Internal Cardioversion of Chronic Atrial Fibrillation in Patients

Transvenous internal cardioversion of chronic AF using a right atrium (RA) coronary sinus (CS) vector requires more energy than cardioversion of paroxysmal AF. Chronic AF is not terminated in 25% of patients using biphasic shocks up to 10 J. We therefore evaluated efficacy, safety, and tolerability of internal cardioversion using a "unipolar' configuration (RA to skin patch) and biphasic shocks in patients with long-lasting AF and different heart disease. In each patient, biphasic R have synchronous shocks were delivered between a large defibrillating surface area electrode in the RA and a skin patch in the left prepectoral position. Defibrillation protocol started with a test shock of 0.4 J. Shocks were repeated and increased until termination of AF or a maximum of 34 J. Sedation was used when the patient described the shock as painful. This study included 11 patients with a mean age of 67 ± 8 years (range 56–83). AF duration was ± 1 month in all patients with a mean duration of 11 ± 11 months (range 2–36). Underlying heart disease was present in all patients and the mean left atrial dimension was 43 ± 9 mm (range 26–57). AF was terminated in 10 of 11 patients (91 %) with a mean delivered energy of the successful shocks of 18.7 ± 8.7 J (median energy 16.9 J; range 7.3–32.5) and a mean leading edge voltage of 564 ± 129 V. The mean shock impedance at the defibrillation threshold was 71 ± 13 Ω, (range 59–103). A total of 131 shocks were delivered without any complication and proarrhythmia episodes. We conclude that low energy "unipolar" internal cardioversion is a simple, safe, and effective technique for termination of chronic AF in patients with heart disease. The procedure is often tolerated under light sedation.     

Low Energy Internal Atrial Cardioversion in Atrial Fibrillation Lasting More Than a Year

The aim of this study was to evaluate the efficacy of low energy internal atrial cardioversion in restoring sinus rhythm (SR) in patients with chronic atrial fibrillation (AF) persisting > 1 year. Fifteen patients with chronic AF lasting > 1 year (from 13–48 months, mean 24 ± 13 months) were studied. R wave synchronized 3/3 ms biphasic shocks were delivered between right atrial and coronary sinus (left pulmonary artery in five patients) electrodes. Sedatives or anesthetics were administered only at the patient's request. Results: Stable SR was restored in 14 (93%)of 15 patients after shocks with a mean leading edge voltage of 377 ± 77 V (range 260–500) and a mean delivered energy of 7.3 ± 3.4 J (range 2.6–12.9). The procedure was performed without anesthesia in 6 (40%) patients. All successfully cardioverted patients were treated with flecainide, sotalol, or amiodarone. During a follow up of 7.7 ± 7.9 months (range 1–24) AF recurred in five (36%) patients. Three of five AF recurrences occurred within 3 days after conversion to SR. Conclusion: Internal low energy atrial cardioversion is highly effective in restoring SR even in patients with AF lasting > 1 year. The long-term results from the standpoint of freedom from AF recurrences, are satisfactory, although additional antiarrhythmic treatment is required, particularly in the first days after conversion.     

Improved Clinical Efficacy of External Cardioversion by Fluoroscopic Electrode Positioning and Comparison to Internal Cardioversion in Patients with Atrial Fibrillation

