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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 7  |  Issue : 3  |  Page : 198-201

A clinical relevance of fossa ovalis and patent foramen ovale: A morphological study of human heart


1 Department of Anatomy, Kannur Medical College, Kannur, Kerala, India
2 Department of Anatomy, College of Medicine, King Khalid University, Abha, Kingdom of Saudi Arabia, Saudi Arabia

Date of Submission25-Sep-2021
Date of Decision12-Nov-2021
Date of Acceptance17-Nov-2021
Date of Web Publication14-Dec-2021

Correspondence Address:
Thittamaranahalli Muguregowda Honnegowda
Department of Anatomy, Kannur Medical College, Kannur, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpcs.jpcs_60_21

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  Abstract 


Background: The anatomical characterization of foramen ovale (FO) along with annulus or limbus varies in size and shape from the heart to heart. Patent FO (PFO) has been implicated in the etiology of a number of diseases, PFO is not an uncommon condition; their prevalence rate is 15%–35% in the population. Hence, morphological study of FO serves importance to know the exact location of the fossa ovalis (FOv) and prevalence of PFO in the Indian population by the autopsy method. Materials and Methods: This study was conducted in 106 apparently normal hearts available in the Department of Anatomy and Forensic Medicine and Toxicology. After opening the right atrium, the shape of FOv was observed, and dimensions were measured with the digital Vernier caliper and thickness of anterior and posterior limbus was noted. Probe patency was confirmed. Results: Area of the FOv (160.20 ± 104.9 mm2), thickness anterior limbus (7.24 ± 1.83 mm), and thickness of posterior limbus (6.38 ± 2.46 mm). The shape of FOv was oval (83%) in majority; in 86.7%, the rim of the limbus was raised and 13.3% it was flat; in 20.75%, a recess was found deep to the margin of the limbus and 10.37% showed probe patency. A significant positive correlation was observed between cardiac weight and area of FOv. Conclusion: By autopsy method, we found the prevalence of PFO is 4.71%, which is lower than Western population, our study also provides the accurate measurements related with several morphometric variation such as shape of FOv and limbus FOv.

Keywords: Fossa ovalis, morphology of heart, patent foramen ovale


How to cite this article:
Honnegowda TM, Alghamdi MA. A clinical relevance of fossa ovalis and patent foramen ovale: A morphological study of human heart. J Pract Cardiovasc Sci 2021;7:198-201

How to cite this URL:
Honnegowda TM, Alghamdi MA. A clinical relevance of fossa ovalis and patent foramen ovale: A morphological study of human heart. J Pract Cardiovasc Sci [serial online] 2021 [cited 2022 May 29];7:198-201. Available from: https://www.j-pcs.org/text.asp?2021/7/3/198/332494




  Introduction Top


The foramen ovale (FO) is an opening in the interatrial septum resulting from incomplete coverage of the ostium secundum – an opening within the septum primum – by the septum secundum.[1],[2] The FO serves as a one-way valve for physiologic right-to-left shunting of oxygenated blood in utero.[3] Blood from the placenta enters the right atrium through the inferior vena cava and crosses the FO into the systemic circulation. Postnatal lung expansion and initiation of the pulmonary circulation reverse the atrial pressure gradient, causing functional closure of the FO. Fibrosis follows closure and complete fusion of the interatrial septae occurs by 2 years of age in most individuals.[3],[4] Lack of septal fusion results in a patent FO (PFO).[5] PFO is a remnant of the fetal FO, which normally closes at birth, and in about 25% of the population, the FO fails to close properly, leaving them with a PFO.[5],[6] The presence of probe patency of FO (PFO) which leads to a number complications such as pulmonary emboli and myocardial infarction by affecting multiple organs, including the brain, heart, and lung.[6] To identify and characterize the complications of PFO several modalities are available such as transesophageal cardiac ultrasound, etc., However, autopsy is a most precise method for detecting PFO and its prevalence reported in past autopsy studies was 24.6% overall.[7] Autopsy studies have shown that the prevalence of PFO is approximately 25% in whites or blacks.[8] However, there is a paucity of data on the Asian population with regard to morphometric variations of fossa ovalis (FOv) and FO.


  Materials and Methods Top


The study was conducted in Kannur Medical College, Kerala, on 106 normal hearts available in the department of anatomy. The hearts were collected from cadavers and also procured from department of forensic medicine and were preserved in 10% formalin. The main objective is to conduct the morphological variations of FO and prevalence of PFO in Asian population as no studies were available with regard to autopsy method. The heart weight was recorded. The right atrium was opened with a cut parallel to the right atrioventricular sulcus, from the inferior vena cava to the base of the right auricle. Observations and measurements were made using digital Vernier calipers to the following parameters.

