Original Article
Age as a Predictive Tool of Aortic Valve Dimensions-An Autopsy Based Observational Study
1Padmini Noone, 2Shirley Vasu
- 1Department of Forensic Medicine and Toxicology, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, India
- 2Department of Forensic Medicine, Thrissur Government Medical College, Thrissur, Kerala, India
- Submitted: Thursday, January 22, 2015
- Accepted: Saturday, January 24, 2015
- Published: Thursday, March 05, 2015
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Abstract
Introduction
Diseases of the aortic valve cause considerable morbidity and mortality. Modern cardiothoracic surgery procedures including valve replacement procedures give tremendous relief to the suffering. In certain transcutaneous procedures used in aortic stenosis, unlike in open heart surgery, there is no way of direct valve sizing. A non-invasive method of estimating valve size would be helpful. The aims of the study were to estimate the average aortic valve dimensions for each age group for male and female and also to compare the valve dimensions with the external and internal parameters of the body and heart.
Study Design
It was a prospective observational type of study. Data collected from consecutive cases over a period of one year was analysed. 585 cases with age ranging from 13 days to 90 years were examined. Mean age was 42.26 years
Material and Methods
Aortic valves from hearts dissected at autopsy were formalin fixed. Measurement of aortic valve circumference was taken at the supra aortic ridge (commissure) level. The valve diameter, circularised orifice area, effective indexed orifice area were calculated from it. The correlations of aortic valve dimensions with the external and internal parameters were assessed. Linear regression between aortic valve diameter and age was done.
Results
The mean aortic valve diameter of adult was 2.1cm (S.D 0.296). The regression equation to derive aortic valve diameter from age in adults aged 21 years or above was 1.718 + 0.009 x age (in years).
Conclusions
From the above study we were able to conclude that the age and aortic valve measurements correlate positively in adults. The results can be of use to the anatomist, pathologist doing autopsy as well as the cardiothoracic surgeons.
Key words
Aortic valve, aortic stenosis, valve replacement, supra aortic ridge, age, valve measurement
Introduction
Diseases of the aortic valve cause considerable morbidity and mortality. Modern cardiothoracic surgery procedures including valve replacement procedures give tremendous relief to the suffering. In certain procedures like Transcutaneous Aortic Valve Replacement procedure, which is used in elderly with aortic stenosis, unlike in open heart surgery, there is no way of direct valve sizing. A noninvasive method of assessing valve size would benefit cardiothoracic surgeons and the patients alike. The aims of the present study were to obtain a regional database of valve measurement and to correlate it with various parameters including, age, sex, height, weight, body mass index, body surface area, left ventricular thickness, weight of the heart. The measurements obtained were compared with previous studies in different ethnic population.
The present study shows that valve measurements increase with age. The regression formula obtained can be a strong predictive tool for finding the appropriate valve size for a patient of a particular age.
Methods
The study was conducted with the approval from the institutional ethics committee. The subjects were selected from consecutive autopsies conducted at the Department of Forensic medicine, Calicut Medical College during the period of one year, dying of non- cardiac causes (inclusion criterion).The age ranged from 13 days to 90 years. Mean age was 42.26 years. Total no of cases 585. Their body surface area ranged from 1.62 to 2.25 m2 .The bodies whose age particulars were not clear, those showing advanced decomposition, trauma involving the heart were excluded from the study. Only cases where the identity was known and details verified as per police requisition was collected for the study. In these cases the age is verified by the police and the relatives prior to autopsy. During autopsy approximate age estimation is done based on physical characteristics and changes in ossification and suture closure.
The valves were examined after dissection because the valves and coronaries had to be routinely exposed and examined during medico legal autopsy in our center. The method of dissection was Virchow’s method modified by Prausnitz [1]. The aortic valves were removed by trimming the ascending aorta 1 cm above the sinotubular junction 3 and 1 cm below the valve and were formalin fixed for 24 hours. The valves were measured by using a ruler [2] measuring to the nearest mm after placing it on wooden board and rechecked using Vernier callipers. The measurements were noted down and the other parameters like age, sex, height, weight, were also noted. The body mass index and body surface area were calculated using Quetlet index and Mosteller formula respectively. The aortic valve area and diameter were calculated from the aortic valve circumference assuming the orifice to be circular [3].
