Detection of myocardial injury after internal cardioversion for atrial fibrillation

BACKGROUND: Cardiac troponin levels do not rise to marked levels after external cardioversion of atrial fibrillation. Subsequent test discharges during implantation of cardioverter defibrillators may cause an elevation of cardiac troponin levels, but are still controversial. OBJECTIVE: To determine whether the biomarkers of cardiac injury increase after internal cardioversion (IC) of atrial fibrillation. METHODS: Forty-four patients with chronic atrial fibrillation were studied (mean age 59 +/-7 years). Electrode catheters were inserted through the femoral vein. One of these was positioned in the lower right atrium. A second defibrillation electrode was placed in the coronary sinus and an additional catheter was positioned in the right ventricular apex in order to obtain satisfactory R wave synchronization and to provide postshock ventricular pacing. The shocks were delivered by external defibrillator. Starting with a test shock of 1 J intensity, the energy was increased in steps (to maximum 15 J) until cardioversion was achieved. At least 1 min was permitted to elapse between unsuccessful defibrillation attempts before the next shock was applied. Blood samples for serum levels of cardiac troponin T, cardiac troponin I, creatine kinase MB and myoglobin were drawn before and 2 h, 4 h, 8 h and 24 h after IC. Each level of biomarker was compared with baseline. RESULTS: In 40 of 44 patients, IC was successful at a mean cardioversion threshold of 7.6+/-3.3 J. Although the serum levels of these biomarkers tended to rise, marked elevation was not detected in any of samples (P>0.05 for each). There was no correlation between the levels of biomarkers and the number and energy of shocks applied. No severe complications were observed. CONCLUSIONS: Following uncomplicated IC of atrial fibrillation, cardiac biomarkers do not rise to marked levels, which indicates that significant myocardial injury does not occur by shocks in the usual dosage.     

Limited internal shocks for atrial fibrillation refractory to external cardioversion.

We investigated the feasibility and long-term results of low-energy internal defibrillation using a limited number of shocks in patients with persistent atrial fibrillation resistant to external cardioversion. A relatively high number of shocks of lower energy are usually required in those cases and can be poorly tolerated. METHODS AND RESULTS: Twenty-five patients with persistent atrial fibrillation underwent internal defibrillation, using biphasic R wave synchronous shocks between two catheters in the high right atrium and the coronary sinus. Conversion to sinus rhythm was obtained in all patients, with a median of two shocks. Early recurrence of atrial fibrillation (AF) occurred in eight cases (32%). Seven patients (41%) out of 17 discharged in sinus rhythm remained free of AF after a median follow-up of 8.9 months. Severe mitral insufficiency (P=0.05) and low left ventricle ejection fraction (P=0.002) were correlated with earlier recurrence. Amiodarone significantly favored (P=0.019) maintenance of sinus rhythm. CONCLUSION: Internal defibrillation using a limited number of shocks equal to or less than 30 Joules is effective in terminating refractory atrial fibrillation and could be more acceptable for patients. However, the recurrence rate remains high, particularly in patients with severe mitral insufficiency or poor ventricular function. Amiodarone delays recurrences of atrial fibrillation.     

Anticoagulation for cardioversion of atrial fibrillation

The cardioversion of chronic atrial fibrillation to sinus rhythm carries a thromboembolic risk of 1.5-6%. These events occasionally occur at the time of cardioversion, but more often happen hours or days later. These strokes and other embolic events may occur even where atrial thrombus has been excluded before cardioversion and it has become apparent that, although atrial electrical activity may be restored by cardioversion, normal mechanical atrial function may take longer to recover. Numerous studies have addressed the role of anticoagulation following cardioversion in patients with atrial fibrillation, however, the mechanism of embolic complications as well as the justification of a standard anticoagulation therapy are not fully established. In this review we will try to present an overview of the mechanisms of thrombosis following cardioversion and give an insight into current anticoagulation strategies.     

Successful external cardioversion of atrial fibrillation in patients referred to an electrophysiologist for internal cardioversion.

