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Biomedical Research

Aortic and heart dimensions of children and adolescents in a Nigerian population

Author(s): Obikili EN, Okoye IJ, Anyanwu GE

Vol. 21, No. 2 (2010-04 - 2010-06)

Obikili EN1, Okoye IJ2, Anyanwu GE1

(1) Departments of Anatomy and
(2)Radiation Medicine, College of Medicine, University of Nigeria Enugu Campus, Nigeria

Abstract

There is a paucity of data on aortic and heart dimensions of children and adolescents in Africans. The aim of our study was to establish normal values of aortic, cardiac and thoracic diameters, and the cardiothoraic ratio in children and adolescents in a Nigerian population. The cardiothoracic ratio of 110 males and females aged between 5 and 19 were calculated from the cardiac and thoracic diameters in posteroanterior chest radiographs in a cross sectional study at a tertiary hospital. Prediction formulae were established for aortic and cardiac diameters. The means and standard deviations of aortic, cardiac and thoracic diameters and cardiothoraic ratio were established. The mean values of cardiothoracic ratio for males in the 5-9, 10-14 and 15-19 age groups were 47.7%, 45.7% and 44.1% respectively. The corresponding values for females were 49.7%, 45.0% and 45.1%. The ratio decreased with age in both sexes. These values were larger than those reported for the Caucasians. Our study highlights the need for the use of standards based on local values for the evaluation of cardiovascular diseases in our population.

Keywords: Aortic diameter, cardiothoracic ratio, children and adolescents, Nigerians
Accepted December 27 2009

Introduction

Chest radiography is the most commonly used modality for the detection of cardiomegaly and the evaluation of cardio-thoracic ratio [1]. It is an important indicator of cardiac size [2[. Danzer [3] was the first to describe the cardiothoracic ratio. Ever since he defined it, there have been several studies on the topic. Opinions differ on its usefulness. The cardiothoracic ratio and the relative heart volume have been used as proxy measures of left ventricular mass [4].

The cardiothoracic ratio is affected by such factors as age, phase of respiration, body posture, physique, altitude and race. Kerwin [5] was the first to suggest that racial differences may affect the cardiac size. Ashcroft and Mial [6] noted a higher cardiothoracic ratio in blacks than in whites. Nickol and Wade [7] observed that athletes tended to have a larger heart than the general population because of the normal physiological dilatation of the heart.

Most of the studies on heart dimensions have been on Caucasians. There is a paucity of studies on heart dimensions in African children and adolescence. Odita et al.[8] studied the cardiothoracic ratio in Nigerian newborn infants. Our study was aimed at establishing normal values of aortic, cardiac and thoracic diameters, and cardiothoracic ratio in frontal chest radiographs in children and adolescents. These values are necessary for a better and more accurate evalua-tion of cardiovascular diseases.

Materials and Methods

The subjects studied were individuals referred to the Department of Radiation Medicine, University of Nigeria Teaching Hospital (UNTH) Enugu for routine chest radiographs. The blood pressure, heights and weights of subjects in the 10-14 and 15-19 year-old groups were measured. The focus film distance was 2 metres. At this distance projection distortion is minimal and the magnification is about 5% [9]. The subject stood erect and the central rays were perpendicular to the plane of the film and centred on the 4th thoracic vertebra. The films were anteroposterior views and they were taken in full inspiration. Films that did not meet the criteria normality formulated by Kabala and Wilde10 and Brockington and Bohrer [11] were excluded from the study.