The ratio of valve area with body surface area was also calculated (effective
Indexed orifice area). SPSS version 15, Chicago, was used for statistical analysis.
The correlation between aortic valve circumference and age, height, weight, body surface area, body mass index, left ventricular thickness, weight of heart, was tested using Pearson’s correlation coefficient. Linear regression between age and aortic valve circumference and diameter respectively was done.
Results
The results of the study were as follows. The mean aortic valve circumference and diameters for the age groups were charted (Table 1).
|
Age group
|
Male
|
Female
|
|
less than 20
|
1.77 +/-0.31
|
1.52+/-0.33
|
|
20 - 29
|
1.95+/- 0.21
|
1.84+/-0.19
|
|
30-39
|
2.12+/- 0.15
|
1.93+/-0.13
|
|
40-49
|
2.16+/-0.20
|
1.99+/-0.14
|
|
50-59
|
2.29+/-0.19
|
2.16+/-0.21
|
|
60-69
|
2.33+/-0.21
|
2.26+/-0.20
|
|
70-79
|
2.42+/-0.21
|
2.28+/-0.12
|
|
More than 80
|
2.54+/-0.17
|
2.29+/-0.17
|
The table showing aortic valve diameter in cms for adult male and female in a particular age group (values +/-1
SD)
The effective indexed orifice area is shown in (Table 2) Aortic valve circumference values were compared with the results of study by Davis
et al.,
[4] in (Table 3). Mean aortic valve diameter of those aged 17 years and above was compared with the results by Capps
et al.,
[5] in (Table 4). Statistical correlation using Pearson’s correlation coefficient revealed the following. The valve measurements correlated significantly with age, heart weight, left ventricular thickness, body surface area, height and weight in adults (Age>/=21 years). Strongest correlation was obtained with age. The Pearson correlation coefficient between age and aortic valve diameter was 0.615 significant at the 0.01 level and no significant correlation was obtained with body mass index. Pearson correlation coefficient being 0.075.
|
Age group
|
Male
|
Female
|
|
less than 20
|
1.78 +/-0.36
|
1.54+/-0.27
|
|
20 -
29
|
1.74+/- 0.39
|
1.72+/-0. 32
|
|
30-39
|
2.04+/- 0.30
|
1.82+/-0.34
|
|
40-49
|
2.22+/-0.41
|
2.05+/-0.34
|
|
50-59
|
2.46+/-0.45
|
2.41+/-0.52
|
|
60-69
|
2.70+/-0.54
|
2.73+/-0.53
|
|
70-79
|
3.04+/-0.56
|
2.89+/-0.34
|
|
More than 80
|
2.25+/-0.59
|
2.05+/-0.59
|
Table showing effective indexed orifice area (cm2/m2) ( Values +/- 1 SD)
|
|
Present Study |
Study by Davis et al [4] |
|
Age group(years)
|
Male
|
Female
|
Male
|
Female
|
|
30-39
|
6.6 ( 5.7-7.6)
|
6.1(5.2-6.9)
|
6.5 ( 5.8-7.5)
|
6.3 (5.8-6.8)
|
|
40-49
|
6.7 (5.5-8.0)
|
6.2(5.4-7.1)
|
6.3 ( 5.8-7.6)
|
6.2 ( 5.6-7.4)
|
|
50-59
|
7.1 (5.7-8.6)
|
6.8(5.5-8.1)
|
6.7 ( 6.3-8.4)
|
6.6 ( 5.6-7.6)
|
|
60-69
|
7.3(6.0-8.6)
|
7.1(5.8-8.3)
|
6.9 ( 5.6-8.4)
|
7.2 ( 6.8-8.5)
|
|
70-79
|
7.5(5.8-9.2)
|
7.2(6.4-7.9)
|
8.0 ( 7.4-9.0)
|
7.9 ( 6.7-9.0)
|
|
80 and above
|
7.9(6.9-9.0)
|
7.2(6.1-8.2)
|
8.6 ( 7.6-9.0)
|
7.0 ( 6.9-8.7)
|
Aortic valve circumference in comparison with the results given by Davis et al.,
[4] ( with values +/- 2
SD)
|
|
Present study
|
Study by Capps
[5]
|
|
Male
|
21.7 (+/-2.5)
|
23.1(+/-2.0)
|
|
Female
|
20.1(+/-2.4)
|
21.0(+/-1.8)
|
Mean aortic valve diameter of those aged more than or equal to 17 years in comparison with the results given by Capps
et al [5] (mms)( Values +/-1SD)
The valve measurements correlated significantly with age, heart weight, left ventricular thickness, body surface area, height and weight in adults (Age>/=21 years). Strongest correlation was obtained with age. The Pearson correlation coefficient between age and aortic valve diameter was 0.615 significant at the 0.01 level and no significant correlation was obtained with body mass index. Pearson correlation coefficient being 0.075.
