|Year : 2017 | Volume
| Issue : 3 | Page : 82-88
Cardiothoracic ratio on chest radiographs as a predictor of hypertensive heart disease among adults with systemic hypertension
Solomon Daniel Halilu1, Joshua Oluwafemi Aiyekomogbon2, Joseph Bako Igashi3, Hamza M Ahmed4, Yningi Salihu Aliyu4
1 Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria; Department of Radiology, Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria
2 Department of Radiology, University of Abuja, Abuja, Nigeria
3 Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
4 Department of Radiology, Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria
|Date of Web Publication||29-Oct-2018|
Dr. Joshua Oluwafemi Aiyekomogbon
Department of Radiology, University of Abuja, Abuja
Source of Support: None, Conflict of Interest: None
Background: Systemic hypertension is a worldwide epidemic and often called a silent killer. It is the commonest cardiovascular disease among Africans, and an acknowledged potential risk factor for the development of cardiovascular diseases such as stroke, hypertensive heart disease, hypertensive heart failure, and end organ damage of the brain, eyes, and kidneys. Hypertensive heart disease results in high cardiothoracic ratio (CTR), which is evident on a chest radiograph. This study was aimed at using CTR on chest radiographs to predict the occurrence of hypertensive heart disease among hypertensive adults in Zaria.
Patients and Methods: The study was carried out in the Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria, using static conventional x-ray machine. Consecutive 305 hypertensive patients and equal number of normal individuals, age and sex matched (as controls), were recruited. The chest radiographs of the participants were taken according to standard technique, and required measurements such as CTR and aortic arch width were taken and documented.
Results: The mean CTR for the hypertensive patients and controls were 0.52 ± 0.07 and 0.45 ± 0.04, respectively. There was significant relationship between CTR and hypertensive heart disease. Other variables such as blood pressure, age, and sex also correlated significantly with CTR.
Conclusion: The CTR showed positive relationship with blood pressure and hypertensive heart disease and it could, therefore, be used to predict the occurrence of these conditions.
Keywords: Cardiothoracic ratio, chest radiograph, hypertension, hypertensive heart disease
|How to cite this article:|
Halilu SD, Aiyekomogbon JO, Igashi JB, Ahmed HM, Aliyu YS. Cardiothoracic ratio on chest radiographs as a predictor of hypertensive heart disease among adults with systemic hypertension. Arch Int Surg 2017;7:82-8
|How to cite this URL:|
Halilu SD, Aiyekomogbon JO, Igashi JB, Ahmed HM, Aliyu YS. Cardiothoracic ratio on chest radiographs as a predictor of hypertensive heart disease among adults with systemic hypertension. Arch Int Surg [serial online] 2017 [cited 2020 Jul 12];7:82-8. Available from: http://www.archintsurg.org/text.asp?2017/7/3/82/244407
| Introduction|| |
Arterial systemic hypertension is defined as blood pressure greater than 140/90 mmHg in adults aged 25 years and above according to the World Health Organization. It is a global epidemic and often called a silent killer with prevalence of about 44% in Europe. The prevalence in Nigeria is about 8%–46.4%, and it is more common in patients older than 55 years. Arterial hypertension is broadly classified into essential (80%–90%) and secondary (10%–20%). The etiology of the former is unknown but related to predisposing factors such as family history and hereditary factors, smoking, cholesterol excess, obesity, and diet including high salt intake. Secondary hypertension is usually due to identifiable secondary event such as chronic kidney disease, renovascular disease, and endocrine disease. Irrespective of its etiology, if untreated, the final common pathway is similar, that is, damage of target organs such as the brain (cerebrovascular disease), eye (hypertensive retinopathy), and kidney (hypertensive nephropathy), and closely associated with diabetes with its myriad of complications. Arterial hypertension is the commonest cause of heart failure in the Sahara region of Nigeria. Several studies have shown that long standing hypertension is associated with hypertensive heart disease and hypertensive heart failure with chest radiograph showing cardiomegaly and aortic arch enlargement.
