Comparison of rectilinear biphasic waveform energy versus truncated exponential biphasic waveform energy for transthoracic cardioversion of atrial fibrillation

Success rates of cardioversion with a defibrillator using the truncated exponential biphasic waveform (with a maximum energy of 360 J) and a defibrillator using the rectilinear biphasic waveform (with a maximum energy of 200 J) were randomly compared in 145 patients. Success rates at 50, 100, 150, and 200 J were not significantly different, but 2 patients who did not achieve cardioversion after a 200-J maximum energy shock by the rectilinear device underwent successful cardioversion with a 360-J shock by the truncated exponential device after crossover.     

Efficacy and impact of monophasic versus biphasic countershocks for transthoracic cardioversion of persistent atrial fibrillation

This report compares the cumulative efficacy of cardioversion and skeletal muscle injury after either damped sine wave monophasic or truncated exponential biphasic transthoracic cardioversion of persistent atrial fibrillation. The trial sought to refute the null hypothesis of therapeutic equivalence between monophasic and biphasic waveforms. Results of the study reveal similar cumulative efficacy of waveforms and greater levels of skeletal muscle damage when patients are younger and male, and when monophasic waveforms are used.     

Impact of biphasic electrical cardioversion of atrial fibrillation on early recurrent atrial fibrillation and shock efficacy

INTRODUCTION: Early recurrent atrial fibrillation (ERAF) after external cardioversion of atrial fibrillation (AF) occurs in 12% to 26% of patients. Whether biphasic cardioversion has an impact on the incidence of ERAF after cardioversion of AF is unclear. METHODS AND RESULTS: Consecutive patients (n = 216, mean age 66 years, 71% male, 88% with structural cardiovascular disease or hypertension) underwent cardioversion with a biphasic (Bi) or monophasic (Mo) shock waveform in randomized fashion. Energies used were 120-150-200-200 Ws (Bi) or 200-300-360-360 Ws (Mo). The two study groups (Bi vs Mo) did not differ with regard to age, sex, body mass index, underlying cardiovascular disease, left atrial diameter, left ventricular ejection fraction, duration of AF fibrillation, and antiarrhythmic drug therapy. Mean delivered energy was significantly lower in the Bi group (Bi: 186 +/- 143 Ws vs Mo: 324 +/- 227 Ws; P < 0.001). Overall incidence of ERAF (AF relapse within 1 minute after successful cardioversion) was 8.9% and showed no difference between the two groups (Bi: 8.1% vs Mo: 9.7%, P = NS). Cardioversion was successful in 95.4% of patients. The success rate was comparable in both groups (Bi: 94.3% vs Mo 96.8%; P = NS). First shock efficacy did not differ between Bi and Mo (76.4% vs 67.7%; P = NS). Mean number of shocks were 1.4 shocks per patient in both groups. CONCLUSION: Biphasic cardioversion allows comparable success rates with significantly lower energies. However, the incidence of ERAF is not influenced by biphasic cardioversion. With the energies used, biphasic and monophasic shock waveforms are comparable with regard to first shock and cumulative shock efficacy.     

External cardioversion of atrial fibrillation: comparison of biphasic vs monophasic waveform shocks.

AIMS: It is well established in transthoracic ventricular defibrillation that biphasic truncated waveform shocks are associated with superior defibrillation efficacy when compared with damped sine wave monophasic waveform shocks. The aim of this study was to explore whether biphasic waveform shocks were superior to monophasic waveform shocks for external cardioversion of atrial fibrillation (AF). METHODS AND RESULTS: Fifty-seven patients in whom cardioversion of AF was indicated were randomized in this prospective study, to transthoracic cardioversion with either monophasic damped sine waveform shocks or biphasic impedance compensating waveform shocks. In the group randomized to monophasic waveform shocks (27 patients), a first shock of 150 J was delivered, followed (if necessary) by a 360 J shock. In the biphasic waveform group (30 patients), the first shock had an energy of 150 J and (if necessary) a second 150 J was delivered. All shocks were delivered in the anterolateral chest pad position. Sinus rhythm was restored in 16 patients (51%) with the first monophasic shock and in 27 patients (86%) with the first biphasic shock. The difference was statistically significant (P=0.02). After the second shock, sinus rhythm was obtained in a total of 24 patients (88%) with monophasic shocks and in 28 patients (93%) with biphasic shocks. No complication was observed in either group and cardiac enzymes (CK, CKmb, troponin I, myoglobin) did not show any significant changes. CONCLUSION: This study suggests that at the same energy level of 150 J, biphasic impedance compensating waveform shocks are superior to monophasic damped sine waveform shocks cardioversion of atrial fibrillation.     

