In order to standardize the clinical application of patent foramen ovale occlusion (PFO) closure, domestic experts in this field have formed the “Chinese Expert Recommendations on Management Strategies for Patent Foramen Ovale Occlusion” based on the relevant contents at home and abroad, combined with the specific situation in China. The foramen ovale is a physiological channel in the embryonic period of the atrial septum of the heart. Around 5 to 7 months after birth, the secondary and primary septum of the atrial septum in most people adhere to each other and fuse to form a permanent atrial septum, and if they do not fuse, they form a patent foramen ovale (PFO). About 25%; to 34%; of adults have incomplete fusion of the two layers of the septum in the fossa ovalis, leaving a permanent fissure-like defect in the middle. Because the fractional flow rate of PFO is so small, it was long thought that PFO would not have clinical consequences. In recent years, more and more studies have found that the risk of stroke, migraine, peripheral arterial embolism, and decompression sickness is several times higher in patients with PFO than in the normal population, and the pathogenic role of PFO has only drawn the attention of a wide range of experts and scholars, who have clinically explored the use of closed PFO to prevent recurrent stroke events, treat migraine, and oblique respiratory-erect hypoxemia. Although most clinical studies have shown good efficacy, evidence-based studies are still controversial. I. PFO and paradoxical embolism Paradoxical embolism is an embolism caused by a thrombus from the venous system and the right atrium entering the left heart system from the right heart through intracardiac traffic. The incidence of paradoxical embolism accounts for 2%; -16%; of arterial embolisms. Cerebral embolism, gas embolism, fat embolism and neurological decompression sickness occurring during diving have been found to be closely related to paradoxical embolism clinically. The necessary conditions for the diagnosis of paradoxical embolism are: ① right-to-left shunt (RLS) mainly present in the PFO; ② unknown source of embolism; ③ exclusion of diseases caused by hemodynamic abnormalities. However, the incidence of lower extremity and pelvic vein thrombosis usually detected in patients with clinical suspicion of paradoxical embolism is not high, which may be related to the imaging detection methods and the difficulty of observing microscopic thrombi. The size of the PFO, the amount of RLS and its structural features are closely related to the occurrence of paradoxical embolism; the larger the PFO and the more RLS fractions, the higher the incidence of paradoxical embolism. The risk of transient ischemic attack (TIA) and ischemic stroke is significantly increased in PFOs >4 mm in diameter, and the risk of paradoxical embolism is higher in PFOs with ASAJE and Chiari networks. De Castro et al. found that primary atrial septal activity was associated with stroke, with activity >6.5 mm or PFO-RLS at rest being a high risk group for stroke and recurrent stroke. 1. Ultrasound diagnosis of PFO PFO is mainly diagnosed by echocardiography, including transthoracic echocardiography (TTE), transesophageal echocardiography (TEE) and transcranial Doppler echocardiography (cTCD), and even by CT or magnetic resonance imaging (MRI). (1) TTE and cTTE The detection rate of PFO by conventional TTE is very low in adults due to various factors such as obesity and excess lung gas. the two atrial views under the sword of TTE have the highest detection rate of PFO and are the best views. The sensitivity of cTTE can be as high as 63&;#xFF05;～100&;#xFF05;～100&;#xFF05;～100&;#xFF05;～100&;#xFF05;～100&;#xFF05;～100&;#xFF05;～100&;#xFF05;～100&;#xFF05 100&;#xFF05;. The cTTE examination is usually selected in the apical four-chamber cardiac view and requires the preparation of activating saline first, which is generally recommended with blood saline. The activation saline is first injected at rest to observe the microbubble development in the right heart followed by the microbubble development in the left heart and the time and amount of the development; the patient is then instructed to inhale deeply and then hold his breath under breath-hold to inject the activation saline, and when the microbubble enters the right heart to rapidly relax and exhale (Valsalva maneuver) to observe the microbubble development in the left heart. It should be noted that the effectiveness of the Valsalva maneuver and the timing of pushing the activated saline have an effect on the cTTE results. The hallmark of a valid Valsalva maneuver is that the septum is observed