Electrical cardioversion after amiodarone administration

Amiodarone in restoration and maintenance of sinus rhythm in patients with chronic atrial fibrillation after unsuccessful direct-current cardioversion

BACKGROUND

When direct-current (DC) cardioversion is used, sinus rhythm can be restored, at least temporarily, in 80-90% of patients with atrial fibrillation. However, there is a small but significant group of patients with chronic atrial fibrillation in whom DC cardioversion has failed to restore sinus rhythm. The value of antiarrhythmic drug pretreatment before DC cardioversion is still controversial.

HYPOTHESIS

The aim of our study was to assess (1) the effectiveness of repeat DC cardioversion in patients with chronic atrial fibrillation after pretreatment with amiodarone, and (2) the efficacy of amiodarone in maintaining sinus rhythm after repeat cardioversion.

METHODS

Forty-nine patients with chronic atrial fibrillation after ineffective DC cardioversion were included in the study. Repeat DC cardioversion was performed after loading with oral amiodarone, 10-15 mg/kg body weight/day for a period necessary to achieve the cumulative dose of over 6.0 g.

RESULTS

Spontaneous conversion to sinus rhythm during amiodarone pretreatment was achieved in 9 of 49 patients (18%). Direct-current cardioversion was performed in 39 patients and sinus rhythm was achieved in 23 of these patients (59%). Mean heart rate decreased from 95 beats/min before to 68 beats/min after DC cardioversion (p < 0.001). Systolic blood pressure significantly (p < 0.05) decreased from 126 +/- 23 to 108 +/- 25 mmHg. Complications occurring in four patients just after electroconversion were well tolerated and of short duration. After 12 months, 52% of patients maintained sinus rhythm on low dose (200 mg/day) amiodarone therapy.

CONCLUSION

Pretreatment with amiodarone and repeat DC cardioversion allows for restoration of sinus rhythm in about 65% of patients with chronic atrial fibrillation after first ineffective DC cardioversion. Direct-current cardioversion can be performed safely with the use of standard precautions in patients who are receiving amiodarone. At 12 months' follow-up, more than 50% of patients maintain sinus rhythm on low-dose amiodarone after successful repeat cardioversion.

Effects of atrial fibrillation substrate and spatiotemporal organization on atrial defibrillation thresholds

BACKGROUND

We previously showed that canine models of atrial fibrillation (AF) have different substrates (either structural or electrical) that lead to differences in AF characteristics.

OBJECTIVE

The purpose of this study was to determine whether the differences in AF characteristics also would lead to differences in atrial defibrillation thresholds (ADFTs).

METHODS

Dogs were divided into five groups: control; MR-mitral regurgitation for 5 weeks; CHF-congestive heart failure for 4 weeks; RAP-rapid atrial pacing for 6 weeks; and METH-acetyl-beta-methylcholine acutely administered. A cross-sectional area of the left atrium was calculated, and AF was induced with rapid atrial pacing. Biphasic shocks with a pulse width of 3/3 ms were delivered through specially constructed shocking catheters with a surface area of 3.7 cm(2) that were placed in the right and left atria. An up-down-up protocol was used to determine the 50% ADFT threshold (ADFT(50)). A wide-bipole AF signal was digitally filtered, and a fast Fourier transform was calculated over a 2-second window every 1 second. The dominant frequency was determined, and the organization index was calculated as the ratio of the area under the dominant peak and its harmonics to the total area of the spectrum.

RESULTS

For left atrial size, the CHF and MR groups had a significantly larger atria than did control. ADFT(50) for control, MR, CHF, RAP, and METH groups were 160 +/- 30 V, 120 +/- 50 V, 132 +/- 20 V, 668 +/- 205 V, and 593 +/- 128 V, respectively (analysis of variance, P <.0001). Dominant frequencies were significantly higher and organization indexes significantly lower in the RAP and METH models compared with the other models.

CONCLUSION

RAP and METH canine models had a significantly higher ADFT(50) compared with the other AF models. The increase in ADFT(50) in these models corresponded with higher global dominant frequencies and lower measured organization indexes.

Serial antiarrhythmic therapy: role of amiodarone in prevention of atrial fibrillation recurrence--a lesson from the HOT CAFE Polish Study

Antiarrhythmic drug prophylaxis is known to improve long-term success of electrical cardioversion (CV) in persistent atrial fibrillation (AF). This prospective study evaluates the efficacy of sequential antiarrhythmic drug therapy in sinus rhythm (SR) maintenance after successful elective CV in patients with persistent nonvalvular AF.

MATERIALS AND METHODS

One hundred and twenty-eight patients (61+/-8 years old) with persistent AF underwent CV. Mean AF duration preceding CV was 268+/-99 days. Following SR restoration, patients were treated sequentially with either of the following antiarrhythmic drugs: propafenone, sotalol or disopyramide. Where arrhythmia recurred, patients received another CV and a new drug from the range defined above. Where such treatment failed, patients were loaded with 14.0- to 16.0-gram doses of amiodarone and a third CV was performed. If the first CV failed to restore SR, patients received a loading dose of amiodarone followed by another CV. When successful, amiodarone was administered on continuous basis.