Left ventricular hypertrophy (LVH) is the best studied marker of hypertensive heart disease and it is a recognized complication of systemic hypertension. Although for many years, LVH was thought to be a beneficial compensatory mechanism for maintaining normal wall stress in left ventricular pressure and volume overload, epidemiological studies using electrocardiography, and more recently echocardiography (Echo), have elucidated the profound independent risk of LVH for congestive heart failure, coronary events, life-threatening dysrhythmias, and cardiac mortality.,
Several left ventricular geometric hypertrophy patterns have been found in hypertensives using echocardiographic methods and these are classified into four on the basis of left ventricular mass index (LVMI) and relative wall thickness (the ratio of wall thickness to cavity diameter), namely, concentric, concentric remodeling, eccentric, and normal geometry. These differences profoundly influence prognosis. Increasing attention is, therefore, being paid to left ventricular geometry as it becomes apparent that these specific types may have different pathophysiologic, etiologic, diagnostic, therapeutic, and prognostic significance.,,
Hypertension affects the arterial wall and the heart in many ways. Studies have shown that long standing hypertension is characterized by aortic unfolding, cardiomegaly, and hypertensive heart failure, which are evident on chest radiograph.,,,,, Aging also affects the heart and aortic arch geometry.,,,,,,
This study was aimed at assessing cardiothoracic ratio (CTR) on chest radiographs, and using it to predict the occurrence of hypertensive heart disease among adults with systemic hypertension in Zaria.
| Patients and Methods|| |
This prospective study was carried out over a period of 6 months from July 2013 to January 2014 in Radiology Department of Ahmadu Bello University Teaching Hospital, Zaria, Nigeria. Three hundred and five patients with clinical diagnosis of systemic hypertension and equal numbers of individuals with normal blood pressure as control (age and sex matched) were used for this study. The age range was 18–90 years. The hypertensive patients were recruited from cardiology unit of the Department of Medicine and controls from Family Medicine Department of Ahmadu Bello University Teaching Hospital, Zaria.
General Electric (GE) conventional static x-ray machine (Germany, 2004) was used for chest radiographic image acquisition. The acquired images on 17 × 14 inch film-cassette were processed with automatic film processor, Medipot 903 Colenta R. The acquired and processed images were reviewed on x-ray viewing box with optimal illumination. The participants were weighed and their respective heights were also measured aimed at obtaining the body mass index (BMI). The blood pressure of the patients was also measured with standard mercury sphygmomanometer.
The hypertensive patients were referred for chest radiograph as part of their management protocols, whereas the age- and sex-matched controls were consecutively selected from the Family Medicine Department of the same institution, referred for chest radiographs, being a requirement for medical examinations for employment, visa application, routine medical check, and pre-school admissions. Consequently, the entire participants bore the cost of the investigation.
The procedure was explained to them and informed consent obtained prior to their inclusion in the study. The participants were positioned erect either standing or sitting facing the chest x-ray stand with the hands by the hips and palms facing outwardly. The shoulders were rotated forward to displace the scapulae away from the chest field, and the chin was elevated and placed over the grid device. The x-ray tube was directed from behind the patients at a distance of 180 or 240 cm (using air-gap technique) with centering point at T4/T5 disc space. Exposure factors (KVp, mAs) were appropriately selected based on participant's habitués (KVp ranging from 65 to 80 and mAs ranging from 12.5 to 20). The participants were instructed to inspire deeply and remain stationary during exposure. Participants' compliance is required for obtaining good-quality radiograph. Adequate inspiration devoid of motional blur and dressing artifacts were strictly observed. A few radiographs that were not satisfactory were repeated once and if they were still suboptimal, such participants were excluded from the study.
Individuals with chest deformities, such as scoliosis and thoracopathies, those with chronic obstructive pulmonary disease, and pregnancy irrespective of gestational age and children were all excluded from the study. The CTR was measured and documented as shown in [Figure 1].
|Figure 1: Chest radiograph PA view showing the cardiac size (B + C), the widest intrathoracic diameter (D) and aortic arch width (A). The ratio of cardiac size (B + C) to widest thoracic diameter (D) is the cardiothoracic ratio ([B + C]/D)|
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Approval for the study was obtained from the ethical and research committee of Ahmadu Bello University Teaching Hospital, Zaria (ABUTH/HREC/TRG/36, Dated 4 April 2013). Anonymity was maintained on all the information obtained from the patients, and the patients had choice to decline consent or opt out of the study at any stage without necessarily affecting the quality of care obtained in the hospital.
