[What is a practical approach to atrial extrasystole?].
Atrial premature beats are caused by premature and abnormal depolarization of the atria, responsible for an anticipated QRS complex. Usually, the shape of this complex is identical to that of sinus beats. The diagnosis is made by electrocardiography, but it may meet with problems due to lack of recognition of premature P waves (and the more so as these may not give a ventricular response) or to the deformation of the QRS complex by a bundle branch block mimicking a ventricular premature beat. As in all instances, premature atrial beats are generally followed by a pause. Atrial premature beats, isolated in most cases, may trigger off supraventricular tachycardia episodes of varying duration. The clinical expression of atrial premature beats ranges from perceptible palpitations to complete latency. The decision to treat is determined by the functional repercussions of the disorder. Supplementary data are always useful to evaluate the significance of the disorder. Using the Holter recording system makes it possible to count the premature beats over a 24 h period, to find out whether they are preponderant in day time (suggesting an adrenergic factor) or at night (suggesting vagotonic disorders), and to identify bouts of atrial fibrillation that would have not been felt. Investigations for an underlying heart disease are mandatory. Any one of the cardiopathies of adulthood, and notably mitral valve lesions, may be encountered, as well as congenital heart diseases such as interatrial communication. The frequency of atrial premature beats tends to increase as cardiac failure develops, and its course can be made worse by some drugs (such as digitalis compounds) or by metabolic disorders (e.g. hypokaliaemia). However, there are many cases where no cardiopathy is detected. Within the group of isolated atrial premature beats, disorders found in athletes (in theory manifestations of hypervagotonia) can be individualized. In practice, therapeutic abstention is the rule, especially when premature beats are latent. In cases with poor functional tolerance, nervous sedatives of beta-blockers may be useful. Antiarrhythmic drugs are rarely necessary, but they may be prescribed if episodes of paroxysmal atrial fibrillation are present.
Touboul
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Service de cardiologie, hôpital cardiovasculaire et pneumologique Louis-Pradel, Lyon.
D005117:Cardiac Complexes, Premature / Q000175:diagnosis / Q000628:therapy*; D006325:Heart Atria; D006801:Humans