The Relationship between Hypertension and Thoracic Aortic Aneurysm of Degenerative or Atherosclerotic Origin: A Systematic Review

Research Article

Austin Hypertens. 2016; 1(1): 1004.

The Relationship between Hypertension and Thoracic Aortic Aneurysm of Degenerative or Atherosclerotic Origin: A Systematic Review

Tong JKT and Rabkin SW*

Department of Medicine (Cardiology), University of British Columbia, Canada

*Corresponding author: Simon W Rabkin, Department of Medicine (Cardiology), University of British Columbia, Vancouver, Canada

Received: April 11, 2016; Accepted: May 20, 2016; Published: May 23, 2016

Abstract

Background: The relationship between hypertension and ‘so called degenerative or atherosclerotic’ Thoracic Aortic Aneurysm (TAA), has not been subjected to rigorous systematic examination. The objective was to evaluate the association between hypertension and this type of TAA and compare it with other risk factors for atherosclerosis.

Methods: Studies of TAA that reported hypertension were extracted through MEDLINE using PubMed and OvidSP platforms.

Results: Fourteen articles fulfilled the eligibility criteria, with twelve having data on hypertension prevalence. The prevalence of hypertension was high; 70% in 1485 patients with TAA. In contrast the prevalence of cigarette smoking and dyslipidemia were considerably and significantly (p <0.01) lower 42.2% and 43.4% respectively. Hypertension was most prevalent (80%) in ascending (80%) TAA. Studies reporting a relationship between hypertension and aneurysm progression, have larger initial aortic diameters and greater rates of TAA expansion.

Conclusion: These data provide evidence for a dominant role for hypertension in this kind of TAA and suggests that hypertension plays an important role in TAA expansion, especially in larger TAA perhaps due to increased wall stress. They also suggest the importance of hypertension in TAAs that are expanding in rapidly.

Keywords: Thoracic aortic aneurysms; Hypertension; Blood pressure; Aorta expansion rate

Introduction

Thoracic Aortic Aneurysm (TAA) is a serious condition because of the potential for aortic rupture and death [1,2]. Although TAA can be due to a variety of different genetic or inherited conditions, the majority of TAAs are ascribed to atherosclerosis or ‘degenerative’ factors that are not always clearly defined [3]. The prevalence of this kind of TAA is steadily increasing [2]. The development of thoracic aneurysm can be conceptualized as the balance of factors operating to distend and those that constrain aortic expansion [4]. Foremost amongst the factors operating to distend the aorta is blood pressure such that elevated blood pressure has been considered by some authorities to be an important risk factor for the development of TAA [5,6]. In contrast, other groups are more cautious in their opinion, suggesting that the role for hypertension and its management in TAA is not strong [7]. While there is general and longstanding acceptance of the relationship between hypertension and thoracic aortic dissection [8,9], there has not been a previous in-depth evaluation of the data on hypertension and TAA in the absence of aortic dissection. The objective of this study was to examine the data on hypertension and TAA due mainly to ‘degenerative factors,’ in the absence of aortic dissection and compare it with other atherosclerotic risk factors.

Methods

Search strategy

A systematic search was conducted to determine the relationship between hypertension and the prevalence and expansion of TAAs. We used MEDLINE with PubMed and OvidSP platforms as our main search strategy for relevant studies from the first available records on MEDLINE through to June 30, 2015. Search keywords included (“thoracic aortic aneurysm”) AND (“hypertension” OR “blood pressure” OR “determinants”) AND/OR (“progression” OR “growth” OR “expansion” OR “natural history). The search was limited to humans and English.

Eligibility criteria

The inclusion criteria were (i) an original study published in a peer-reviewed journal, (ii) subjects were adults (over 18 years of age), and (iii) used either chest radiography, echocardiograms, CT Scan or MRI for diagnosis or to measure aortic diameter. In addition, the study must either have (a) reported the prevalence of hypertension in patients with TAAs or (b) investigated how hypertension relates to the expansion of thoracic aneurysms. Studies were excluded if 30% or greater of the study population had aortic dissections, or if 30% or greater had genetic conditions and gene mutations producing TAA, or valvular diseases, coarctation of the aorta, previous aortic surgery, aortic infections, trauma of the aorta or aortic ruptures. Studies that focused primarily or exclusively on abdominal aortic aneurysms were excluded. Review articles, case reports, letters, and abstracts were also excluded. Because publications with different analysis of the same patient population can occur, only the most recent study was used for our evaluation.

Data extraction

For each eligible study, the sample size, country of study, patient characteristics specifically BMI, history of dyslipidemia and cigarette use, definitions of hypertension and TAA, mean aortic diameter, expansion rates, the inclusion and exclusion criteria and main conclusions were recorded. For studies that had appropriate controls, the characteristics of the control group were also noted.

Statistical analysis

Data analysis calculated the mean and weighted mean. When a study reported only the median value it was considered to be the mean for our analysis. For comparison of two datasets the nonparametric Mann Whitney U test was used. Meta-analyses of the aggregate patient data were conducted using the Comprehensive Meta-analysis Version 2 (Biostat, Englewood, New Jersey, USA). Statistical significance was set as p <0.05.

Results

The systematic search is summarized in (Figure 1), following the format for preferred reporting items for systematic reviews [10]. The systematic search yielded 718 unique records. Animal studies and non-English language studies excluded 169 citations. After screening the titles, 132 articles were removed because they were reviews, case reports, editorials or letters. The titles of 417 records were examined and studies were removed that did not fulfill the entry criteria. The remaining papers were read and 18 publications were identified from reference lists, author searches or article recommendations. We removed 12 studies that did not provide imaging information for TAA or did not report blood pressure or hypertension information. Fourteen fulfilled the eligibility criteria and were the basis for this review.