Asystolie perstimulus résultant d’une hypertonie parasympathique au cours des électroconvulsivothérapies : cas clinique, brève revue de la littérature et discussion

Abstract

Electroconvulsive therapy (ECT) is most frequently indicated for episodes of melancholic depression, but is also useful in the treatment of maniac syndrome and some schizophrenia subtypes. ECT is part of the treatment of movement disorders, neuroleptic malignant syndrome and even in the treatment of severe conversions. Although the therapeutic results are excellent when used appropriately, the mortality rate is estimated between 2and 4for 100,000shocks. Despite this mortality rate, the benefit-risk ratio remains very positive and serious complications are extremely rare. ECT results in a biphasic cardiological effect: firstly a perstimulus parasympathetic hypertonia contemporary to the seizure's tonic phase, then a phase of contemporary sympathetic hypertonia during the epileptic clonic movement. We will focus on the perstimulus asystole as it is by far the most frequent. Very few cases and even less studies have been referenced in the literature; here, we present a clinical case followed by a discussion. The patient is in his fifties and has been treated for many years for a unipolar mood disorder with recurrent melancholic depressive episodes. With each new depressive episode, the clinical evolution is rapidly positive after a few sessions of ECT. Maintenance ECT was not retained due to the supra-annual periodicity of the melancholic depressive episodes and rapid recovery after electric treatment. Then, this patient developed another depressive decline in mood comparable to the previous one, despite adapted blood lithium levels associated with a new generation antidepressant treatment. According to his history, a hospitalisation was programmed to carry out a new course of ECT. Considering the short duration of the first seizures, the intensity of the stimulus was progressively increased. At 180joules, the patient presented an immediate per-stimulus asystole of 20seconds which ceased spontaneously. The specialized cardiologic consultation following the rhythmic episode was reassuring: the patient's cardiac condition remained stable. However, after discussion with the patient and his family, we decided to stop the ECT. Was this a reasonable decision? According to the literature, the patient's medical history, sex, psychiatric diagnosis, the shock parameters (level of energy applied, duration of the stimulus, number of shocks) and clinical results, are not predictive factors in the occurrence of an asystole. Concerning the ECT protocol, the vagus nerve seems less stimulated during bifrontal stimulations in opposition to unilateral stimulations. Perasystolic patients are younger and have less prior history of cardiovascular disease or ECG abnormalities. Although the patients receiving ECT are often taking several medications (antipsychotics, benzodiazepines, antidepressants, anticholinergic correctors, calcium channel blockers, loop diuretics, converting enzyme inhibitors), these drugs are not considered as facilitating asystoles. No increase in the frequency of asystole had been observed when taking an average dose psychotropic treatment allowing the continuation of an antidepressant treatment at the recommended dose. Differently, lithium is regularly stopped during the shock phase as it could -even a few days after being stopped- potentiate the effects of succinylcholine and increase the vagal tone. Succinylcholine seems to promote asystole, whilst caffeine, methohexital and trimethaphan do not. The hypersympathetic phase can be controlled by a betablocker (propranolol, esmolol, labetalol) that does not increase the prior risk of asystole. Anticholinergic premedication using atropine does not appear to be systematic and could even potentially induce tachy-dysarrhythmia. However, in the case of perstimulus asystole, most authors recommend continuing the shocks with doses of atropine around 0.4to 1mg. Vagal stimulation is preferentially central and directly linked to the electric excitation of the lateral dorsal motor nucleus of the vagus nerve. Younger patients with no cardiac history are more at risk. This could be explained by the fact that juvenile tissue conducts electricity more rapidly than senescent (the difference being probably due to the fibrosis and adipose tissue which reduce its conductive capacity). Finally, it is appropriate to question the direct therapeutic aspect of vagal stimulation which constitutes an experimental treatment of resistant depression. The occurrence of perstimulus asystole is not considered as a serious complication of ECT and therefore as a contra-indication to any future sessions. On the contrary, most authors are campaigning for the continuation of shocks with the possibility of adding prophylactic intravenous atropine. Cardiac arrest reminds us that ECT requires a special attention to its cardiovascular effect, which emphasizes the role of interdisciplinarity between anaesthesiologists and psychiatrists.