BACKGROUND: Internal cardioversion of atrial fibrillation with direct current energy has become an increasingly employed technique for patients who fail external cardioversion. HYPOTHESIS: The purpose of this study was to determine whether internal cardioversion could be avoided by careful attention to cardioversion technique in a group of patients referred specifically for internal cardioversion after failed external cardioversion by community cardiologists. METHODS: We performed external cardioversion utilizing two operators applying significant pressure to the thorax with up to 360 J prior to the planned internal cardioversion in 20 patients referred for internal cardioversion after failed attempts at external cardioversion. RESULTS: Sixteen patients (80%) were successfully cardioverted and avoided the risk, inconvenience, and cost of internal cardioversion. CONCLUSION: External cardioversion with significant anterior paddle pressure by two operators can decrease the need for internal cardioversion in a significant portion of patients referred to electrophysiologists for internal cardioversion and should be considered prior to an invasive procedure.     

Pharmacological cardioversion of atrial fibrillation

Atrial fibrillation is a very common rhythm disorder that can be therapeutically reverted into sinus rhythm by means of pharmacological or electrical cardioversion. This article reviews options for drug therapy and tries to elucidate the mechanisms of AF termination by antiarrhythmics. We will explain the clinical basis of different therapeutic approaches and review the efficacy of selected substances according to recent clinical studies. Finally, we will focus on some important aspects of anticoagulation in the setting of pharmacological cardioversion.     

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.     

Electrical cardioversion of atrial fibrillation

External direct current cardioversion remains the most common and effective method for restoration of normal sinus rhythm in patients with persistent AF. The development of biphasic defibrillators allows for higher success rates of conversion using standard energy levels. For persistent AF, an initial energy of 200 J is recommended for biphasic defibrillators, and 300 to 360 J are recommended for monophasic defibrillators, with the electrodes placed in the anterior posterior position. For refractory cases, alternatives are available such as dual defibrillators or internal cardioversion. Antiarrhythmic drugs may enhance the results of cardioversion by helping overcome shock failure or by preventing immediate recurrence of AF. Thromboembolism is the most important complication associated with cardioversion, but it can be prevented by providing 3 weeks of anticoagulation before the procedure or by excluding the presence of thrombi by transesophageal echocardiography, followed by an additional 4 weeks of anticoagulation.     

心房颤动的同步直流电心脏复律

心房颤动因心房规则有序的电活动丧失,代之以无序的快速颤动波。致使心房不能产生有效的收缩与舒张。令心室出现极不规律的反应。其造成的影响是：①心房电重构及心房肌重构加重心房电生理及病理改变：②心房泵血功能丧失;③快速且不规则的心室率可致心输出量显著下降引起低血压、心肌缺血和心力衰竭。使原有的心脏病迅速恶化;④持续快速的心室率,可致心动过速性心肌病：⑤左心耳及心房血流淤滞,易发生心房血栓及栓塞事件。     

Recurrence of atrial fibrillation after internal cardioversion of persistent atrial fibrillation: prognostic importance of electrophysiologic parameters.

BACKGROUND: The purpose of this study was to determine whether the extent of atrial electrical remodeling affects the recurrence of atrial fibrillation (AF) after cardioversion of persistent AF (PAF). METHODS AND RESULTS: Internal atrial cardioversion was performed in 47 patients with PAF. The right atrial monophasic action potential duration (RA-MAPD) at pacing cycle lengths (PCLs) of 800-300 ms and P wave signal-averaged electrocardiogram were recorded after cardioversion. Bepridil (150-200 mg/day) and carvedilol (10 mg/day) were administered to all patients after cardioversion. Of the 47 patients, 20 had recurrent AF within 3 months. No relation was observed between age, left atrial dimension, left ventricular ejection fraction, and AF recurrence. The AF duration was significantly longer (p<0.05) and RA-MAPD at PCLs of 800 to 300 ms were significantly shorter (p<0.05) in patients with AF recurrence than in those without recurrence. The mean slope of the RA-MAPD for PCLs between 600 and 300 ms did not differ between the patients with and without AF recurrence. The filtered P-wave duration (FPD) was significantly longer in the patients with AF recurrence than in those without (p<0.05). Multivariate analysis also showed that the RA-MAPD at a PCL of 300 ms and FPD were predictors of AF recurrence (RAMAPD: p=0.038; FPD: p=0.052). CONCLUSION: These results suggest that electrical remodeling related to the repolarization and depolarization may be the main contributors to early AF recurrence after cardioversion under the administration of bepridil and carvedilol.     

