Atrial flutter is atrial flutter and can be considered as an intermediate type between atrial tachycardia and atrial fibrillation. When the frequency of the atrial ectopic pacing point reaches 250 beats/min – 350 beats/min in a regular pattern, causing a fast and coordinated contraction of the atria, it is called atrial flutter. Atrial flutter is most often seen in organic heart disease. It is often seen clinically in coronary artery disease, hypertension, pulmonary heart disease, pulmonary embolism, and sick sinus node syndrome. The clinical manifestations of atrial flutter are as follows: First, atrial flutter into 1:1 downward transmission can make the ventricular rate as fast as about 250 beats/min, which can lead to hypotension, dizziness, palpitations, angina pectoris, and even cardiogenic shock. Second, the fluctuations in the veins are faster than the ventricular rate. Third, when the heart is auscultated, it is most often a fast and regular heart rate of about 150 beats/min, with an atrial to ventricular ratio of 2:1 downward transmission. When the atrioventricular ratio becomes 3:1 or 4:1 downward transmission, the heart rate slows down, and at this time, on careful auscultation, a fast and low atrial systolic sound can be heard.