Pacemaker et radiofréquence

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Home > For Patients > Everything you need to know about radiofrequency

Everything you need to know about radiofrequency

The goal of interventional catheterism through radiofrequency (RF) is to destroy an "arythmogène" substrate, which enables to permanently cure the patient. It is effective in 90 to 100% of the cases and complications are rare. Sometimes, the substrate is only modified and arrhythmia becomes more sensitive to antiarrythmics. Most cardiac arrhythmias can be treated through this technique but applying it to atrial fibrillation is not yet widespread practice. The intervention takes place under local anesthesia, very rarely under general anesthesia. The energy of the RF current acts through thermic/thermal effect. It is conveyed thanks to big surface electrodes, which are adjustable and single-use, placed through intraveinous or retrograde arterial injection according to the type of arrhythmia. The session includes a stage of diagnosis when we determine how the tachycardia works, a stage of ablation per se with a precise radioscopic and electrophysiologic location of the arythmogène substrate followed by RF shots. The last stage consists in checking the efficiency of the ablation 30 to 60 minutes after the last shot using some molecules such as triphosphate adenosine and/or isoprenaline. Post-surgery continuous ECG monitoring lasts 24 hours and hospitalization less than a week. An aspirin treatment of a few weeks is recommended. Radiofrequency enables to destroy cardiac tissue zones which are implicated in the tachycardia circuit. Radiofrequency is an alternative current identical to that used in electrical bistouries. The energy is conveyed to the heart thanks to electrodes set through the veinous and/or arterial tract. This technique started being applied clinically in the beginning of the 90s.

RF acts through thermal/thermic effect. The energy used is an alternative current of 300 to 3000 kHz, close to that of electrical bistouries. This energy is conveyed to the heart through electrodes. The single-use electrodes are set through the veinous or retrograde arterial tract through the desilet technique. Their orientation and curve can be adapted thanks to mechanical systems which thus facilitate their positioning. The energy is transmitted between the RF electrode and a plaque located in the scapulo-humeral zone. The active tip of the catheter is 4 or 8 mm long (active surface of 25mm2). Before the shot, the target parameters are determined: the temperature of the electrode, the duration/length of the shot, the maximal strength/power. In case of brutal impedance elevation, marking the possibility that a thrombus has formed, the modern systems automatically interrupt the shot. The size of the lesions varies from 80 to 800 mm3.

The intervention takes place in an operating room with a nurse ± an anesthetic-nurse. Most often there is no need for a general anesthesia.

The electrodes are carried to the level of the heart by the operator/surgeon who/which has already punctured the veins and, if need be, the femoral artery. He/it guides the electrodes up to the to the zone which must be destroyed, led at the same time by the electrical signals which are registered at the level of the heart and by the radioscopy since the electrodes are opaque to X-rays.

Another operator/surgeon follows the electrical signals, carries out the manipulations necessary to the triggering and the checking/stop of the tachycardia that needs to be treated.

To carry out an ablation you need an electrophysiologist physician who fulfils the training criteria of the Société Française de Cardiologie (SFC) recommendations. After the vascular punctures under local anesthesia, the various electrodes are positioned, guided by the radioscopy and the endocavitarian signals. Those electrodes enable the electrophysiological study of the arythmogène substrate and the RF electrode which will destroy it. The stability of the electrode during the shooting is essential and is ascertained by careful radioscopic monitoring. The electrophysiological study includes a precise diagnosis of how the arrhythmia works. It often requires the triggering of programmed/ set atrial or ventricular stimulation of the tachycardia which needs to be treated. The conduction and excitability properties of the various cardiac structures before the shot are also determined. We precisely determine the electrophysiological location of the tissue zone which has to be destroyed. During the shot, we need to be extremely vigilant. Indeed, if complications arise, mainly in the auriculo-ventricular block in case of ablation of the "voie lente" or certain secondary para-septal beams, it twill be automatically stopped. To finish, we carry out electrophysiological and often pharmacological tests (triphostate adenosine and isoprenaline) so as to check the efficiency of the process at least 30 mn after the last shot. The technical and diagnostic difficulties depend on the indication of an ablation and certain processes require two electrophysiologists. Nowadays, there are some systems for endocavitarian cartography which enable us not to use X-rays. However, these systems are used mainly in complex arrhythmias such as atrial tachycardia after heart surgery and some ventricular tachycardia. Since some RF shots can be painful, they sometimes require a small anesthesia. This is dealt with by a nurse and/or the anesthesiologist. In very rare cases, a general anesthesia is necessary when the passage in atrial fibrillation requires an external electric shock or when the process is long, difficult and hard to bear.

