Resident Journal Review: Management of Acute A-Fib in the ED
Resident Journal Review: Management of Acute A-Fib in the ED
While there exists a significant amount of literature comparing the efficacy of pharmacological versus electrical cardioversion, one major advantage of pharmacological cardioversion is that, unlike electrical, it does not require sedation or anesthesia. One of the agents that can be used for pharmacological cardioversion is ibutilide, a Class III antiarrhythmic which acts by activation of a slow, inward sodium current, thereby prolonging the action potential and increasing the refractory period of the myocardium. While it has been found to be safe in most instances, ibutilide has been shown to induce torsades de pointes in 1.7-4.3% of patients, though this risk is increased further in patients with heart failure and reduced left ventricular ejection fraction.
This study is a retrospective chart review which aims to assess the efficacy and safety of using ibutilide for cardioversion of AF or AFL in cancer patients, a subset of patients which usually have other comorbidities and may be taking other medications which have the potential for QT prolongation. All patients had EKGs and/or telemetry monitoring recorded before and after drug administration. Most patients had a baseline corrected QT interval on a 12-lead EKG or telemetry of <450 milliseconds. Ibutilide was initially administered at a dose of 1mg in 50mL of normal saline which was infused over 10 minutes. If the arrhythmia persisted 10 minutes after the end of the initial infusion, a second 10-minute infusion of ibutilide 1mg was given. Cardioversion was considered successful if conversion to NSR was accomplished during administration and up to four hours after the end of drug infusion. Maintenance of NSR at 24 hours was also recorded.
Eighty-one patients who received ibutilide for cardioversion of AF or AFL over a four year period were included. Fifty-three (65%) of these patients had AF, while 11 patients (14%) had AFL, and 17 patients (21%) had AF/AFL. Only 5% of patients had left ventricular ejection fraction <50%, and 22% had history of coronary artery disease.
Successful cardioversion with intravenous ibutilide was achieved in 75% of patients and only five patients (6%) required a second dose of ibutilide after the initial infusion failed to convert to NSR. Sixty-eight (84%) of patients were taking at least one other medication with potential for QT prolongation. Although patients who were concomitantly taking amiodarone (47% of study population) were found to have a significant change (mean of 37 milliseconds) in QT interval after ibutilide administration, no adverse cardiovascular events occurred.
The authors conclude that ibutilide is a safe and effective agent for pharmacologic cardioversion of patients with AF and AFL. They address the potential risk for QT prolongation and torsades de pointes in patients who are given ibutilide while taking another medication that can prolong the QT interval. As nearly 50% of the study population was concomitantly taking amiodarone and suffered no adverse cardiovascular events, the authors infer that administration of ibutilide in these patients may be safe with proper monitoring of EKGs and serum electrolytes.
The two major limitations of this study are its retrospective design and small sample size. The latter casts doubt that the results are sufficiently powered to support the authors’ conclusions. In addition, there was no follow up to assess maintenance of NSR beyond 24 hours. Furthermore, only a very small percentage of the study population had left ventricular dysfunction with depressed ejection fraction. Therefore the study results cannot be applied to these patients who are at highest risk for arrhythmias.
Bickford, CL; Agarwal R; Urbauer DL; Durand JB; Lenihan DJ. Efficacy and Safety of Ibutilide for Chemical Cardioversion of Atrial Fibrillation and Atrial Flutter in Cancer Patients. Am J Med Sci. 2013 Apr 12.
While there exists a significant amount of literature comparing the efficacy of pharmacological versus electrical cardioversion, one major advantage of pharmacological cardioversion is that, unlike electrical, it does not require sedation or anesthesia. One of the agents that can be used for pharmacological cardioversion is ibutilide, a Class III antiarrhythmic which acts by activation of a slow, inward sodium current, thereby prolonging the action potential and increasing the refractory period of the myocardium. While it has been found to be safe in most instances, ibutilide has been shown to induce torsades de pointes in 1.7-4.3% of patients, though this risk is increased further in patients with heart failure and reduced left ventricular ejection fraction.
This study is a retrospective chart review which aims to assess the efficacy and safety of using ibutilide for cardioversion of AF or AFL in cancer patients, a subset of patients which usually have other comorbidities and may be taking other medications which have the potential for QT prolongation. All patients had EKGs and/or telemetry monitoring recorded before and after drug administration. Most patients had a baseline corrected QT interval on a 12-lead EKG or telemetry of <450 milliseconds. Ibutilide was initially administered at a dose of 1mg in 50mL of normal saline which was infused over 10 minutes. If the arrhythmia persisted 10 minutes after the end of the initial infusion, a second 10-minute infusion of ibutilide 1mg was given. Cardioversion was considered successful if conversion to NSR was accomplished during administration and up to four hours after the end of drug infusion. Maintenance of NSR at 24 hours was also recorded.
Eighty-one patients who received ibutilide for cardioversion of AF or AFL over a four year period were included. Fifty-three (65%) of these patients had AF, while 11 patients (14%) had AFL, and 17 patients (21%) had AF/AFL. Only 5% of patients had left ventricular ejection fraction <50%, and 22% had history of coronary artery disease.
Successful cardioversion with intravenous ibutilide was achieved in 75% of patients and only five patients (6%) required a second dose of ibutilide after the initial infusion failed to convert to NSR. Sixty-eight (84%) of patients were taking at least one other medication with potential for QT prolongation. Although patients who were concomitantly taking amiodarone (47% of study population) were found to have a significant change (mean of 37 milliseconds) in QT interval after ibutilide administration, no adverse cardiovascular events occurred.
The authors conclude that ibutilide is a safe and effective agent for pharmacologic cardioversion of patients with AF and AFL. They address the potential risk for QT prolongation and torsades de pointes in patients who are given ibutilide while taking another medication that can prolong the QT interval. As nearly 50% of the study population was concomitantly taking amiodarone and suffered no adverse cardiovascular events, the authors infer that administration of ibutilide in these patients may be safe with proper monitoring of EKGs and serum electrolytes.
The two major limitations of this study are its retrospective design and small sample size. The latter casts doubt that the results are sufficiently powered to support the authors’ conclusions. In addition, there was no follow up to assess maintenance of NSR beyond 24 hours. Furthermore, only a very small percentage of the study population had left ventricular dysfunction with depressed ejection fraction. Therefore the study results cannot be applied to these patients who are at highest risk for arrhythmias.