When a person has atrial fibrillation, he or she has a greater risk of developing blood clots. This happens because the heart isn't able to completely pump the blood out of the upper chambers of the heart.
Your doctor will probably recommend that you take drugs to keep your blood from clotting before you have a cardioversion procedure. This is done to avoid having a blood clot that can become dislodged once the heart starts beating normally again.
Between 75 and 93% of people who have atrial fibrillation and who undergo cardioversion are successfully returned to a normal heart rhythm. (The difference in the success rate is due to factors such as how long the individual has had atrial fibrillation and the size of his or her left atrium.) If a person has had atrial fibrillation for less than one year, there is about a 90% rate of success in bringing the heart back to a normal rhythm after cardioversion. On the other hand, if a person has had atrial fibrillation for more than five years, the success rate drops to about 50%.
A person who is going to have cardioversion is usually given an antiarrhythmic drug 24 to 48 hours before the procedure. This helps bring the heart back to a normal rhythm for the critical first few hours after cardioversion. During this time, a recurrence of the atrial fibrillation is most likely. Taking the antiarrhymic drug may even help restore a normal heart rhythm without cardioversion. If not, the drug may mean that less energy has to be used during cardioversion.
If You Have a Pacemaker or Implanted Defibrillator or Cardioverter
Cardioversion can damage the device that generates the electrical pulse, the leads that come from the device or the tissue of the heart itself. All of these things can cause the pacemaker not to work correctly.
Your doctor will take special precautions to lower the risk of damage. These include being careful to place the electrode paddle on the patient's back at least six inches away from the pacemaker's battery. After a cardioversion, the doctor will evaluate the pacemaker to be sure it still works normally.
Complications from Cardioversion
As with any procedure, complications sometimes follow internal cardioversion. These can include:
- Reduced blood flow from the heart (low blood pressure)
- Fluid inside the pericardium, the membrane that covers the heart inside the chest (pericardial effusion)
- Setting off other irregular heart rhythms or disturbing the heart's ability to conduct the electrical impulses that make it beat.