[Application of endocavitary mapping to the study of auricular flutter]

Many in vitro and animal experimental studies seem to support the hypothesis of reentry as the physiopathological mechanism of atrial flutter. Clinically, these studies are much more difficult because of problems in determining the different sequences of atrial depolarisation. In this study, the authors attempted to improve the technique of endocavitary atrial mapping. Three or four multi-recording electrodes were positioned in the atria using biplane 30 degrees RAO and 60 degrees LAO incidences. Right atrial angiocardiography showed up the atrial borders and enabled the recording catheters to be more accurately positioned. Thirty to 47 recordings points were thereby determined within the atrial cavities, the left atrium being studied via the coronary sinus, right pulmonary artery, patent foramen ovale or by the endooesophageal approach. This method of spatial orientation of the catheters associated with recording of the endocavitary potentials allowed the construction of an isochronic map of atrial depolarisation, which was then analysed for each case of flutter. The study confirmed two hypotheses: the asynchronism of right and left atrial depolarisation, and the circus motion of depolarisation. Three types of flutter were observed: --The first two types were similar with cirus motion within the right atrium. The wave front ascended in part or all of the septum and descended in the external free wall of the right atrium. There was a transitional zone, possibly reentrant, in the groove located anterior to the inferior vena cava. --The third type of flutter was atypical and was associated with cirus motion in the left atrium. Two transitional zones, similar to those encountered in the right atrium, were detected in one patient between the orifices of the pulmonary veins, and, in another patient, on the anterior part of the roof of the left atrium. These transitional zones seem to be at the basis of the physiopathological mechanism of flutter. Unfortunately, their small size makes their analysis by endocavitary mapping difficult.