The mechanism of action of digitalis is as follows: first, it enhances myocardial contractility; second, it reflexly excites the vagus nerve; third, it delays atrioventricular conduction. Cardiology is the main department where digitalis is used to treat chronic systolic heart failure with supraventricular tachycardia and atrial fibrillation, which is the most desirable. Digitalis has a wide range of clinical applications, but also has significant side effects, such as slowing down the heart rate and aggravating some arrhythmias, so it is best to be under professional guidance for reasonable symptomatic treatment. If used well, digitalis is a life-saving drug, but if used poorly, it can lead to digitalis poisoning, which can be life-threatening.