The cardiac and thoracic diameters were measured by the Ungerleider and Gubner [9] method. The cardiac diameter was the sum of the maximum extensions of the heart to the left and right of the midline. The thoracic diameter was measured from the internal surfaces of the ribs above the costal attachments of the diaphragm at the point where the chest diameter was greatest (Fig. 1). The cardiothoracic ratio was calculated from the cardiac and thoracic diameters. Statistical Package for Social Science (SPSS) 6.0 for Windows was used for statistical analysis.

ortic diameter = AL+AR

Figure 1. Aortic diameter = AL+AR; Cardiac diameter = CL+CR; TD= Thoracic diameter.
AL and AR : Maximum extension of the aorta to the left and right of the midline respectively. CL and CR : Maximum extension of the heart to the left and right of the midline respectively

Results

There were 60 males and 50 females in the study. There ages ranged from 5 to 19. Table 1 shows that, in both sexes, the aortic diameter increased with age. There was no significant sex difference in the aortic diameter. The correlation coefficients between the real and predicted val-ues of aortic diameter were significant in both sexes, p< 0.001.

Predicted aortic diameter (cm) of 10-19 year-old males
= 0.005 × age + 0.013 × weight + 0.021 × height + 0.592.
Predicted aortic diameter (cm) of 10-19 year-old females
= 0.042 × age – 0.001 × weight + 0.020 × height + 1.005

The correlation coefficients between the real and predicted values were as follows:

10-19 year-old males: r = 0.7898, p< 0.001
10-19 year-old females: r = 0.6913, p< 0.001

TDCRCLARAL Table 2 shows that the cardiac diameter increased with age in both sexes. In males, the increase was statistically sig-nificant at all age groups, p <0.01. There was no signifi-cant sex difference in the 5-9 and 10-14 age groups whereas in the 15-19 age group, males had significantly larger mean cardiac diameter than females. Using age, weight and height as variables, formulas were established for the prediction of cardiac diameter in males and females. Correlation coeffi-cients between the real and predicted values were statisti-cally significant in both sexes p<0.001. Predicted formulas for the cardiac diameter and the cor-relation between the real and predicted values were also calculated.

Predicted cardiac diameter (cm) of 10-19 year-old males:

= 0.060 x age + 0.040 x weight + 0.021 x height + 5.734

Predicted cardiac diameter (cm) of 10-19 year-old females:

= 0.224 x age + 0.007 x weight – 0.029 x height + 12.306

The correlation coefficients between the real and pre-dicted values were as follows:

10-19 year-old males: r = 0.7798, p< 0.001
10-19 year-old females: r = 0.6746, p< 0.001

As highlighted in table 3, the males in the 5-9 year-old age group had larger mean thoracic diameter than the females of corresponding age, but the difference was not significant. The reverse was the case in the 14-19 year-old age group. In the 15-19 year age group, the males had significantly larger thoracic diameter than the females, p<0.001.

Table 4 shows that in both sexes the cardiothoracic ratio decreased with age and that there was no significant differ-ence in the mean values of males and females.

Table 1. Aortic diameter (cm) of males and females by age

MALES FEMALES
AGE (yr) No. MEAN SD MIN MAX No. MEAN SD MIN MAX P
5 9 7 3.7 0.3 3.3 4.3 5 3.7 0.4 3.0 4.2 0.990
10-14 28 4.4 0.7 3.4 5.7 16 4.5 0.5 3.5 5.7 0.659
15-19 25 4.9 0.3 4.3 5.5 29 5.0 0.4 3.7 5.7 0.889

Table 2. Cardiac diameter (cm) of males and females by age

MALES FEMALES
Age (yr) No. MEAN SD MIN MAX No. MEAN SD MIN MAX P
5 -9 7 9.5 1.0 8.0 11.0 5 9.4 0.5 8.8 10.2 0.809
10-14 28 10.9 1.2 9.2 13.8 16 11.1 0.7 9.8 12.2 0.568
15-19 25 12.6 1.0 10.7 15.0 29 11.9 0.6 10.7 13.0 0.004

Table 3. Thoracic diameter (cm) of males and females by age

MALES FEMALES
AGE (yr) No. MEAN SD MIN MAX No. MEAN SD MIN MAX P
5-9 7 20.1 1.6 17.6 22.2 5 19.0 1.7 17.2 22.1 0.315
10-14 28 24.0 2.6 18.9 30.5 16 24.8 2.0 22.3 29.5 0.281
15-19 25 28.6 2.0 24.0 32.5 29 26.4 1.2 23.0 28.5 0.000