Prospective, randomized comparison of two biphasic waveforms for the efficacy and safety of transthoracic biphasic cardioversion of atrial fibrillation

OBJECTIVES: The purpose of this study was to determine if there is a difference in commercially available biphasic waveforms. BACKGROUND: Although the superiority of biphasic over monophasic waveforms for external cardioversion of atrial fibrillation (AF) is established, the relative efficacy of available biphasic waveforms is less clear. METHODS: We compared the effectiveness of a biphasic truncated exponential (BTE) waveform and a biphasic rectilinear (BR) waveform for external cardioversion of AF. Patients (N = 188) with AF were randomized to receive transthoracic BR shocks (50, 75, 100, 120, 150, 200 J) or BTE shocks (50, 70, 100, 125, 150, 200, 300, 360 J). Shock strength was escalated until success or maximum energy dose was achieved. If maximum shock strength failed, patients received the maximum shock of the opposite waveform. Analysis included 141 patients (71 BR, 70 BTE; mean age 66.5 +/- 13.7. Forty-seven randomized patients were excluded because of flutter on precardioversion ECG upon blinded review (n = 25), presence of intracardiac thrombus (n = 7), or protocol deviation (n = 15). Groups were similar with regard to clinical and echocardiographic characteristics. RESULTS: The success rate was similar for the two waveforms (93% BR vs 97 BTE, P = .44), although cumulative selected and delivered energy was less in the BTE group. Only AF duration was significantly different between successful and unsuccessful patients. No significant complications occurred. CONCLUSIONS: Biphasic waveforms were very effective in transthoracic cardioversion of AF, and complication rates were low. No significant difference in efficacy was observed between BR and BTE waveforms. Impedance was not an important determinant of success for either biphasic waveform.     

A randomized trial comparing monophasic and biphasic waveform shocks for external cardioversion of atrial fibrillation

Background

We compared efficacy of and pain felt after biphasic truncated exponential (BTE) and monophasic damped sine (MDS) shocks in patients undergoing external cardioversion of atrial fibrillation (AF).

Methods

Patients with AF were randomized to BTE or MDS waveform cardioversion. Successive shocks were delivered at 70, 100, 200, and 360 J until successful cardioversion, with one 360 J attempt of the alternate waveform when all 4 shocks failed. Success was determined by blinded over-read of electrocardiograms. Peak current was calculated from energy and impedance. Patients rated their pain at 1 and 24 hours after cardioversion.

Results

Fourteen of 37 (38%) patients treated with MDS and 34 of 35 (97%) treated with BTE shocks were cardioverted at ≤200 J (P < .0001). Success rates of MDS versus BTE shocks were 5.4% versus 60% for 70 J, 19% versus 80% for ≤100 J, and 86% versus 97% for ≤360 J. BTE shocks cardioverted with less peak current (14.0 ± 4.3 vs 39.5 ± 11.2 A, P < .0001), less energy (97 ± 47 vs 278 ± 120 J, P < .0001), and less cumulative energy (146 ± 116 vs 546 ± 265 J, P < .0001). Patients felt less pain after BTE than MDS shocks at 1 hour (P < .0001) and 24 hours (P < .0001) after cardioversion.

Conclusion

This BTE waveform is superior to the MDS waveform for cardioversion of AF, requiring much less energy and current, and causing less postprocedural pain.     

Monophasic versus biphasic waveform shocks for atrial fibrillation cardioversion in patients with concomitant amiodarone therapy.

