Patients with atrial fibrillation may suffer from disabling symptoms such as palpitations, shortness of breath or worsening heart failure. In such patients, it may be beneficial to convert their rhythm to sinus rhythm. Cardioversion can be achieved either pharmacologically or electrically. Pharmacological cardioversion is less successful acutely than electrical cardioversion and may be associated with complications such as prolongation of the QT interval and torsades de pointes (polymorphic ventricular tachycardia). Thus, cardioversion is most often accomplished electrically, using biphasic synchronized shocks of 75-200 Joules. Biphasic electrical cardioversion in atrial fibrillation has shown to be successful (i.e., converting to sinus rhythm) about 88% of the time, on average. The success rate appears to largely depend upon the duration of the arrhythmia and the presence and severity of structural heart disease.
In this study, we will evaluate the effect of intravenous magnesium sulfate on the success rate of electrical cardioversion, and also assess its effect in decreasing the energy levels needed for successful cardioversion. If the study is successful, we will have shown that a simple and inexpensive intervention can increase the success rate of electrical cardioversion, increasing the proportion of patients who can be restored to sinus rhythm. In addition, success with lower energy levels may improve the safety of cardioversion, as high energy levels are more likely to be associated with side effects
