The pacemaker delivers the basic frequency of stimulation pulses according to the patient’s needs. Generally, 70 to 90 beats/min is the optimal heart rate, and a pacing frequency greater than 10% of the patient’s own heart rate is appropriate. Pacemaker syndrome is a group of clinical syndromes caused by hemodynamic and electrophysiological abnormalities after pacemaker implantation. It can occur in any pacing mode as long as there is atrial separation. It is usually seen in the VVI (suppressed on-demand ventricular) pacing mode. The main manifestations are neurological symptoms, low cardiac output and congestive heart failure. Syncope occurs in approximately 38% of clinical cases. What symptoms are easily confused with increased pacing frequency? 1. The presence of escape beats: The so-called escape beats refer to the opportunity for the diastolic de-polarization of the occult pacing point to reach the threshold potential when the excitability of the sinus node decreases or when the pacing stops, which leads to excitation and drives the whole heart, called escape beats. Passive ectopic rhythm is a physiological protective mechanism and does not require treatment by itself. If the ventricular rate is too slow and produces symptoms or hypotension, the ventricular rate needs to be increased and treatment given. 2. Premature beats: Prematurebeat (cardiovascular medicine) is abbreviated as premature beat. Premature beats are heart beats caused by premature impulses from ectopic pacing points and are the most common cardiac arrhythmia. It can occur on the basis of sinus or ectopic (e.g., atrial fibrillation) rhythms. It can be occasional or frequent and can occur irregularly or regularly after each or several normal beats, forming a diphasic or associative premature beat. According to the site of origin, there are four types: sinus, atrial, atrioventricular junction, and ventricular. Among them, ventricular premature beats are the most common, followed by atrial, and junctional are less common. Sinus premature contractions are rare. Premature beats can be seen in normal subjects or in patients with organic heart disease, commonly coronary artery disease, rheumatic heart disease, hypertensive heart disease, cardiomyopathy, etc. Premature beats can also be seen in patients with quinidine, procainamide, digitalis or antimony poisoning; hypokalemia; mechanical stimulation of the heart during cardiac surgery or cardiac catheterization, etc. 3. Accelerated atrial escape rhythm: also known as non-paroxysmal atrial tachycardia, accelerated atrial voluntary rhythm, accelerated atrial self-rhythm, etc. The diagnosis can be clearly made according to the medical history, symptoms, signs and electrocardiogram performance. 4. Apical pulsation diffusion: In myocarditis, in addition to a weakened apical pulsation, there is often apical pulsation diffusion. Myocarditis is a limited or diffuse inflammation of the myocardium that can originate in the myocardium or be part of a systemic disease. Fatigue, fever, chest tightness, palpitations, shortness of breath, dizziness, and in severe cases, cardiac insufficiency or cardiogenic shock may occur. The heart rate increases, disproportionate to the increase in body temperature, enlarged heart borders, altered murmurs, and arrhythmias. The clinical manifestations of pacemaker syndrome are mainly a series of signs and symptoms due to low cardiac output. However, the manifestations vary from one individual to another due to the different compensatory capacity of the heart function. Generally speaking, it is more common in the elderly.