Pacemaker syndrome is usually caused by VVI pacing but can also occur with AAI (inhibited on-demand atrial pacing) or frequency-adapted atrial pacing (AAIR). The clinical manifestations of pacemaker syndrome are mainly a series of signs and symptoms due to low cardiac output. However, the presentation varies among individuals due to different compensatory capacities of cardiac function. Generally, it is more common in the elderly. What are the causes of increased pacing frequency? Loss of synchronous atrial contraction can reduce the volume of cardiac output by 20% to 30%, or more than 50% in cases of pre-existing cardiac insufficiency; atrioventricular valve insufficiency causes regurgitation of systolic blood back into the atria, increasing the atrial load; increased atrial pressure inhibits the normal contraction reflex of the peripheral vessels, leading to a drop in blood pressure; right ventricular pacing leads to biventricular contraction asynchrony; and ventricular atrial electrical activity leads to retrograde ventricular conduction. Further intracardiac electrophysiological examination and hemodynamic examination should be performed in patients with normal pacing function but recurrent syncope or congestive heart failure. Neurological disorders and discomfort and intolerance to pacing therapy in the short term should be excluded. If ventricular pacing is associated with ventricular-atrial reverse conduction and symptoms, and the symptoms improve significantly or disappear after changing to atrial pacing or sequential atrioventricular pacing. Or if arterial blood pressure decreases >20-30 mmHg (2.67-4.0 kPa) and right atrial pressure increases >20 mmHg (2.67 kPa) during ventricular pacing, along with symptoms, the diagnosis of pacemaker syndrome should be made.