Background: Despite using different electrode positions, “conventional” external DC cardioversion in patients with atrial fibrillation is ineffective in 6%–50% of cases. An alternative when DC cardioversion is not successful is low energy internal cardioversion, which is performed at increased risk. We tested the hypothesis that optimization of electrode pad position under fluoroscopy to encompass as much atrial muscle as possible might improve the success rate of external cardioversion and thus minimize the need for internal cardioversion. Methods: Fifteen (9 males, 6 females) patients (age: 54 ± 15 years, weight: 124 ± 35 kg) with chronic atrial fibrillation (> 8 weeks) who had undergone unsuccessful conventional external cardioversion entered the study. Repeat conventional external cardioversion with electrodes in standard (right anterior and left posterior) positions was followed by “optimized” external cardioversion by positioning electrodes under fluoroscopy (using metallic markers). In case of failure, internal cardioversion was performed. Results: All 15 patients had undergone unsuccessful conventional external cardioversion with 360-J shocks. Eight patients (group A) reverted to sinus rhythm with one or two 360-J shocks using fluoroscopy-guided pad placement (53%). Six of the remaining 7 (86%) patients (group B) had successful internal cardioversion with biphasic shocks (12 ± 3 J). The body weight and body mass index were statistically lower in group A vs group B (106 ± 27 vs 145 ± 33 kg, p = 0.03 and 35 ± 8 vs 45 ± 8 kg/m², P = 0.48, respectively). There was no statistically significant in age, height, body surface area, duration of atrial fibrillation, amiodarone therapy, ejection fraction, or underlying heart disease. Conclusion: Unsuccessful external DC cardioversion, in some patients, is in part due to suboptimal conventional positioning of electrode pads that can be improved under fluoroscopic guidance by achieving the best possible vector encompassing the right and left atria. The optimized external cardioversion technique may minimize the need for internal cardioversion, which remains an effective approach when external cardioversion fails.     

Quadruple Pads Approach for External Cardioversion of Atrial Fibrillation

MARROUCHE, N.F., et al. : Quadruple Pads Approach for External Cardioversion of Atrial Fibrillation. This study examined the alternative of transthoracic quadruple pads shock delivery of two simultaneous 360-J shocks to convert refractory AF in patients failing standard external cardioversion. Forty-six patients (  mean age 58 ± 11 years, 23 men  ) with chronic AF (  duration 14 ± 17 months, range 1–60 months  ) were included. The left atrial diameter was  47 ± 7 mm  . The left ventricular ejection fraction was  59 ± 11%  . Antiarrhythmic drugs had failed to convert 44 (96%) of these patients. All patients underwent conventional external transthoracic cardioversion with pads applied in the antero-apical position using energy settings of 200 and 360 J, consecutively. In all patients who failed conventional cardioversion, quadruple pads were applied. Quadruple pads consisted of four pads, two in the antero-posterior position and two in a second apex-posterior position. Standard cardioversion to sinus rhythm was successful in 19 (41%) patients after use of a single 200-J shock and an additional 8 (17%) after a single 360-J shock. The total success rate was 58% after conventional cardioversion. The quadruple pads were successful in 14 (74%) of the remaining 19 patients. Four of the five patients who failed the quadruple pads approach subsequently also failed internal cardioversion. Thus, the cardioversion success rate was increased from 48% using the conventional approach to 89% using the quadruple pads approach. Quadruple pads external cardioversion is highly effective in converting chronic AF refractory to standard shock protocols to sinus rhythm. Moreover, the failure of the quadruple pads approach seems to predict poor response to internal cardioversion.     

Internal Cardioversion in Two Patients with Atrial Fibrillation Refractory to External Cardioversion

A-26year-old man underwent an electrophysiological study for evaluation of a history of congenital heart disease, presyncope, and wide complex tachycardia. During the study the patient developed sustained atrial fibrillation with a rapid ventricular response. A 17-year-old man with a history of sick sinus syndrome developed sustained atrial fibrillation. Both patients failed four attempts at external Cardioversion with a maximum delivered energy of 360 J. Low energy Cardioversion was successful in both patients using biphasic waveforms and internal transvenous defibrillation electrodes. Internal Cardioversion using a transvanous electrode system can be successful in patients with atrial fibrillation refractory to external Cardioversion.     

