Slow arrhythmia is a disease of the heart’s pacing or conduction system that causes a reduced heart rate of less than 55 beats per minute, including sinus bradycardia, sinus arrest, and severe atrioventricular block. A slow heart rate can cause insufficient blood displacement from the heart, triggering ischemia in vital organs, such as cerebral ischemia and myocardial ischemia, and setting up cardiac arrest, which is life-threatening. Such arrhythmias are often secondary to severe heart disease and should be treated aggressively with medication for the primary cause. If medication does not improve the heart rhythm, a pacemaker should be applied to improve symptoms and prevent serious dangerous situations of cardiac and cerebral ischemia. A pacemaker can ensure a basic heart rhythm and is an important cure and life-saving method. A pacemaker may be considered if one of the following conditions exists: the slowest rhythm is less than 35 beats on an ambulatory ECG or the long interval of the rhythm is greater than 4.5 seconds (ventricular arrest).