The QRS wave is a part of the ECG, mainly responding to ventricular depolarization, and the QRS time limit is usually between 0.06 and 0.10 seconds, mostly less than 0.11 seconds. Drugs such as digitalis can also cause abnormalities, and if a cardiac ventricular pacemaker is placed, it can also manifest as a widening of the QRS wave time frame. In R-wave dominant leads, the Q-wave is normally less than 1/4 the amplitude of the R-wave, and the time limit is less than 0.04 seconds. ECG with abnormal time limit requires further clarification of the etiology for symptomatic treatment.