Cardioversion for Arrhythmia: When Is It Needed and Is It Safe?

When a doctor recommends cardioversion after finding a rhythm disturbance on an ECG, the term “electric shock” can sound alarming. You might immediately picture a resuscitation scene involving a patient in cardiac arrest. In fact, cardioversion has a different purpose, mechanism, and context of use.

Cardioversion is a medical procedure that helps restore certain heart rhythms that are too fast or irregular to a more organized rhythm. Doctors can perform it using medication or electrical energy synchronized with the heart’s electrical activity. However, not every arrhythmia requires this procedure. The decision always takes into account the type of rhythm disturbance, the symptoms, how long the arrhythmia has lasted, the patient’s condition, and test results.

This article will help you understand when cardioversion is considered, what needs to be prepared, how the procedure is performed, and what may happen afterward. This information is not a substitute for medical consultation, but it can help you and your family talk with your doctor in a calmer and more focused way.

01 / Cardiovascular Therapy

What Is Cardioversion?

Cardioversion is a procedure that helps change certain heart rhythms that are too fast or irregular into a more organized rhythm. It is one of the options within a strategy to control the heart rhythm, known as rhythm control.

In general, doctors can perform cardioversion in two ways:

• Electrical cardioversion, by delivering controlled electrical energy through pads placed on the chest, or on the chest and back.
• Pharmacological cardioversion, by giving antiarrhythmic medication to help restore the rhythm.

A regular rhythm that originates from the heart’s natural pacemaker is called sinus rhythm. However, successfully restoring the rhythm does not always mean the cause of the arrhythmia is gone. Medication and further monitoring may still be needed.

To understand the underlying condition, read also the Heartology article on heart rhythm disorders, or arrhythmia.

How Does Cardioversion Regulate the Heart Rhythm?

The heart has an electrical system that controls the timing of contractions of the atria and ventricles. In arrhythmia, electrical signals may form too quickly, travel along abnormal pathways, or spread irregularly.

In electrical cardioversion, the device first reads the heart’s electrical activity. Energy is then delivered at a specific point in the cardiac cycle. This process is called synchronization.

The energy helps stop the abnormal electrical pattern so that the heart’s natural pacemaker system has the chance to take over again. Because it is delivered in a synchronized way, this procedure differs from the defibrillation used in certain types of cardiac arrest. Synchronized cardioversion is performed on patients with a rhythm disturbance who still have a pulse.

Cardioversion is sometimes compared to “resetting” the heart rhythm. This analogy makes it easier to understand, but the heart is of course not an electronic device. Doctors still need to adjust the timing, energy, sedation, and monitoring to each patient’s condition.

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Who Needs Cardioversion?

Cardioversion may be considered for patients with certain arrhythmias, especially when the rhythm disturbance causes symptoms, impairs heart function, or makes the patient’s condition unstable. However, palpitations do not automatically mean someone needs cardioversion.

The doctor will assess several things before recommending the procedure, including:

• The type of rhythm disturbance on the ECG.
• How long the arrhythmia has lasted.
• How severe the symptoms are.
• Blood pressure and how stable the patient’s condition is.
• The structure and function of the heart.
• Medical history and the medications being used.
• The risk of blood clots forming.
• Response to previous treatment.

Cardioversion is most often discussed in the management of atrial fibrillation and atrial flutter. In addition, doctors may use it for certain types of tachycardia.

Cardioversion for Atrial Fibrillation

Atrial fibrillation is a rhythm disturbance in which the electrical activity in the upper chambers of the heart is rapid and irregular. Some patients have no symptoms. However, other patients may experience:

• A pounding or irregular heartbeat.
• Getting tired easily.
• Shortness of breath.
• Dizziness or feeling close to fainting.

In certain patients, cardioversion may help restore the rhythm and reduce symptoms. Even so, doctors do not look only at ECG results. The duration of the arrhythmia and the risk of blood clots forming and traveling are also important considerations.

Furthermore, the management of atrial fibrillation does not end once the rhythm has been restored. The European Society of Cardiology 2024 guidelines use the AF-CARE framework, which treats the management of coexisting conditions, stroke prevention, rate or rhythm control, and individualized reassessment as parts of ongoing care.

Cardioversion for Atrial Flutter

In atrial flutter, abnormal electrical signals usually circulate in a repeating pattern in the upper chambers of the heart. As a result, the heartbeat can become fast even though the electrical pattern is more organized than in atrial fibrillation.