  • FO shape (FOv) was observed (circular, oval, or elliptical) and recorded. (Circular type-two diameters were equal: Oval type-one of the diameters was longer than the other with floor of the fossa flat and elliptical type-one of the diameters was longer than the other with floor of the fossa lax)
  • Dimensions of FO were measured (in mm) with the help of digital Vernier caliper
  • Thickness anterior and posterior limbus (mm) was measured
  • Redundancy of FO was observed (aneurysmal and redundant) and recorded
  • Probe patency of FOv was confirmed.


Statistical analysis

The data were expressed in mean and standard deviation. Correlations between the heart weight and morphologic parameters of the FOv were analyzed using the Wilcoxon test. P < 0.05 was considered to be statistically significant. Statistical analysis was performed using the SPSS software 15th version (SPSS, Chicago, Illinois).


  Results Top


The thickness of the anterior and posterior limbus of the FOv and the area of the FO is summarized in [Table 1]. The shape of FOv is oval in 88 (83%) cases, circular in 14 (13.2%) cases, and elliptical in 4 (3.7%) [Figure 1]. Annulus or limbus of FOv was raised in 92 cases (86.7%) and flat in 14 cases (13.3%) [Figure 2]. Recess in relation to annulus: Deep recess, which was 5–10 mm in depth, was found in 22 cases (20.75%), whereas it was merely slit-like in 9 cases (8.5%), and in another 10 cases (9.5%), pouch or pocket was present deep to annulus [Figure 2]a. The floor of Fov was flat in 82 cases (77.35%). Aneurysmal in 15 cases (14.15%). The floor was redundant or lax in nine cases (8.5%) [Figure 2]a and [Figure 2]b. PFO: 5 cases (4.71%) showed PFO, whereas 11 cases (10.37%) had only probe patency [Figure 3]. A positive correlation between cardiac weight and area of FOv (r = 0.038), and cardiac weight and thickness of the anterior limbus (r = 0.030) and posterior limbus (r = 0.045) of the fossa was obtained. In the present study, one of the specimen showed the presence of fibrous strands of approximately 0.5–1.0 cm in length arising from the right surface of FOv from about its middle and were directed to the anteroinferior part of the limbus [Figure 4]a. The branching and anatomizing of the strands formed a network in FOv. Moreover, in another one specimen, a very interesting variation has been found in one specimen where the FO is perforated with the presence of 8–10 pores [Figure 4]b.
Table 1: Area of the fossa ovalis and thickness of the anterior and posterior limbus

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Figure 1: Shapes of fossa ovalis. (a) Oval and (b) circular. Double-headed red arrow indicates the long axis.

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Figure 2: Annulus fossa ovalis. (a) The annulus is raised along the whole circumference (black arrows). The fossa ovalis show redundancy. (b) The annulus is flat except in its upper part which shows a prominent recess (red arrows).

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Figure 3: (a) Probe patency where red probe has been negotiated through the right atrium (black arrow) (b) Patent foramen ovale showing (red arrow) via the right atrium.

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Figure 4: Photograph (a) Showing a large number of fibrous strands (red arrows) in the anteroinferior part of fossa ovalis. (b). Several openings showing in (white arrows) in the floor of the fossa.

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  Discussion Top


During fetal development, the FO allows blood to pass from the right atrium to the left atrium, bypassing the nonfunctional fetal lungs while the fetus obtains its oxygen from the placenta.[3],[4] A flap of tissue called the septum primum acts as a valve over the FO during that time. After birth, the introduction of air into the lungs causes the pressure in the pulmonary circulatory system to drop. This change in pressure pushes the septum primum against the atrial septum, closing the foramen. The septum primum and atrial septum eventually fuse together to form a complete seal, leaving a depression called the FOv. By age two, about 75% of people have a completely sealed FOv. An unfused FOv is called a PFO.[9] The reasons for PFO is poorly understood. Accumulating evidence suggests that genetic factors contribute to the persistence of PFO and other defects of atrial septation, including atrial septal defects (ASDs)[10],[11] A number of studies have shown that ASD exhibits autosomal dominant inheritance, and a list of causative genes encoding cardiac transcription factors and their targets, (NKX25, TBX5, ATA4, MYH6 ACTC, and TBX20) have been identified. Variation in these genes or their expression may contribute to the development of PFO.[12],[13]

