What is it about ?
The heart consists of a left atrium, a right atrium, a left ventricle, and a right ventricle. These cavities are separated by partitions. Blood enters the heart through the atria. The ventricles eject blood into the body.
There are two phases in the movement of the heart: the contraction phase (systole) during which the heart ejects blood to the body, and the relaxation phase (diastole) during which the heart relaxes and fills with blood.
The heart works autonomously, that is, it beats without intervention on our part. The heart muscle (myocardium) contracts under the effect of an electrical stimulation (stimulus). This stimulus is created in a node of nerves called the sinus node, located in the heart wall of the right atrium. This sinus node is the natural pacemaker. From the sinus node, current travels to the heart muscle through a special electrical conduction system. Thus, the electrical impulses pass through the entire myocardium. These impulses stimulate this muscle, which contracts.
Normally, this is done on a regular basis, at a rate of between 60 and 100 beats per minute (rhythm or heart rate) while resting. The heart rate increases with effort.
Sometimes electric current is produced irregularly and far too quickly in the atrium. This is called a atrial fibrillation. In this case, the rate at which the ventricle pumps also becomes irregular. This rhythm disorder can be dangerous: the risk of blood clots increases and sometimes the heart beats so fast that it no longer performs its pump function and leads to sudden death.
Electrical cardioversion is a technique whereby a defibrillator is used to deliver an electric shock to the muscle of the heart and thereby put an end to heart rhythm disturbances. It is literally resetting the electrical system of the heart. The chances of restoring a normal heart rhythm depend on person to person. The chances of success are determined by the following factors:
- age: the younger the person, the greater the chances of success;
- the absence of other heart problems;
- recent onset of arrhythmia: a few weeks or a few months at most.
Electrical cardioversion is usually performed in the hospital, under short-term general anesthesia, after a preparation period during which treatment with drugs has been prescribed. It is applied for heart rhythm disorders such as atrial fibrillation and atrial flutter.
Cardioversion is a safe procedure but, as with any procedure, complications can occur:
- a heart rhythm disorder can trigger blood clots. When your heart beats at a normal rate again, this clot can be washed away with the blood and, in some cases, cause cerebral thrombosis (Stroke). To avoid this complication, the person will be given anticoagulants for 4 to 6 weeks before cardioversion.
- electroshock therapy may cause redness and a burning sensation on the skin at the administration site, resembling sunburn.
How does the preparation go?
The doctor prescribes you anticoagulants, which you must take very strictly for 4 to 6 weeks before the procedure. If the doctor is not sure that the blood is flowing enough, he or she can check the heart for clots using a transesophageal ultrasound. Shortly before the operation, a blood test and a electrocardiogram (ECG) are carried out. You discuss, in consultation with the general practitioner and / or the specialist (cardiologist), the medicines that you can continue to take.
You must be on an empty stomach for cardioversion. This means that you are no longer allowed to smoke, drink or eat for at least 6 hours before the procedure. However, with your doctor’s consent, you can take your medicine with a very small amount of liquid up to 2 hours before cardioversion.
How does cardioversion work?
You are given an IV. An ECG monitor is set up to monitor your heart rate using electrodes. Your blood pressure is measured.
The anesthetist puts you to sleep by giving you medicine through the infusion. You will sleep throughout the procedure, then wake up after 5 to 10 minutes.
During anesthesia, an electric shock is administered. After a first attempt without effect, the amount of energy per electric shock is increased. Sometimes the heart rate normalizes for a few beats, but then becomes abnormal again. In this case, a new attempt is made with the same amount of energy. In general, 3 to 5 attempts are sufficient to regain a normal rhythm.
After the procedure, your blood pressure and heart rate will be monitored and, if necessary, you will be given fluids and medicines through the infusion to bring your blood pressure back up. The anesthesia required for the procedure usually has no unpleasant side effects afterwards.
What happens if cardioversion fails?
If the electrical conversion fails, the doctor often decides to accept the arrhythmia, such as atrial fibrillation, and just make sure that it is well ‘supported’. To do this, he usually uses drugs that slow down the heart rate to a reasonable rate. In this case, he will also take care to avoid the formation of clots by prescribing anti coagulants.
If it is still necessary to restore the heartbeat, a new electrical cardioversion may be tried after you have been on treatment for some time with medicines to normalize the heartbeat. Sometimes intracardiac cardioversion may be an option. The procedure consists of inserting an electrode at the level of the groin and sliding it to the heart to directly deliver an electroshock.
Another option is ablation. To do this, the doctor will insert a catheter in the groin and slide it through to the heart. Once there, it will destroy, by the application of heat or cold, the heart tissue which poorly transmits electrical stimulation. This forms a scar, preventing the electrical stimulus from passing through. In total, the treatment lasts between 2 and 4 hours. The chances of success vary depending on the condition and the individual, but on average, arrhythmias go away in 7 to 8 out of 10 people.
What does the follow-up consist of?
After electrical cardioversion, you should be observed in the hospital for at least 4 hours. You will have to wait 2 hours before you can eat and walk.
You cannot drive a vehicle, use machines or drink alcohol for 24 hours after the procedure. It is advisable to have someone accompany you on the day of the operation.
If the procedure is successful, the use of anticoagulants is continued for at least 4 weeks, but sometimes also for life. The general practitioner and the cardiologist will give you the necessary advice on this matter.
Want to know more?
- Cardioversion (video) – Erasme Hospital
- Transesophageal cardiac echo – Erasme Hospital
- Electrophysiological study and ablation, here, Where to find on this page of Cliniques St Luc UCL
Source