Internal Cardioversion of Persistent Atrial Fibrillation Using Rectilinear Biphasic Waveform

Internal electrical cardioversion is currently used in patients with persistent atrial fibrillation resistant to external electrical cardioversion. In external cardioversion, biphasic waveforms have shown a greater efficacy than monomorphic waveforms. The present study aimed to test the safety and efficacy of rectilinear biphasic waveform in converting patients with persistent atrial fibrillation to sinus rhythm using internal electrical cardioversion, and to compare it with that of classical monophasic waveform. Twenty-seven consecutive patients with persistent AF received 31 internal cardioversions, using monophasic waveform in 11 (group I), and rectilinear biphasic waveform in 20 cases (group II). Baseline patients characteristics were similar in both groups. Multipolar catheters were positioned in the distal coronary sinus and in the high right atrium. Synchronised shocks were delivered using an escalating protocol of 2, 5, 10, 15, 20, 30, and 50 Joules. In group I, 1 patient was resistant to maximal energy (success rate 91%). The mean energy of the maximal shock was 18 ± 13 J. In group II, all patients were converted to sinus rhythm. The mean energy of the maximal shock was 9 ± 5 J (p < 0.01 vs. group I). No significant complications occurred. At 3 months follow-up, 45% of group I and 60% of group II patients remained in sinus rhythm (p = NS).We conclude that internal cardioversion using rectilinear biphasic waveform is feasible and safe, and requires less energy than classical monophasic waveforms.     

Maintenance of Sinus Rhythm after Cardioversion of Atrial Fibrillation in Patients with Lone Atrial Fibrillation and Patients with Hypertension

Background: The success rate and prognosis of cardioversion of atrial fibrillation (AF) in patients with organic heart disease is well known. In contrast, little data exist about cardioversion success and maintenance of sinus rhythm (SR) in patients with lone AF and in patients with hypertension as the only underlying cardiovascular disease. Methods: In a prospective cardioversion registry 148 of 181 patients (81.8%) with lone AF (age 58 ± 13 years, duration of AF 7.6 ± 19 weeks) and 120 of 148 patients (81.1%) with hypertension (age 62 ± 10 years, duration of AF 6.6 ± 21 weeks) had successful cardioversion and were followed for 7.7 ± 1.9 months. Results: At follow-up, 120 patients (81.1%) with lone AF were in SR, and 18 of these patients had had repeated cardioversion during follow-up (AF total recurrence rate 31.1%). In stepwise regression analysis, the number of previous cardioversions was predictive of rhythm at follow-up (P = 0.0453). Rhythm at follow-up did not differ between patients who were or were not on antiarrhythmic drugs. At follow-up 96 patients (80%) with hypertension were in SR, and 9 of these had had repeated cardioversion during follow-up (AF total recurrence rate 27.5%). As in lone AF, the recurrence rate of AF did not differ between patients with or without antiarrhythmic drug treatment, and in multivariate regression analysis, the number of previous cardioversions was the only clinical predictor of rhythm at follow-up (P = 0.0284). Conclusions: Even in patients with such benign conditions as lone AF or hypertension as the only underlying disease, the prognosis of cardioversion in terms of maintenance of SR is poor. Future studies of rhythm control versus rate control need to include not only patients with organic heart disease but also patients with lone AF and patients with hypertension, since the long-term benefits of these two strategies remain unclear even in these subsets of patients.     

Prospective Randomized Trial of External Versus Internal Transcatheter Cardioversion in Patients with Chronic Atrial Fibrillation

