Cardioversion is a procedure used to reset an abnormal heart rhythm to a normal rhythm. This procedure is used when the heart is beating very fast or irregular. This is called an arrhythmia. Arrhythmias can cause problems such as fainting, stroke, heart attack, and even sudden cardiac death. With electrical cardioversion, a high-energy shock is sent to the heart to reset a normal rhythm. It's different from chemical cardioversion, in which medicines are used to try to restore a normal rhythm.
Normally, a special group of cells begin the electrical signal to start your heartbeat. These cells are in the sinoatrial (SA) node. This node is in the right atrium, the upper right chamber of the heart. The signal quickly travels down the heart’s conducting system on the way to the ventricles, the two lower chambers of the heart. As it travels, the signal triggers nearby parts of the heart to contract. This organized pattern helps the heart contract in a coordinated way.
Various problems can disrupt this signaling pathway and lead to abnormal heart rhythms. The heart might beat very quickly, not leaving it enough time to fill with enough blood between beats. This can prevent your heart from pumping enough blood to the body. Some abnormal heart rhythms raise your risk of stroke. Some also raise the risk of life-threatening rhythms that can lead to sudden death. Cardioversion interrupts the abnormal signaling and lets the heart reset itself back into a normal rhythm.
Cardioversion is usually a scheduled procedure. But sometimes healthcare providers need to do it on an urgent basis if symptoms are severe. You will likely be given medicine to put you to sleep before delivering the shocks. Cardioversion is not the same as defibrillation. Both use shocks to reset the heart. But in a cardioversion, the shock is synchronized with the heartbeat. Defibrillation is typically done in an emergency to stop very severe rhythms that can cause sudden death.
Electrical cardioversion can help treat several different abnormal heart rhythms. It's commonly used to treat sustained arrhythmias such as atrial fibrillation (Afib). With this condition, the atria of the heart quiver instead of beating the right way. Symptoms of Afib may include shortness of breath, fatigue, and a very fast heartbeat. It can also increase risk for stroke.
If this is your first time having Afib, your healthcare provider may be more likely to suggest cardioversion. Your provider may also want you to have it if you have ongoing Afib, especially if it gives you severe symptoms. Electrical cardioversion works better and is used more often than chemical cardioversion. It's also faster.
Your healthcare provider may not recommend cardioversion if you don't have symptoms from the Afib or if your symptoms are very minor. It also may not be recommended if you are elderly, if you have had Afib a long time, or if you have other major medical problems. Other treatments might be better for you, like heart rate control with medicines.
Electrical cardioversion is also useful for treating other abnormal heart rhythms, like atrial flutter, which is similar to Afib. It can also be used to treat certain kinds of supraventricular tachycardias and ventricular tachycardia (VT). These types of heart rhythms can cause heart rates that are too fast. This can prevent the heart from pumping enough blood.
Before trying electrical cardioversion, your healthcare provider may try to reset the heart rate in other ways. This might include the Valsalva maneuver. This is a method where you hold your breath and increase the pressure in your belly. This can help bring the heart rate down. Your healthcare provider may then try medicines to change the rhythm to normal. If these methods don’t work, electrical cardioversion is often the next step. In other cases, electrical cardioversion is the first recommended step.
You may need an electrical cardioversion soon if you have severe symptoms from your heart rhythm.
Although most people have a successful electrical cardioversion, it does have certain risks. Your own risks may vary based on your age, the type of abnormal heart rhythm you have, and your other medical conditions. Ask your healthcare provider about your risks.
Rarely, the procedure causes a more dangerous heart rhythm. If that happens, someone will give you medicines or a stronger electric shock to stop this rhythm. Some other risks are:
Problems breathing if you had medicine (sedation) to help you sleep during the procedure
Other less dangerous abnormal rhythms
Slow heart rate afterwards
Temporary low blood pressure
Heart damage (usually temporary and without symptoms)
Dislodged blood clot, which can cause stroke or other problems
In certain situations, healthcare providers lower this last risk by giving medicines to help prevent clots (blood thinners). They give people these medicines before and after the procedure.
In some cases, the cardioversion may not be able to reset a normal heart rhythm. There is also a risk that you might go back to your abnormal rhythm shortly after your cardioversion. Sometimes people need to take medicines to help control the heart rhythm before the procedure. They may need to take medicines after the procedure and prevent the problem from happening again.
Talk with your healthcare provider about what you should do to get ready for your electrical cardioversion. Follow any directions you are given for not eating or drinking before the procedure.
Follow your healthcare provider’s instructions about what medicines to take before the procedure. This includes any medicines to prevent abnormal rhythms. Don’t stop taking any medicine unless your healthcare provider tells you to do so. You might need blood tests before the procedure to make sure the procedure is safe to do.
If you are at higher risk of blood clots, your healthcare provider may want you to take anti-clotting medicine. These are commonly taken for several weeks before and after the procedure. Not everyone needs this medicine, but most people do. You are likely to need anti-clotting medicine if your abnormal rhythm has lasted more than 48 hours or if you have had a blood clot in the past.
Your healthcare provider may want a transesophageal echocardiography (TEE) test before the procedure. This test is a special kind of ultrasound. A thin, flexible tube is put down your throat and into your esophagus. Here, the tube is close to your heart. It lets your healthcare provider see if you have any blood clots in the heart. Your cardioversion will be delayed if a clot is found. You’ll likely need to take blood-thinner medicine such as warfarin for a while until your risk for clots is low. You may have a repeat TEE to make sure the clot has gone away. It’s important to take any blood-thinning medicines exactly as your healthcare provider tells you.
Talk with your healthcare provider about what to expect during your procedure. It may differ if you need an urgent or emergency electrical cardioversion. In general, you can expect the following:
Soft electrode pads are placed on your chest and maybe on your back. You might need some areas of skin shaved to get the electrode pads to stick.
These electrodes will connect to a cardioversion machine.
You will get medicine through a vein in your arm to make you fall asleep.
Using the cardioversion machine, a programmed high-energy shock is sent to your heart. This should convert your heart back to a normal rhythm.
Your team will closely monitor your heart rhythm. They will watch for any signs of complications.
The procedure only takes a few minutes. When it is done, you will wake up.
Ask your healthcare provider about what to expect. You will likely:
Wake up 5 to 10 minutes after the procedure
Be closely watched for signs of complications for several hours
Feel sleepy for several hours after the cardioversion. Arrange to have someone drive you home
Go home the same day as the procedure
Have some redness or soreness on your chest that lasts for a few days
Ask your healthcare provider about what medicines you’ll need to take when you get home. Many people need to take an anti-clotting medicine such as warfarin or another blood thinner. Some people also need medicines to prevent abnormal heart rhythms. Take all your medicines exactly as your healthcare provider tells you. Tell your healthcare provider right away if any of your symptoms come back.
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how you will get the results
Who to call after the test or procedure if you have questions or problems
How much you will have to pay for the test or procedure