to project into the left atrium after expiration. RLS can be determined to originate from intracardiac or pulmonary arteriovenous channels (PAVMs) based on the timing of cTTE left heart microbubble visualization. There is no widely accepted grading scheme for assessing RLS, and RLS is usually graded by the number of microbubbles present in the left atrium on a single frame of a still image. Class I: 1-10 microbubbles/frame in the left atrium, a small amount of RLS; Class II: 11-30 microbubbles/frame in the left atrium, a moderate amount of RLS; Class III: >30 microbubbles/frame in the left atrium, or the left atrium is almost full of microbubbles and the heart chamber is cloudy, a large amount of RLS. (2) TEE and cTEE TEE is the “gold standard” and the preferred method for diagnosing PFO. method. TEE is performed when there is a high suspicion of cardiogenic embolism and may reveal cases of missed TTE. When cTTE reveals the presence of RLS in a PFO, TEE can clarify the septal anatomy, classify the PFO, and guide the treatment of PFO occlusion, such as the morphology and location of the PFO, the number and size of concurrent defects, the length of the residual septum, the softness and stiffness, and other anatomical structures that may affect the placement of the occluder. It is important to note that the PFO opening diameter is variable, and the opening diameter measured after a valid Valsalva maneuver is close to its true size. As with cTTE, cTEE can also be used to determine the amount of RLS. However, TEE is a semi-invasive examination, and the patient is in pain during the operation, and it is difficult to cooperate with the Valsalva maneuver. Although these do not hinder the diagnostic ability, they will affect the sensitivity of the PFO to the appearance of RLS. cTEE diagnoses PFO-RLS with a lower detection rate than cTTE. (3) Three-dimensional TEE Real-time three-dimensional TEE is a supplement to two-dimensional images, and can clearly show the morphological structure of the PFO The relationship between PFO and surrounding tissue structures and blockers. (4) cTCD cTCD test is also a common method to detect the presence or absence of RLS, and RLS can be inferred by observing the number of bubbles in the cranial circulation at rest and after the Valsalva maneuver. cTCD microbubble number is graded bilaterally as follows: Grade 0 – no microembolus signal, no RLS; Grade I – 1-20 microbubble signals (1-10 unilaterally), a small amount of RLS Grade II: ≥20 microbubble signals (unilateral for ≥10), non-curtain, for moderate RLS; Grade III: curtain or shower type of embolus signal, for massive RLS. cTCD has the greatest advantage of being non-invasive, and the disadvantage of being difficult to distinguish the source of RLS. cTCD has a sensitivity of 68%; ~100%; and a specificity of 65%; ~100%; for RLS, while cTTE The specificity is %; ~100%;. 2. Clinical clues to PFO The diagnosis of unexplained stroke (CS) is a diagnosis of exclusion, and it is often difficult to determine whether PFO is its cause. Imaging features of stroke, clinical characteristics of the patient and ultrasound features of high-risk PFO can provide valuable information. A study comparing AF or PFO leading to stroke found that PFO causing stroke was more likely to have a single cortical infarct (34.2%; 3.1%;; p<0.01) or multiple small scattered infarct lesions (23.1%; 5.9%;; p<0.01). Similarly, in a large database of patients with CS and definite PFO, a significant correlation between superficially distributed stroke and PFO was confirmed (OR 1.54; <0.001). PFO should be clinically suspected as the cause in patients <55 years of age, lacking predisposing factors, and presenting suddenly with a stroke. Some patients have a clear trigger, such as after prolonged air travel or autopilot, or after physical activity such as bathing or lifting heavy objects. Pregnancy is also a trigger, and pregnancy is a predisposing factor for venous thrombosis. Kent et al. used the RoPE score to try to analyze the correlation between stroke and PFO, calculating the score by cortical stroke, no diabetes, no hypertension, no smoking, no previous stroke or TIA, and found that those with a high RoPE score were more likely to have a concurrent PFO. TTE/cTTE should be routinely tested for unexplained migraine, especially aura migraine, oblique respiratory-erect hypoxemia and unexplained arterial embolism, except for the presence of PFO. further TEE can be performed if PFO is found. The characteristics of high-risk PFO are: PFO combined with ASA, PFO combined with excessive primary septal activity (>6.5 mm), large PFO and the presence of resting RLS, etc.