To evaluate the safety and long-term efficacy of internal transcatheter cardioversion, forty patients with chronic, lone atrial fibrillation were studied. The patients were randomised to internal transcatheter cardioversion or to conventional external cardioversion. In cases where the procedure was unsuccessful, cross-over to the alternate method was performed. Oral anticoagulation therapy was started three weeks prior to the procedure and was maintained for another three weeks following successful cardioversion.Sinus rhythm was restored in 16/18 patients (88%) in the internal cardioversion group, versus 9/22 patients (40%) in the external cardioversion group (p < 0.01). In addition, 8/13 (61%) patients who were crossed-over to internal cardioversion were successfully cardioverted to sinus rhythm. In contrast, both patients who were crossed-over to external cardioversion remained in atrial fibrillation.During a mean follow-up period of 23 months, 13 (39.3%) patients maintained sinus rhythm. Using the intention to treat principle, the recurrence rate was not statistically different between the two methods.It is concluded that internal cardioversion is more effective in acutely restoring sinus rhythm compared to external cardioversion. However, both methods have similar long-term recurrence rates.     

Pharmacological Cardioversion of Recent Onset Atrial Fibrillation with Intravenous Amiodarone in Patients Receiving Long-Term Amiodarone Therapy: Is It Reasonable?

In clinical practice the use of intravenous amiodarone has been proposed for the conversion of recurrent atrial fibrillation in patients already under chronic treatment with the same drug. Given that intravenous amiodarone exhibits different electrophysiological properties than when the drug is taken orally over a long period, this approach seems reasonable, but its effectiveness and safety have not been investigated systematically before.Of 45 patients under chronic treatment with amiodarone for the maintenance of sinus rhythm who had atrial fibrillation of recent onset, 23 were given intravenous loading of the same drug for 24 hours and 22 received placebo. Nine patients underwent an electrophysiological study several months after the successful restoration of sinus rhythm, before and after another intravenous loading dose of amiodarone, in order to examine the possible electrophysiological changes.In the amiodarone group 20 patients were successfully converted to sinus rhythm, compared to 13 of the placebo group (p < 0.05). No serious side effects of the intravenous administration were observed. Prolongation of refractoriness was seen in all 9 patients who underwent electrohysiological study after intravenous loading, without any effect on repolarization, atrioventricular conduction or sinus node function.In conclusion an intravenous loading dose of amiodarone exerts an additional electrophysiological effect in patients already under chronic treatment with the same drug. Such a combined therapy could be used with a high efficacy and safety for the conversion of recent onset atrial fibrillation in patients who are receiving long-term amiodarone therapy.     

Cardioversion Related Thromboembolism: Value of Transesophageal Echocardiography to Guide Cardioversion in Patients with Atrial Fibrillation

The aim of this article is to review two recent investigations of the value of transesophageal echocardiography to guide direct current cardioversion in different patient populations. In the Ludwigshafener Observational Cardioversion Study (LOCS) a TEE was performed prior to electrical cardioversion in patients with atrial fibrillation who had been receiving oral anticoagulation adjusted to an international normalized ratio of 2 to 3 for at least three weeks. In contrast, the ACUTE study investigated the value of transesophageal echocardiography in patients with atrial fibrillation in whom long-term oral anticoagulants had not been initiated in comparison to standard anticoagulation therapy. Furthermore, the following questions in respect to anticoagulation therapy are addressed: (1) how should patients be approached for pharmacological or spontaneous conversion; (2) how to treat emergency situations, (3) what is the importance of the postcardioversion period and long-term anticoagulation therapy; and (4) what is the role of low molecular weight heparin in the pericardioversion period.     

An Update on Electrical Cardioversion of Atrial Fibrillation

Atrial fibrillation is the most frequently encountered sustained arrhythmia in clinical practice. Electrical cardioversion of atrial fibrillation using damped sine wave shocks has been a mainstay of therapy for nearly 4 decades; its limitation remains a failure rate that approaches 20%. Although several alternatives have been proposed, including delivering 720 J shocks using dual monophasic defibrillators, ibutilide pretreatment and internal cardioversion, each of these approaches has significant limitations, which preclude its routine use. Recent data demonstrate that routine use of biphasic shocks for cardioversion of atrial fibrillation is associated with a marked improvement in cardioversion efficacy and suggest that biphasic shocks may be the preferred method for the transthoracic electrical cardioversion of atrial fibrillation.     

