Bicuspid aortic valve disease and ascending aortic aneurysms: gaps in knowledge. Cardiol Res Pract. 2012;2012:145202. [PMID: 23198270 PMCID: PMC3503270 DOI: 10.1155/2012/145202]

Elevated circulating fasting glucagon-like peptide-1 in surgical patients with aortic valve disease and diabetes

BACKGROUND

Diabetes is a risk factor for peripheral, coronary, and cerebrovascular disease. In contrast, results also indicate that patients with diabetes have reduced prevalence of aortic aneurysms, although the mechanisms remain largely unknown. We hypothesize that altered endogenous secretion of the intestinal hormone glucagon-like peptide-1 (GLP-1)-previously shown to protect from aneurysm formation, and governing many of the mechanisms thought to be involved in aneurysm formation-may provide insights into the mechanisms underlying the inverse relationship of diabetes and aneurysm.

METHODS

We undertook a case-control study to characterize circulating plasma GLP-1 levels in diabetic and non-diabetic surgical patients with aortic valve disease, and with or without ascending aortic dilation. The cohort included patients with a bicuspid aortic valve (BAV), a common congenital disorder associated with ascending aortic aneurysm, as well as patients with a tricuspid aortic valve (TAV).

RESULTS

In our patient group, diabetes was characterized by a significant increase in fasting plasma GLP-1 levels. Further, we show that aortic dilation in these patients was associated with a significant increase in fasting plasma GLP-1, although a significant increase in the intact and bioactive peptide could not be detected in BAV patients with aortic dilation.

CONCLUSION

A subgroup of diabetic patients with aortic valve pathology have increased fasting plasma GLP-1 levels, which may be of importance for the low prevalence of aortic dilation in this patient group. Further, in TAV patients, GLP-1 secretion and plasma levels of intact GLP-1 are upregulated in association with aortic dilation, possibly indicating a compensatory mechanism.

Ross, Hybrid Arch, and Frozen Elephant Trunk Reconstruction for Late Complications of Bicuspid Aortic Valve and Aortopathy

Young patients with bicuspid aortic valve disease and aortopathy remain a clinical challenge, with many requiring multiple corrective operations throughout their lifetimes. Innovative surgical approaches are often required to address complex aortic pathologic conditions but leave patients at risk for reintervention, lifelong anticoagulation, and suboptimal hemodynamics. We describe an active 44-year-old female triathlete with recurrent bicuspid aortic stenosis, a small aortic root, a hypoplastic aortic arch and complex distal arch, and a descending aortic aneurysm, who underwent a single-stage reconstruction with a combined Ross procedure, hybrid arch, and frozen elephant trunk reconstruction.

Identification of Reference Genes for Quantitative Real Time PCR Assays in Aortic Tissue of Syrian Hamsters with Bicuspid Aortic Valve

Bicuspid aortic valve (BAV) is the most frequent congenital cardiac malformation in humans, and appears frequently associated with dilatation of the ascending aorta. This association is likely the result of a common aetiology. Currently, a Syrian hamster strain with a relatively high (∼40%) incidence of BAV constitutes the only spontaneous animal model of BAV disease. The characterization of molecular alterations in the aorta of hamsters with BAV may serve to identify pathophysiological mechanisms and molecular markers of disease in humans. In this report, we evaluate the expression of ten candidate reference genes in aortic tissue of hamsters in order to identify housekeeping genes for normalization using quantitative real time PCR (RT-qPCR) assays. A total of 51 adult (180-240 days old) and 56 old (300-440 days old) animals were used. They belonged to a control strain of hamsters with normal, tricuspid aortic valve (TAV; n = 30), or to the affected strain of hamsters with TAV (n = 45) or BAV (n = 32). The expression stability of the candidate reference genes was determined by RT-qPCR using three statistical algorithms, GeNorm, NormFinder and Bestkeeper. The expression analyses showed that the most stable reference genes for the three algorithms employed were Cdkn1β, G3pdh and Polr2a. We propose the use of Cdkn1β, or both Cdkn1β and G3pdh as reference genes for mRNA expression analyses in Syrian hamster aorta.