The collected data were analyzed using Statistical Package for Social Science (IBM SPSS) version 20. The Student's t-test, Chi-square test, correlation coefficient, and regression test were used to compare the CTR. Independent sample t-test was used to compare data obtained from male and female participants. All tests of significance were two-tailed, and P ≤ 0.05 was considered statistically significant.
| Results|| |
In total, 305 patients with clinically diagnosed systemic hypertension and 305 age/sex-matched controls were used for the study. The age range for hypertensive patients and controls was 18–90 years with a mean age of 50.11 ± 14.18 years. Majority of the patients were in the third to seventh decades of life. The hypertensive patients and controls consisted of 144 males (47.2%) and 161 females (52.8%) with a male to female ratio of 1:1.1 [Table 1]. The CTR in hypertensive patients was 0.52 ± 0.07, whereas that of controls was 0.45 ± 0.04 [Table 2]. The relationship between CTR and sex among hypertensive patients and controls is shown in [Table 3]. Female subjects had higher CTR in both hypertensive and the control groups but the differences that existed were not significant. A significant relationship was established between CTR and blood pressure and other covariates as shown in [Table 4] and [Table 5]. This relationship is more significant in hypertensive patients below the age of 50 years (P < 0.001) [Table 5].
|Table 3: Relationship of CTR with sex among the hypertensive and control groups|
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|Table 4: Correlations of cardiothoracic ratio with other variables among the entire participants|
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|Table 5: Correlations of CTR with blood pressure and other variables for hypertensive patients below 50 years|
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Hypertensive patients with hypertensive heart disease, defined by CTR >0.52, are many. About 194 of 305 hypertensive patients, constituting 63.6%, had hypertensive heart disease. Systemic hypertension and hypertensive heart disease significantly affect CTR with highest effects in the third tertiles (P < 0.05), as shown in [Table 6] and [Table 7]. The findings of CTR of the previous studies in Nigeria, Zambia, and Ghana, and index study among hypertensive patients are shown in [Table 8]. The observations of previous authors concur largely with the outcome of the index study.
|Table 6: Effect of hypertension on CTR among the entire participants (n=610)|
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|Table 8: Findings of cardiothoracic ratio of previous and present studies|
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In both sexes, there is significantly higher CTR in hypertensive patients compared with controls with no overlap [Figure 2] and [Figure 3]. Scattered graph [Figure 4] showed the relationship between CTR and mean blood pressure (MBP) (mmHg), and it revealed linear increase in CTR with increasing MBP.
|Figure 3: The bar chart of cardiothoracic ratio among controls and hypertensive patients by gender|
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|Figure 4: Scattered graph showing the relationship between cardiothoracic ratio and mean blood pressure (mmHg)|
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| Discussion|| |
The assessment of heart size remains an important and useful diagnostic parameter on chest radiographs., CTR is a simple and useful tool for the assessment of cardiac size in screening for cardiovascular disease when the normal value for the local population is known.,
Hypertension being a global epidemic and a silent killer affecting about one billion people out of the world's over seven billion population can be evaluated with basic radiographic chest examination among other things.,, X-ray is readily available and cheap and should, therefore, be employed as a basic tool for the evaluation of hypertensive patients.
