What is Cardioversion?
Cardioversion is a procedure used to treat abnormal and rapid heart rhythms known as cardiac arrhythmias. Cardioversion is most commonly used for atrial fibrillation.
Cardioversion delivers an electrical ‘shock’ to the heart to restore the heart to its normal rate and rhythm.
The energy delivered can be given in one of two ways. The electrical energy can be delivered externally with the use of electrodes attached to the chest, or directly to the heart with the use of paddles to the heart during open heart surgery.
An alternative mode of delivery is by the use of a permanent implantable device known as an implantable cardioverter defibrillator (ICD).
How does a normal heart beat?
Heart muscle cells are activated by electrical impulses that cause them to contract regularly and in sync. This contraction produces a heartbeat, allowing blood to be pumped out to the entire body.
Electrical impulses originate from specialized cells called the sinoatrial (SA) node, which is the hearts natural pacemaker. The SA node is located in the upper right chamber of the heart, the right atrium. From the SA node, the impulse spreads across the upper chambers of the heart to reach the atrial ventricular (AV) node located between the atria and lower ventricles. After leaving the AV node, impulses spread across the pumping chambers of the heart, the ventricles. As impulses are spread along the heart, the cardiac muscle cells are stimulated to contract, producing a heartbeat.
What is an arrhythmia?
During a rapid cardiac arrhythmia, an abnormal electrical mechanism overrides the action of the sinoatrial node. Some arrhythmias start in the atria, while others are produced by the ventricles.
Sometimes, cardiac tissue can form an electrical loop or short-circuit. If the hearts electrical energy goes through this loop, it will cycle over and over again, repeating itself indefinitely causing a re-entrant loop. Each loop through this cycle causes the heart to contract.
Arrhythmias occurring by a re-entrant loop are usually regular, organized, and can be treated with cardioversion. Atrial flutter and ventricular tachycardia are examples of organized arrhythmias. Rapid, disorganized, chaotic arrhythmias include atrial fibrillation.
Cardioversion involves a high energy shock to the heart muscle which activates all of the cardiac muscle and conduction tissue simultaneously. This interrupts and breaks the re-entrant loop ceasing the arrhythmia, triggering the sinoatrial node to fire again and restoring a normal heart rhythm.
What to do before the procedure?
Prior to a cardioversion, if not already on anticoagulation therapy, your physician will determine your risk of blood clot formation and choose an anticoagulant medicine (i.e. Coumadin) to prevent the risk of stroke or heart attack.
Arrive at least one hour before your procedure to allow for prep time.
Make arrangements to have someone drive you to and from the clinic. You will not be permitted to drive after the procedure.
What happens during the procedure?
An external cardioversion is common and is performed in a specially equipped procedure room in our office.
The patient’s heart rate and rhythm, blood pressure, breathing rate, and oxygen levels are monitored.
An I.V. medication is given to sedate the patient to avoid any pain for when the shock is given. Patients will be asleep during the cardioversion and most will not recollect the procedure.
Two pads will be applied to the skin. One pad will be placed near the breast bone and the second pad on the back, under the left shoulder blade.
After the patient is sedated, the doctor will deliver the shock given through these pads.
The cardioversion itself only takes a few seconds.
The patient usually wakes up within 5 to 10 minutes.
What happens after the procedure?
The patient will be monitored for at least one hour after the procedure.
You may also be required to wear a Holter monitor for 24 hours to monitor the electrical activity of the heart after the procedure.
What are the benefits?
The benefits of cardioversion include:
· The return of normal heart rhythm
· Improvement of the heart’s ability to effectively pump blood
· Decrease symptoms including palpitations, chest pain, light headedness, difficulty breathing etc.
· Decrease the risk of clot formation in the heart
What are the complications?
Several complications can occur with cardioversion. These include:
· Provocation of other arrhythmias or heart block
· Myocardial necrosis
· Skin burns