Biphasic low-energy internal cardioversion in atrial fibrillation induced during electrophysiologic study

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

Defibrillation threshold of internal cardioversion prior to ablation predicts atrial fibrillation recurrence

BackgroundMany studies have reported the predictors of atrial fibrillation (AF) recurrence after persistent AF (peAF) ablation. However, the correlation between the atrial defibrillation threshold (DFT) for internal cardioversion (IC) and AF recurrence rate is unknown. Here we investigated the relationship between the DFT prior to catheter ablation for peAF and AF recurrence.HypothesisDFT prior to ablation was the predictive factor for AF recurrence after peAF ablation.MethodsFrom June 2016 to May 2019, we enrolled 82 consecutive patients (mean age, 65.0 ± 12.4 years), including 45 with peAF and 37 with long‐standing peAF, at Hamamatsu Medical Center. To assess the DFT, we performed IC with gradually increasing energy prior to radiofrequency application.ResultsForty‐nine and 33 patients showed DFT values less than or equal to 10 J (group A) and greater than 10 J or unsuccessful defibrillation (group B). During the mean follow‐up duration of 20.5 ± 13.1 months, patients in group B showed significantly higher AF recurrence rates than those in group A after the ablation procedure (p = .017). Multivariate analysis revealed that DFT was the only predictive factor for AF recurrence (odds ratio, 1.07; 95% CI, 1.00–1.13, p = .047).ConclusionsThe DFT for IC was among the strongest prognostic factors in the peAF ablation procedure.     

Ventricular fibrillation in intra-atrial cardioversion of atrial fibrillation

Recently intra-atrial defibrillation has become an interesting alternative to external defibrillation and drug therapy for the treatment of atrial fibrillation. Low-energy intra-atrial defibrillation can be used to restore sinus rhythm f.ex. after a failed external cardioversion or during an electrophysiologic study when the administration of antiarrhythmic drugs should be avoided. Additionally this new technique has led to the development of implantable atrial defibrillators for the treatment of selected patients suffering from chronic atrial fibrillation. Intra-atrial defibrillation seems to be a highly effective and safe method, but little experience exists concerning the outcome so far. Especially the potential risk of inducing ventricular pro-arrhythmia is subject of current controversy. We report the case of a 79-year-old patient suffering from WPW syndrome with a concealed bypass tract who was subject to an intra-atrial defibrillation during an electrophysiologic study. At the beginning of the study atrial fibrillation could be converted to sinus rhythm by a single low-energy atrial defibrillation (3 J.). After a short period of time a second intra-atrial defibrillation had to be performed in the same way because of recurrent atrial fibrillation. By this atrial shock ventricular fibrillation was induced, so that high energy external defibrillation became necessary. Analyzing the ECG a correct R-wave synchronization was found, but a rather short preceding RR interval (252 ms). In conclusion, low energy atrial defibrillation is gaining importance as a highly effective new technique to restore sinus rhythm in patients suffering from atrial fibrillation resistant to conventional therapies. Nevertheless potential risks have to be considered such as the induction of ventricular pro-arrhythmia. Therefore, a correct R-wave synchronization is obligatory and shock delivery should be withheld after short RR intervals. Future prospective randomized studies will have to show whether this new technique is really safe enough and superior to the conventional methods for restoring sinus rhythm in patients suffering from atrial fibrillation.     