Persistent Atrial Flutter in Patients Treated for Atrial Fibrillation with Amiodarone and Propafenone:

INTRODUCTION: Antiarrhythmic drugs have been reported to promote the conversion of atrial fibrillation to atrial flutter in patients with paroxysmal atrial fibrillation. However, information about the electrophysiologic mechanism and response to radiofrequency ablation of these drug-induced atrial flutters is limited. Furthermore, the determinants of the development of persistent atrial flutter in patients treated for atrial fibrillation with antiarrhythmic drugs are still unknown. METHODS AND RESULTS: Among the 136 patients treated for atrial fibrillation with amiodarone (n = 96) or propafenone (n = 40), 15 (11%, mean age 65.5 +/- 12.3 years) were identified to have subsequent development of persistent atrial flutter based on surface ECG characteristics during antiarrhythmic drug treatment. The mean interval between the beginning of drug treatment and the onset of atrial flutter was 5.0 +/- 5.5 months. Intracardiac mapping and entrainment studies revealed that 11 patients had counterclockwise typical atrial flutter, and 4 had clockwise typical atrial flutter. All 15 patients underwent successful ablation with creation of complete bidirectional isthmus conduction block. After a mean follow-up of 12.3 +/- 4.2 months, 14 (93%) of 15 patients who underwent successful ablation and continued taking antiarrhythmic drugs have remained in sinus rhythm. Univariate analysis of clinical variables demonstrated that only atrial enlargement was significantly related to the occurrence of persistent atrial flutter. CONCLUSION: In patients with atrial fibrillation, persistent typical atrial flutter might occur during antiarrhythmic drug treatment, and atrial enlargement was a risk factor for the development of such an arrhythmia. Radiofrequency ablation and continuation of pharmacologic therapy offered a safe and effective means of achieving and maintaining sinus rhythm.     

Outcomes in Patients Requiring Cardioversion Following Catheter Ablation of Atrial Fibrillation

Outcomes of Cardioversion Post AF Ablation.   Introduction: Early recurrence of atrial tachyarrhythmias is commonly noted after catheter ablation of atrial fibrillation (AF). The long-term outcomes of patients who require cardioversion for persistent AF after AF ablation is not known. This study reports the outcomes of patients who underwent cardioversion for persistent AF or atrial flutter following an AF ablation procedure.
Methods: The patient population comprised 55 patients (mean age 58 ± 10 years, 35% paroxysmal) who underwent catheter ablation of AF and subsequently required electrical cardioversion for persistent AF (45 patients) or atrial flutter (10 patients). Cardioversion was defined as early (within 90 days of the ablation procedure) or late (between 90 and 180 days following ablation).
Results: The mean follow-up duration was 15 ± 8 months. Forty-six of the 55 patients (84%) patients experienced recurrence during follow-up. The average time to recurrence after cardioversion was 37 days. Of the 55 patients, 8 (15%) patients had a complete success, 11 (20%) patients had a partial success and 36 patients (65%) had a failed outcome. Seven of the 43 patients (16%) who underwent early cardioversion had a complete success as opposed to one of 12 patients (8%) who underwent late cardioversion (P = 0.49).
Conclusions: This study shows that >80% of patients who undergo cardioversion for persistent AF or atrial flutter after AF ablation have recurrence. The timing of cardioversion did not affect the outcome. These findings allow clinicians to provide realistic expectations to patients regarding the long-term outcome and/or requirement for a second ablation procedure. (J Cardiovasc Electrophysiol, Vol. 21, pp. 27–32, January 2010)     

Early Reinitiation of Atrial Fibrillation Following External Electrical Cardioversion in Amiodarone-Treated Patients

