Studies on flutter and fibrillation: II. The influence of artificial obstacles on experimental auricular flutter

In denervated normal dog's auricles, enduring activity with the characteristics of flutter, as defined by the circus-movement theory, can be elicited only rarely by electrical stimuli. If the conduction of impulses through the auricular fibers which lie between the orifices of the two venae cavae is blocked reversibly (cocaine) or irreversibly (crushing), however, activity of this type may be readily evoked and may last as long as the block persists. The importance of this simple preparation for the study of flutter is emphasized.The activity in question is not initiated at the pacemaker. It is rhythmic and regular (Fig. 2, D). Its rate is greater than that of the normal beats (Fig. 2, D). This rate is slightly accelerated by vagal stimulations (Fig. 2, E) and by injections of adrenaline (Fig. 2, F) that have an important typical influence on the rate of the heartbeats (Fig. 2, B and C). These features are reasonably explained by the circus-movement theory of flutter. In agreement with the theory, additional injuries to the auricle that increase the effective perimeter of the obstacle constituted by the two cavae (Fig. 3) proportionately decrease the rate of flutter. Also in harmony with the theory is the fact that flutter can be obtained only if the obstacle is entirely surrounded by conducting tissue.     

The efficacy of propafenone in preventing recurrent auricular fibrillation and flutter]

In order to investigate the efficacy of propafenone in the prevention of paroxysmal flutter or fibrillation, we treated 21 patients without left ventricular disfunction. Age was 60 +/- 14 (mean +/- sd) years, left atrial diameter by echocardiography 37 +/- 7 mm, cardiothoracic index 0.48 +/- 0.05 (0.41-0.57) and P wave duration 100 +/- 17 ms. The frequency of recurrences before treatment was: daily in five (23%), weekly or more in eight (38%), monthly-weekly in seven (33%) and quarterly-monthly in one (5%). Propafenone (671 +/- 187 mg/24 h) was given after recurrences were demonstrated under treatment with 1-3 antiarrhythmic drugs per patient. During 8.9 +/- 3.5 months of follow-up (range 6-19) 5 patients (23%) were completely free of recurrences; in seven (33%) the incidence decreased by greater than 50% with a marked decrease in duration. Side effects appeared in 12 cases (57%), leading to its discontinuation in four (19%). Arrhythmogenic effects were observed in 2 cases (9%). Propafenone is effective in greater than 50% of patients with paroxysmal atrial flutter or fibrillation, resistant to other antiarrhythmic agents. The incidence of side effects is high, but they are usually not severe and reversible.     

Treatment of supraventricular paroxysmal tachycardia and auricular flutter by auricular stimulation]

Although the management of supraventricular tachycardias (SVT) and atrial flutter (AF1) with drugs or cardioversion is usually effective, their use in the high risk patient commonly digitalized, may be dangerous. Since the availability of an alternate therapeutic method is desirable, the usefulness of atrial pacing was evaluated in 31 episodes of tachyarrhythmia in 31 patients with varied heart conditions. The arrhythmia diagnosis and the stimulation were done through a right atrial electrode. In most cases the rate of stimulation was higher than that of the atria (up to 400 stimuli per min). Of 17 cases with SVT (four with preexcitation syndrome), pacing led to sinus rhythm (SR) in all, even though it was transient in two. SR was obtained in six of eleven cases of AF1, through a short lasting atrial fibrillation (AF) in three of them. Four patients with paroxysmal atrial tachycardia with A-V block changed to AF. SR was achieved shortly after termination of the procedure in two of the latter. It is concluded that atrial pacing is a valuable therapeutic method since it is effective, it has very low risk specially in digitalized patients, its does not require anesthesia and because it may be used repeatedly in case of recurrence. The technique of atrial pacing permits, in some cases, the identification of the mechanism responsible for the arrhythmia.