom conventional external cardioversion failed. This technique is safe and does not require general anaesthesia.

Favorable effects of flecainide in transvenous internal cardioversion of atrial fibrillation

ObjectivesThe aim of the study was to evaluate the effects of intravenous (IV) flecainide on defibrillation energy requirements in patients treated with low-energy internal atrial cardioversion.BackgroundInternal cardioversion of atrial fibrillation is becoming a more widely accepted therapy for acute episode termination and for implantable atrial defibrillators.MethodsTwenty-four patients with atrial fibrillation (19 persistent, 5 paroxysmal) underwent elective transvenous cardioversion according to a step-up protocol. After successful conversion in a drug-free state, atrial fibrillation was induced by atrial pacing; IV flecainide (2 mg/kg) was administered and a second threshold was determined. In patients in whom cardioversion in a drug-free state failed notwithstanding a 400- to 550-V shock, a threshold determination was attempted after flecainide.ResultsChronic persistent atrial fibrillation was converted in 13/19 (68%) patients at baseline and in 16/19 (84%) patients after flecainide. Paroxysmal atrial fibrillation was successfully cardioverted in all the patients. A favorable effect of flecainide was observed either in chronic persistent atrial fibrillation (13 patients) or in paroxysmal atrial fibrillation (5 patients) with significant reductions in energy requirements for effective defibrillation (persistent atrial fibrillation: 4.42 ± 1.37 to 3.50 ± 1.51 J, p < 0.005; paroxysmal atrial fibrillation: 1.68 ± 0.29 to 0.84 ± 0.26 J, p < 0.01). In 14 patients not requiring sedation, the favorable effects of flecainide on defibrillation threshold resulted in a significant reduction in the scores of shock-induced discomfort (3.71 ± 0.83 vs. 4.29 ± 0.61, p < 0.005). No ventricular proarrhythmia was observed for any shock.ConclusionsIntravenous flecainide reduces atrial defibrillation threshold in patients treated with low-energy internal atrial cardioversion. This reduction in threshold results in lower shock-induced discomfort. Additionally, flecainide may increase the procedure success rate in patients with chronic persistent atrial fibrillation.