Doctors may consider cardioversion to help restore a more regular rhythm. Even so, the risk of blood clots and the need for anticoagulants still need to be assessed, especially if the rhythm disturbance has lasted for quite a while or there are other stroke risk factors.

Cardioversion for Certain Tachycardias

Tachycardia means the heart is beating faster than is appropriate for the body’s condition at that moment. Its causes and types vary widely. That is why the term “fast heartbeat” alone is not enough to determine treatment.

Electrical cardioversion may be used for some tachyarrhythmias when the patient still has a pulse, especially if their condition becomes unstable. However, doctors must identify the rhythm on an ECG before deciding on the procedure. Not every fast heartbeat needs to be, or should be, treated with an electric shock.

Scheduled and Urgent Cardioversion

Cardioversion can be performed on a scheduled or urgent basis, depending on the patient’s condition.

When a fast arrhythmia causes an unstable condition, medical staff may perform urgent cardioversion. Conversely, if the patient is stable, the doctor has time to assess the risk of blood clots, adjust medications, and determine the most suitable approach.

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What Are the Types of Cardioversion?

Cardioversion consists of two main approaches: electrical cardioversion and cardioversion with medication. No single option is always better for every patient. Doctors tailor the choice to the type of arrhythmia, clinical condition, urgency, and individual risk.

Electrical Cardioversion

Electrical cardioversion uses pads or electrodes placed on the chest, or on the chest and back. The pads are connected to a device that records the rhythm and also delivers electrical energy.

In a scheduled procedure, the patient usually receives sedation through an IV. Once the patient is asleep or very drowsy, the doctor delivers energy that has been synchronized with the cardiac cycle. The doctor then assesses whether the rhythm has changed.

Some patients need a single delivery of energy. Other patients may need it repeated, depending on how the rhythm responds and on the doctor’s judgment.

Cardioversion With Medication

Pharmacological cardioversion uses antiarrhythmic medication to influence how the heart’s electrical signals are formed or conducted.

The medication can be given through an IV or another route, depending on the drug chosen. Compared with the electrical approach, the change in rhythm may take longer. In addition, the patient still needs monitoring because the medication can affect the heart rate, blood pressure, and heart rhythm pattern.

Do not start, stop, or change the dose of heart medications without your doctor’s guidance.

How Does the Doctor Decide?

Doctors usually consider:

• The type and duration of the arrhythmia.
• Whether or not the patient’s condition is stable.
• How quickly the rhythm needs to be restored.
• History of heart disease.
• The medications currently being taken.
• The risk of blood clots and bleeding.
• Response to previous treatment.
• The benefits and risks of each approach.

So the difference is not simply “electricity or medication”. The most important question is which approach offers the most suitable balance of benefits and risks for the patient.

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What Is the Difference Between Cardioversion, Defibrillation, and Ablation?

Cardioversion, defibrillation, and ablation all relate to the heart’s electrical system, but their purposes and uses differ. Understanding these differences helps reduce worry and prevents the assumption that every “electric shock” is the same procedure.

Cardioversion vs. Defibrillation

In electrical cardioversion, energy is delivered in sync with the heart’s electrical activity. This procedure is generally performed when the patient still has a pulse.

In contrast, defibrillation uses unsynchronized energy. Doctors or trained rescuers use it in certain emergencies when the heart rhythm does not produce effective circulation, such as ventricular fibrillation or pulseless ventricular tachycardia. In these situations, resuscitation must not be delayed.

Cardioversion vs. Ablation

Cardioversion aims to restore the rhythm at the time of the procedure. However, it does not always eliminate the tissue or electrical pathway that causes the arrhythmia.

Ablation has a different goal. The doctor inserts a catheter through a blood vessel to the heart, then targets the area that triggers or sustains the abnormal signals. For this reason, ablation may be considered for certain arrhythmias that recur or continue to cause symptoms.

Not every patient who has undergone cardioversion needs ablation.

Heartology provides arrhythmia evaluation and treatment services, including ablation, pacemakers, and ICDs, for suitable patients.

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What Should You Prepare Before Cardioversion?

Preparation before cardioversion aims to make sure the type of arrhythmia has been identified, the risks of the procedure have been assessed, and the patient is ready to undergo the procedure safely and comfortably. Instructions may differ for each patient. For this reason, follow the guidance of the medical team treating you first and foremost.

