They can now be treated with targeted radiotherapy. Explanations from the co-director of the first interventions in France.
Paris Match. What are severe ventricular tachycardias and what are their causes?
Doctor Xavier Mirabel. We speak of ventricular tachycardia when more than three ventricular extrasystoles (ESV) follow one another. An ESV is a premature beat of the ventricles that is inserted between two normal beats. This is a mild, commonplace, frequent arrhythmia that all healthy hearts occasionally produce. Ventricular tachycardias (VT) can occur on the latter (10% of cases) or on hearts that are already diseased (90% of cases). They can cause instability of the circulatory state and turn into ventricular fibrillation with sudden death: this risk is low when the heart is healthy and very high when it is pathological. The patients most at risk are those who are refractory to all standard treatments, and in whom several VT per day are triggered. Their vital prognosis is then threatened. They usually carry an implantable defibrillator that delivers an electric shock with each attack. It is these patients that this new technique is primarily intended for.
What is the usual support for bass TV?
Antiarrhythmic drugs have limited effectiveness in preventing recurrent VT. In this situation, the reference technique is endocavity ablation by radiofrequency. It consists in getting into the heart, from the femoral vessels, probes which, in the ventricles, will burn by ultrasound the foci that emit arrhythmias. Effective in healthy heart VTs (coronary arteries and valves free from significant lesions), this method is less effective in other forms, with, in addition, a rate of possible complications (5 to 10%) related to this procedure ( long and complex) and failures in a third of cases.
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This technique permanently destroys the focus that caused the dysfunction, and nothing else
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What is the principle of the new process?
The Cyberknife is a robotic device with an on-board X-ray system. It includes three tubes: two which observe and locate the target to position the third tube, a photon accelerator whose firing precision, much greater than the radiofrequency, is infra-millimeter (0.1 mm). This targeted radiotherapy administers, externally and non-invasively, a strong dose of radiation that destroys the focus that causes VT, and nothing else. This results in intense tissue sclerosis which, by reshaping the critical area, permanently extinguishes it.
What does the protocol at the Lille University Hospital consist of?
Patients are referred to the Heart Lung Institute to Dr Sandro Ninni, in the service of Professor Didier Klug. Cardiologists first carry out, in the catheterization room, by endocavitary electrical stimulation, a mapping that locates the TV-emitting focus (s), in the form of computerized images. They are then superimposed on those of a scanner producing 3D images of the heart, then transferred to the Cyberknife imaging system. The latter integrates all the useful parameters, the target zone and the dose to be delivered. The radiotherapy session is held at the Oscar-Lambret center and lasts 30 to 90 minutes. One session is enough. It takes into account in real time the movements of the heart and respiration, the coronary arteries and the healthy areas to be respected.
Also read.Cardiac arrhythmia: a tailor-made technique
What are the results ?
We treated eight patients with VT and refractory to any treatment. These are the first French cases: TVs have disappeared in six of them and have been greatly reduced in the other two. Our results are in line with those of the pioneering team of this technique (in Saint-Louis, United States), which treated 19 patients. Several expert hospital centers are now interested in it.
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