Preface An arrhythmia is an abnormality in the frequency or rhythm of the heartbeat. Abnormalities in the function of any part of the cardiac conduction system can lead to the development of arrhythmias. During an arrhythmia attack, patients often experience palpitations, chest tightness, shortness of breath, and in severe cases, vertigo, syncope, or even sudden death. According to the frequency of heartbeat during the attack, it can be divided into two categories: fast and slow arrhythmias. Normal heart and arrhythmia Normal heart anatomy and physiological functions The human heart has four chambers: the left atrium, left ventricle, right atrium, and right ventricle. The heart is a hollow, muscular organ, filled with blood, and the blood does not flow between the left and right chambers. It acts as a “pump”, sending blood to all organs of the body through rhythmic contraction and diastole to deliver the oxygen and nutrients needed to maintain normal function of the body’s organs. The normal cardiac conduction system The contraction and diastole of the heart are triggered by electrical excitation. In the heart, there are not only places to generate “electrical excitation” but also channels to conduct “electrical excitation”, which is usually called the cardiac conduction system. In this system, the sinus node, located in the right atrium, is responsible for generating regular electrical excitation, which is transmitted rapidly and sequentially throughout the heart through the cardiac conduction system in the atria, atrioventricular node and ventricles, and triggers the heart’s rhythmic contraction and diastole to complete the pumping function. A normal heartbeat with a regular rhythm of 60-100 beats per minute is called sinus rhythm. What is an arrhythmia? An arrhythmia is an abnormality in the frequency or rhythm of the heartbeat. An abnormality in the function of any part of the heart’s conduction system can lead to an arrhythmia. During an arrhythmia attack, patients often experience palpitations, chest tightness, shortness of breath, and in severe cases, vertigo, syncope, or even sudden death. According to the heart rate during the attack, there are two major categories of arrhythmias: fast and slow. Diagnosis of arrhythmias A preliminary diagnosis can be made by the ECG or 24-hour ambulatory ECG monitoring (Holter) recorded during an arrhythmia attack, supplemented by some symptoms that accompany the attack. However, if the location of the arrhythmia and the mechanism of its occurrence need to be clarified, electrophysiological examination is required.