RESULTS

The first CV proved successful in 55.5% of patients. During 1-year of follow-up, 31 patients (43.7%) presented with SR were treated with one antiarrhythmic agent (median does not exist). Application of the second drug proved to be effective in 6 patients (15.0%; median 13 days). Amiodarone was administered as the third antiarrhythmic agent to patients who had AF recurrence on the first two antiarrhythmic agents (propafenone, sotalol or disopyramide). It proved to be effective in 18 patients (52.9%; median does not exist) remaining free from AF for a period of 1 year as of commencement of the sequential antiarrhythmic therapy. Fifty-seven patients, in whom the first CV was ineffective, received amiodarone. During the loading period, SR was restored in 7 patients (12.3%). The remaining 50 patients underwent repeated CV, with SR restored in 37 (74.0%) of them. Long-term amiodarone treatment maintained SR in 30 (68.2%) patients during the follow-up period. Amiodarone helped to maintain SR in a total of 56.5% of patients.

CONCLUSIONS

Amiodarone seems to be the drug most effectively restoring and maintaining SR in patients with persistent AF resistant to CV and standard antiarrhythmic drug prophylaxis.

Effects of diltiazem pretreatment on direct-current cardioversion in patients with persistent atrial fibrillation: a single-blind, randomized, controlled study

BACKGROUND

Electric conversion of atrial fibrillation is the most widely used and effective treatment for sinus rhythm restoration. However, it has a limited success rate and a high recurrence rate.

HYPOTHESIS

Pretreatment with calcium channel blocker may improve the efficacy by reversing the so-called "electric remodeling" phenomenon, also related to overload in cytosolic calcium.

METHODS

The efficacy of diltiazem or amiodarone pretreatment (oral, 1 month before and 1 month after conversion) on direct-current conversion of persistent atrial fibrillation was assessed in 120 patients, randomly assigned to 3 matched groups: A (n = 44, diltiazem); B (n = 46, amiodarone), and C (n = 30, digoxin).

RESULTS

Before electric conversion, all treatments significantly decreased mean heart rate. Spontaneous conversion to sinus rhythm was achieved in 6% of patients of group A (3 of 46) versus 25% of group B (11 of 44) and 3% (1 of 30) of group C (A/C vs B, P < .005). Current conversion was more successful in group B (91%) compared with group A (76%) and group C (67%) (B vs A/C, P < .05), with no difference in the electric threshold for effective conversion (P = not significant). At the 24-hour time point, early relapse of atrial fibrillation was similar between groups A and B (A, 2%; B, 3%; P = not significant) and lower than group C (12%) (P < .01), whereas at the 1-month time point the recurrence rate was lower in group B (28%) versus groups A (56%) and C (78%) (B vs A/C, P < .01). No significant side effects were reported.

CONCLUSIONS

Although diltiazem seems to be as effective as amiodarone in reducing early atrial fibrillation recurrences, diltiazem is less effective in determining spontaneous or electric conversion, with a higher recurrence rate at 2 months. Diltiazem pretreatment could be considered as only a second choice treatment in those patients in whom amiodarone is contraindicated.

Usefulness of ibutilide in facilitating successful external cardioversion of refractory atrial fibrillation

We repeated direct-current cardioversion of atrial fibrillation after ibutilide injection in patients who failed conventional cardioversion. Eleven of 12 patients (92%) had successful cardioversion and avoided the need for internal cardioversion.

Pretreatment with verapamil in patients with persistent or chronic atrial fibrillation who underwent electrical cardioversion

OBJECTIVES

To evaluate, in a prospective and randomized fashion, the efficacy of a pretreatment with verapamil (V) in reducing recurrences of atrial fibrillation (AF) after electrical cardioversion (C).

BACKGROUND

The increased vulnerability for AF recurrence is probably due to AF-induced changes in the electrophysiologic properties of the atria. This electrical remodeling seems to be due to intracellular calcium overload.

METHODS

One hundred seven patients with persistent or chronic AF underwent external and/or internal C. All patients received oral propafenone (P) (900 mg/day) three days before and during the entire period of follow-up (three months). In the first group, patients received only the P. In the second group, in adjunct to P, oral V (240 mg/day) was initiated three days before C and continued during the follow-up. Finally, in the third group, oral V was administered three days before and continued only for three days after electrical C.

RESULTS

During the three months of follow-up, 23 patients (23.7%) had AF recurrence. Mantel-Haenszel cumulative chi-square reached a significant level only when comparing AF free survival curves of group I versus group II and group III (chi-square = 5.2 and 4, respectively; p < 0.05). Significantly, 15 (65.2%) AF relapses occurred during the first week after cardioversion with a higher incidence in group I (10/33 patients, 30.3%) than group II (2/34 patients, 5.9%; p = 0.01) and group III (3/30 patients, 10%; p = 0.04).