Initial Experience with a New Balloon-Guided Single Lead Catheter for Internal Cardioversion of Atrial Fibrillation and Dual Chamber Pacing

Background: Based on the observation that internal cardioversion (IntCV) of atrial fibrillation is effective with electrodes in the right atrium and pulmonary artery, a new balloon-guided catheter and external defibrillation device with optional dual chamber pacing was evaluated. Methods: IntCV was attempted in 27 patients (age: 57 ± 10 years, duration: 14 ± 18 months, left atrial diameter 56 ± 8 mm) using a new defibrillation device (Alert, EP MedSystems, Inc., NJ, USA) that allows the delivery of biphasic shocks (0.5–15 J, variable tilt), atrial and ventricular pacing, and online signal recording. Pacing and defibrillation shocks were applied via a 7.5 Fr balloon-guided catheter (EP MedSystems, Inc.). Pacing, sensing, and triggering were established through the proximal atrial array and an electrode ring between both defibrillation arrays and a single ventricular electrode ring. Catheters were inserted from the antecubital vein. Results: In 25 of 27 patients sinus rhythm was restored with a mean energy of 6.7 ± 4.5 J. In five patients, atrial postshock pacing was required for bradycardia and atrial premature beats. The mean fluoroscopy time was 2.0 ± 1.3 minutes. Conclusion: The high success rate, ease of application, and backup dual chamber pacing suggest that this system is an alternative to established methods of cardioversion. In certain indications, such as failure of prior external cardioversion and situations in which a standard pulmonary balloon catheter is needed, this system would be advantageous.     

Efficacy of Biphasic Shock for Transthoracic Cardioversion of Persistent Atrial Fibrillation:

Although electrical cardioversion of atrial fibrillation (AF) is frequently performed, initial energy requirements for cardioversion of persistent AF is still a matter of debate. The aim of the study was to determine the efficacy of biphasic shocks for transthoracic cardioversion of persistent AF and to predict adequate initial energy. A prospective study enrolled 94 consecutive patients with persistent AF, who were referred for elective cardioversion with a biphasic waveform. The paddles were placed in the anterolateral position. A step-up protocol was used to estimate the cardioversion threshold. The initial shock energy was 50 J, with subsequent increments to 100, 200, and 300 J in the event of cardioversion failure. The mean age of the study group was of about 65 years (6 ± 11 years) and a median duration of AF was 65 days (3–324). Sixty-two out of 94 patients were men, 55% of the study population was classified as having well-controlled hypertension. The overall success rate of cardioversion was 89%, with a mean 2.2 ± 1.4 shocks, and effective J 217.8 ± 113 delivered during repeated cardioversions. The success rate of low energy shocks: 50 and 50 +100 J was 51%. By logistic regression analysis the only independent predictor of success at low energy shock was shorter duration of AF (r =−0.51; P = 0.02). Patients with shorter duration of AF have a higher probability for successful cardioversion with low energy. In patients with longer AF duration, a 200 J shock should be considered for cardioversion as the initial energy. (PACE 2004; 27[Pt. I]:764–768)     

Atrial Ejection Force in Patients with Atrial Fibrillation: Comparison Between DC Shock and Pharmacological Cardioversion

It is well known that the restoration of sinus rhythm is not always associated with the return of effective atrial contraction. Atrial ejection force (AEF) is a noninvasive Doppler derived parameter that measures the strength of the atrial contraction. The aim of the present study was to use pulsed-Doppler echocardiography to determine if different modalities of cardioversion influence the delay in the return of effective atrial contraction after cardioversion. DC shock and pharmacological therapy were compared. Sixty-eight patients were randomly cardioverted, either using DC shock or i.v. procainamide. The patients who were restored to a sinus rhythm had a complete Doppler echocardiographic examination within 1 hour after the restoration, after 24 hours, after 1 month, and after 3 months. AEF was measured and compared in the two groups of patients and within the same group. AEF was greater immediately and at 24 hours after cardioversion in patients who underwent pharmacological therapy compared to patients treated with DC shock (peak A wave, 60 ± 9 vs 31 ± 8 msec, P < 0.001; AEF 11.3 ± 3 vs 5 ± 2.9 dynes, P < 0.001). In both groups, AEF increases over time. In conclusion, AEF is a noninvasive parameter that can be easily measured after cardioversion and can give accurate information about the recovery of left atrial mechanical function. This finding may have important implications for guiding the anticoagulant therapy after cardioversion.     