Marfan syndrome: current perspectives

Marfan syndrome (MFS) is a pleiotropic connective tissue disease inherited as an autosomal dominant trait, due to mutations in the FBN1 gene encoding fibrillin 1. It is an important protein of the extracellular matrix that contributes to the final structure of a microfibril. Few cases displaying an autosomal recessive transmission are reported in the world. The FBN1 gene, which is made of 66 exons, is located on chromosome 15q21.1. This review, after an introduction on the clinical manifestations that leads to the diagnosis of MFS, focuses on cardiovascular manifestations, pharmacological and surgical therapies of thoracic aortic aneurysm and/or dissection (TAAD), mechanisms underlying the progression of aneurysm or of acute dissection, and biomarkers associated with progression of TAADs. A Dutch group compared treatment with losartan, an angiotensin II receptor-1 blocker, vs no other additional treatment (COMPARE clinical trial). They observed that losartan reduces the aortic dilatation rate in patients with Marfan syndrome. Later on, they also reported that losartan exerts a beneficial effect on patients with Marfan syndrome carrying an FBN1 mutation that causes haploinsufficiency (quantitative mutation), while it has no significant effect on patients displaying dominant negative (qualitative) mutations. Moreover, a French group in a 3-year trial compared the administration of losartan vs placebo in patients with Marfan syndrome under treatment with beta-receptor blockers. They observed that losartan decreases blood pressure but has no effect on aortic diameter progression. Thus, beta-receptor blockers remain the gold standard therapy in patients with Marfan syndrome. Three potential biochemical markers are mentioned in this review: total homocysteine, serum transforming growth factor beta, and lysyl oxidase. Moreover, markers of oxidative stress measured in plasma, previously correlated with clinical features of Marfan syndrome, may be explored as potential biomarkers of clinical severity.

Elevated expression levels of lysyl oxidases protect against aortic aneurysm progression in Marfan syndrome

Patients with Marfan syndrome (MFS) are at high risk of life-threatening aortic dissections. The condition is caused by mutations in the gene encoding fibrillin-1, an essential component in the formation of elastic fibers. While experimental findings in animal models of the disease have shown the involvement of transforming growth factor-β (TGF-β)- and angiotensin II-dependent pathways, alterations in the vascular extracellular matrix (ECM) may also play a role in the onset and progression of the aortic disease. Lysyl oxidases (LOX) are extracellular enzymes, which initiates the formation of covalent cross-linking of collagens and elastin, thereby contributing to the maturation of the ECM. Here we have explored the role of LOX in the formation of aortic aneurysms in MFS. We show that aortic tissue from MFS patients and MFS mouse model (Fbn1(C1039G/+)) displayed enhanced expression of the members of the LOX family, LOX and LOX-like 1 (LOXL1), and this is associated with the formation of mature collagen fibers. Administration of a LOX inhibitor for 8weeks blocked collagen accumulation and aggravated elastic fiber impairment, and these effects correlated with the induction of a strong and rapidly progressing aortic dilatation, and with premature death in the more severe MFS mouse model, Fbn1(mgR/mgR), without any significant effect on wild type animals. This detrimental effect occurred preferentially in the ascending portion of the aorta, with little or no involvement of the aortic root, and was associated to an overactivation of both canonical and non-canonical TGF-β signaling pathways. The blockade of angiotensin II type I receptor with losartan restored TGF-β signaling activation, normalized elastic fiber impairment and prevented the aortic dilatation induced by LOX inhibition in Fbn1(C1039G/+) mice. Our data indicate that LOX enzymes and LOX-mediated collagen accumulation play a critical protective role in aneurysm formation in MFS.