CONCLUSIONS

Six days of oral V administration centered on the C day, combined with P, significantly reduce the incidence of early recurrences of AF compared with P alone.

Effect of the implantable atrial defibrillator on the natural history of atrial fibrillation

INTRODUCTION

The purpose of our study was to evaluate the effect of repeated cardioversion with an implantable atrial defibrillator on the clinical outcome of patients with atrial fibrillation.

METHODS AND RESULTS

The effects of the implantable atrial defibrillator on the total duration of atrial fibrillation, number of atrial fibrillation recurrences, and left atrial size were evaluated prospectively in 16 patients with atrial fibrillation (13 men and 3 women; mean age 58 +/- 11 years). Seven patients had no cardiovascular disease, 5 patients had hypertension, 3 patients had coronary heart disease, and 1 patient had congenital heart disease. Eight patients had paroxysmal atrial fibrillation for a mean duration of 80 +/- 61 months, and eight patients had persistent atrial fibrillation for a mean duration of 68 +/- 119 months. Except for one patient who received digoxin throughout the study, all patients received the same Class I or III antiarrhythmic agent throughout the study. The implantable atrial defibrillator successfully converted 50 (93%) of 54 spontaneous episodes of atrial fibrillation in 12 patients. During the initial 3 months of clinical follow-up, the atrial defibrillator documented 261 +/- 270 hours of atrial fibrillation compared with 126 +/- 172 hours (P = 0.01) during the subsequent 3 months. The left atrial size decreased from 4.4 +/- 0.7 cm at the time of atrial defibrillator implantation to 4.1 +/- 0.6 cm (P = 0.02) 6 months later. The number of atrial fibrillation recurrences did not change. These findings were observed in the absence of changes in drug therapy. No complications were observed.

CONCLUSION

Restoration and maintenance of sinus rhythm in patients with atrial fibrillation by repeated cardioversion with an implantable atrial defibrillator was associated with a reduction in the total arrhythmia duration and a reduction in left atrial size. These results suggest that maintenance of sinus rhythm with the atrial defibrillator may reverse the remodeling process associated with atrial fibrillation.

Favorable effects of flecainide in transvenous internal cardioversion of atrial fibrillation

OBJECTIVES

The 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.

BACKGROUND

Internal cardioversion of atrial fibrillation is becoming a more widely accepted therapy for acute episode termination and for implantable atrial defibrillators.

METHODS

Twenty-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.

RESULTS

Chronic 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.

CONCLUSIONS

Intravenous 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.

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.

Effects of oral propafenone administration before electrical cardioversion of chronic atrial fibrillation: a placebo-controlled study

OBJECTIVES

Our aim was to evaluate the benefits and risks of administering propafenone before electrical defibrillation for chronic atrial fibrillation.

BACKGROUND

In this context, an antiarrhythmic drug-although potentially useful in preventing early recurrence of arrhythmia-could adversely affect the defibrillation threshold and reduce the cardioversion success rate.

METHODS

We randomly assigned 100 patients with chronic atrial fibrillation to oral treatment with either placebo (51 patients) or 750 mg/day of propafenone (49 patients) for 48 h before administration of direct current shock. After successful cardioversion, all patients received propafenone therapy and were followed up for 48 h.

RESULTS

Before defibrillation, three patients in the propafenone group (6.1%) had reversion to sinus rhythm and one had sustained ventricular tachycardia. Shock efficacy (82.4% vs. 84.4%) and the cumulative effective energy (395 +/- 258 vs. 421 +/- 236 J) were not different between the placebo and propafenone groups. In the propafenone group, 11 patients had their arrhythmia transformed into atrial flutter and required a lower energy level for arrhythmia conversion than did the other patients with continued atrial fibrillation (245 +/- 197 vs. 493 +/- 215 J, p < 0.01); the latter patients showed a trend (p < 0.10) toward higher energy requirements than that of patients who received placebo. The incidence of asymptomatic bradyarrhythmias was higher in the propafenone group (28.9% vs. 7.1%, p < 0.02), but more patients who received placebo had early recurrence of atrial fibrillation (16.7% vs. 0%, p < 0.02). Two days after cardioversion, more patients given propafenone (73.5% vs. 52.9%, p < 0.05) were discharged from the hospital with sinus rhythm. During the in-hospital stay, propafenone was withdrawn from six patients (6.6%) because of side effects.

CONCLUSIONS

Propafenone, given before electrical cardioversion for chronic atrial fibrillation does not affect the mean defibrillation threshold or the rate of successful arrhythmia conversion. It decreases the recurrence of atrial fibrillation early after shock, thus allowing more patients to be discharged from the hospital with sinus rhythm.