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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 11  |  Issue : 1  |  Page : 13-18

Hypertension and Size of Aortic Root – Cause-and-Effect Relationship


1 Department of Interventional Cardiology, Fortis Escorts Heart Institute and Research Centre, New Delhi, India
2 Department of Cardiology, Hero Heart Institute, Dayanand Medical College, Ludhiana, Punjab, India

Date of Submission12-Jul-2020
Date of Decision29-Jul-2020
Date of Acceptance06-Aug-2020
Date of Web Publication18-Feb-2021

Correspondence Address:
Dr. Vivudh Pratap Singh
Department of Interventional Cardiology, Fortis Escorts Heart Institute and Research Centre, Okhla Road, New Delhi - 110 025
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JICC.JICC_52_20

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  Abstract 


Background and Objectives: Hypertension and aortic root diameter have been the subject of recent studies. Dilation of the diameter of the aortic root been noted in individuals with Hypertension. A larger aortic root is also recognized as a marker of CVD Incident. A parallel set of cross-sectional studies has repeatedly demonstrated an inverse association between aortic root diameter and Hypertension. Our study try to look at this specific point. Material and Methods: This study was done in patients attending Outdoor Clinic in Dayanand Medical College and Hospital- Unit Hero DMC Heart Institute. 105 patients in Normotensive and 94 patients in the Hypertensive group were enrolled. Study comprised of Normotensive (n=105) and hypertensive (n=94) group. Results: Aorta size was significantly different in both the group. Aorta at annulus was 27.71±3.28 m.m. in Normotensive individual as compared to 31.36±3.39 m.m. in hypertensive individual. Similarly, Aorta at Sinus was 38.68±5.25 and 41.62±6.08 m.m. in both groups. Aorta at Sinotubular junction was 32.31±7.17 m.m. as compared to 36.25±4.88 m.m. Conclusion: Hypertension is associated with a significant but small increase in aortic root size, most notably at the proximal ascending aorta.

Keywords: Aorta size, hypertension, cardiovascular disease


How to cite this article:
Singh VP, Wander GS, Mohan B, Aslam N, Tandon R, Chhabra ST, Singh B, Goyal A. Hypertension and Size of Aortic Root – Cause-and-Effect Relationship. J Indian coll cardiol 2021;11:13-8

How to cite this URL:
Singh VP, Wander GS, Mohan B, Aslam N, Tandon R, Chhabra ST, Singh B, Goyal A. Hypertension and Size of Aortic Root – Cause-and-Effect Relationship. J Indian coll cardiol [serial online] 2021 [cited 2021 Mar 6];11:13-8. Available from: https://www.joicc.org/text.asp?2021/11/1/13/309622




  Introduction Top


Hypertension (HTN) is a significant risk factor for cardiovascular disease (CVD) estimated to account for 7.1 million deaths per year worldwide.[1] In an analysis of comprehensive data for the global burden of HTN, 20.6' of Indian men and 20.9' of Indian women were suffering from HTN in 2005.[2] The rates for HTN in percentage are projected to go up to 22.9 and 23.6 for Indian men and women, respectively, by 2025.[3] HTN is directly responsible for 57' of all stroke deaths and 24' of all coronary heart disease deaths in India.[3],[4]

Given the public health importance of HTN, considerable attention has been focused recently on the complex relations of the aortic root diameter and HTN risk. Dilation of the aortic root is noted in individuals with HTN.[3] A larger aortic root is also recognized as a marker for the presence of cardiac and extracardiac target organ damage and a predictor of CVD incident.[5],[6] These studies would seem to suggest that a larger aortic root is a marker of higher vascular risk. Yet, on the other hand, a parallel set of cross-sectional studies has repeatedly demonstrated an inverse association between aortic root diameter and blood pressure (BP) measurements, especially pulse pressure.[5],[6],[7],[8],[9],[10] These observations have hypothesized that a smaller aortic root may be a marker of higher BP and possibly of future HTN risk.[11],[12] Our study tried to look into the specific point.

