A schematic representation of the aortic valve from a top view, showing the relationship between the valve and the aortic valve. A schematic representation of the aortic root showing the four components (i) annulus, (ii) leaflets, (iii) aortic sinuses and the (iv).
LIST OF TABLES
LIST OF PLATES
LIST OF ABBREVIATIONS ABBREVIATION INTERPRETATION
Furthermore, the study demonstrates the difference between the curvature of the aortic annulus and the sino-tubular junction. For the aortic root morphometry study, 30 heart samples were selected for this study.
INTRODUCTION
SIGNIFICANCE OF THE STUDY
The purpose of this study is that an appropriately sized prosthesis can induce changes in the morphology and morphometry of the aortic root orifice, with particular reference to the effect on the left coronary ostium (LCO). To investigate the influence of race, height and sex on aortic root morphometry and LCO.
LITERATURE REVIEW
THE AORTIC ROOT: HISTORICAL BACKGROUND
The earliest detailed study of the anatomy of the aortic valvular complex was attributed to Leonardo da Vinci, who published descriptions and drawings of the cardiac chambers, valves, and coronary vasculature (Figures 1 and 2) (Piazza et al., 2008). Given the increasing incidence of coronary artery disease, aortic valve disease, and surgery, many studies of aortic root anatomy have been performed.
THE AORTIC ROOT: NOMENCLATURE OF AORTIC ROOT
- GROSS ANATOMY
- AORTIC ANNULUS
- AORTIC VALVE LEAFLETS
- AORTIC SINUSES
- SINO-TUBULAR JUNCTION
- CORONARY OSTIA
The aortic root is a continuation of the left ventricular outflow tract that extends to the sinotubular junction where the aortic aorta begins (Anderson, 2000). The valve leaflets are thin, flexible structures that occlude the lumen of the aortic root by coaptation during diastole (Butcher et al., 2011).
FUNCTIONS OF THE AORTIC ROOT
However, at the level of the sino-tubular junction, there are more elastic fibers than fibrous tissue in the aortic root wall, which can increase the aortic root diameter by 16 percent (Standring et al., 2008). During diastole, the heart muscle relaxes and blood returns from the aorta, forcing coaptation of the semilunar valves and closure of the aortic valve (Figure 21).
- NORMAL AORTIC ROOT DIMENSIONS
- THE NARROW AORTIC ROOT
- CORONARY ARTERY STENOSIS AFTER AORTIC VALVE REPLACEMENT
- TRANSCATHETER AORTIC VALVE IMPLANTATION
Normal aortic sinuses promote smooth, non-turbulent blood flow in the coronary vessels (Standring et al., 2008). Aortic valve stenosis was initially treated by passing dilators through the aortic root (Townsend et al., 2004). Patients with aortic stenosis and regurgitation are relieved by this procedure (Townsend et al., 2004).
The diameters of the aortic root tend to increase significantly with age from childhood (Biaggi et al., 2009; Vritz et al., 2011;. The prosthesis is positioned obliquely and partially over the annulus by taking advantage of the bulging coronary sinus (Ishida et et al., 2001).
CLINICAL RELEVANCE
A significant number of patients with aortic valve disease are refractory to AVR due to advanced age, left ventricular failure, and other medical conditions (Iung et al., 2005). According to Leon et al. 2010), TAVI is associated with a higher risk of stroke than AVR in the postoperative period. Surgical enlargement of the aortic root is associated with prolonged operative time, exposing the myocardium to hypoxic conditions for a longer period of time (Castro et al., 2002).
Up to 5% of patients undergoing AVR may develop life-threatening coronary artery stenosis (Zaikas et al., 2010). Aortic valve function has been shown to depend on the anatomical and dynamic relationship of the aortic valve and root (Bierbach et al., 2010).
MATERIALS AND METHODS
SELECTED HEART SPECIMENS
Of the heart samples examined (n = 75), only 60 samples met the inclusion criteria and were selected for the study. Cadaveric unfixed heart samples (n = 60) for this study were obtained during forensic autopsies at the Gale Street State Mortuary in the eThekwini Municipality of Durban, South Africa. The procedure was a simulation of the "shoe horn" technique used to implant a large valve in a narrow aortic root.
Of these 30 samples, 15 hearts were used in a further experimental study to investigate and compare aortic root bendability at the annulus and sino-tubular junction. Ethical approval for the study was obtained from the University of KwaZulu-Natal Biomedical Research Ethics Committee (Ethics number BE 307/15).
