A heart rate of 30 to 40 beats per minute may be the occurrence of third-degree atrioventricular (AV) block, but also pathological sinus node syndrome, toxins, electrolyte disorders, etc. caused by the sinus node autoregulation and conduction is reduced, this time the heart rate is unable to pump enough blood to maintain the normal function of the body, is very dangerous, and requires immediate emergency care. Third-degree atrioventricular block, which is complete atrioventricular block, means that the electrical signals from the atria do not reach the ventricles at all. At this time, the contraction of the ventricles, that is, the heartbeat, is governed by the pacing signals from the ventricles or the junctional area and the AV node area, and because of the low autoregulation in these areas, the heart rate will be particularly slow. This is when pacemaker therapy is needed. Sick sinus node syndrome, low heart rate caused by toxins and electrolyte disorders, is the “commander-in-chief” of the cardiac contraction signal problems, the treatment can be prescribed to apply the elevation of the heart rate of drugs such as atropine, isoproterenol, and so on, the serious cases need to be treated with a pacemaker, cardiac arrest should be carried out immediately for cardiopulmonary resuscitation.