upper sinus venosus<unk> ; 2: lower sinus venosus<unk> ; 3: secundum<unk> ; 4:<unk>  involving coronary sinus; 5; primum<unk> . The six types of<unk> s are differentiated from each other by whether they involve other structures of the heart and how they are formed during the developmental process during early fetal development. Ostium secundum The ostium secundum<unk>  is the most common type of<unk>  and comprises 6–10% of all congenital heart diseases. It involves a patent ostium secundum (that is, a patent foramen secundum). The secundum<unk>  usually arises from an enlarged foramen ovale, inadequate growth of the septum secundum, or excessive absorption of the septum primum. About 10 to 20% of individuals with ostium secundum<unk> s also have mitral valve prolapse. An ostium secundum<unk>  accompanied by an acquired mitral valve stenosis is called Lutembacher's syndrome. Natural history Most individuals with an uncorrected secundum<unk>  do not have significant symptoms through early adulthood. More than 70% develop symptoms by about 40 years of age. Symptoms are typically decreased exercise tolerance, easy fatigability, palpitations, and syncope. Complications of an uncorrected secundum<unk>  include pulmonary hypertension, right-sided congestive heart failure. While pulmonary hypertension is unusual before 20 years of age, it is seen in 50% of individuals above the age of 40. Progression to Eisenmenger's syndrome occurs in 5 to 10% of individuals late in the disease process. Patent foramen ovale Patent foramen ovale A patent foramen ovale (PFO) is a remnant opening of the fetal foramen ovale, which normally closes after a person's birth. In medical use, the term "patent" means open or unobstructed. In about 25% of people, the foramen ovale fails to close properly, leaving them with a PFO or at least with what some physicians classify as a "pro-PFO", which is a PFO that is normally closed, but can open under increased blood pressure. On echocardiography, shunting of blood may not be noted except when the patient coughs. PFO is linked to stroke, sleep apnea, migraine with aura, cluster headache, decompression sickness, Raynaud's phenomenon, hyperventilation syndrome, transient global amnesia (TGA), and leftsided carcinoid heartdisease (mitral valve). No cause is established for a foramen ovale to remain open instead of closing naturally, but heredity and genetics may play a role. In rats research showed a link to the amount of Cryptosporidium infestation and the number of newborn rats that failed to close their foramen ovale article in Russian. PFO is not treated in the absence of other symptoms. The mechanism by which a PFO may play a role in stroke is called paradoxical embolism. In the case of PFO, a blood clot from the venous circulatory system is able to pass from the right atrium directly into the left atrium via the PFO, rather than being filtered by the lungs, and thereupon into systemic circulation toward the brain. Also multiple substances -including the prothrombotic agent serotonin- are shunted bypassing the lungs. PFO is common in patients with an<unk>  septal aneurysm (ASA), a much rarer condition, which is also linked to cryptogenic (i.e., of unknown cause) stroke. PFO is more common in people with cryptogenic stroke than in those with a stroke of known cause. While PFO is present in 25% in the general population, the probability of someone having a PFO increases to about 40 to 50% in those who have had a cryptogenic stroke, and more so in those who have a stroke before the age of 55. Treatment with anticoagulant and antiplatelet medications in this group appear similar. Ostium primum A<unk>  in the ostium primum is occasionally classified as an<unk> , but it is more commonly classified as an atrioventricular septal<unk> . Ostium primum<unk> s are less common than ostium secundum<unk> s. This type of<unk>  is usually associated with Down syndrome. Sinus venosus A sinus venosus<unk>  is a type of<unk>  septum<unk>  in which the<unk>  involves the venous inflow of either the superior vena cava or the inferior vena cava. A sinus venosus<unk>  that involves the superior vena cava makes up 2 to 3% of all interatrial communication. It is located at the junction of the superior vena cava and the right atrium. It is frequently associated with anomalous drainage of the right-sided pulmonary veins into the right atrium (instead of the normal drainage of the pulmonary veins into the left atrium). Ultrasound picture of the heart, seen in a subcostal view: The apex is towards the right, the<unk> are to the left.<unk>  secundum seen as a discontinuation of the white band of the<unk>  septum. The enlarged right atrium is below. The enlarged pulmonary veins are seen entering the left atrium above. Common or single atrium Common (or single) atrium is a failure of development of the embryologic components that contribute to the<unk>  septal complex. It is frequently associated with heterotaxy syndrome. Mixed The interatrial septum can be divided into five septal zones. If the<unk>  involves two or more of the septal zones, then the<unk>  is termed a mixed<unk> .
Atrial septal defect
Atrioventricular septal defect
Heart septal defect
Ventricular septal defect
Aortopulmonary septal defect
Tricuspid atresia
Persistent truncus arteriosus
Double inlet left ventricle