High Energy Transcatheter Cardioversion for Chronic, Poorly Tolerated Atrial Fibrillation

Between August 1991 and May 1993, 14 patients affected by chronic, poorly tolerated atrial fibrillation (AF) were submitted to high energy transcatheter Cardioversion. Mean duration of AF was 27.4 ± 45.1 months. In nine patients (56%), AF lasted for > 1 year. All patients had underlying heart disease, with a mean LVEF of 45.2%± 11.8% and a NYHA Class ≥ II. Previously, a mean of 2.9 ± 1.3 patients failed external electrical Cardioversion, with and without antiarrhythmics, have been attempted. Transcatheter conversion was performed by pulling the His-bundle catheter back in the right atrial cavity until no His bundle activity was recorded on distal poles, and then delivering the shock between a proximal electrode (cathode) and a back plate (anode). In all patients, transcatheter conversion restored sinus rhythm. Transient complete atrioventricular (AV) block was observed in four patients (28%), and treated by prophylactic temporary pacing. At 1 year, seven patients (50%) were still in sinus rhythm. In this series, only younger age could be related to AF recurrence (46.1 ± 10.8 vs 63.4 ± 6.8 years, P ≤ 0.004), even if prophylaxis with amiodarone showed a positive trend versus sinus rhythm maintenance (71 % vs 14%, P = NS). In conclusion, high energy transcatheter Cardioversion is a safe and effective method of restoring sinus rhythm in patients with chronic, poorly tolerated AF. In these patients, high energy transcatheter Cardioversion could be considered as an alternative to AV node ablation techniques, avoiding pacemaker implant and embolic risk. Larger studies are needed to determine better patient selection and delineate drug strategy after the procedure.     

Ventricular Fibrillation Following Successful DC Cardioversion for Atrial Fibrillation

Cardioversion remains an important therapy in the management of atrial fibrillation. Here, we report a case where direct current cardioversion resulted in a sudden dramatic change of heart rate that was associated with multiple ventricular fibrillation arrests in a manner akin to that previously observed post-atrioventricular node ablation. (PACE 2012;35:e361-e364).     

Prediction of Maintenance of Sinus Rhythm after Cardioversion of Atrial Fibrillation by Analysis of Serial Signal-Averaged P Waves

After cardioversion from atrial fibrillation (AF) many patients develop early recurrence of the arrhythmia. While these patients may be appropriate for immediate prophylaxis against AF recurrence their identification at the time of cardioversion is not possible. Since the signal-averaged P wave (SAPW) is abnormal in individuals with atrial arrhythmia, we assessed its utility for predicting early AF recurrence after cardioversion. Seventy-five cardioversions in 31 patients were evaluated. The mean age was 59 (range 28–79) years; 26 were male. Fifty-eight cardioversions were internal using low energy biphasic DC shocks delivered via electrodes placed in the right atrial appendage and coronary sinus. P wave specific signal averaging was performed at 3 and 24 hours after each cardioversion to estimate filtered P wave duration and energy from 20, 40, and 60 to 150 Hz. Follow-up was by regular clinic visits and transtelephonic ECG monitoring. Early recurrence of AF (prospectively defined as sinus rhythm duration < 1 week) occurred after 30 cardioversions. No differences were found in any P wave variable measured at 3 hours between these cardioversions and those that resulted in a longer duration of sinus rhythm. Paired 3- and 24-hour signal-averaged data were available in 47 cardioversions. There were significant falls in P wave energy from 3 to 24 hours after 31 cardioversions that resulted in sinus rhythm for > 1 week, (P40: 3 hours 11.2 [±1.5] μV²· s, 24 hours 8.6 [±1.2] μV²· s, P < 0.001), but not following the 16 after which AF returned within 1 week (P40: 3 hours 9.0 [±1.2] μV²· s, 24 hours 8.5 [±1.2] μV²· s, P = NS). A fall in P40 of > 25% had a positive predictive accuracy for maintenance of sinus rhythm of 87%; negative predictive accuracy was only 37%. Similar falls in P wave energy occurred after cardioversions that resulted in longer term (> 4 weeks) sinus rhythm, but not in those that did not. However, the predictive accuracy of a fall in P40 was less (positive predictive accuracy 38%, negative predictive accuracy 62%). Patients with relapsing permanent AF who remain in sinus rhythm for at least 1 week after cardioversion show a fall in P wave energy within the first 24 hours. However, in these patients the technique does not predict recurrent AF within 1 week nor sinus rhythm > 4 weeks. These observations suggest persistent disordered atrial activation as a mechanism for early recurrence of AF after cardioversion.     

