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Initial energy setting, outcome and efficiency in direct current cardioversion of atrial fibrillation and flutter
Initial Energy Setting, Outcome and Efficiency in Direct Current Cardioversion of Atrial Fibrillation and Flutter
Role of Dispersion of Atrial Refractoriness in the Recurrence of Clinical Atrial Fibrillation. A Manifestation of Atrial Electrical Remodeling in Humans?
Gallagher MM, Xiao-Hua G, Poloniecki JD, et al. J Am Coll Cardiol 2001;38:1498 –504.
Fynn SP, Todd DM, Hobbs JC, Armstrong KL, Garratt CJ. Eur Heart J 2001;22:1822–34.
Study Question: What is the most efficient protocol for transthoracic cardioversion of atrial fibrillation (AFib) and atrial flutter (AFl)? Methods: This was a retrospective review of 1838 attempts at cardioversion of AFib and 678 attempts at cardioversion of AFl. The strength and outcome of every shock were recorded. Successful cardioversion was defined as at least two sinus beats following a shock. Lone AFib was present in 21% of patients, and the remainder had structural heart disease, most commonly coronary artery disease. Results: A total of 5152 shocks for AFib and 1238 shocks for AFl were analyzed. The probability of a successful outcome was related directly to the shock strength and indirectly to the duration of AFib. When the AFib duration was ⬎30 days, a first shock of ⬍200 J was successful in 5.5% of cases, compared to 56% when the first shock was 360 J. When the AFib duration was ⬎180 days, a first shock of 360 J was associated with eventual successful cardioversion with a mean of 581 J, compared to a mean of 758 J when the first shock was ⱕ100 J. For AFl, an initial shock of 100 J was successful in 68% of cases. Conclusion: The efficiency of transthoracic cardioversion of AFib is greatest when the initial shock is 360 J, particularly when the AFib has been present for ⬎180 days. Perspective: The findings of this study are tempered by a host of limitations, including a retrospective study design, the absence of a standardized cardioversion protocol, an end point that may not be clinically meaningful (sinus rhythm lasting two beats) and the failure to account for important confounding variables such as body size, left atrial size and antiarrhythmic drug therapy. Furthermore, the current availability of biphasic defibrillators, which are more effective than the conventional defibrillators used in this study, also limit the clinical value of the findings. FM
Study Question: Are recurrences of atrial fibrillation (AF) after cardioversion (CV) related to dispersion of atrial refractoriness? Methods: Internal CV was performed in 37 patients with AF that had been present for a mean of 30 months. Electrode catheters were positioned in the right atrial (RA) appendage, lateral RA wall, upper septum, and coronary sinus. The AF cycle length (AFCL) was measured at these 4 sites before CV. Fifteen minutes after CV, the atrial effective refractory period (AERP) was measured by pacing at the 4 RA sites. Except for 4 patients treated with amiodarone, no antiarrhythmic drug therapy was used after cardioversion. Twenty-eight patients had recurrent atrial fibrillation within 1 month, and 13 of these patients underwent a 2nd CV, again with measurements of AFCL and AERP. Results: Before CV, dispersion in AFCL among the 4 atrial sampling sites was significantly greater in the patients who went on to have recurrent AF than in those who did not (35 vs. 19 ms). At the time of the 2nd CV, dispersion of AFCL was less than at the time of the 1st cardioversion (19 vs. 35 ms). Conclusions: Recurrent atrial fibrillation after cardioversion is associated with dispersion of the AFCL. The extent of dispersion of AFCL is related to the duration of AF. Perspective: This study elucidates one of the possible mechanisms by which “AF begets AF.” As the duration of AF increases, dispersion in AFCL (a measure of atrial refractoriness) also increases, and the greater the dispersion in AFCL, the higher the likelihood of recurrent AF after CV. Therefore, drugs that specifically prevent dispersion of atrial refractoriness may be particularly helpful in preventing recurrent atrial fibrillation. As of yet, such drugs are not clinically available. FM
ACC CURRENT JOURNAL REVIEW Mar/Apr 2002
69
Role of Dispersion of Atrial Refractoriness in the Recurrence of Clinical Atrial Fibrillation. A Manifestation of Atrial Electrical Remodeling in Humans?
