Spontaneous onset of type I atrial flutter in patients

Objectives. This study sought to characterize the spontaneous onset of atrial flutter in patients. Background. Temporary epicardial electrodes are routinely placed on the atri of patients at the time of open heart surgery and brought out through the anterior chest wall for potential diagnostic and therapeutic use in the postoperative period. We utilized these electrodes to study the spontaneous onset of type I atrial flutter in 16 patients in the postoperative period after open heart surgery. Methods. Twenty-seven episodes of the spontaneous onset of type I atrial flutter from sinus rhythm were studied in these 16 patients by recording bipolar atrial electrograms simultaneously with at least one electrocardiographic lead during each episode. Results. In all 27 episodes, the onset of type I atrial flutter was through transitional rhythm of variable duration (mean 9.3 s) precipitated by premature atrial beat. In 21 episodes, the transitional rhythm was atrial fibrillation; in 3 episodes it was type II atrial flutter that appeared to generate atrial fibrillation; and in 3 episodes it was brief (3 to 6 beats), rapid, irregular arrhythmia. Conclusions. Type I atrial flutter does not start immediately after premature atrial beat. Rather, it starts after transitional rhythm that is usually atrial fibrillation. Extrapolating from mapping studies of the onset of atrial flutter in the canine pericarditis model, we suggest that transitional rhythm is required for the initiation of type I atrial flutter because during that rhythm, the requisites for development of the atrial flutter reentry circuit evolve