Cardioversion of Atrial Fibrillation and Subsequent Maintenance of Sinus Rbythm

This article gives an overview of electrical cardioversion of AF and includes the discussion of newer strategies. DC external cardioversion is highly effective and carries a low risk of complications. Other approaches, like transesophageal cardioversion and high energy internal cardioversion, may improve the acute success rate but do not enhance long-term maintenance of sinus rhythm compared to external cardioversion. An atrial defibrillator may have important advantages which relate to the fact that the duration and possibly also the number of AF episodes become reduced. Supposedly, shortening the attacks of AF may exert an antiarrhythmic effect by limiting electrical, anatomical, and neurohumoral remodeling. So far. low energy biatrial defibrillation using an atrial defibrillator seems to be effective and safe (i.e., does not induce ventricular arrhythmias). However, discomfort limits its tolerability in clinical practice. Future improvement of leads and light sedation that is easy to administer may overcome this problem. In the second part of this overview, the probability of AF recurrence using a serial cardioversion approach is discussed. In middle-aged patients with a fair exercise tolerance and an arrhythmia duration < than 36 months this approach may be worthwhile. Young patients (age < 57 years) with an arrhythmia duration < 3 months and without hypertension may be cured from the arrhythmia with a single shock and without the institution of antiarrhythmic drugs. However, the serial electrical cardioversion approach is unlikely to succeed in elderly patients with a duration of AF exceeding 36 months and a poor exercise tolerance (NYHA Functional Class III or IV).     

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.     

Multiple Shocks Affect Thoracic Electrical Impedance During External Cardioversion of Atrial Fibrillation

Background: Thoracic impedance (TI) influences the success of external cardioversion (ECV) or defibrillation because current intensity traversing the heart is inversely related to TI. Experimental data suggest that TI decreases after multiple shocks. We undertook a clinical study to determine changes of TI values in patients with atrial fibrillation or flutter requiring ECV. Methods: We enrolled 222 consecutive patients (age 73 ± 11 years; males 67%; body weight 75 ± 13 kg) who underwent ECV between January 2004 and February 2007. Biphasic shocks were delivered through adhesive pads placed in the anteroposterior position. The initial energy was set at 1 J/kg, with progressive increases up to a maximum of 180 J in case of failure. In the last 39 elective patients, plasma concentration of interleukin‐6 (IL‐6) and tumor necrosis factor (TNF)‐α were determined before and 6 hours after ECV. Results: Sinus rhythm was restored in 202 patients (91.0%). Of these, 155 (69.8%) required more than one shock (on average, 2.5 ± 1.5 shocks/patient). Final values of energy and peak current intensity were 136 ± 47 J and 50 ± 14 A, respectively. TI decreased significantly by 6.2% from baseline after ≥2 shocks (P < 0.001). The absolute reduction was correlated with baseline TI, number of delivered shocks, and hemoglobin oxygen saturation. IL‐6 and TNF‐α increased with ECV (P < 0.001 and P = 0.014, respectively). Conclusions: TI decreases significantly after multiple shocks, possibly by activation of acute inflammation.     