Early reinitiation of atrial fibrillation (ERAF) following external or internal electrical cardioversion is one of the factors determining unsuccessful electrical cardioversion. Prevention of ERAF has not been studied systematically in patients on amiodarone therapy. Methods and Results: 22 patients had ERAF within 1[emsp4 ]min after external electrical cardioversion of atrial fibrillation. 11 patients were on amiodarone therapy and 11 patients had no antiarrhythmic medication. The effect of atropine, post-shock atrial pacing and intravenous ajmaline on ERAF was consecutively tested in these patients. Administration of atropine before repeated defibrillation or post-shock atrial pacing prevented ERAF in 9 of the 11 patients (82%) on amiodarone therapy but in only 3 of 11 patients (27%) without amiodarone (p<0.05). In the remaining patients, intravenous ajmaline was effective in the suppression of ERAF in 5 patients without amiodarone and in 1 patient with amiodarone. The PP interval preceding the atrial premature beat reinitiating atrial fibrillation was nonsignificantly longer in amiodarone-treated patients (1127±419[emsp4 ]ms) in comparison to patients without amiodarone (896±271[emsp4 ]ms). 27% of patients without amiodarone at the time of electrical cardioversion and 55% of patients with amiodarone remained in sinus rhythm during the follow-up of 29±14 and 30±14 months, respectively. Conclusions: ERAF in patients on amiodarone can be treated by atropine or atrial pacing to prevent bradycardia-dependent ERAF. ERAF in amiodarone-treated patients does not apparently predict late recurrence of atrial fibrillation on continued amiodarone therapy.     

The Spatial Dispersion of Atrial Refractoriness and Atrial Fibrillation Vulnerability

The local dispersion of conduction and refractoriness has been considered essential for induction of atrial arrhythmias. This study sought to determine whether a difference of refractoriness and vulnerability for induction of atrial fibrillation between trabeculated and smooth as well as high and low right atrium may contribute to initiation of atrial fibrillation in dogs.In 14 healthy mongrel dogs weighing 22.4 ± 1 kg, closed-chest endocardial programmed stimulation was performed from four distinct right atrial sites. Atrial refractory periods and vulnerability for induction of atrial fibrillation or premature atrial complexes were determined during a basic cycle length of 400 and 300 ms and an increasing pacing current strength.For a pacing cycle length of 300ms, atrial refractory periods were longer on the smooth, as compared to the trabeculated right atrium (102 ± 25 vs. 97 ± 17ms, p < 0.05), whereas for a pacing cycle length of 400ms, there was no significant difference. The duration of the vulnerability zone for induction of atrial fibrillation was longer on the smooth right atrium, for a cycle length of both 400 ms (40 ± 30 vs. 31 ± 22 ms; p < 0.05) and 300 ms (33 ± 25 vs. 23 ± 21 ms; p < 0.01). When comparing high and low right atrium, refractory periods were longer on the the low right atrium, for a cycle length of both 400 ms (111 ± 23 vs. 94 ± 24ms; p < 0.01) and 300 ms (104 ± 20 vs. 96 ± 23ms; p < 0.01). For a pacing cycle length of 300 ms, the duration of the atrial fibrillation vulnerability zone was longer for the high, as compared to the low right atrium (34 ± 22 vs. 22 ± 22, p < 0.01). Seven dogs with easily inducible episodes of atrial fibrillation demonstrated significantly shorter refractory periods as compared to 7 non-vulnerable dogs, regardless of pacing site and current strength.In conclusion, significant differences in refractoriness and vulnerability for induction of atrial fibrillation can be observed in the area of the crista terminalis in healthy dogs. Thus, local anatomic factors may play a role in the initiation of atrial fibrillation.     

Low-Energy Transvenous Cardioversion of Atrial Fibrillation Using a Single Atrial Lead System

Atrial Cardioversion Using a Single Atrial Lead System. Introduction: Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option. Methods and Results: The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AE. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 ± 9 min) and eight patients with chronic AF (6.6 ± 5 months) were included. The fluoroscopy time for lead placement was 3.5 ± 4.3 minutes. The atrial defibrillation threshold was 2.0 ± 1.4 J for patients with acute AE and 9.2 ± 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 ± 1.1 mV during AF and 4.0 ± 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 ± 3.3 V (0.5-msec pulse width). Conclusions: Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. Tbis system might lead to a simpler, less invasive approach for internal atrial cardioversion.     