Consultation and ECG Testing

First, the doctor reviews your symptoms, medical history, allergies, and all the medications and supplements you take. Next, an ECG helps confirm the type of rhythm that is occurring.

If available, bring:

• Previous ECG results.
• Holter monitoring results.
• Echocardiography results.
• Laboratory results.
• A list of prescription drugs, over-the-counter medicines, vitamins, and supplements.

Also learn about the role of an ECG test in recording the heart’s electrical activity.

Why Does the Risk of Blood Clots Need to Be Assessed?

In atrial fibrillation and some arrhythmias that originate in the upper chambers of the heart, the atria contract less effectively. As a result, blood can move more slowly in certain areas and form clots in some patients.

When the rhythm is restored, these clots may travel. If they reach the brain, this can cause a stroke. That is why assessing the risk of thromboembolism is an important part of preparation, not just an additional test.

The Role of Blood Thinners

The term “blood thinner” usually refers to anticoagulants. These medications do not actually thin the blood, but they reduce the blood’s tendency to form clots.

In certain patients, the doctor gives anticoagulants before and after the procedure. The type and duration of use depend on how long the arrhythmia has lasted, medication history, and individual stroke risk.

Even after the rhythm becomes regular again, anticoagulants may still be needed. Stroke risk is not determined only by how the rhythm looks at a single point in time. So do not skip or stop the medication without your doctor’s approval.

When Is TEE Needed?

Transesophageal echocardiography (TEE) is an ultrasound examination of the heart that uses a probe inserted through the esophagus.

Because the esophagus lies close to the heart, TEE can give a clearer view of certain areas, including the area where clots often form. Doctors may use it before cardioversion to make sure there are no clots that could travel.

If a clot is found, the doctor may postpone the procedure and arrange anticoagulant therapy and further evaluation. Even so, not every patient needs a TEE.

Fasting and Routine Medications

Patients undergoing scheduled electrical cardioversion are usually asked to fast because they will receive sedation. However, how long to fast and the rules about drinking must follow the hospital’s instructions.

Before the day of the procedure, make sure you know:

1. When to stop eating and drinking.
2. Which medications to keep taking.
3. Whether diabetes medications need to be adjusted.
4. Your anticoagulant schedule.
5. What to do if you miss a dose.
6. Whether lotion, powder, or ointment may be used on the chest and back.

We recommend that patients bring a list of all their medications and follow the specific instructions about fasting and routine medications.

A Companion and Transportation Home

Sedation can make patients drowsy and slow their reactions for some time. For this reason, patients usually need an adult who can take them home.

If you have a busy work schedule, make the following preparations:

• Do not schedule meetings or important decisions on the day of the procedure.
• Arrange transportation to and from the hospital.
• Ask when you may drive again.
• Discuss when you can return to work.
• Make sure your companion understands the medication schedule and discharge instructions.

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How Is Electrical Cardioversion Performed?

Electrical cardioversion is performed in a medical facility with sedation and monitoring of the heart rhythm, blood pressure, breathing, and oxygen levels. The energy delivery itself is brief, but the whole process takes longer because it includes preparation and observation.

1. Preparation and Monitoring

The medical team first verifies the patient’s identity, medication history, fasting rules, and readiness.

Then the team attaches:

1. An IV line.
2. ECG electrodes.
3. A blood pressure monitor.
4. An oxygen level monitor.
5. Cardioversion pads on the chest, or on the chest and back.

Pad placement may differ depending on the doctor’s judgment and the patient’s condition.

2. Giving Sedation

Next, the team gives sedative medication through the IV. Sedation helps the patient fall asleep or become very drowsy so that the procedure is more comfortable.

During this process, the team monitors:

1. Breathing.
2. Oxygen levels.
3. Blood pressure.
4. Heart rate and rhythm.
5. The patient’s response.

Sedation for cardioversion is not always the same as general anesthesia for major surgery. Its type and depth are tailored to the patient’s condition.

3. Delivering Synchronized Energy

The cardioversion device reads the ECG pattern and determines the right moment to deliver energy. The doctor then delivers the energy in a synchronized way.

The doctor immediately assesses the change in rhythm. If the rhythm has not changed as expected, the doctor may repeat the procedure with adjusted settings.

Synchronization is an important difference between cardioversion and defibrillation.

4. Evaluation and Observation

After the procedure, the team monitors the patient as the sedation wears off. The ECG and vital signs continue to be checked.

