P055. Aortic Wall Lamellar Structure in Phylogeny and in Humans
Presented During: POD Abstracts (Available for viewing in the exhibit hall for the duration of the meeting)
Yale University
Trumbull, CT
United States - Contact Me
12th Grade Student at Hopkins School, New Haven, CT
Over the past year, I have been working with the Yale Aortic Institute's research team to conduct thorough literature reviews and write articles in hopes of deepening our understanding of the aorta.
Thursday, April 25, 2024: 5:38 PM - 7:00 PM
Sheraton Times Square
Room: Central Park
Description
Objective: Despite a voluminous literature on the aorta in health and disease, relatively little has been written about the lamellar architecture constituting the aortic wall. In this study, we provide a histological overview of the lamellar organization of the developing aorta in individuals with a tricuspid aortic valve (TAV). We further have undertaken literature review to elucidate (1) the number of aortic wall lamellae in various animals, as well (2) in (adult) humans, the number of aortic lamellar layers, and the decrement in lamellar layers in proceeding distally along the course of the aorta.
Methods: Non-dilated (n=60) ascending aortic wall samples were collected (embryonic–70 years of age), categorized in eight age groups. On PubMed we queried the following search terms: "aortic lamellar layers", "lamellar layers in ascending aorta", "lamellar layers in descending aorta", "extracellular matrix", "elastin", "vascular smooth muscle cells". This yielded 287 articles pertinent to our quest, which were reviewed in detail. Only five of these articles contained estimations of lamellar counts.
Results: Our study demonstrated that in the premature aorta, the medial layer consists of neatly organized elastic lamellae without pathological features such as elastic fiber thinning, fragmentation, or degeneration, whereas in the adult aorta progressive elastic fiber pathology is seen resulting in decreased aortic wall strength. A significant difference in the number of lamellae is further seen between the various age categories (figure 1). The neonate group contains the lowest number of lamellae, which increases significantly till the age of 6 years (p<0.01). In adolescence a slight decrease in the number of lamellae is observed (p = 0.049), and a further decrease is seen in the adult group (p=0.018) (figure 1).
Our literature review revealed: (A) Animals The number of lamellar units in mammals is closely proportional to the aortic radius, which itself is proportional to the animal body size: The smaller the mammal, the fewer the lamellar layers. (B) Humans The first published studies in humans estimated a thickness of 53 to 78 lamellar layers in the ascending thoracic segment of the aorta. Additional studies reported thoracic aortic lamellar counts ranging from 45 to 56. For the abdominal aorta, recent studies have disclosed about 28 layers. Thus, the lamellar count decreases as one descends the human aorta.
Conclusion: Dedicated studies on lamellar number in phylogeny is scant. Dedicated studies on number and progression of aortic lamellar layers with aging are also scant. Nonetheless, our study on the lamellar architecture in human aortic tissue and literature review supports the following conclusions: (1) In phylogeny, number of aortic layers increases proportionately with animal body size. (2) In human children, the number of lamellae increases progressively until age 6. (3) Adult human aortas carry approximately 50 to 75 lamellar layers. (4) In humans, lamellar layers decrease slowly but progressively from adulthood to old age, which in combination with progressive lamellar pathology likely contributes to the enhanced adverse event rate in the elderly.
Authors
Mohammad Zafar (1), Nicole Kargin (2), Bulat Ziganshin (1), Nimrat Grewal (3), John Elefteriades (1)
Institutions
(1) Yale New Haven Hospital, New Haven, CT, (2) Aortic Institute, New Haven, CT, (3) Amsterdam UMC, Amsterdam, NA
Methods: Non-dilated (n=60) ascending aortic wall samples were collected (embryonic–70 years of age), categorized in eight age groups. On PubMed we queried the following search terms: "aortic lamellar layers", "lamellar layers in ascending aorta", "lamellar layers in descending aorta", "extracellular matrix", "elastin", "vascular smooth muscle cells". This yielded 287 articles pertinent to our quest, which were reviewed in detail. Only five of these articles contained estimations of lamellar counts.
Results: Our study demonstrated that in the premature aorta, the medial layer consists of neatly organized elastic lamellae without pathological features such as elastic fiber thinning, fragmentation, or degeneration, whereas in the adult aorta progressive elastic fiber pathology is seen resulting in decreased aortic wall strength. A significant difference in the number of lamellae is further seen between the various age categories (figure 1). The neonate group contains the lowest number of lamellae, which increases significantly till the age of 6 years (p<0.01). In adolescence a slight decrease in the number of lamellae is observed (p = 0.049), and a further decrease is seen in the adult group (p=0.018) (figure 1).
Our literature review revealed: (A) Animals The number of lamellar units in mammals is closely proportional to the aortic radius, which itself is proportional to the animal body size: The smaller the mammal, the fewer the lamellar layers. (B) Humans The first published studies in humans estimated a thickness of 53 to 78 lamellar layers in the ascending thoracic segment of the aorta. Additional studies reported thoracic aortic lamellar counts ranging from 45 to 56. For the abdominal aorta, recent studies have disclosed about 28 layers. Thus, the lamellar count decreases as one descends the human aorta.
Conclusion: Dedicated studies on lamellar number in phylogeny is scant. Dedicated studies on number and progression of aortic lamellar layers with aging are also scant. Nonetheless, our study on the lamellar architecture in human aortic tissue and literature review supports the following conclusions: (1) In phylogeny, number of aortic layers increases proportionately with animal body size. (2) In human children, the number of lamellae increases progressively until age 6. (3) Adult human aortas carry approximately 50 to 75 lamellar layers. (4) In humans, lamellar layers decrease slowly but progressively from adulthood to old age, which in combination with progressive lamellar pathology likely contributes to the enhanced adverse event rate in the elderly.
Authors
Mohammad Zafar (1), Nicole Kargin (2), Bulat Ziganshin (1), Nimrat Grewal (3), John Elefteriades (1)
Institutions
(1) Yale New Haven Hospital, New Haven, CT, (2) Aortic Institute, New Haven, CT, (3) Amsterdam UMC, Amsterdam, NA
Presentation Duration
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