Reversal of Atrial Remodeling after Cardioversion of Persistent Atrial Fibrillation Measured with Magnetocardiography

Background : Atrial fibrillation (AF) causes electrical, functional, and structural changes in the atria. We examined electrophysiologic remodeling caused by AF and its reversal noninvasively by applying a new atrial signal analysis based on magnetocardiography (MCG).
Methods : In 26 patients with persistent AF, MCG, signal-averaged electrocardiography (SAECG), and echocardiography were performed immediately after electrical cardioversion (CV), and repeated after 1 month in 15 patients who remained in sinus rhythm (SR). Twenty-four matched subjects without history of AF served as controls. P-wave duration (Pd) and dispersion (standard deviation of Pd values in individual channels) and root mean square amplitudes of the P wave over the last 40 ms portions (RMS40) were determined.
Results : In MCG Pd was longer (122.8 ± 18.2 ms vs 101.5 ± 14.6 ms, P < 0.01) and RMS40 was higher (60.4 ± 28.2 vs 46.9 ± 19.1 fT) in AF patients immediately after CV as compared to the controls. In SAECG Pd dispersion was increased in AF patients. Mitral A-wave velocity and left atrial (LA) contraction were decreased and LA diameter was increased (all P < 0.01). After 1 month, Pd in MCG still remained longer and LA diameter greater (both P < 0.05), while RMS40 in MCG, Pd dispersion in SAECG, mitral A-wave velocity, and LA contraction were recovered.
Conclusions : Magnetocardiographically detected atrial electrophysiologic alterations in persistent AF diminish rapidly although incompletely during maintained SR after CV. This might be related to the known early high and late lower, but still existent tendency to AF relapses.     

A Decrease in Serum Aldosterone Level is Associated with Maintenance of Sinus Rhythm after Successful Cardioversion of Atrial Fibrillation

Background: The activation of the renin–angiotensin–aldosterone system has been implicated in the progression of atrial structural remodeling during atrial fibrillation (AF). However, consequences of the changes of aldosterone in AF have not been evaluated. Objectives: This study's aim was to evaluate changes of serum aldosterone concentration after successful cardioversion of persistent AF and to determine the prognostic value of these changes. Methods: The prospective, single center study included 45 consecutive patients with nonvalvular persistent AF and preserved left ventricular systolic function, referred for cardioversion. None of the patients were taking aldosterone antagonists. Blood samples for aldosterone measurement were collected twice: 24 hours before and 24 hours after cardioversion. Results: Forty‐three patients were successfully converted to sinus rhythm. On the 30th day following cardioversion, 24 patients maintained sinus rhythm (group A), 19 patients relapsed to AF (group B). Serum aldosterone concentration before cardioversion did not differ significantly between both groups (175.6 ± 112.82 pg/mL vs 125.8 ± 51.2 pg/mL; P = 0.25). However, in group A serum aldosterone level decreased significantly within 24 hours after cardioversion, from 175.6 ± 112.8 pg/mL to 101.4 ± 44.2 pg/mL (P = 0.0034). In group B, the aldosterone level before and after cardioversion did not differ significantly (125.8 ± 51.2 pg/mL vs 118.2 ± 59.6 pg/mL; P = 0.68). Logistic regression analysis revealed that a decrease in plasma aldosterone concentration after direct current cardioversion more than 13.2 pg/mL predicted sinus rhythm maintenance in a 30‐day follow‐up, with 87% sensitivity and 64% specificity. Conclusions: There is a positive correlation between the fall in aldosterone concentration 24 hours after cardioversion and maintenance of sinus rhythm during 30 days of observation. (PACE 2010; 561–565)     

Cardioversion for Atrial Fibrillation: Treatment Options and Advances

Atrial fibrillation (AF) is associated with significant morbidity and mortality. There are two basic approaches to managing AF: slowing the ventricular rate, while allowing the arrhythmia to continue (the rate-control approach), and restoring and maintaining sinus rhythm (the rhythm-control approach) with antiarrhythmic drugs (AADs) and/or ablation, electrical cardioversion (CV), if needed, or both. Strategy trials comparing rate and rhythm control have found no survival advantage of one approach over the other, but other considerations, such as symptom reduction, often necessitate pursuit of rhythm control. Electrical, or direct current, CV is a widely used and effective method for termination of nonparoxysmal AF, although its success can be affected by patient- and technique-related variables. Pharmacological CV options also exist and are preferable in specific circumstances. Both pharmacological and electrical CV are associated with the risk of proarrhythmia. Many AADs are under development for both CV and maintenance of sinus rhythm. Some are atrioselective, such as vernakalant, and target ion channels in the atria, with little or no effects in the ventricle. Vernakalant, currently under Food and Drug Administration review, appears to offer a safer profile than current CV agents and is likely to expand the role of pharmacological CV. Other new AADs that provide increased efficacy or safety while maintaining normal sinus rhythm may also be better than current drugs; if so, rate-rhythm comparisons will differ from those of previous studies. In conclusion, further trials should clarify the long-term safety profiles of new atrioselective agents and other investigational drugs and define their role in the treatment of AF.     

