ATRIAL (AURICULAR) FLUTTER

Unlike atrial fibrillation the disordered atrial mechanism in this condition is influenced considerably by digitalis. In doses sufficient to produce ventricular slowing, this drug also converts nutter to fibrillation in most cases. Stopping the drug once fibrillation has developed is followed in about one-third of the cases by return to normal rhythm; in another one-third the rhythm reverts to flutter;
in the remainder fibrillation persists indefinitely. If flutter recurs, a second course of digitalis may succeed in establishing normal rhythm, or cardioversion or quinidine may be tried. If atrial fibrillation persists, it is treated in the usual way, and again cardioversion or quinidine may be tried.
Digitalis if used is given as for atrial fibrillation. Whenever marked slowing occurs together with total irregularity at the apex, fibrillation may be assumed to have developed. This may ensue after a single intravenous dose of strophanthin or digoxin, but it is more usual to give digitalis orally over a period of some days. Electrocardiographic control is desirable. When fibrillation supervenes, digitalis is stopped for a few days-and a return to normal rhythm awaited.
An alternative method is to use quinidine. After preliminary digitalization, to slow the ventricular rate and abolish congestive failure, quinidine is given in similar dosage and method as for atrial fibrillation. Quinidine slows the atrial rate, so that a rate originally between 250 and 300 per minute falls gradually —it may be to below 200 per minute. At this stage there is a danger that the ventricles may follow the full atrial rhythm (1 : 1 flutter) instead of responding to every second, third or fourth atrial cycle as at the beginning of treatment. Should this occur a dangerous tachycardia at 180 to 200 per minute may occasionally arise. The slowing of the atrial rhythm to 200 or thereabouts is frequently followed by abrupt resumption of normal rhythm. Large doses of the drug are then stopped, and after twenty-four hours small doses of 0-2 g. (3 gr.) once or twice a day are given and maintained for a few weeks.
It has been our practice to use digitalis for cases of nutter in the first instance, quinidine being reserved for those who fail to respond to digitalis. In either case, should normal rhythm be restored, its duration depends on the same factors as apply in cases of fibrillation treated with quinidine. Recurrence of flutter or fibrillation at an early date is likely in patients with grossly enlarged hearts or old-standing disorders of rhythm, and in those in whom a toxic factor is still operative, such as hyperthyroidism.