A heart interval is generally the time between two heartbeats. If the interval is too long, the patient may experience panic, chest tightness, shortness of breath, or even transient syncope. The presence of long cardiac intervals requires 24-hour ambulatory ECG monitoring to specify the long intervals, the duration of the interval, and the frequency of the interval occurrence. If the long intervals are too long and the patient is clearly showing clinical manifestations of various symptoms, pacemaker therapy should be considered. Long intervals generally occur after various types of arrhythmias, commonly including ventricular asystole, atrial asystole, and in some patients with atrial fibrillation. The new treatment guidelines for patients with atrial fibrillation state that a long interval of more than five seconds is an indication for pacemaker implantation. Patients with atrial fibrillation generally have a fast heart rate and are more likely to have long intervals at night, which is a relatively high risk.