Ablation: Minimally Invasive Procedures for Cardiac Arrhythmias

What is Cardiac Ablation?

Ablation is a minimally invasive procedure used to treat cardiac arrhythmias. It uses various methods to eliminate the cells responsible for the abnormal heart rhythm. During ablation, small pieces of heart tissue responsible for generating the currents that trigger the arrhythmia are burned. It is performed by inserting a catheter (a thin, flexible tube) into a peripheral blood vessel and guiding it to the heart.

Cardiac ablation treats certain types of arrhythmias and reduces symptoms caused by abnormal heart rhythms, such as dyspnea, fatigue, asthenia, and weakness, when these are disabling and resistant to drug treatment.

Due in part to the lack of effectiveness of drug treatments in treating certain forms of arrhythmia (such as atrial fibrillation), the number of cardiac ablation procedures has increased worldwide in recent years.

More generally, ablation is an operation during which small, limited portions of tissue are removed using heat or other energy sources. Ablation for the removal of certain types of tumors, a minimally invasive procedure widely used in oncology, is one example.

When does a doctor use ablation?

Ablation is mainly used to treat certain types of arrhythmias (particularly supraventricular), for which it is the first-line treatment:

• Paroxysmal tachycardia related to intranodal reentry. This is a frequent condition, even in healthy individuals, with a low risk of serious consequences but correlated with a low quality of life due to the frequency and duration of episodes or the need for chronic pharmacological treatment.
• Wolff-Parkinson-White syndrome. Compared to paroxysmal tachycardia related to intranodal reentry, an additional conduction pathway (Bundle of Kent) is involved;
• Incessant tachycardia with reduced cardiac contractility.
• Treatment of disabling cardiac arrhythmias associated with heart failure, when drug treatment is insufficient (this is then a second-line treatment) to control symptoms or prevent serious consequences, such as cardiac arrest, the worst risk associated with ventricular fibrillation.

What are the different types of cardiac ablation?

Radiofrequency Ablation

Radiofrequency ablation transforms radio waves into heat and leads to the neutralization of abnormal currents by creating micro-burns in the tissues. It's a kind of electrocautery. It is performed using a transvenous catheter supplied with low-voltage, high-frequency (300 to 750 MHz) radiofrequency electrical energy. The energy heats the cells and causes their necrosis. The treated area is less than 1 cm in diameter and is located up to 1 cm deep.

Cryoablation

This result is obtained through cooling, by circulating a refrigerant (which can reach -70°C) inside the catheter, which freezes and destroys the cells located at the entrance of the pulmonary veins, thus preventing them from interfering with the normal heart rhythm. During freezing, the destroyed tissues remain attached to the catheter, making the device more stable. Ice produced by nitric oxide is generally used as an energy source.

Laser Ablation

This is a cutting-edge method based on the use of laser technology, which is largely similar to thermoablation.

Laser Ablation of the Saphenous Vein

Endovascular thermal laser ablation is a minimally invasive technique that destroys the pathological vessel from the inside, thanks to the thermal energy emitted by the laser fiber. It can be performed for the treatment of pathologies of the great saphenous vein, the small saphenous vein, or perforating vessels.

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Ablation for Atrial Fibrillation

Atrial fibrillation can be caused by a series of abnormal currents that circulate from the large pulmonary vessels to the heart, altering its rhythm. This is why, in some cases, an ablation procedure is used.

In this form of arrhythmia, electrophysiological study is conducted on the left side of the heart, inside the left atrium, along the outflow of the pulmonary veins, to understand the location and electrical characteristics of the target areas.

In preparation for the operation, the patient undergoes a transesophageal echocardiogram to rule out the presence of thrombi in the heart and coronary arteries. This would be an absolute contraindication to the ablative procedure.

At the end of their hospitalization, a transthoracic echocardiogram is generally performed.  

In other cases, when atrial fibrillation is associated with a high ventricular response, ablation is performed on the atrioventricular node, which is ablated after being replaced by the implantation of a permanent pacemaker.

Cardiac Ablation in Children

The most common arrhythmia in children, nodal reentrant tachycardia, can be treated effectively and safely by ablation. As in adults, radiofrequency ablation or cryoablation is used to treat this condition.

For the treatment of certain forms of epilepsy due to hypothalamic hamartoma in pediatric patients, stereotactic laser thermoablation procedures guided by magnetic resonance imaging have been performed. The method consists of a minimally invasive surgical procedure during which a micro-hole is drilled in the skull, through which a laser probe is implanted in the hamartoma, necessary to perform the thermoablation. This procedure allows precise action only on the lesion while respecting the integrity of the surrounding brain structures.

What are the risks of cardiac ablation?

Ablation is a relatively safe but complex procedure that requires good operator training.

Serious risks are less than 1% when performed in a specialized center by experienced professionals. Mortality is less than one patient in 2,000 for uncomplicated ablation procedures and can reach one in 500 for pulmonary vein isolation procedures in case of atrial fibrillation or ablation of the substrate of ventricular tachycardia.

Some of the consequences associated with this practice are linked to anatomical variations of the heart, which do not constitute a disease in themselves, but which can increase the risk of procedural error. The presence of conditions such as diabetes and kidney disease, as well as a history of stroke or heart attack, can increase the risk of complications during the ablation procedure.