非瓣膜病心房颤动病人电复律前后左心房功能变化研究

目的评价经食道超声心动图(TEE)对非瓣膜病心房颤动(房颤)病人电复律前后左心房功能变化.方法选择房颤持续2周以上的非瓣膜疾病病人18例,其中原发性高血压6例,扩张型心肌病6例,脑血栓4例,缺血性心肌病2例.应用TEE确定左心房内无血栓后行电复律,转为窦性心律者测定左心耳血流最大速度及流速积分,肺静脉血流最大速度及流速积分、二尖瓣血流最大速度、流速积分及减速时间.结果左心耳排空速度于复律后显著减少,有显著性差异(P＜0.05),排空指数增加(P＞0.05),电复律后肺静脉收缩期、舒张期最大流速及其流速积分比值无显著差异(P＞0.05),收缩期最大流速积分在左、右肺静脉均有显著差异(P均＜0.05).复律前后舒张期最大流速积分在右肺静脉有显著性差异(P＜0.05),左肺静脉差异不显著(P＞0.05).二尖瓣血流E波最大速度及E波与A波比值(E/A)增加.结论适合的抗凝治疗及TEE确认心房内无附壁血栓后进行电复律治疗,安全又无并发症.TEE能评价房颤病人电复律后的左心房功能变化.电复律后心房的电活动及机械活动均微弱,能引起左心房功能不全及栓塞,所以心房功能完全恢复前均有必要进行抗凝治疗.     

Low-Energy Internal Cardioversion for Atrial Fibrillation Resistant to External Cardioversion

Internal Cardioversion. introduction : This report describes the electrical conversion of atrial fibrillation in two morbidly obese patients refractory to external cardioversion at 360 J.
Methods and Results : The two patients were lightly sedated and underwent placement of decapolar catheters in the coronary sinus and right atrial appendage. All ten electrodes of each decapolar catheter were electrically coupled, and defibrillation was attempted at successively increasing levels using a biphasic decaying exponential waveform generated by an external defibrillator. Both patients were returned to normal sinus rhythm using <10 J without complication.
Conclusion : Internal cardioversion is effective in restoration of sinus rhythm in some patients refractory to conventional forms of therapy     

Amiodarone for the Restoration of Sinus Rhythm in Patients with Atrial Fibrillation

Although the use of amiodarone for the treatment of atrial fibrillation has increased, reports of its use for the restoration of sinus rhythm have been conflicting. In a recent prospective, randomized, single-blind, placebo controlled study, we examined the efficacy and safety of amiodarone as initial treatment to restore sinus rhythm in patients with atrial fibrillation of varying duration. We studied 335 patients (169 men, 166 women), aged 27-78 years (mean age 65 +/- 10 years), with symptomatic atrial fibrillation, who presented to the emergency room or to our clinic. Patients randomized to amiodarone ( n = 173) received 300 mg intravenously over 1 hour followed by 20 mg/kg over 24 hours. Oral administration was initiated simultaneously at 600 mg/day in 3 divided doses for one week followed by 400 mg/day, in two doses, for three weeks. Amiodarone was almost twice as likely as placebo to restore sinus rhythm (85% vs. 43%, p < 0.0001). Larger left atrial size and longer duration of atrial fibrillation decreased amiodarone's effectiveness. These factors were also associated with longer duration of treatment before conversion to sinus rhythm. We observed relatively few and only minor complications despite relatively high doses of amiodarone administered to achieve high serum concentrations. In conclusion, our findings indicate that amiodarone is an effective and safe antiarrhythmic drug even when administered in large doses. It may be used for the restoration of sinus rhythm when rapid cardioversion is not needed.     

