At least one study has suggested that placebo is at least as affective. Intravenous verapamil and, more recently, diltiazem are safe and effective in reducing heart rate during atrial fibrillation and flutter. The short half-life of verapamil may necessitate repeated boluses. One usually starts with an injection of 5mgs and this can be repeated at five to ten minute intervals to a maximum of 20mgs. It too should be given over 2 minutes.
Beta blockers are effective in the control of exercise heart rate.
In many cases, sinus rhythm will be restored spontaneously in patients who have no underlying structural heart disease. In patients with congestive heart failure, attempts to convert to sinus rhythm usually fail until the heart failure is treated. In this situation, digoxin is the agent of choice despite the limitations noted above. If a patient is unstable, Cardioversion is prefered.