The principle of the method of trans-catheter ablation consists of positioning a probe at the level of critical areas for pathological circuit and delivered energy through the probe, which can create a smooth scar, capable of interrupting the circuit. Trans-catheter radiofrequency current ablation involves the application of a current of radiofrequency (RF) catheter through a probe, in order to create a focal, discrete, uniform lesion at the level of cardiac tissue (later scars), able to interrupt the paths necessary to maintain the pathological circuit.
In the emitted frequency range used (between 300-3000kHz), their application at the level of tissue via a catheter cause a localized heating at the point of contact between the wire extremity (distal electrode) and target tissue.
This local heating, which ideally should be between 60 and 90 degrees to cause a burn injury, small in size with an ovoid form which subsequently evolves to a well-defined fibrous scar.
These scars are created in areas considered responsible for the genesis or for maintenance of cardiac rhythm disorders. Once scar is formed, the rhythm disorder is permanently stopped.
Radiofrequency current is delivered by a generator that is consisted of several screens that allow tracking of electric and thermal constants during application of electric current. This generator is equipped with safety systems that stop the current administration if the parameters exceed critical established values .
Used catheters (one that generates electricity, others are used to locate the region responsible for the rhythm disorder) are introduced through the percutaneous way under local anesthesia. Their introduction is made by the peripheral vessel usually the femoral vein. Subsequently are routed up, inside the cavities of the heart under control.
Heart rhythm disorders that can be treated with radiofrequency ablation
Currently, only certain rhythm disorders can benefit from this treatment. The intervention results and difficulties depend on the mechanism of the heart rhythm disorder.
1. In certain arrhythmias, the lesion induced by applying radiofrequency current corresponds to the critical area responsible for tachycardia. In this case the results are generally good (> 90% success) and can be obtained with a limited number of shootings of current (ideally one) because the responsible area for inducing the arrhythmia can be identified with high accuracy. These are:
Atrioventricular junction ablation (area between the atria and the ventricles), which subsequently require implantation of a pacemaker.
Ablation of a slow path from the atrioventricular node (path that underlies tachyarrhythmia by nodal reentrant).
Ablation of one or more accessory atrioventricular pathways that underlie arrhythmias in Sd. Wolf-Parkinson-White.
Ablation of an atrial hyper-excitability center.
2. In other cases tachycardia is based on a compulsory passing circuit through a certain narrowed area that once ablated it stops the arrhythmia. The objective is to create a block area, a dam, and thus tachycardia, is blocked.
Atrial flutter with a success rates of > 90% if the block line created is complete.
Some ventricular tachycardias where the success rate is lower because it is about complex circuits.
3. Finally radiofrequency by ablation of atrial fibrillation is increasingly used but is still in the evaluation stage.
During the procedure the patient is lying on the bed, in a room specially equipped for such procedures, equipped with radioisotope. The procedure is performed by a team of cardiologists specialized in electrophysiology using a team of nurses.
Basically the procedure is performed under local anesthesia at the site of puncture of the vessel, usually at the root of thigh.
The exam is not painful, but applying radiofrequency current can be accompanied by a slight burning sensation to the chest.
Length of the procedure depends on complexity of the tachycardia, anatomical conditions, and the teams’ experience. Generally a procedure does not exceed more than 90 minutes.
To prevent bleeding at the place of puncture is done a compression bandage.
The duration of hospitalization is generally short, between 1 and 3 days.
Complications and Risks
Hematoma at the puncture site;
Transient chest pain;
More severe complications but fortunately rare (2-3%): the occurrence of pericardial fluid which may require urgent drainage, atrioventricular blocks that may require implantation of a pacemaker, heart rhythm disturbances, embolic stroke by forming blood clots in the heart of the pore migration.