Digitalis toxicity can cause bradycardia. Digitalis is an inhibitor of the sodium-potassium ATPase, which affects the transfer of sodium and potassium in cells, leading to electrolyte disturbances and arrhythmias. Common arrhythmias include premature beats, bradycardia, and conduction blocks, and severe cases may experience sudden cardiac arrest. Therefore, in patients with heart failure, it is important to closely monitor the blood concentration of digitalis during long-term use, and adjust the dosage of digoxin and digitalis based on its concentration to avoid toxicity. Once toxicity occurs, the first step is to stop the medication and then take appropriate symptomatic treatment to prevent accidents.