[Idiopathic dilatation of the atria: a syndrome? Description of a case of idiopathic biatrial dilatation, review of the literature and a proposal for a pathogenetic interpretation].

Idiopathic severe dilatation of bilateral atrial and urethero-pelvic systems was found in a 53-year-old woman. Degeneration of muscle fibers without inflammation is a constant feature of idiopathic atrial enlargement. Degenerative process can extensively involve atrial wall (generalized dilatation) or can be localized (aneurysmal dilatation). In both types of lesion clinical features are related to atrial arrhythmias and to compression on atrio-ventricular valves and ventricles by the enlarged atria. Only the outcome of the atrial arrhythmias can help to distinguish between the two conditions: development of irreversible atrial standstill in generalized dilatation and definitive restoration of sinus rhythm, following surgery, in aneurysmal dilatation. In each atrium, a different rate of incidence of the two types of dilatation has been documented in the literature: as for the right atrium, more than 40 cases of generalized dilatation have been reported and only 4 of the aneurysmal type. On the other hand, isolated left atrial enlargement was of aneurysmal type in all 30 reported cases. Biatrial dilatation was generalized in 7 cases and due to multiple aneurysms in a single case. The Authors support the hypothesis that idiopathic atrial dilatation could be due to a degenerative process affecting the atrial components derived from primitive atria, in which the muscular layer is structured into pectinate muscles. They also suggest to distinguish, even from the etiopathogenetic point of view, between aneurysmal dilatation (localized and fortuitous lesion) and generalized dilatation (diffuse degeneration of pectinate muscles). This distinction could well related with the different outcome of atrial arrhythmia in the two types of dilatation.(ABSTRACT TRUNCATED AT 250 WORDS)