It is apparent that hypertensive patients have higher CTR due to the effect of hypertension in increasing LVMI, which results in LVH with its attendant increase in oxygen consumption, reduced coronary blood flow, and subsequent sequela.,,,, The mean CTR for the controls in this study concurs with similar studies in Jos, South Eastern Nigeria, Rivers, and Ghana.,,, The similarity observed in Nigeria and Ghana may be explained by the fact that the populations studied are Africans and in the same West African subregion.,,, The index study revealed that CTR in the hypertensive and control groups was higher in females than male counterparts. This is in agreement with observations of other authors in South Eastern Nigeria, Jos, and Ghana, and this may be due to high health seeking behaviors of women coupled with the fact that many women are prone to hypertensive disorder in pregnancy that may persists afterward.,,,
Transverse cardiac diameter and by extension CTR increase with age in Caucasians, Asians, and Africans due to increased cardiac ventricular muscles resulting from increased vascular resistance, loss of elasticity of the great vessels, or more pronounced decrease in transverse thoracic diameter in the elderly., There was significant correlation between the CTR of hypertensives with all the covariates of age, diastolic blood pressure, systolic blood pressure, pulse pressure (PP), MBP, height, weight and BMI. The same observation was made for controls except for PP, MBP, height, and weight. These findings concur with those of Danbauchi, where 23% of his hypertensive subjects had definite cardiomegaly and 47% had borderline cardiomegaly. The CTR in Danbauchi's studies ranged from 0.48 to 0.62 with a mean of 0.53 ± 0.29. This mean CTR is slightly higher than the 0.52 ± 0.07 obtained in the index study probably because his study involved patients with severe hypertension, whereas this study involved all hypertensive patients irrespective of the level of severity. In the index study also, the number of hypertensives with hypertensive heart disease was 194 (63.6%), which is lower when compared with the study of Danbauchi, where 70% of the hypertensive patients had hypertensive heart disease. Again this might not be unconnected with the fact that his study involved patients with severe hypertension.
Cardiomegaly detected by chest radiograph was shown to be the best predictor for eventual development of congestive heart failure, and it is associated with increased mortality compared with cases without cardiomegaly according to Stoke et al. and Dunn. It is also an indication for further evaluation with Echo where available according to Sokolow et al. Hartford et al. reported lower incidence of cardiomegaly in his report but concurs with Sokolow et al. on the observation that patients with radiographic cardiomegaly have worse prognosis at any level of blood pressure elevation than those without radiographic cardiomegaly. Also, Rayner et al. opined that chest radiograph provides important predictive information of associated target organ damage.
Hemingway et al. in the Whitehall study of a 25-year follow-up of CTR and relative heart volume as predictors of coronary heart disease mortality among hypertensive patients showed that participants with CTR >0.47 and <0.50, who are within the conventionally “normal” hearts, were associated with elevated coronary heart disease risk in the age- and blood pressure-adjusted models. This showed that hypertensive patients with conventionally normal heart are at risk; hence, the need for baseline chest radiographs to measure and document the CTR and to monitor the increase in the CTR over time might help predict their eventual outcome. CTR shows positive relationship with aortic arch width in the index study, and Ikeme et al. also reported that gross dilatation of the aortic arch is almost invariably associated with cardiomegaly. He suggested that aortic arch shadow enlargement could help to distinguish idiopathic cardiomegaly from hypertensive cardiac failure.
One of the goals of management of hypertensive patients with cardiomegaly is to give an angiotensin converting enzyme inhibitor in severe heart failure to help reduce relative heart volume by reducing LVMI, thereby reducing LVH which also reduces myocardial oxygen consumption and increases coronary blood flow. Exercise among those with hypertension also leads to lowering of left ventricular mass.
In the index study, hypertension and hypertensive heart disease show significant effect on CTR (P < 0.05). The tertiles of CTR as predictors of hypertension and hypertensive heart disease were shown in this study to be stronger in the third tertiles with a CTR greater than 0.49. This agrees with the findings by Danbauchi and Ikeme et al.
Some of the participants could not inspire deeply and remained stationary during the x-ray exposure. This resulted in poor inspiratory radiograph and motional blur, respectively, necessitating repeated exposure. Before repeating the examination, rehearsal of the procedure with the participants was done to ensure compliance. Those who could not still comply were excluded from this study.
| Conclusion and Recommendations|| |
CTR showed positive linear relationship with increasing age and blood pressure, the relationship being stronger with blood pressure and hypertensive heart disease. Consequently, measuring and documenting the CTR on chest radiograph should be done as a baseline by any physician who sees hypertensive patients.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]