When the pacing impulse from the high pacing point suddenly stops and the low potential pacing point just starts to deliver impulses at a frequency slower than its intrinsic frequency before gradually returning to its intrinsic frequency, this phenomenon is called the warm awakening phenomenon. This phenomenon is called warm awakening. It is commonly seen in arrhythmias or sinus reflex tachycardia. How is the warm awake phenomenon diagnosed? The ECG shows a gradual increase in heart rate. When sinus tachycardia occurs, it is often accompanied by the warm up phenomenon, in which the heart rate is irregular during the first 3 to 5 cardiac cycles, and often increases gradually and steadily. Dynamic ECG is more valuable to identify tachycardia caused by different mechanisms, especially tachycardia of folding mechanism and non-folding mechanism. The former is characterized by the sudden onset and cessation of tachycardia, and the heart rate during the attack is relatively uniform, while the latter is characterized by a less uniform heart rate during the attack, and may have the phenomenon of warming and cooling, i.e., the heart rate gradually increases during the attack (warming phenomenon) and tends to gradually slow down before termination (cooling phenomenon).