Rounded Biphasic Waveform Reduces Energy Requirements for Transvenous Catheter Cardioversion of Atrial Fibrillation and Flutter

We postulated that reducing peak leading edge shock voltage and its rate of rise (waveform rounding) would reduce energy requirements for cardioversion of AF and AFI, and may therefore reduce patient discomfort. Transvenous defibrillating catheters (In-Control Inc.) were placed in the RAA (active fixation) and the CS of six anesthetized sheep. AF or AFI was induced by electrical stimulation (100 Hz, 2 V; Grass stimulator). A standard trapezoidal biphasic (S) waveform (3-ms duration each phase) was compared with a similar waveform that had the first phase rounded (R). Cardioversion was attempted after 30 seconds of arrhythmia, using a Ventritex HVS-O₂ defibrillator modified to allow waveform rounding. Each waveform was randomly tested several times at 100-, 150-, and 200-V leading edges, and percentage cardioversion success calculated. Shock energy was calculated from delivered current and voltage using Flukeview (Fluke, Inc.) software. At 100-V leading edge R (64% success) and S (59%), shocks were similarly efficacious (P = 0.37). However. R delivered less current, voltage, and energy than the comparable S shock (means 1.30 A, 65.0 V, 0.33 J R vs 1.92 A, 94.2 V, 0.47 J S; P = 0.0001). Both waveforms were equally successful at 150 V (88% vs 100%; P = NS) and 200 V(100% vs 100%), but again R delivered less current, voltage, and energy (2.05 A, 102.5 V, 0.82 J R vs 2.78 A, 142.3 V, 1.11 J S at 150 V; 2.76 A, 141.2 V, 1.58 J R vs 3.77 A, 189.4 V, 2.03 J S at 200 V; both P = 0.0001). No arrhythmic or other complications occurred in the 174 shocks delivered. Waveform rounding reduces delivered peak voltage, current, and energy without reducing defibrillation efficacy. To determine if these changes are associated with a reduction in discomfort, patients with AF are currently being cardioverted with these waveforms during electrophysiological studies.     

Factors Influencing Long Term Persistence of Sinus Rhythm After a First Electrical Cardioversion for Atrial Fibrillation

It is conventionally thought that electrical cardioversion in patients with atrial fibrillation (AF) of longstanding duration or with a large lefi atrial diameter, only seldom results in long term success. Recurrence is common, although antiarrhythmic drugs often effectively decrease the number and duration of recurrent AF episodes. We analysed clinical, functional and pharmacological variables which could possibly infiuence the long term outcome after a first electrical cardioversion for AF in a retrospective study on 85 patients. Univariate and multivariate analysis was used to identify factors predicting maintenance of sinus rhythm at 100 days, and absence of recurrence during the entire follow-up. In univariate analysis, the only significant predictor for maintenance of sinus rhythm at 100 days was the duration of the preceding AF episode. Multivariate analysis with persistence of sinus rhythm at 100 days as endpoint confirmed this as a prognostic factor (p <0.03), but sotalol treatment also contributed to maintenance of sinus rhythm (p <0.05). When considering ihe entire observation period, class III antiarrhythmic drugs, i.e. sotalol ami amiodarone, were useful in preventing recurrence (p <0.01 and < 0.02). High age (above 75 years) was a predictor of recurrence. In conclusion, class III antiarrhythmic drugs, the duration of atrial fibrillation and high age were the most important determirumts of long term outcome, while echocardiographic parameters and the presence of heart disease played no role.