AIMS: With transthoracic cardioversion of atrial fibrillation (AF), biphasic are more effective than monophasic waveforms. We sought to determine the ideal energy levels for biphasic waveforms. Methods We compared biphasic truncated exponential waveforms with monophasic damped sine waveform defibrillators, in a prospective, single-centre, randomized (1:1 ratio) study. The study included 154 patients receiving concomitant amiodarone; 77 received serial biphasic (50, 100, 150, up to 175 J) and 77 monophasic shocks (100, 200, 300, up to 360 J), as necessary. Results First-shock efficacy was similar in the two groups (57 vs. 55%, P = 0.871, respectively), as were serial-shocks (90 vs. 92%, P = 0.780). Both groups received equal numbers of shocks (1.8 +/- 1.1 vs. 1.7 +/- 1.0, P = 0.921). In both groups, serum creatine kinase levels showed a small but significant increase. The increase was, however, higher in the monophasic group. CONCLUSION: In patients with concomitant amiodarone therapy, biphasic truncated exponential shocks, using half the energy, were as effective as monophasic damped sine shocks. The biphasic scheme was not more efficacious for cardioverting AF. In our population, a first shock of at least 100 J seemed advisable with either waveform. If necessary, escalating shocks must be performed, but ideal levels of increase per shock are still uncertain for biphasic waveforms.     

Comparison of the rectilinear biphasic waveform with the monophasic damped sine waveform for external cardioversion of atrial fibrillation and flutter

External cardioversion using the monophasic damped sine (MDS) waveform is successful 70% to 94% of the time when using up to 360 J. The rectilinear biphasic (RLB) defibrillator has been shown to be superior in efficacy to the MDS waveform in atrial cardioversion in a small randomized study. This larger, retrospective study compares the results of the RLB waveform with those of the MDS waveform for cardioversion of atrial fibrillation (AF) and atrial flutter in a large cohort of patients. We performed 1,877 external cardioversion procedures in 1,361 patients for AF and atrial flutter by using the RLB defibrillator. We compared these results with those of the MDS defibrillator in 2,025 patients who underwent 2,818 cardioversion procedures. The overall success rates for the RLB defibrillator were 99.1% for AF and 99.2% for atrial flutter, and the corresponding success rates for the MDS defibrillator were 92.4% and 99.8% (p <0.001; RLB superior for AF). The median overall successful energy level for the MDS waveform was 200 J, whereas the corresponding RLB energy level was 100 J. Multivariate analyses demonstrated that underlying clinical conditions or use of antiarrhythmic drugs does not significantly affect overall success rates. Our results from >4,000 procedures confirmed and extended those of the previous report by showing a very high success rate for cardioversion of AF and atrial flutter using the RLB waveform. The MDS waveform was equally effective for atrial flutter but significantly less effective in terminating AF.     

Evaluation of the defibrillation threshold in atrial fibrillation by transoesophageal cardioversion using a biphasic impulse

INTRODUCTION: Recurrent atrial fibrillation (AF) in the setting of haemodynamic disturbances requires frequently repeated cardioversions, which is associated with the risk of myocardial damage. It is thus necessary to identify methods which can minimise the cardioverter impulse energy. AIM: To define the defibrillation threshold in recent-onset AF using a biphasic impulse, following an infusion of magnesium, potassium, and amiodarone. METHODS: Transoesophageal cardioversion was performed in 32 patients with AF lasting < or =48 hours, in whom prior administration of 40 mEq K+, 4.0 g MgSO4 and 300 mg amiodarone did not restore sinus rhythm. Cardioversion was performed under short intravenous anaesthesia using a biphasic impulse travelling from a multi-annular oesophageal electrode to two electrodes on the anterior chest wall. The initial energy was set to 1 J, which was subsequently increased according to the following protocol: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50 and 70 J. RESULTS: Electrical cardioversion following the administration of electrolytes and amiodarone restored sinus rhythm in all the patients (100% efficacy). The mean defibrillation threshold was 12.9+/-14.3 J, with a minimal effective energy of 1 J and a maximum effective energy of 70 J. The defibrillation threshold was in the range from 1 to 10 J in 75% of the patients. The mean cumulative energy transferred between electrodes during evaluation of the defibrillation threshold was 39.7 J (SD, 38.8). CONCLUSIONS: Transoesophageal cardioversion using a low-energy (mean, 12.9 J; range, 1-70 J) biphasic impulse, following the intravenous administration of potassium chloride and amiodarone, was 100% effective in restoring sinus rhythm in AF.     

