The circulatory system and hormones
Frank J. Dye in Human Life Before Birth, 2019
In addition, a second partition arises from the wall of the atrial region of the heart, the septum secundum. This crescent-shaped partition has its limbs directed toward where the sinus venosus enters the atrial region of the developing heart. The initial opening of the septum secundum does not close. Rather, the edges of its opening provide a valvular mechanism for the foramen ovale (see Figure 15.4B). This valve is designed so that blood returning from the rest of the body will supply both atria. The necessity for this valve has to do with the flow of blood. In the adult, blood returns to the left atrium from the lungs. However, because of the underdeveloped nature of the lungs during prenatal existence, the lungs supply essentially no blood to the left atrium. Instead, blood is supplied to the left atrium from the right atrium via the foramen ovale. This provides the left atrium with a load to pump, which is necessary for its proper development.
Transition to extrauterine life
Prem Puri in Newborn Surgery, 2017
Anatomically, the foramen ovale comprises overlapping portions of septum primum and septum secundum, acting as a one-way flap valve allowing continuous right-to-left flow during fetal life.20 Immediately after birth, with the acute increase in pulmonary blood flow, left atrium pressure rises to exceed right atrium pressure, pushing septum primum rightward, against septum secundum, shutting the flap of the foramen ovale. Afterward, septum primum fuses to septum secundum, completing septation of the atria. However, in 20% to 25%, incomplete fusion leads to the persistence of the flap valve, leaving a patent foramen ovale.20 In general, individuals with patent foramen ovale are never identified because they have no symptoms. However, there is increasing interest in the evaluation and treatment of patent foramen ovale, which has been associated with various pathologic conditions, such as cryptogenic stroke, decompression sickness, platypnea–orthodeoxia syndrome, and migraine.21
Cardiovascular system
Jagdish M. Gupta, John Beveridge in MCQs in Paediatrics, 2020
8.16. Which of the following statements is/are true of atrial septal (septum secundum) defect?The systolic murmur is usually present at birth.The systolic murmur is due to increased flow across pulmonary outflow tract and valve.There is fixed splitting of the second heart sound.The lung fields are plethoric.There is no risk of pulmonary hypertension.
Closing the gap on patent foramen ovale and cryptogenic stroke
Published in Expert Review of Cardiovascular Therapy, 2019
Fahed Darmoch, Yasser Al-Khadra, Homam Mousa Bacha, Mohammad Soud, M Chadi Alraies
Foramen ovale is an anatomical intra-atrial communication between the right and left atria. Normally, in embryonic phase of life inferior vena cava blood flows from right side of the heart to the left atrium through the PFO, avoiding the lungs as part of the normal fetus circulation physiology. During birth, pulmonary circulation increases significantly causing left atrial pressure increment. This difference in atrial pressures pushes the septum premium against the septum secundum and eventually functionally closing the PFO [5]. The spontaneous closure of PFO occurs later in life, but clinical observational studies through autopsy and detailed contrast two-dimensional echocardiography showed that this anatomical closure can be incomplete in 1 out of 4 of every adult [6]. Therefore, PFO theoretically considered a normal anatomic variant and not a pathological finding in the absence of possible paradoxical embolism or other specific clinical conditions.
Patent Foramen Ovale Closure, A Contemporary Review
Published in Structural Heart, 2018
Raouf Madhkour, Bernhard Meier
The foramen ovale consists of a short interatrial channel (average length 5 mm) which lies exactly in the axis of the blood stream coming from the inferior vena cava. During fetal life, the foramen ovale allows the oxygenated blood coming from the umbilical vein to pass from the right to the left atrium in order to bypass the nonfunctional pulmonary circulation. With pressure diminution of the right atrium due to the resistance drop in the pulmonary circulation at the first breath, the left-sided septum primum will be pressed against the right-sided septum secundum, closing the foramen ovale. The two septa will normally fuse during the first year of life.1 However, in 25–30% there is not a complete anatomical occlusion and the foramen ovale remains patent or, more precisely, openable. This is called PFO and is generally not considered a disease but rather a variant of the norm.
Transcatheters for closure of patent foramen ovales
Published in Expert Review of Medical Devices, 2018
Gianluca Rigatelli, Marco Zuin
The more important to mention include: (1) the fusion between the two septa may be irregular and more than one orifice may be detected; (2) the degree of overlapping between the two septa (defined as tunnel) is variable, and as a result, it is possible to have either a very long or a very short tunnel of the PFO; (3) when septum primum is thin and redundant, it may be excessively mobile and create a aneurysmal fossa ovalis [6]; and (4) the presence of abundant adipose tissue within the infolding septum secundum may result in a very thick and bulky septum [7]. Other important structures that may pose issues with the device delivery and placement are the redundant Eustachian valve and the Chiari network, two embryonic remnants [8]. Based on the anatomic features, we may therefore differentiate simple from complex PFOs, where one or more of the characteristics described in Table 1 are present.
Related Knowledge Centers
- Birth
- Heart Development
- Atrium
- Cardiac Muscle
- Septum Primum
- Foramen Secundum
- Foramen Ovale
- Primitive Atrium
- Septum Intermedium
- Endocardial Cushions