Low Energy Internal Atrial Cardioversion Research Articles

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.

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

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.

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.

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.

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.

Atrial Fibrillation: Favorable Effects of Flecainide in Transvenous Low Energy Internal Atrial Cardioversion

Atrial Fibrillation: Favorable Effects of Flecainide in Transvenous Low Energy Internal Atrial Cardioversion

Atrial fibrillation: favorable effects of flecalnide in transvenous low energy internal atrial cardioversion

Atrial fibrillation: favorable effects of flecalnide in transvenous low energy internal atrial cardioversion

Efficacy and Tolerability in Fully Conscious Patients of Transvenous Low-Energy Internal Atrial Cardioversion for Atrial Fibrillation

Transvenous low-energy atrial cardioversion was performed in a series of fully conscious patients (30 patients with chronic atrial fibrillation and 5 patients with paroxysmal atrial fibrillation). The results show that internal atrial defibrillation is effective and tolerable in most patients.

Tolerability of Internal Low-Energy Shock Strengths Currently Needed for Endocardial Atrial Cardioversion

There seems to be no relation between shock strength and patient's tolerability using energy levels currently needed for low-energy internal atrial cardioversion. Every patient felt that the second delivered shock, independent of the amount of energy, was more uncomfortable than the first one, which indicates that psychological conditioning may also play an important role in determining discomfort.

Low energy conversion of atrial fibrillation in the sheep

Objectives. In this study, the feasibility, efficacy and safety of low energy internal atrial cardioversion were investigated in a sheep model. The relation between the level of energy used for atrial defibrillation and the probability of successful cardioversion was examined.Background. Atrial fibrillation is a common clinical arrhythmia that frequently recurs after termination with high energy external cardioversion. In some patients with drug-refractory and poorly tolerated atrial fibrillation, an automatic implantable cardioverter may prove useful by providing rapid restoration of sinus rhythm.Methods. In 16 pentobarbital-anesthetized sheep, a right atrial spring electrode was implanted percutaneously and a left thoracic cutaneous patch electrode was placed on the thorax. Sustained atrial fibrillation was induced by rapid atrial pacing and terminated by biphasic cathodal shocks synchronized to the R wave of the surface electrocardiogram (ECG).Results. During 768 defibrillation attempts in 16 sheep, the percent of successful cardioversion attempts increased in a doseresponse manner, reaching a plateau at the average energy level of 5 J. With ≥ 1.5 and ≥ 2.5 J energy levels, cardioversion was achieved, respectively, in > 50% and > 80% of attempts. Ventricular fibrillation occurred in 18 (2.4%) of 768 cardioversion attempts; in all 18 cases, the shock was poorly synchronized with the ECG R wave.Conclusions. Low energy cardioversion of atrial fibrillation to sinus rhythm is feasible with use of a right atrial spring/cutaneous patch electrode configuration. The percent of successful cardioversion attempts depends on the level of energy output, and there is a risk of ventricular fibrillation if cardioversion is poorly synchronized with ventricular depolarization.