Aortic size is a critical component in guiding clinical and therapeutic decisions. It is known to vary significantly by age and body size. The establishment of reference ranges and normative equations is essential in clinical practice. Average values of proximal aortic diameters and area have been reported using different imaging techniques, from the pioneer studies based on M-mode echocardiography[7],[8],[9] to the more recent ones using cardiac computed tomographic (CT) imaging and magnetic resonance imaging (MRI).[10] However, the intermodality comparison is limited by several methodological discrepancies, including the site of measurement, the considered cardiac phase, and the fact that CT and MRI measurements are made using the inner edge-to-inner edge method. In contrast, echocardiographic studies are mainly based on the leading-edge convention. Although two-dimensional (2D) transthoracic echocardiographic (TTE) imaging can be used to quantify the inner edge-to-inner edge diameter of the thoracic aorta, available normative ranges relate to the leading-edge approach and extensive series of average values with the inner edge-to-inner edge method is lacking. Our study also looks at this part.

Furthermore, the new ultrasound 2D TTE equipment and transducers allow the accurate evaluation of the proximal aorta at different levels, and not only of the aortic root. Accordingly, we aimed to derive average 2D TTE values of thoracic aortic size at different levels in an extensive series of varied subset adult subjects and to investigate the influence of aging, gender, and body size on these measurements.


  Materials and Methods Top


This study was done in patients attending the Outdoor Clinic in Dayanand Medical College and Hospital-Unit Hero DMC Heart Institute. One hundred five patients in normotensive and 94 patients in the hypertensive group were enrolled from March 2013 to December 2013. All of the study participants had undergone routine transthoracic echocardiography using a standardized protocol [Figure 1].
Figure 1: The thoracic aorta can be divided into three segments: the ascending aorta that extends from the aortic annulus to the innominate artery and is typically measured at the level of the aortic annulus, the sinuses of Valsalva, the sinotubular junction, and the proximal (tubular) ascending aorta; the aortic arch that extends from the innominate artery to the ligamentum arteriosum; and the descending aorta that extends from the ligamentum arteriosum to the level of the diaphragm

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Inclusion criteria

Patients who were more than 18 years of age were enrolled in the study.

Exclusion criteria

Patients were excluded if they had:

  1. Renal failure
  2. Associated moderate-to-severe valve regurgitation
  3. Associated aortic stenosis with a mean gradient >25 mmHg
  4. Moderate-to-severe mitral stenosis (mitral valve area >1.5 cm2)
  5. History or laboratory feature suggestive of coronary artery disease
  6. Familial hypercholesterolemia
  7. Previous stroke
  8. Chronic obstructive pulmonary disease
  9. Receiving oral contraception or hormone replacement therapy.<


Patients were informed about the study protocol, and written consent was obtained from each patient. This study was conducted under the Declaration of Helsinki.

All of the study participants underwent routine transthoracic Echocardiography using a standardized protocol. Each patient was assessed for great vessel diameter at the following level in accordance with the American Society of Echocardiography guidelines using an inner-edge to-inner-edge measurement.

  1. The annulus of the ascending aorta
  2. Sinus of the ascending aorta
  3. Sinotubular (ST) junction.


2D/Doppler echocardiography study was done using Philips HD 11XE echo machine using a sector probe of the frequency range between 3 and 5 Hz.

Analysis of data

Quantitative data were described in mean and standard deviation and were compared using Student's t-test. Categorical data were described by absolute and percentage frequencies and were compared using the Chi-square test. Pearson correlation and regression analysis were used to evaluate the association of different parameters. Differences were considered significant when P = 0.05.


  Results Top


The number of individuals was matched in both normotensive (n = 105) and hypertensive (n = 94) groups (P = 0.107). Normotensive had equal sex distribution (n = 54 and 51 M: F) as compared to the predominant male distribution in hypertensive subset (n = 77 and 17 M: F). Age in both the subset was matched, with normotensive population of 52.83 ± 11.43 years and hypertensive population of 56.12 ± 11.09 years. The overall mean age was 54.38 ± 11.36 (P = 0.042).

The aorta size was significantly different in both the groups. The aorta at the annulus was 27.71 ± 3.28 mm in normotensive individuals as compared to 31.36 ± 3.39 mm in hypertensive individuals. The mean was 29.43 ± 3.79 mm [Figure 2].
Figure 2: Age-wise correlation of aortic annulus in normotensive and hypertensive individuals

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The aorta at the sinus was 38.68 ± 5.25 mm in normotensive individuals as compared to 41.62 ± 6.08 mm in hypertensive patients. The mean was 40.07 ± 5.83 mm [Figure 3].
Figure 3: Age-wise correlation of aortic sinus in normotensive and hypertensive individuals

