Cardiac rhythm disorders

Cardiac fibrillation is the most complex of the pathologies associated with cardiac rhythm. It results in the rapid and disorganised contraction of the area of the heart in which it occurs. Atrial fibrillation which occurs in the auricle, affects 1% of the population and is the principle cause of embolic cerebrovascular accidents. As for ventricular fibrillation – which as its name suggests occurs in the ventricles – it is behind the great majority (> 80 %) of cases of sudden death in adults, affecting 350’000 persons, young and old, every year in Europe.

Since the early 80’s, it was thought that these disorders were linked with multiple fibrillating wavelets propagating in a chaotic manner, thus maintaining the disturbance in the cardiac rhythm and rendering it uncontrollable. Drug treatments against these arrhythmias did exist, but they were no more than moderately effective. Michel Haïssaguerre and his team have studied the genesis of these two pathologies and their work has resulted in the development of a curative treatment that is widely used against atrial fibrillation.

The origin of atrial fibrillation

By tirelessly and meticulously mapping the hearts of patients suffering from atrial fibrillation, Michel Haïssaguerre and his team showed that disorder did not originate in the heart muscle, as had been thought for a long time, but outside the heart in the cells situated in external wall of the pulmonary veins.

This discovery has since been confirmed in numerous studies around the world, involving both normal hearts and hearts exhibiting pathologies, under varying conditions. These various studies have also described the properties of the cells involved and demonstrated their ability to generate ultra-rapid discharges (400 per minute) which act as «triggers».

The observations made by Michel Haïssaguerre and his team have led to the development of a curative therapy involving the ablation of the cells causing atrial fibrillation, using cryotherapy or ultrasounds. Having been validated by scientific societies, this treatment is now applied on 150’000 patients every year, and the number of cases thus managed is growing constantly.

Nowadays a technical innovation is used to facilitate the operation, namely remote-controlled magnetic navigation (RMN). Using large magnets, RMN permits catheters to be remotely tracked and piloted by computers. Michel Haïssaguerre was the first to use this technology in France.

This diagram illustrates the continuous movement of fibrillating wavelets in the auricles of the heart. These wavelets are not the cause (as had been previously thought) but rather the consequence of external stimuli (*) originating in the pulmonary veins.

Ventricular fibrillation

Michel Haïssaguerre and his team adopted this same original approach (searching for the origins / “triggers”) to look for the causes of ventricular fibrillation. In this case however, the heart mapping technique was more difficult due to the instantaneous nature of the disorder, which calls for immediate defibrillation of the patient using electric shocks, meaning that the researchers had no more than a few seconds to map the heart. The cardiologist and his team nonetheless managed to observe that these «electrical tornados» emanated from the tissue known as «de Purkinje», which only accounts for the tiniest fraction (2%) of the cardiac mass.

This finding was further confirmed by Michel Haïssaguerre and his team. With some of the patients and using thermoablation focused on this tissue, they succeeded in totally eliminating their arrhythmias. The first operations of this nature took place eight years ago and the patients involved have suffered no relapses, thus lending some credence to the concept.

The impossibility of creating more elaborate maps obliges researchers to fall back on experimental and theoretical studies (modelling) of this most serious condition, in order to better understand the properties of the «de Purkinje» tissue, its interactions with the myocardial contractile function and to envisage means of screening and treating the general public for sudden death. The funds made available by the Louis-Jeantet Prize for Medicine will be used for equipping the experimental laboratory for electrophysiology and modelling.

Ventricular fibrillation causes an extremely fast cardiac rhythm resulting in the death of the affected person in a few minutes.

The research conducted by Michel Haïssaguerre and his team is interesting from a conceptual standpoint as it demonstrates that apparently highly complex phenomena deriving from chaos theory may have discreet sources. It has opened the way to treating atrial fibrillation and brought considerable hope for the treatment of extremely serious arrhythmias leading to sudden death.

Professeur Michel Haissaguerre
Hôpital Cardiologique du Haut-Lévêque
Avenue de Magellan
F-33604 PESSAC Cedex

Tel.: + 33 (0)5 57 65 64 71 (PA direct line)
Tel.: + 33 (0)5 57 65 64 01 (Service)
Fax : + 33 (0)5 57 65 65 09

laurence.bayle@chu-bordeaux.fr