A pulse rate of 45 beats per minute in the elderly may be a reaction to taking potassium chloride, or it may be due to other causes, including arrhythmia, viral myocarditis, sick sinus node syndrome, and drug side effects. Depending on the specific cause, medication may be given or pacemakers may be fitted. Potassium chloride must be used in strict compliance with the doctor’s instructions in the elderly, as overuse can cause hyperkalemia, in which case the pulse can be below 60 beats per minute, i.e. bradycardia. In this case, infusion therapy is needed to correct electrolyte disorders, intravenous hypertonic glucose and insulin, and intravenous calcium. In addition to decreased heart rate caused by hyperkalemia, the following causes may also cause decreased heart rate: 1. Arrhythmia, such as atrioventricular block of second degree type II or above, which is treated with anti-arrhythmic drugs. 2. Viral myocarditis, which affects myocardial contractile function and leads to sinus bradycardia. Take nutritive myocardial medication, such as trimetazidine, fructose diphosphate, coenzyme Q10 and so on. 3. Sick sinus node syndrome, degenerative fibrosis of the sinus node and surrounding atrial tissue, abnormal formation and conduction of the atrial impulse, resulting in bradycardia syndrome. Pacemaker therapy is required. 4. Some drugs influence, such as antihypertensive drugs beta-blockers, antiarrhythmic drugs propafenone, opioid analgesics and so on. Discontinue the use of drugs or reduce the dose of drugs used, etc.. If there is any discomfort, you should seek medical advice and follow the doctor’s instructions.