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A 63 year old man with ischemic heart disease underwent two sessions of catheter ablation in the inferior right atrium for poorly tolerated resistant and recurrent atrial flutter. After endocavitary mapping and comparison with surface recordings of the f waves, a shock of 50 joules was delivered to the zone situated anteriorly to the inferior vena cava, under the orifice of the coronary sinus and behind the tricuspid valve. Early recurrence of the arrhythmia led to a second attempt and another 50 joules shock was administered to the same area. Another short term recurrence led to definitive nodohisian interruption with a 270 joules shock. Thirty months later, the patient died suddenly during an episode of cardiac failure. Macroscopic examination of the right atrium showed a zone of parietal congestion measuring 4 x 3 cm with a very thin, translucid, central zone measuring 3 x 1.5 cm, just anterior to the inferior vena cava in the right atrial free wall. Histological examination of this zone showed an intense, mutilating fibrosis dissociating the muscular fibres, of the pectinate muscle and even replacing the myocardium in certain regions. In the Eustachian valve, there were muscular fibres, probably representing the posterior internodal pathway, which were also fibrosed. These observations suggest that: 1) in view of the extreme thinness of the atrial wall at the site of ablation there is a high risk of perforation even when right endoatrial catheter ablation is performed with low energy shocks; 2) the posterior internodal pathway does not seem to be an essential component for atrial 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.

Endocardial catheter fulguration has been recently proposed for treatment of arrhythmias originating within the right atrium. In this study the authors attempted to use this technique in eight patients with paroxysmal common atrial flutter. Numerous antiarrhythmic agents failed to prevent recurrences of the episodes, which occurred frequently over periods of at least 4 months. In every procedure, we used a 7F quadripolar catheter electrode introduced via the subclavian vein into the lower part of the right atrium. The two distal electrodes allowed the recording of bipolar double potentials where the critical slow pathway of the reentrant circuit was localized. A unipolar electrogram recording by the tip electrode gave us the location of the area to be ablated when this electrogram was in complete concordance with a small step in the descending part of the F waves in II, III and aVF. This step corresponded to the very depolarization of the reentry area. A DC shock of 100 to 120 J was delivered between the tip electrode and a paddle applied to the left chest wall. Sinus rhythm resumed instantaneously. No mechanical or electrical complications were noted. Three patients are free of relapses without antiarrhythmic drugs (follow-up: 14 to 17 months); three others are also free of relapses, but antiarrhythmic agents were required for treatment of other supraventricular dysrhythmias (follow-up: 3 to 17 months); atrial flutter recurred within several days and persisted in spite of two more procedures in two patients. We conclude that endocardial catheter fulguration of paroxysmal and recurrent atrial flutter seems to be effective therapy. Nevertheless, more experience is required in order to confirm these results.