METHODS
- ASSESSMENT OF GROUP B SPECIMENS: AORTIC VALVE REPLACEMENT REPLACEMENT
The internal aortic diameters at the level of the aortic annulus and sino-tubular junction were measured using a mathematical divider and a millimeter ruler (Figure 25). A probe with a sizer attached is inserted into the aorta to measure the size of the aortic annulus (Adapted from Ueda 2010). After measuring the diameter of the aortic annulus, an artificial valve (Figure 28) at 4 millimeters (two sizes larger) than the estimated diameter of the annulus was deliberately fitted into the annulus to simulate AVR in a narrow aortic root.
The valve is attached to the pieces and at the lower attachment of the valve tips. The distance from the lower border of the LCO to the aortic annulus was also measured.
STATISTICAL ANALYSIS (a) Group A
Ethical approval was obtained from the University of KwaZulu-Natal Biomedical Research and Ethics Committee (BREC No. 307/15). Concierge permission and approval was sought and obtained from the Chief Forensic Pathology Services Specialist, Gale Street State Mortuary.
RESULTS
GROUP A: NORMAL AORTIC ROOT .1 SAMPLE DEMOGRAPHICS .1 SAMPLE DEMOGRAPHICS
- AORTIC ROOT DIAMETERS
In this group, 30 normal postmortem hearts were analyzed for the morphometric variations in the aortic root and LCO.
AGE DISTRIBUTION
THE AORTIC ROOT DIAMETERS IN RELATION TO SEX
There was no significant difference in the mean aortic annulus diameter between men and women (p = 0.85) (Table 10). b) The aortic diameter at the sinotubular junction. There was no statistically significant difference in the diameter of the sino-tubular junction between men and women (p-value = 0.72) (Table 10).
THE DIAMETERS OF THE AORTIC ROOT IN RELATION TO RACE
THE DIAMETERS OF THE AORTIC ROOT IN RELATION TO HEIGHT In assessing the influence of height of individuals on the aortic root diameters, the subjects
THE DIAMETERS OF THE AORTIC ROOT IN RELATION TO AGE
THE RELATIONSHIP BETWEEN DIAMETER AT THE AORTIC ANNULUS AND SINO-TUBULAR JUNCTION
SHAPE OF THE LEFT CORONARY OSTIUM (LCO)
The shape, position and size of the left coronary ostia were analyzed in 30 heart samples. Key: LCO= Left coronary ostium, RCO = Right coronary ostium, RAS = Right aortic sinus, NCAS = Non-coronary sinus, LAS = Left aortic sinus, LV = Left ventricle.
POSITION OF THE LCO
Oduu durii: LCO = Ostium koroonaa bitaa, RCO = Ostium koroonaa mirgaa, RAS = Saayinisii aortic mirgaa, NCAS = Saayinisii koroonaa hin taane, LAS = Saayinisii aortic bitaa.
HEIGHT OF LCO FROM AORTIC ANNULUS
There was no significant relationship between the height of the LCO and the height of individual subjects (p = 0.339) (Table 15). The difference between the two diameters in males and females was statistically significant (p = 0.009) (Table 16). b) The diameter of the LCO in different racial groups. There was no significant relationship between LCO diameter and age of individuals (Table 16). d) The diameter of the LCO in relation to height of individuals.
There was a statistically significant correlation between the diameter of the LCO and the height of the individuals (p = 0.04) (Table 16). Key: LCO = left coronary ostium, RCO = right coronary ostium, NCAS = Non-coronary aortic sinus, LV = Left ventricle, h = height of LCO from aortic annulus.
GROUP B: AORTIC VALVE REPLACEMENT
- CHANGES IN DIAMETER OF LCO
- CHANGES IN HEIGHT OF LCO FROM AORTIC ANNULUS
- DISTORTION OF AORTIC WALL
It was observed that the shape of the LCO for this specimen was circular in all (100%) specimens before insertion of the prosthesis (Plate 11). After insertion of the prosthesis, the shape of the LCO changed to elliptical in all 30 specimens (Plate 12). There was significant difference (p-value 0.00) between the normal diameter before prosthesis insertion and vertical diameter of the LCO after prosthesis insertion.
The mean distance from the lower border of the LCO to the aortic annulus was mm. It was located just above the LCO and almost buried the orifice of the left coronary artery (Plate 12).