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The aorta at the sinotubular junction was 32.314 ± 7.165 mm in normotensive individuals as compared to 36.245 ± 4.883 mm in hypertensive patients. The mean was 34.171 ± 6.483 mm [Figure 4].
Figure 4: Age-wise correlation of the aorta at the sinotubular junction in normotensive and hypertensive individuals

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The aortic annulus size was more in hypertensive as compared to normotensive individuals across all age groups. The aortic annulus size was more in hypertensive as compared to normotensive individuals across all age groups. [Table 1] It was significant in most of the groups. It was significant in age groups; 41–50 years [29.70 ± 3.496 (mm) as compared to 26.96 ± 3.641 (mm)]; age group 51–60 years [28.44 ± 2.623 (mm) as compared to 31.22 ± 3.506 (mm))] and age groups more than 60 years old [28.29 ± 2.192 (mm) as compared to 33.33 ± 2.123 (mm)] However, it was nonsignificant in the age group of 20–40 years [28.20 ± 1.304 (mm) as compared to 26.24 ± 4.711 (mm) ].
Table 1: Aorta size at annulus, sinus, and sinotubular junction

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The aortic sinus size was more in hypertensive as compared to normotensive individuals across all age groups. However, the value was significant only in age more than 60 year (39.93 ± 4.018 as compared to 45.23 ± 4.099). It was nonsignificant 35.71 ± 6.362 as compared to 39.60 ± 5.128 (age group: 20–40 years), 37.92 ± 5.149 as compared to 39.35 ± 6.035 (age group: 41–50 years), and 39.61 ± 5.151 as compared to 40.33 ± 6.437 (age group: 51–60 years).

In general, the aorta at the sinotubular junction size was more in hypertensive as compared to normotensive individuals. It was significant across all age groups for more than 40 years of age.

On applying the correlation coefficient, the age was significantly related to the aorta size. On applying multivariate analysis of the dependent variable, sex, age, weight, height, and body surface area were related to these parameters. Body surface area was inversely related to the aortic size.

As per the Indian HTN guidelines-II, we divided patients into four groups: Group A BP: <130/80, Group B BP: 130–139 and/or 81–89, Group C BP: ≥140–159 and/or 90–99, and Group D BP: ≥160/100. On comparing the groups, there was a uniform increase in the artery size from Stage A to Stage D. Aorta annulus in Stage A was 26.92 ± 2.62, Stage B: 28.64 ± 3.78, Stage C: 31.33 ± 3.26, and Stage D: 31.45 ± 3.45. Group A had a statistically significant difference with Group D [Table 2].
Table 2: Aorta size at various stage of Hypertension (Staged as per Indian Society of Hypertension guidelines)

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  Discussion Top


The main findings and novelties of this study were as follows:

  1. We described normal values for each aortic segment in a large population, separately for age and gender, using the inner edge convention
  2. The applied method is highly feasible and reproducible
  3. Age, sex, weight, height, and body surface area were independently associated with the aortic size at different sites.


Assessment of thoracic aortic size is of crucial importance in routine clinical practice, as alterations from normal morphology are associated with risk factors and adverse prognosis. Transesophageal echocardiography is a semi-invasive technique, CT imaging uses X-rays and contrast agents, and MRI is a more expensive, time-consuming, and less accessible method. Thus, each of these techniques has its pitfalls, preventing it from becoming a routine technique for aortic size monitoring. Currently, M-mode echocardiography is used in everyday clinical practice for the assessment of the aortic root. However, the correct alignment of the M-mode cursor may be difficult in some patients, mainly because of the cyclical motion of the heart, resulting in systematic underestimation by M-mode imaging compared with 2D measurement.[13],[14] Recent advances in TTE techniques, including the introduction of second-harmonic imaging and high-resolution transducers, have improved 2D TTE visualization, making a quantitative assessment of the proximal thoracic aorta feasible in nearly all patients, with good agreement with gold standard techniques.[15]

The present study provides 2D TTE reference values for aortic parameters at different sites obtained using the inner edge-to-inner edge approach, as suggested by current recommendations. This is an important aspect, as aortic values derived from CT imaging and MRI are based mainly on the inner edge convention. In the current era of multimodality assessment, a comparison between different methods of imaging is mandatory in attempting to facilitate communicability, data exchange, and patient monitoring among different laboratories. Conventionally, the aortic diameter has been evaluated by M-mode echocardiography in the parasternal longitudinal long-axis view, using the leading-edge convention. The comparisons between the two different approaches applied to CT data sets showed an overestimation of approximately 2 mm of the leading edge over the free edge convention.[16] In our study, we demonstrated the inner edge method applied to 2D TTE evaluation to be highly feasible and reproducible, providing measurements very similar to those reported in other studies using different techniques, such as CT imaging and MRI.