经胸体外直流电复律治疗心房颤动的进展

虽然心房颤动的治疗已取得很大的进展,经胸体外直流电复律仍然是临床上常用的治疗心房颤动的方法,它高效、安全,近年来,为使其效率进一步提高,现就采取的一些改进措施进行综述。包括:(1)电极板的位置、数量:多数研究证实前-后位置复律优于前-前(侧)位置,表现在复律的成功率高、用电量低上;还可应用X线透视以优化电极板的位置,使其尽可能包绕心房肌,以此来提高复律成功率;另外,同时应用2台体外除颤器的更高能量的电复律对那些标准能量复律无作用的心房颤动患者有效,并且同样安全。(2)输出波形为双相波形时对心房颤动的转复具有比单相波形更高的效率,要求的电量更低,且同样对心肌无损害。(3)首次放电量较高,如≥150 J时复律的成功率高。(4)除了抗心律失常药物,近几年新出现的一些药物如血管紧张素转换酶抑制剂、血管紧张素Ⅱ受体拮抗剂以及他汀类药物也可影响心房颤动体外电复律的效果。     

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.     

Amiodarone in Atrial Fibrillation

ABSTRACT Twenty-seven patients with atrial fibrillation without any concomitant conduction abnormality have been treated with oral amiodarone in a daily maintenance dose of 200 mg. The drug has been used for three purposes: 1) to block atrioventricular conduction, thereby decreasing the ventricular rate during atrial fibrillation (9 patients), 2) as prophylaxis against paroxysmal atrial fibrillation (8 patients), 3) as prophylaxis against recurrence of atrial fibrillation after DC conversion to sinus rhythm (13 patients). All patients were considered refractory to other antiarrhythmic drugs in these respects. In the second group, 4 of the 8 patients reported complete cessation of attacks and the others a marked reduction of the attack rate. In the third group, 10 of the 13 patients have maintained sinus rhythm for a longer period on treatment with amiodarone than with other drugs, resulting more than a triple prolongation of the time in sinus rhythm. In 3 patients the drug has been discontinued because of side-effects. In conclusion, amiodarone affords protection from episodes of paroxysmal atrial fibrillation, as well as from recurrence of atrial fibrillation after DC conversion to sinus rhythm. If the drug is ineffective in either of these respects, it may still be useful as a means of moderating the ventricular response in atrial fibrillation.     

Haemostatic Activity in Patients with Atrial Fibrillation Treated with Low-Molecular-Weight Heparin Before and After Electrical Cardioversion

BACKGROUND: Electrical cardioversion of atrial fibrillation (AF) is associated with a thromboembolic risk, and this risk can be reduced by the use of antithrombotic therapy. International guidelines recommend an effective oral anticoagulant therapy (OAT) for at least 3 weeks before, and 4 weeks after cardioversion. We studied whether electrical cardioversion in it self causes changes in the level of activity in the haemostatic system during treatment with either low-molecular-weight heparin (LMWH). METHODS: Thirty-eight patients with AF were randomised consecutively to either LMWH administered subcutaneous in a fixed daily dose, or conventional OAT. Changes in the biochemical markers prothrombin fragment 1+2 (F1+2), D-Dimer, and soluble fibrin, all reflecting the activity in the haemostatic system, were assessed at baseline, before and after electrical cardioversion in patients treated with LMWH for 3 weeks prior to cardioversion. A follow up compared the time spent on anticoagulation prior to cardioversion, and eventual complications in the two group (LMWH vs. OAT). RESULTS AND CONCLUSIONS: No significant differences between the levels of the biochemical markers measured before, and after cardioversion were seen, indicating that during anticoagulant therapy with LMWH, electrical cardioversion in itself, does not cause an increased activity in the haemostatic system. Also the level of F1+2 had declined significantly after cardioversion, when compared to baseline level in patients, whom had a normal sinus rhythm (NSR) re-established. This indicates that even in patients on a stable anticoagulant treatment, restoration of a NSR can cause a further decrease in thrombin generation.The median time spent on antithrombotic treatment prior to cardioversion, was significantly different between the LMWH (27 days) and the OAT group (138 days). Our study indicates that cardioversion in patients on LMWH does not cause a hypercoagulable state and that LMWH significantly shortens the time spent on anticoagulant therapy prior to cardioversion.