Table 4. Cardiothoracic ratio (%) of males and females by age

MALES FEMALES
AGE (yr) No. MEAN SD MIN MAX No. MEAN SD MIN MAX p
5-9 7 47.7 5.6 36.9 56.4 5 49.7 2.1 46.2 52.2 0.500
10-14 28 45.7 3.6 37.5 54.0 16 45.0 3.2 37.3 50.7 0.525
15-19 25 44.1 3.0 38.9 50.4 29 45.1 2.3 40.6 50.0 0.184

Discussion

In our study, the cardiothoracic ratio decreased with age. The mean values for males in the 5-9, 10-14 and 15-19 age groups were 47.7%, 45.7% and 44.1% respectively. The corresponding values for females were 49.7%, 45.0% and 45.1%. Cowan12 in a study of the British noted a mean cardiothoracic ratio of 41.6% and 42.7% in the 19 year-old males and females respectively. For the 14 year-old, his values were 42.6% for males and 43.4% for females while for the 9 year-old the values were 45.1% and 46.4% respectively. The males and females in our study had larger car-diothoracic ratio than the values reported by Cowan [12] at the corresponding age groups. Many authors have made similar observations in the adult populations. Ashcroft and Miall [6] comparing the radiographic measurements made in Wales and Jamaica, attributed the greater cardiothoracic ratio in Africans to a smaller thoracic diameter rather than to a larger cardiac diameter. Although Munro-Faure et al.[13] noted a smaller thoracic diameter in Africans, they attributed the greater cardiothoracic ratio primarily to a larger cardiac diameter and secondarily to a smaller thoracic diameter. Eveleth and Tanner [14] showed that African-American boys and girls have considerably narrower hips relative to shoulders than their British or Chinese counterparts. It is possible that the shorter trunk of Africans cou-pled with their narrower hips may partly account for the differences in the body physique between Africans and Caucasians or Asians and consequently of the larger cardio-thoracic ratio in Africans.

It is also known that environmental factors such as poor nutrition and infections may cause cardiac enlargement with resultant increase in the cardiothoracic ratio. The mean values of cardiac diameter in our study was larger than the values reported for the British by Cowan[12]. Nicko[l] and Wade[7] in a study in adults indicated that Africans tended to have a larger cardiac diameter than Asians or Caucasians. Ashcroft and Miall[6] indicated that Africans may have a type of physique in which the heart tends to lie more horizontal than is usual in Caucasians. The concept that infections and malnutrition might be responsible for the larger cardiothoracic ratio of Africans is not valid in our study. Our subjects were well nourished. The peculiar physique of Africans due to environmental and racial factors is probably responsible for their larger cardiothoracic ratio.

A number of authors have highlighted the usefulness of the cardiothoracic ratio. Hemingway et al.[15] reported that the ratio predicted the coronary heart disease mortality as good as the relative heart volume. Rautaharju et al [4] showed that in women, the ratio is a stronger predictor of cardiovascular disease risk than the cardiac diameter or the electrocardiogram estimate of the left ventricular mass. Both studies indicated that the ratio may still retain its practical utility as an indicator of cardiac abnormality, notwithstanding the recent improvements in the echocardiographic and radiographic procedures to estimate the left ventricular and cardiac size. Our study indicates that there are racial differrences in heart dimensions. It highlights the need for the use of standards based on local values in the evaluation of cardiovascular diseases in our population

References

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Correspondence:
Anyanwu GE

Departments of Anatomy
College of Medicine
University of Nigeria Enugu Campus, Nigeria
E-mail: anyanwugemeks(at)yahoo.com

Biomedical Research Volume 21 Issue 2 195
Biomedical Research 2010; 21 (2): 195-198

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