Several biologic variables are known to influence thoracic aorta size, including age, gender, body size, and systemic BP.[17],[18] Age-related dilation of the aortic root and ascending aorta has been reported in both autopsy and imaging studies.

To the best of our knowledge, no other previous study investigated the 2DTTE measurements related to aortic dimensions at levels other than the aortic annulus. Thus, we could not compare our findings with similar regression models.

Normal values of the aorta will aid clinical and preoperative assessment across various aortic root disorder.

In our study, population was divided into normotensive and hypertensive groups. The number of individuals was matched in both ormotensive (n = 105) and hypertensive (n = 94) individuals. P value was suggestive of no difference in an age-matched subset. There was a male preponderance in the hypertensive group.

The aorta size was significantly different in both the groups. The aorta at the annulus was 27.71 ± 3.28 mm in normotensive individuals as compared to 31.36 ± 3.39 mm in hypertensive individuals. The aorta at the sinus was 38.68 ± 5.25 mm in normotensive individuals as compared to 41.62 ± 6.08 mm in hypertensive population. The aorta at the sinotubular junction was 32.31 ± 7.17 mm in normotensive individuals as compared to 36.25 ± 4.88 mm in hypertensive population.

Aging, in a complex interplay with associated and aggravating factors such as disease, genetics, and environmental factors, contributes to metabolic, structural, and functional alterations of both large conduit arteries and microvessels.

When age was standardized, then there was a significant rise in the decades preceding 41–50 in the aortic annulus and aorta at the ST junction. Size of the aorta at the sinus was also significantly increased from decades onward 60 years of age. These data suggest that age and HTN were significant parameters affecting the aorta size.

Early reports suggested that HTN predisposed to aortic root enlargement, whereas more recent pathological and M-mode echocardiographic studies have not found an association between HTN and aortic enlargement when the age is considered. These discrepancies partially reflect methodological shortcomings in the accuracy and reproducibility of aortic and BP measurements. In our study, age and HTN were significant parameters affecting the aorta size. Kim et al.[19] noted similar observation.

On applying multivariate analysis of the dependent variables body surface area (BSA) weight, and height, weight in kg was most strongly related to the aorta size. Body surface area was inversely related to the aortic size. This is different from Pearce WH et al.[20] who noted that BSA is a better predictor of size than height or weight.

On comparing the groups as per the Indian HTN guidelines-II [Figure 5], four groups were formed (Group A BP: <130/80, Group B BP: 130–139 and/or 81–89, Group C BP: ≥140–159 and/or 90–99, and Group D BP: ≥160/100); there was a uniform increase in the artery size from Stage A to Stage D. Aorta annulus in Stage A was 26.92 ± 2.62, Stage B: 28.64 ± 3.78, Stage C: 31.33 ± 3.26, and Stage D: 31.45 ± 3.45. Group A had a statistically significant difference with Group D.This observation concurs the same opinion put forwarded by Kim et al.[19] that more the uncontrolled hypertension greater the size of Aorta. HTN thus per se affecting the aorta and other great vessel sizes Kim et al.[19] reported a similar result in HTN.
Figure 5: Classification of blood pressure for adults age 18 and older. Source: From second Indian guidelines for hypertension by the Association of Physicians of India

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In summary, aorta and other great arteries showed an increase in size with age and particularly so in hypertensive patients.


  Summary and Conclusions Top


Normative values for proximal thoracic aortic segments were obtained using 2D TTE imaging in a large population of normal adults from the normotensive and hypertensive groups. Similar to CT and MRI techniques, the inner edge convention was applied to minimize intermodality discrepancies, and the obtained normal ranges thus could be useful in everyday clinical practice.

HTN is associated with a significant but small increase in the aortic root size, most notably at the proximal ascending aorta. Age, height, weight, and sex were studied as a determinant of aortic root dimensions. In general, there was a significant increase in size, per se, with HTN.

Whether increased vascular size is an antecedent factor of HTN has to be probed. Additional long-term, population-based follow-up studies are needed in this regard.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

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