A study by Reig et al.[14] reported dimensions of FOv by the method of (transesophageal echo cardiography, [TEE]) in European population: Area of FOv was 176.15 ± 106.9 mm2, thickness anterior limbus was 7.24 ± 1.83 mm and thickness of posterior limbus was 6.38 ± 2.4 mm, whereas in the present study, average area of FOv is 160.20 ± 104.9 mm2, thickness anterior limbus is 7.24 ± 1.83 mm and thickness of posterior limbus is 6.38 ± 2.4 mm. We found a positive correlation between heart weight and dimensions to concluded that in the individuals with high cardiac weight, the area of FOv is larger than those who have low cardiac weight. In a study by Joshi et al.[15] reported the shape FOv was oval in 41 (82%) cases, circular in 7 (14%) cases, and elliptical in 2 (4%) cases. In the present study, we found the oval shape in 88 (83%) cases, circular in 14 (13.2%) cases, and elliptical in 4 (3.7%). George A. Christie gave a detailed description of the development of limbus FOv.[16] Annulus or limbus FOv was raised cases (86.7%) and flat in 14 cases (13.3%) in the present study and deep recess in relation to annulus was found in 22 cases (20.75%) which had a depth ranging from 5 to 9 mm, whereas it was merely slit-like in nine cases (8.5%), and in another 10 cases (9.5%), pouch or pocket was present deep to annulus and depth ranges from 3 to 8 mm. No other study elaborates the presence of deep recess or slit deep to annulus. Anthony Pearson et al.[17] described the atrial septal aneurysm (ASA) as a localized out-pouching of the FOv region of the atrial septum and found aneurysmal FOv in 1% of autopsies but by TEE, it was found to be 8%. Kydd et al.[9] observed ASA in 12%. In the present study, the floor of Fov was flat in 82 cases (77.35%) and aneurysmal in 15 cases (14.15%). The floor was lax or redundant in nine cases (8.5%).

Marelli et al.[18] and Bergman et al.[19] have reported an incidence of probe patency of FO is 25% in the general population. A transesophageal cardiac ultrasound study showed that the frequency of PFO was similar among whites (34%), blacks (31%), and Hispanics (37%).[20] However, their participants did not include Asians. Rana et al. have reported an incidence of 25%–35%.[6] Fisher et al. reported PFO incidence of 9.2%,[21] whereas in the present study, it was 4.71%. However, Shirani et al.[22] reported PFO in 70% cases who had aneurysm of FOv. It is possible that in cases with aneurysmal FOv, the incidence is much higher and such high incidence may be due to inclusion of PFO with the probe patency.

The presence of fibrous strands in FOv was observed in 2 (1.25%) of the specimen studied and one specimen where floor of the FOv is perforated with 8–10 pores. This unique feature of fibrous strands in FOv and perforated floor of FO has not been reported in the available literature. In such cases, difficulty may be encountered in transcatheteric closure of PFO. Babaliaros et al.[23] have stated that in 20% to 25% of adult patients, the FOv is probe patent (PFO) and may not require needle puncture.[12],[13] In approximately two-thirds of patients, the fossa is paper thin, and the catheter can be passed into the LA and they advocated that echocardiographic visualization of the atrial septum has aided in the safety of transseptal catheterization TTE has limited utility, but TEE is more useful, particularly when visualizing a specific area of the FOv to be punctured.

Study limitations

First, it may not represent the general population since it was an autopsy study. Second, age and gender were not taken into accountability, although the study was done on adult heart specimen. Depending on the age and gender of population, the prevalence could be different. Finally, we did not make a direct comparison of the prevalence of PFO among different ethnic groups because our study included only an Indian population.


  Conclusion Top


We conclude that the prevalence of PFO is 4.71% found through the autopsy method, which is lower than western population, our study also provide the accurate measurements related with several morphometric variation such as shape of FOv, its limbus which remain customary in evaluating the every case of ASD and in treating PFO patients by cardiologist and interventionist.

Ethics clearance

Ethical clearance was taken before the collection of specimens.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Hagen PT, Scholz DG, Edwards WD. Incidence and size of patent foramen ovale during the first 10 decades of life: An autopsy study of 965 normal hearts. Mayo Clin Proc 1984;59:17-20.  Back to cited text no. 8
    
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Garg V, Kathiriya IS, Barnes R, Schluterman MK, King IN, Butler CA, et al. GATA4 mutations cause human congenital heart defects and reveal an interaction with TBX5. Nature 2003;424:443-7.  Back to cited text no. 12
    
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Joshi SD, Chawre HK, Joshi SS. Morphological study of fossa ovalis and its clinical relevance. Indian Heart J 2016;68:147-52.  Back to cited text no. 15
    
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Shirani J, Zafari AM, Roberts WC. Morphologic features of fossa ovalis membrane aneurysm in the adult and its clinical significance. J Am Coll Cardiol 1995;26:466-71.  Back to cited text no. 22
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1]



 

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