Gallagher MM, Xiao-Hua G, Poloniecki JD, et al. J Am Coll Cardiol 2001;38:1498 –504.
Fynn SP, Todd DM, Hobbs JC, Armstrong KL, Garratt CJ. Eur Heart J 2001;22:1822–34.
Study Question: What is the most efficient protocol for transthoracic cardioversion of atrial fibrillation (AFib) and atrial flutter (AFl)? Methods: This was a retrospective review of 1838 attempts at cardioversion of AFib and 678 attempts at cardioversion of AFl. The strength and outcome of every shock were recorded. Successful cardioversion was defined as at least two sinus beats following a shock. Lone AFib was present in 21% of patients, and the remainder had structural heart disease, most commonly coronary artery disease. Results: A total of 5152 shocks for AFib and 1238 shocks for AFl were analyzed. The probability of a successful outcome was related directly to the shock strength and indirectly to the duration of AFib. When the AFib duration was ⬎30 days, a first shock of ⬍200 J was successful in 5.5% of cases, compared to 56% when the first shock was 360 J. When the AFib duration was ⬎180 days, a first shock of 360 J was associated with eventual successful cardioversion with a mean of 581 J, compared to a mean of 758 J when the first shock was ⱕ100 J. For AFl, an initial shock of 100 J was successful in 68% of cases. Conclusion: The efficiency of transthoracic cardioversion of AFib is greatest when the initial shock is 360 J, particularly when the AFib has been present for ⬎180 days. Perspective: The findings of this study are tempered by a host of limitations, including a retrospective study design, the absence of a standardized cardioversion protocol, an end point that may not be clinically meaningful (sinus rhythm lasting two beats) and the failure to account for important confounding variables such as body size, left atrial size and antiarrhythmic drug therapy. Furthermore, the current availability of biphasic defibrillators, which are more effective than the conventional defibrillators used in this study, also limit the clinical value of the findings. FM
Study Question: Are recurrences of atrial fibrillation (AF) after cardioversion (CV) related to dispersion of atrial refractoriness? Methods: Internal CV was performed in 37 patients with AF that had been present for a mean of 30 months. Electrode catheters were positioned in the right atrial (RA) appendage, lateral RA wall, upper septum, and coronary sinus. The AF cycle length (AFCL) was measured at these 4 sites before CV. Fifteen minutes after CV, the atrial effective refractory period (AERP) was measured by pacing at the 4 RA sites. Except for 4 patients treated with amiodarone, no antiarrhythmic drug therapy was used after cardioversion. Twenty-eight patients had recurrent atrial fibrillation within 1 month, and 13 of these patients underwent a 2nd CV, again with measurements of AFCL and AERP. Results: Before CV, dispersion in AFCL among the 4 atrial sampling sites was significantly greater in the patients who went on to have recurrent AF than in those who did not (35 vs. 19 ms). At the time of the 2nd CV, dispersion of AFCL was less than at the time of the 1st cardioversion (19 vs. 35 ms). Conclusions: Recurrent atrial fibrillation after cardioversion is associated with dispersion of the AFCL. The extent of dispersion of AFCL is related to the duration of AF. Perspective: This study elucidates one of the possible mechanisms by which “AF begets AF.” As the duration of AF increases, dispersion in AFCL (a measure of atrial refractoriness) also increases, and the greater the dispersion in AFCL, the higher the likelihood of recurrent AF after CV. Therefore, drugs that specifically prevent dispersion of atrial refractoriness may be particularly helpful in preventing recurrent atrial fibrillation. As of yet, such drugs are not clinically available. FM
ACC CURRENT JOURNAL REVIEW Mar/Apr 2002
69