A pre-surgery heparinotherapy "par bolus of 5000Ul"or a continuous one with an electrical syringe enables to prevent thromboembolic accidents. Oral anticoagulants will be replaced by heparin beforehand.

The rhythmology group of the Société Française de Cardiologie has issued some recommendations.

Important progress has been made over the past few years not only in the understanding of the mechanisms/workings of rhythm disorders but also in their invasive treatment through radiofrequency ablation. This treatment enables the permanent treatment of patients on whom medication had only a palliative effect. Those patients, until then, were not safe from new recurrences and repeated hospitalizations.

RF electrodes are orientable on every plane thanks to wheels, so that it can be positioned anywhere in the heart. They are expensive and single-use. The choice of a catheter depends on the indication of an ablation and the size of the cardiac cavities. Some tachycardias require the minute destruction of a small tissular zone. That is the case through the slow tract, the HIS beam, of the right branch in the VT by branch to branch entering or secondary beam. The efficiency must be obtained with as few shots as possible. Here, we will use 4mm electrodes. Other ablations require, on the contrary, the destruction of the most important zone. That is the case of the atrial flutter, the principle of which is to create an RF line between the inferior vena cava and the triscupidian ring and the majority of VT on cardiopathy.

The shots are more numerous with the need to progressively relocate the catheter so as to make a real linear lesion. We will preferably use 8 mm electrodes in that situation. The use, in those types of indications, of 4mm catheters irrigated by physiological serum enables to increase the size and depth of the lesions. Their efficiency seems greater than that of 8 mm electrodes. Some deep secondary tracts rarely require this technique. The electrodes have adaptable curves, the choice of which depends mainly on the ablation indication and the anatomical data.

Most tachycardia can be treated with this method but the most frequent arrhythmia, atrial fibrillation, which is a real issue of public health, is harder to cure through this technique. For this pathology, RF was only a dream not more than a few months ago. But, if recent research publications are anything to go by, it is becoming more and more a reality, even though we can't offer its use on a daily basis.

Most arrhythmias are curable through RF:
- the atrio-ventricular junction or, more commonly, the HIS beam, when the medical treatment doesn't control the ventricular frequency of a permanent atrial fibrillation or the recurrences of paroxystic fibrillation,
- the atrial flutters as well as the reentering or ectopic atrial tachycardia,
- the tachycardia by intra-nodal reentry through ablation of the slow tract,
- the ventricular preexcitations with Kent beams in the Wolf-Parkinsome-White syndrome and the Mahaim beams,
- the ventricular tachycardia with branch to branch reentries of dilated cardiomyophaties, the VT on right ventricular dysplasia, the VT of ischemic cardiopathies, the fascicular VT and the benign infundibular VT,
- the inappropriate sinusal tachycardia and the benign ventricular extrasystoles/premature beat when they resist medical treatment and when they are very symptomatic,
- and finally, more and more often, but it is not yet a widespread practice, the atrial fibrillation through isolation of the pulmonary veins where the extrasystoles which start arrhythmia originate.

Informing the patient is fundamental. Those practical methods of RF ablation will be explained in detail to the patient, insisting on the good results of this technique without forgetting the rare but sometimes serious complications however. Hemopericardium should be mentioned because it can sometimes require surgery, as well as the auriculo-ventricular block for some indications which can lead to the implantation of a pacemaker, and thrombo-embolic accidents. Less serious complications should not be omitted, in particular haematomas at the puncture points which can be prevented with adapted compression after the equipment is taken out. You might be given informative cards destined to the patients, published by the SFC. We will warn the patient about palpitations caused by the trigerring of the tachycardia which is to be treated and unpleasant effects of certain drugs injected during the process such as ATP isoprenaline. The duration of the process varies but it lasts on average one to two hours.

After the process, you are monitored in ICUor through an ECG telemetric monitoring system during 24h. The hospitalization lasts between 4 to 7 days on average.

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