Impedance compensated biphasic waveforms for transthoracic cardioversion of atrial fibrillation: a multi-centre comparison of antero-apical and antero-posterior pad positions.

AIMS: To compare the success rate for transthoracic direct current cardioversion (DCC) of atrial fibrillation (AF) with antero-posterior (AP) and antero-apical (AA) electrode positions using an impedance compensated biphasic (ICB) waveform. METHODS AND RESULTS: Three-hundred and seven patients [mean age 66 (SD+/-13), 195 male] with AF were recruited in three centres. Patients were randomized to an AA (n=150) or AP (n=144) pad position. Thirteen patients with implanted pacemakers were defaulted to the AP pad position. Cardioversion was performed using an ICB waveform with a 70, 100, 150, and 200 J energy selection protocol. If the fourth shock was unsuccessful, the pads were crossed over to the alternative position for a final 200 J shock. Shock 1 was successful in 54/150 (36%) AA and 45/144 (31%) AP patients, whereas success was achieved by shock 2 in 99/150 (66%) AA and 74/144 (51%) AP, by shock 3 in 123/150 (82%) AA and 109/144 (76%) AP, and by shock 4 in 143/150 (95%) AA and 127/144 (88%) AP and after cross-over in 144/150 (96%) AA and 135/144 (94%) AP. Overall success rate was higher than expected at 95%. Pad position was not associated significantly with success. There was a trend towards an improved outcome with the AA configuration (P=0.05). CONCLUSION: The influence of pad position for DCC of AF may be less pertinent with ICB waveforms than with monophasic waveforms.     

Initial energy for biphasic external electrical cardioversion of atrial fibrillation.

BACKGROUND: No international guidelines indicate the initial energy in biphasic external electrical cardioversion of atrial fibrillation (AF) actually. The aim of this study was to determine this value in order to find a reasonable compromise between the necessity of limiting tissue damage and of quickly restoring sinus rhythm as well. METHODS: Fifty-six consecutive patients with AF candidate to external electrical cardioversion were treated using adhesive anterior-posterior paddles and biphasic wave defibrillator Lifepack 12, with steps of 50 J. After 6 hours troponin I levels were measured. RESULTS: Thirty-four patients were cardioverted by 50 J (group A), 18 by 100 J (group B) and 3 by 150 J (group C). One patient was not cardioverted (success rate 98%). No significant differences were noted between groups A and B with regard to age, sex, weight, height, thoracic circumference, body mass index, body surface area, impedance, NYHA class, left ventricular ejection fraction, left atrial diameter, causes of heart disease, antiarrhythmic medications, and duration of current AF episode. No increase of troponin I levels occurred. CONCLUSIONS: An initial shock of 100 J in the biphasic external elective cardioversion of AF is a valid and highly effective option. An initial shock of 50 J was effective in 61% of our population, and it is probably appropriated in patients with a lower weight and body mass index.     

Intracardiac low-energy versus transthoracic high-energy direct-current cardioversion of atrial fibrillation: a randomised comparison

Of 54 patients with long-standing atrial fibrillation (mean duration 8.3 months), 27 patients were randomised to transvenous low-energy intracardiac biphasic direct-current (DC) cardioversion (ICV) using a single-lead balloon-tipped catheter, and 27 patents were randomised to conventional high-energy transthoracic monophasic DC cardioversion (TCV). ICV was performed with increasing energy levels (7.5-10-12.5-15 J) during mild sedation. TCV was performed with 200-360-360 J during general anaesthesia. Cardioversion to sinus rhythm occurred in 93% (25/27) following ICV and in 67% (18/27) following TCV (p = 0.04). Due to the higher cardioversion rate following ICV, more patients were in sinus rhythm during 180 days of follow-up (log rank test, p = 0.04). Low-energy intracardiac cardioversion represents a highly efficacious alternative to high-energy transthoracic cardioversion.