The doctor then assesses:

• Whether the rhythm is more regular.
• Whether there are any new complaints.
• Whether medications need to be continued or adjusted.
• Whether the patient can go home.
• When the next follow-up visit will take place.

The energy delivery itself lasts only a short time. However, the preparation and recovery period make the visit last longer.

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Is Cardioversion Painful?

In scheduled electrical cardioversion, patients usually receive sedation so that they are asleep or very drowsy when the energy is delivered. For this reason, most patients are not aware of the moment the energy is delivered.

After waking up, some patients may experience:

• Drowsiness.
• Redness where the pads were placed.
• A warm or mildly stinging sensation on the skin.
• Mild discomfort in the chest or back.

However, each patient’s experience may differ. Tell the medical team if the discomfort is severe, gets worse, or comes with other symptoms.

The phrase “being put under” is often used loosely. Before the procedure, you can ask what type of sedation will be used, who will monitor you, and what the recovery process will be like.

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Is Cardioversion Safe?

Cardioversion is generally performed with special preparation and monitoring, but like other medical procedures, it still carries risks. Each patient’s risk is different, depending on the type of arrhythmia, age, heart condition, coexisting conditions, and the medications being used.

The evaluation before the procedure is not just about meeting administrative requirements. Doctors use it to identify risks and prepare appropriate precautions.

Risk of Blood Clots and Stroke

In atrial fibrillation, clots can form in the upper chambers of the heart. When the rhythm is restored, these clots may travel to the brain or other organs.

To reduce this risk, the doctor may:

• Give anticoagulants.
• Perform a TEE.
• Postpone the procedure if a clot is found.
• Choose another strategy based on the patient’s condition.

Changes in Heart Rhythm

In rare cases, cardioversion may be followed by another rhythm disturbance. For this reason, the team monitors the ECG before, during, and after the procedure and has medications or additional measures ready if needed.

Effects of Sedation

Sedation can cause:

• Drowsiness.
• Nausea.
• A drop in blood pressure.
• Changes in breathing.
• Reactions to the medication in certain patients.

Monitoring breathing, oxygen, and blood pressure helps the medical team recognize these changes more quickly.

Skin Irritation

The area where the pads were attached may become red, sore, or temporarily irritated. Avoid applying creams or certain medications without your doctor’s guidance.

Although serious complications are uncommon, the risks still need to be explained openly. Ask your doctor which risks are most relevant to your condition and how the team will prepare for them.

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What Happens After Cardioversion?

After cardioversion, the patient is observed until the sedation wears off and their condition is judged to be stable. When you can go home and return to your activities depends on the outcome of the procedure, your health, the effects of sedation, and the type of work you do.

Observation and Discharge

In the recovery room, the team monitors:

• Level of consciousness.
• Heart rhythm.
• Blood pressure.
• Oxygen levels.
• The patient’s complaints.

Many patients who undergo a scheduled procedure can go home on the same day. However, some patients need longer observation or additional care.

Driving and Returning to Work

Even if you already feel alert, the effects of sedation can still affect your concentration, reflexes, and ability to make decisions. For this reason, do not drive yourself after the procedure.

The time to return to work is not the same for every patient. Office work has different demands from work that involves:

• Driving.
• Heavy machinery.
• Heights.
• Strenuous physical activity.
• Responsibility for safety.

So discuss the type of work you do with your doctor and follow the discharge instructions you are given.

Medications and Follow-Up After the Procedure

A more regular rhythm does not mean all medications can be stopped. After the procedure, patients may still need:

• Anticoagulants.
• Antiarrhythmic medications.
• Medications to control the heart rate.
• Medications for blood pressure or coexisting conditions.

In addition, the doctor may schedule an ECG, Holter monitoring, or other tests to make sure the rhythm stays under control.

Symptoms to Watch for at Home

Contact a medical professional if you experience:

• Palpitations that return or get worse.
• Persistent dizziness.
• New or worsening shortness of breath.
• Chest pain.
• Severe skin irritation.
• Unusual bleeding while taking anticoagulants.
• Confusion about your medication schedule.

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Can Arrhythmia Return After Cardioversion?

Yes, the heart rhythm can become irregular again after cardioversion. This procedure helps restore the rhythm at the time it is performed, but it does not always eliminate the condition or electrical pathway that triggers the arrhythmia.

Even so, a returning arrhythmia does not automatically mean the previous procedure was in vain. Information about how the rhythm responded and how long it lasted can help the doctor plan the next treatment.

