In the last 20 years there has been a greater interest in the physiological and pathological changes in the cardiovascular system during different sleep states. Gradually, it has become increasingly important to recognize the hemodynamic, cardiac rhythm and cardiac function effects in patients with sleep apnea. Here, we will give an overview of the relationship between sleep apnea syndrome and various types of cardiovascular diseases. 1, hypertension Currently, some research data show that at least 30% of patients with hypertension are combined with obstructive sleep apnea syndrome, and the incidence of hypertension in patients with obstructive sleep apnea syndrome is 50%-80%, and it is now considered that obstructive sleep apnea syndrome is one of the factors for the development of hypertension independent of age, weight, diet, genetics and other causes, and is an important risk factor for the occurrence and development of hypertension. It is an important risk factor for the development of hypertension. The characteristics of blood pressure in these patients are: (1) Patients exhibit the highest blood pressure in the morning immediately after waking up, and the blood pressure decreases after activity. Generally, blood pressure is significantly higher in the early morning than at night before sleep. (2) The effect of anti-hypertensive medication alone is poor, and it is difficult to maintain within the normal range, and the blood pressure is more volatile. 24-hour ambulatory blood pressure monitoring loses the normal circadian rhythm of blood pressure, which is “non-spoon type”. (3) The hypertension may appear as transient hypertension, which occurs at night during apnea, and the high peak of blood pressure appears at the end of apnea when ventilation is about to resume. It may manifest as nocturnal transient hypertension. 2, coronary artery disease, angina Most patients with coronary artery disease are over 40 years old, and men are more common; and patients with obstructive sleep apnea syndrome are also predominantly male, and the incidence of men over 40 years old is 20%-40%. Foreign studies have confirmed that 35% of coronary patients with single or multiple coronary artery stenosis shown by coronary angiography have combined obstructive sleep apnea syndrome by polysomnography, and found that 85.4% of ischemic episodes were in sleep apnea with oxygen saturation decrease >3%. The incidence of obstructive sleep apnea syndrome was significantly higher in patients with coronary artery disease than in normal subjects of the same age. (1) The occurrence of pain is not significantly related to the increase in myocardial oxygen demand caused by mental and physical activity, but to the decrease in coronary blood flow reserve; (2) The pain is severe and prolonged, and is not easily relieved by nitroglycerin; (3) The pain occurs mostly at rest or during sleep, often in the middle of the night and occasionally during lunch break; (4) Sometimes this type of pain occurs at rest or during sleep. (4) Sometimes the pain in the anterior thoracic region in these patients lasts longer, up to 30 minutes to 1 hour, but there is no objective evidence of myocardial infarction. (3) Cardiac arrhythmias and sudden nocturnal death The cardiac risks of recurrent breathing and resulting hypoxemia during sleep in patients with obstructive sleep apnea syndrome are now receiving increasing attention and concern. The incidence of ventricular ectopic beats is 57%-74%, the incidence of second degree AV block is more than 10%, and frequent ventricular anterior contractions can occur when the blood oxygen is <60%. In patients with obstructive sleep apnea syndrome, ventricular ectopic beats are the most common arrhythmia, with various types of manifestations, mainly frequent transient ventricular tachycardia, frequent atrial premature, short-onset atrial tachycardia, or second- or third-degree AV block, mainly occurring immediately after the termination of apnea and when systolic blood pressure is elevated. Treatment with commonly used antiarrhythmic drugs is ineffective. At the same time, some scholars found that the arrhythmia seen at night in patients with obstructive sleep apnea syndrome has the appearance of sinus arrest, although its incidence is low, but its risk is greater and not easy to be noticed, the biggest risk is sudden death at night. 4, heart failure Hypoxia during apnea causes pulmonary vasoconstriction, resulting in pulmonary hypertension, increased right ventricular load, coupled with changes in blood rheology, increased return blood volume, prone to right heart failure. Long-term increased right ventricular load can also cause left heart insufficiency. The most prominent clinical manifestation is right heart insufficiency, which is often confused with pulmonary heart disease and can also cause some special cardiac lesions that are not easy to attract attention, so we should be vigilant to detect and treat heart failure related to patients with obstructive sleep apnea syndrome at an extremely early stage. Especially for some unexplained heart failure, refractory heart failure and some dilated cardiomyopathy, attention should be paid to the combination of obstructive sleep apnea syndrome.