Immediate recurrence of atrial fibrillation after internal cardioversion: importance of right atrial conduction variations

This study investigates the importance of right atrial conduction features in predicting of immediate recurrence of atrial fibrillation (AF) after internal cardioversion (IC). Patients with chronic AF who were resistant to external cardioversion were studied. Twenty-four patients (16 female, 8 male mean age 58 +/- 7 years) who were successfully converted to sinus rhythm (SR) by IC, and experienced recurrence of AF within 1 minute of restoration of SR were enrolled in group A. Thirty-four patients, who were converted to SR by IC and in whom SR was maintained at least 1 minute after IC, were enrolled in group B (24 female, 10 male mean age 56 +/- 6 years) as control. There was no difference in age, left atrial diameter, use of antiarrhythmic drug, etiology and duration of AF between the groups. After successful IC, His bundle electrocardiograms via placed electrode catheters, and surface electrocardiograms were recorded for 1 minute. P-A interval duration, as a marker of right atrial conduction, was measured from the onset of the earliest registered surface P wave to the onset of the atrial deflection on His-bundle catheter recording. The difference between the recorded maximum P-A duration and minimum P-A duration obtained in 1 minute after IC was described as P-A interval absolute difference. There were no differences in the maximum P-A duration and minimum P-A duration between two groups. But, the P-A absolute difference was more pronounced in group A compared to group B (16.9 +/- 7.7 ms versus 10.3 +/- 6.4 ms, P < .001) and was significantly correlated with P wave dispersion derived from the surface electrocardiogram (r = .72, P < .001) In conclusion, variations in right atrial conduction might play an important role in predicting immediate recurrence of AF in patients converted to SR by IC.     

Oesophageal electrical cardioversion of atrial fibrillation

Atrial fibrillation is the most common cardiac arrhythmia and the most frequent cause of hospitalization and utilization expense among all heart diseases. Taking into account persistent atrial fibrillation we know that, in order to cardiovert persistent atrial fibrillation, external direct current cardioversion is the method most frequently used to restore sinus rhythm. But external cardioversion has also some limitations: it requires high energy direct current shocks so that patients have to be anaesthetised, which means a dedicated apparatus and place to adequately assist the patients. The oesophageal cardioversion is an alternative method to restore sinus rhythm, which could obviate some of these limitations of external cardioversion. Compared to external cardioversion oesophageal one has lower defibrillation impedance and requires lower energies to restore sinus rhythm, increasing for the same energy level, success rate. Using low energy shocks, a mild sedation is sufficient to make the procedure well tolerated by most of patients. Other 2 important advantages coming from low energy shocks are the safety in patients with pacemaker or implantable cardioverter-defibrillator and the availability of a back up atrial pacing. Oesophageal cardioversion is not indeed a new technique. Looking at literature, studies in animals and in humans have been performed since the 60s, assessing feasibility, effectiveness and safety of such a procedure. The oesophageal-precordial cardioversion is usually performed on an outpatient regimen, resulting in a very cost-effective method to cardiovert patients with persistent atrial fibrillation, which may definitely represent a real alternative technique to external cardioversion.     

Ambulatory electrical cardioversion of atrial fibrillation

Elective electrical cardioversion of atrial fibrillation is an effective and safe cardiac procedure in selected patients. It is most often performed during a short hospital stay or in an outpatient setting of a hospital. In a retrospective analysis, we report our experience on electrical cardioversions in private practice without a hospital stand-by performed by a cardiologist and an anesthesiologist in concert. Sixty patients with a mean age of 66+/-8 years and a typical spectrum of cardiac diseases in stable condition were chosen for the ambulatory procedure. The immediate success rate of electrical cardioversion was 83%. Within the next 3 months, a relapse of atrial fibrillation occurred in 46%. Following 87 procedures in 60 patients, 3 complications requiring a hospital admission occurred. One of these three patients had suffered from a short syncope without other deficits potentially due to cerebral embolism. Apart from these complications, no patient suffered a thromboembolic complication or a cerebral problem following electrical cardioversion. We conclude that elective electrical cardioversion of atrial fibrillation can be performed safely, effectively and comfortable for patient and physician following a preceding evaluation and counseling by a cardiac specialist.