Linear regression between age and aortic valve measurements were as follows. The regression formula for aortic valve circumference was obtained (Table 5). Graph is depicted in (Figure 1).
|
1.718 + 0.009
x age (years)
|
|
{r2
= 0.379}
|
Regression formula for deriving aortic valve diameter from age in adults (more than or equal to 21 years)
Figure 1: Graph showing linear regression between age and aortic valve circumference in adults aged 21 years or above
Discussion
Various autopsy studies have been conducted on the aortic valve. Rowlatt
et
al., [6] calculated the mean normal value of aortic valve dimensions and standard deviation, based on body surface area. According to studies conducted by Krovetz et al., [7] and Westaby et al., [8] aortic orifice enlarges as adults age. According to them and Sholtz et al., [9] aortic valve dimensions correlate poorly with body surface area. However studies by Capps and colleagues [5] showed that aortic diameter is closely related to body size and body surface area.
The rate of growth of aortic valve in childhood has been described [6, 10, 11]. The aortic valve size area increases at a lower rate than the body surface area of the human body until maturity is reached at approximately 18-21 years of age. After that age, aortic valve size increases nearly linearly with age [7]. In the present study formula was derived for the adult valve size.
In the present study it was found that the aortic valve circumference increases with age and it also correlated significantly with other parameters like left ventricular thickness, heart weight, body weight, body height, body surface area. The age was selected as the predictive tool as it had the strongest correlation.
Conclusions
The key message is that age is a predictive tool of aortic valve measurement in adults. The regression equation derived can be help in choosing appropriate valve size for a patient. The average valve measurements of a particular age group and sex also help in assessing valve dimensions better especially in the regional population.
Learning points
The mean aortic valve diameter of adult = 2.1cm (S.D 0.2960)
The regression equation to derive aortic valve diameter from age in adults aged 21 years or above = 1.718 + 0.009 x age (in years).
Competing interest
The authors declare that there are no competing interests.
Authors’ contributions
PN:: conceived the study, participated in the design data collection and preparation of draft and edited the final manuscript.
SV: conceived the study, participated in the design data collection and preparation of draft and edited the final manuscript.
The authors have read and approved the final version of the manuscript.
Ethical Considerations
The study was approved by the Institute Ethics Committee.
Acknowledgement
We humbly bow in respect to the dead, who in their death did leave behind a lesson for us. Thanking all our colleagues in the dept. of Forensic medicine and dept. of Anatomy for the support. Thanking friends and family for all the help rendered. (Special thanks to Dr Thomas Mathew, Dr Sujith, Dr Sonu, Dr Sanjay, Dr Prajith, Dr Govindraj, Dr Ashalata, Dr Nitin (cardiothoracic surgeon), Dr Oliver Noone, and Dr. Mohan)
Funding
None declared
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