A new disease: bicuspid aortic valve aortopathy syndrome

Update in Biomolecular and Genetic Bases of Bicuspid Aortopathy

Bicuspid aortic valve (BAV) associated with aortopathy is the most common congenital heart disease in the general population. Far from being a simple harmless valve malformation, it can be a complex and heterogeneous disease and a source of chronic and acute pathology (early valvular disease, aneurysm, dissection). In the previous years, intense research has been carried out to find out and understand its mechanisms, but the pathophysiology of the disease is still not fully understood and many questions remain open. Recent studies have discovered several genetic mutations involved in the development of valvular and aortic malformations, but still cannot explain more than 5–10% of cases. Other studies have also focused on molecular alterations and cellular processes (TGF-β pathway, microRNAs, degradation of the extracellular matrix, metalloproteinases, etc.), being a field in constant search and development, looking for a therapeutic target to prevent the development of the disease. Increased knowledge about this multifaceted disorder, derived from both basic and clinical research, may influence the diagnosis, follow-up, prognosis, and therapies of affected patients in the near future. This review focuses on the latest and outstanding developments on the molecular and genetic investigations of the bicuspid aortopathy.

Search for genetic factors in bicuspid aortic valve disease: ACTA2 mutations do not play a major role

OBJECTIVES

Mutations in ACTA2 have been reported as a cause of familiar thoracic aortic aneurysm (TAA) with associated bicuspid aortic valve (BAV) in some individuals. Our aim is to investigate the role of ACTA2 mutations in BAV associated with TAA in 20 patients.

METHODS

We recruited 20 patients who underwent surgery for BAV and TAA; clinical genetic evaluation and ACTA2 mutation analysis were performed on each patient, along with next-generation sequencing analysis of BAV-related genes. Available first-degree relatives were enrolled and evaluated with echocardiography and clinical genetic examination.

RESULTS

No mutations were found in ACTA2 or in BAV-related genes in our probands nor any common clinical signs possibly related to their heart disease. One-third of probands did not have any cardiovascular risk factor. Surgery was required at a young age (mean age 47.2 years) and at relatively small ascending aortic diameters (mean size 49.7 mm). In 77 first-degree relatives, 1 new diagnosis of TAA requiring surgery was made and 8 previous BAV/TAA diagnoses (9/77 = 11.7%) were confirmed. The phenotype BAV ± TAA segregated in 25% of our families.

CONCLUSIONS

Although based on a small cohort, our results seemed to justify the conclusion that ACTA2 did not play a significant role in the pathogenesis of BAV aortopathy. The underlying genetic factors of this condition remain elusive and both large association studies and exome or genome sequencing could represent promising tools to unravel its pathogenesis. Aortic resection of TAA at elective surgery in these patients should be recommended as well as echocardiography in their first-degree relatives.

Associations of GATA4 genetic mutations with the risk of congenital heart disease: A meta-analysis

BACKGROUND

GATA4 gene is a cardiac transcriptional factor playing important role in cardiac formation and development. Three GATA4 gene mutations, 99 G>T, 487 C>T, and 354 A>C, have been reported in congenital heart disease (CHD). Therefore, a meta-analysis was performed to explore the associations between 99 G>T, 487 C>T, or 354 A>C mutations and the risk of CHD.

METHODS

We searched the relevant studies in electronic databases, including ISI Science Citation Index, Embase, PubMed, CNKI, and Wan fang, from January 2006 to March 2016. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to estimate the associations between 99 G>T, 487 C>T, or 354 A>C mutations and the risk of CHD.

RESULTS

A total of 11 studies including 2878 CHD cases and 3339 controls were evaluated. There was no significant association between GATA4 99 G>T (OR = 1.22, 95% CI = 0.74-2.01, P = .43) or 487 C>T (OR = 1.16, 95% CI = 0.48-2.78, P = .74) mutations and the risk of CHD, whereas GATA4 354 A>C (OR = 1.49, 95% CI = 1.15-1.93, P = .003) mutation was significantly associated with CHD risk. Subgroup analysis was further performed for GATA4 99 G>T, 487 C>T, and 354 A>C mutations based on sample size and ethnicity, and no significant association between GATA4 99 G>T or 487 C>T mutations and the risk of CHD was found in all subgroups, whereas GATA4 354 A>C mutation was significantly associated with CHD risk in large-sample-size and Asian subgroups. However, subgroup analysis by types of CHD indicated that there was no significant association between GATA4 354 A>C mutation and the risk of ventricular septal defects.

CONCLUSIONS

Our findings suggested that GATA4 99 G>T and 487 C>T mutations may not be related to the incidence of CHD. However, GATA4 354 A>C mutation was significantly associated with CHD risk.

Marfan's syndrome and other aortopathies in pregnancy

Aortopathies, or disease affecting the aorta, are associated with a significant mortality risk for the mother and foetus during pregnancy because of an increased rate of aortic dissection. The hereditary aortopathies; Marfan's syndrome, bicuspid aortic valve, Loeys-Dietz syndrome, Ehlers-Danlos (type IV) syndrome, Turner's syndrome and nonsyndromic familial thoracic aortic aneurysm and dissection are all associated with an increased risk of aortic dissection particularly during the third trimester and early postpartum period. Maternal outcome in pregnancy depends on the underlying disorder and the aortic dimensions prior to pregnancy. The foetus has up to 50% chance of inheriting the underlying genetic defect. Vasculitis, particularly Takayasu's arteritis may also be a problem in pregnancy and predispose to aortic dissection. Prepregnancy review, including careful assessment of the aorta and prophylactic aortic surgery for an aortic aneurysm may reduce the risk of aortic dissection in pregnancy for some of the aortopathies but for women with Marfan's syndrome, Loeys-Dietz syndrome and Ehlers-Danlos (vascular type IV) who have had surgery, the risk of death remains high. A subgroup of women with Marfan's syndrome or a bicuspid aortic valve and normal aortic dimensions prepregnancy should do well in a pregnancy. Multidisciplinary pregnancy care with agreement on pregnancy follow-up, delivery and postpartum care with a crisis plan for an aortic dissection can improve pregnancy outcome and ensure prompt management of an aortic dissection should it occur.