Factors That Affect the Outcome

The outcome of the procedure and the chance of recurrence may be influenced by:

• The type of arrhythmia.
• How long the arrhythmia has lasted.
• The structure and function of the heart.
• Coexisting conditions.
• Taking medications as prescribed.
• Individual triggers.
• The care strategy after the procedure.

No single factor can be used on its own to predict the outcome for a particular person.

What Is Done If the Rhythm Becomes Irregular Again?

The doctor may consider:

• An ECG or Holter monitoring.
• Adjusting medications.
• Repeat cardioversion in certain conditions.
• An electrophysiology evaluation.
• Ablation.
• A rate control strategy.

Evaluation needs to be done dynamically because atrial fibrillation and its coexisting conditions can change over time.

Is Ablation Still Needed?

Not every patient needs ablation after cardioversion.

The doctor may consider it if:

• The arrhythmia keeps coming back.
• Symptoms remain bothersome.
• The type of arrhythmia is suitable for ablation.
• The benefits of the procedure are judged to outweigh its risks.

Cardioversion and ablation are not simply two procedures that can replace each other. Each can serve a different role in the care plan.

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When Do You Need Urgent Help?

Seek medical help immediately if palpitations come with fainting, severe chest pain, worsening shortness of breath, or reduced consciousness. Do not try to decide for yourself whether you need cardioversion in these situations.

Watch out for the following signs:

• Fainting or reduced consciousness.
• Severe pain or pressure in the chest.
• Worsening shortness of breath.
• Feeling very weak or breaking out in a cold sweat.
• Sudden confusion.
• A drooping face.
• Weakness or numbness in one arm.
• Slurred speech or difficulty understanding speech.
• Sudden problems with balance or vision.

A drooping face, arm weakness, difficulty speaking, balance problems, and changes in vision are warning signs of stroke. These symptoms still require immediate evaluation even if they later improve.

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Heart Rhythm Evaluation at Heartology

Evaluating a heart rhythm disorder begins with confirming the type of arrhythmia, understanding the symptoms, and assessing the patient’s condition as a whole. Two patients with the same diagnosis do not necessarily need the same care plan.

Heartology has an Arrhythmia & Device Center that lists cardiology consultants with competence in interventional electrophysiology. Services at the center include arrhythmia evaluation and treatment options such as ablation, pacemakers, and ICDs for suitable patients.

During a consultation, the doctor can help you discuss:

• The type of arrhythmia detected.
• Further tests that are needed.
• Whether cardioversion is relevant to the patient’s condition.
• The benefits and risks of each option.
• Use of medications before and after the procedure.
• The possibility of monitoring, ablation, or a cardiac device.
• A long-term care plan.

Heartology also has dr. Sunu Budhi Raharjo, Sp.JP (K), Dr. dr. Faris Basalamah, Sp.JP (K), and Dr. dr. Dicky Armein Hanafy, Sp.JP (K) as interventional electrophysiologists in its arrhythmia service.

The EnSite X and HD Grid technologies mentioned on the Heartology page are used for electrophysiological mapping and ablation. They are not devices that are automatically needed for every cardioversion.

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Questions to Ask Your Doctor Before Cardioversion

Preparing questions can make your consultation more efficient and help you fully understand medical decisions.

Consider asking:

1. What type of arrhythmia do I have?
2. Why is cardioversion being considered?
3. Is the electrical approach or medication more suitable?
4. What benefits are realistic for my condition?
5. What tests are needed before the procedure?
6. Do I need a TEE?
7. Do I need to take anticoagulants?
8. What are the rules for fasting and my routine medications?
9. What type of sedation will be used?
10. Do I need someone to accompany me home?
11. When can I drive and return to work?
12. What happens if the rhythm becomes irregular again?
13. Might ablation be considered?
14. Which symptoms should I report right away?
15. Who can I contact after I go home?

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Conclusion

Cardioversion is one option to help restore certain heart rhythms that are too fast or irregular. It can be performed using medication or synchronized electrical energy.

Before the procedure, the doctor needs to confirm the type of arrhythmia, review medications, and assess the risk of blood clots. In scheduled electrical cardioversion, patients usually receive sedation and are monitored before, during, and after the procedure.

The rhythm can become irregular again. For this reason, medication, follow-up visits, and further tests may still be needed. Ultimately, understanding cardioversion helps you take part in care decisions with more confidence, not by deciding on a procedure yourself, but by asking the right questions and planning the next steps together with your doctor.