Incomplete intra-atrial block is due to ectopic excitation of the impulse within the atria, which during depolarization invades the sinus node and prevents or delays the downward transmission of the excitation. Although incomplete intra-atrial block is not hemodynamically significant, half of the patients often have recurrent episodes of paroxysmal atrial fibrillation or atrial flutter (atrial flutter is referred to as atrial flutter, a common type of rapid atrial arrhythmia. The electrocardiogram shows regular flutter waves with an atrial excitation frequency of 250 to 350 beats per minute. Atrial flutter can manifest as paroxysmal and persistent episodes, and in some patients atrial flutter can alternate with atrial fibrillation as impure atrial flutter. The incidence of atrial flutter increases with age, and is about 2.5 times more common in men than in women. (With the development of marker technology, the mechanism of atrial flutter has been largely clarified, and radiofrequency ablation is gradually becoming the main treatment.) Medical history, 40% of patients may have a history of atrial prophase contraction and atrial tachycardia. Patients may have symptoms such as chest tightness, shortness of breath and irregular heartbeat.