Abnormal aortic elastic properties in adults with congenital valvular aortic stenosis

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Abstract

Background

Abnormalities of the aortic root are common in patients with a bicuspid aortic valve. Our aim was to investigate the elastic properties of the aortic root in patients with congenital aortic valvular stenosis (AS) in comparison with age- and gender-matched controls, and to investigate the influence of stenosis severity and aortic size on aortic root elasticity.

Methods

Thirty-two adults (mean age 30.4 ± 7.5 years, 22 men) with congenital AS without previous cardiovascular surgery were prospectively studied. Aortic root elasticity indices such as aortic stiffness index (ASI), aortic root distensibility (ARD), and aortic strain were calculated with the use of M-mode echocardiography.

Results

ASI was significantly higher in patients compared to controls, 8.5 ± 8.4 versus 4.0 ± 1.4, respectively (P < 0.01). Other indices of aortic root elasticity were similar between patients and controls: ARD was 4.2 ± 3.6 versus 4.3 ± 1.9 × 10 6 cm2/dynes, respectively, and aortic strain was 12.4 ± 9.6 versus 13.5 ± 5.0%, respectively (P = NS for all). Correlations were found between aortic size and indices of aortic elasticity (i.e., aortic strain and ARD), denoting that an increased aortic dimension is associated with a stiffer aorta. Interestingly, no correlations were found between indices of severity of AS and aortic elasticity, suggesting that an abnormal aortic elasticity is independent of stenosis severity.

Conclusions

Congenital AS results in abnormal aortic elastic properties, independent of stenosis severity. Furthermore, there seems to be a relationship between aortic dimensions and aortic stiffness.

Introduction

Abnormalities of the thoracic aorta are common in patients with a bicuspid aortic valve (BAV). Approximately 50% of patients with BAV have a dilated aortic root regardless of the presence or absence of hemodynamically significant valve dysfunction [1], [2], [3], which is probably due to aortic medial disease (i.e., fragmentation of elastin, abnormal collagen and smooth muscle cell, increased ground substance) [4], [5], [6], [7], [8]. These abnormalities within the aortic media results in BAV being responsible for 6–10% of all aortic dissections [9]. It has been estimated that approximately 5% of BAV patients will develop aortic dissection during their lifetime [9]. Besides aortic dilatation and dissections, a clear correlation with the presence of aortic coarctation has been found. BAV occurs in 25–85% of patients with coarctation of the aorta [10].

Once thought to be the consequence of post-stenotic dilatation, currently aortic medial disease (“cystic medial degeneration”) has been found to be the underlying cause of aortic dilatation and possibly abnormal aortic elastic properties [4], [5], [6], [7], [8]. Patients with normally functioning BAV have been shown to have abnormal elastic properties of the aortic root compared to controls, expressed by an increased aortic stiffness and a decreased aortic distensibility assessed by M-mode echocardiography [11]. Moreover, a recent MRI study has shown that the aortic stiffness in BAV patients is comparable to those of Marfan patients [12]. However, the effect of a stenotic BAV on the elastic properties of a structurally deficient aortic wall has not been investigated. Local flow perturbations above the stenotic valve could have an influence on the aortic elasticity. The aim of the present study was to compare the elastic properties of the aortic root in a homogenous population of patients with congenital valvular aortic stenosis (AS) to age- and gender-matched controls. In addition, we investigated whether stenosis severity or aortic dimensions influenced aortic elasticity.

Section snippets

Study population

Thirty-two young adults with congenital valvular AS (aortic jet velocity ≥ 2.5 m/s, all BAV) were prospectively examined from May 2005 till November 2006. Exclusion criteria were: 1) previous cardiovascular surgery; 2) the presence of moderate-to-severe aortic regurgitation; 3) aortic coarctation. All results were compared with those of 32 age- and gender-matched controls. All patients underwent transthoracic echocardiography. The study was approved by the local ethics committee, and informed

Results

Clinical, echocardiographic, hemodynamic, and aortic elasticity data are presented in Table 1. Patients and controls were similar with regard to age, body surface area, systolic blood pressure, and pulse pressure. As expected, patients with congenital AS had a higher LV mass and larger aortic roots compared to controls. Furthermore, there was a small but significant difference in the DBP between groups (73.5 ± 7.8 in patients versus 78.7 ± 11.7 mm Hg in controls, P = 0.04). When comparing indices of

Discussion

Although numerous studies have demonstrated abnormalities of the aortic wall in BAV patients [1], [2], [3], [4], [5], [6], [7], [8], the number of studies evaluating the effect of BAV on the vascular function of the aorta is limited [11], [12], [16], [17]. In the present study, we demonstrated that these patients have an abnormal aortic elasticity, which seems to be related to the dimensions of the aorta, but is independent of stenosis severity.

BAV is associated with aortic root dilatation [1],

Acknowledgements

The Netherlands Organisation for Health Research and Development provided funding for Dr. Yap (920-03-405, The Hague, The Netherlands). Dr. Nemes is a visiting fellow from the University of Szeged (Szeged, Hungary) and is supported by the “Research Fellowship of the European Society of Cardiology”.

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