PLIABILITY OF THE AORTIC ANNULUS AND SINO-TUBULAR JUNCTION
The flexibility of the aortic annulus was believed to be the extent to which the aortic annulus could be stretched, viz. the difference between normal and expanded diameters. The mean difference between normal and stretched diameters was mm and this represented the extent to which the sino-tubular junction could be stretched, viz. the flexibility of the sino-tubular junction. The relationship between the flexibility at the aortic annulus and at the sino-tubular junction is shown in Figure 31.
Figure 15.2 represents the flexibility of the sino-tubular junction when the flexibility at the aortic annulus is zero. Therefore, the sino-tubular junction is more flexible than the aortic annulus by a factor of 1.5.
SU MMARY OF RESULTS .1 AORTIC ROOT DIAMETERS
- MORPHOLOGY AND MORPHOMETRY OF LCO
- AORTIC VALVE REPLACEMENT
For any change in diameter at the aortic annulus, the sino-tubular junction will change 1.5 times more.
DISCUSSION
- GROUP A: AORTIC ROOT DIAMETERS .1 SAMPLE DEMOGRAPHICS
- THE AORTIC ROOT DIAMETERS IN RELATION TO SEX
- THE DIAMETERS OF THE AORTIC ROOT IN RELATION TO RACE
- THE DIAMETERS OF THE AORTIC ROOT IN RELATION TO HEIGHT
- THE DIAMETERS OF THE AORTIC ROOT IN RELATION TO AGE
- THE RELATIONSHIP BETWEEN DIAMETER AT THE AORTIC ANNULUS AND SINO-TUBULAR JUNCTION
- THE LEFT CORONARY OSTIUM
- SHAPE OF THE LCO
- POSITION OF THE LCO
- THE HEIGHT OF THE LCO
- THE DIAMETER OF LCO
- GROUP B: AORTIC VALVE REPLACEMENT
- CHANGES IN SHAPE OF THE LCO
- CHANGES IN THE DIAMETER OF THE LCO
- CHANGES IN THE HEIGHT OF THE LCO
- RIDGE FORMATION ABOVE THE LCO
- PLIABILITY OF THE AORTIC ANNULUS AND SINO-TUBULAR JUNCTION The present study showed that the sino-tubular junction is more pliable than the aortic
This study was designed to investigate the morphometry of the aortic root and LCO. The present study showed no correlation between aortic root diameter at annulus and sino-tubular junction and height (p = 0.859) (Table 12). The observed diameters of the aortic annulus and the diameter of the aortic root at the sino-tubular junction showed a significant correlation (Figure 28).
In the present study, the LCO was located below the sino-tubular junction in the majority (73.3%) of the cases. The distance of the LCO from the aortic annulus is often used to locate the LCO.
CONCLUSION
- AORTIC ROOT DIAMETERS
- THE LEFT CORONARY OSTIUM
- AORTIC VALVE REPLACEMENT
- PLIABILITY OF THE AORTIC ANNULUS AND SINO-TUBULAR JUNCTION The sino-tubular junction is relatively more pliable in comparison to the valve annulus being
- STUDY LIMITATIONS
The gross anatomical features of the aortic root in this study confirmed with the description of the aortic root in standard textbooks (Townsend et al., 2004;. Age was noted to be a strong determinant of the size of the aortic root, confirming previous reports that the aortic root size increases with age. The size of the aortic root in white men was significantly larger than in black native South African men, however, no significant differences were noted in Indians.
The present study concluded that gender, race, height and age did not significantly affect the distance between the LCO and the aortic annulus. This enables placement of a prosthetic valve significantly larger than the size of the annulus i.
Oblique aortic valve replacement and coronary artery bypass grafting for severely calcified narrow aortic root with unstable angina. Enlargement of the aortic valve annulus by enlarging the aortic incision in the anterior mitral leaflet. Anatomy of the aortic valve complex and its implications for transcatheter aortic valve implantation.
Impact of valve prosthesis and patient mismatch on left ventricular mass regression after aortic valve replacement. A framework for systematic characterization of the aortic valve complex by real-time three-dimensional echocardiography: Implications for transcatheter aortic valve replacement.
APPENDIX
Gender Aortic annulus diameter. cm) Gender Aortic annulus diameter. mm) Diameter on the Chinese pipe connection (mm). cm) Gender Aortic annulus diameter. mm) Diameter on the Chinese pipe connection (mm). cm) Gender Aortic annulus diameter. mm) Diameter on the Chinese pipe connection (mm). cm) Gender Aortic annulus diameter. mm) Diameter on the Chinese pipe connection (mm).