The Association Between Aortic Valve Leaflet Morphology and Patterns of Aortic Dilation in Patients With Bicuspid Aortic Valves

BACKGROUND

Dilation of the aorta is a frequent complication in patients with bicuspid aortic valves. The aim of this study was to determine the relationship between the subtype of leaflet fusion, right and noncoronary leaflet (R/N) fusion versus right and left leaflet (R/L) fusion, and the patterns of aortic dilation and valve dysfunction in young patients with bicuspid aortic valves.

METHODS

We performed a retrospective review of 642 patients who presented with bicuspid aortic valves between 1994 and 2014. Of these patients, 210 (33%) had aortic dilation (z score >3) by echocardiogram. For each patient, the most recent study or the last study before intervention was reviewed.

RESULTS

Median patient age was 15 years (range, 0 to 40 years) with patients with R/N fusion being younger. The most prevalent subtype was R/N fusion (R/N, n = 114, 54% versus R/L, n = 96, 46%). Dilation of the ascending aorta was seen more often in patients with R/N fusion (R/N, 88% versus R/L, 68%; p = 0.004), whereas the prevalence of dilation of the sinuses of Valsalva was significantly higher in patients with R/L fusion (R/L, 46% versus R/N, 20%; p = 0.01). The magnitude of dilation differed as well. The z value of the sinuses of Valsalva was significantly higher in patients with R/L fusion (R/L, 2.03 versus R/N, 1.2; p = 0.003), whereas the z values of the ascending aorta and sinotubular junction were similar between the groups. Patients with R/N fusion were more likely to have aortic stenosis, and within the R/N group, patients with aortic insufficiency had a greater degree of ascending aorta dilation (p = 0.04).

CONCLUSIONS

Our study suggests that in young patients with bicuspid aortic valves and aortic dilation, aortic valve morphology may be associated with the patterns of aortic dilation and valve dysfunction. Patients with R/N fusion were more likely to have ascending aorta dilation, whereas patients with R/L fusion were more likely to have dilation of the aortic root. In addition, patients with R/N fusion presented at a younger age and were more likely to have aortic stenosis. Recognition of these differences may eventually be helpful for patient counseling and the planning of follow-up.

Etiology of bicuspid aortic valve disease: Focus on hemodynamics

The bicuspid aortic valve (BAV) is the most common form of inheritable cardiac defect. Although this abnormality may still achieve normal valvular function, it is often associated with secondary valvular and aortic complications such as calcific aortic valve disease and aortic dilation. The clinical significance and economic burden of BAV disease justify the need for improved clinical guidelines and more robust therapeutic modalities, which address the root-cause of those pathologies. Unfortunately, the etiology of BAV valvulopathy and aortopathy is still a debated issue. While the BAV anatomy and its secondary complications have been linked historically to a common genetic root, recent advances in medical imaging have demonstrated the existence of altered hemodynamics near BAV leaflets prone to calcification and BAV aortic regions vulnerable to dilation. The abnormal mechanical stresses imposed by the BAV on its leaflets and on the aortic wall could be transduced into cell-mediated processes, leading ultimately to valvular calcification and aortic medial degeneration. Despite increasing evidence for this hemodynamic etiology, the demonstration of the involvement of mechanical abnormalities in the pathogenesis of BAV disease requires the investigation of causality between the blood flow environment imposed on the leaflets and the aortic wall and the local biology, which has been lacking to date. This editorial discusses the different hypothetical etiologies of BAV disease with a particular focus on the most recent advances in cardiovascular imaging, flow characterization techniques and tissue culture methodologies that have provided new evidence in support of the hemodynamic theory.

Identification and surgical repair of familial thoracic aortic aneurysm and dissection caused by TGFBR1 mutation

BACKGROUND

This study aimed at exploring the causative gene and summarizing the clinical characteristics in a Chinese thoracic aortic aneurysm and dissection (TAAD) family.

METHODS

Family members were examined for features of syndromic genetic diseases by clinician and geneticist. Genomic DNA was extracted from 2 distantly related members with definite TAAD for exome sequencing.

RESULTS

A pathogenic mutation (rs111426349, c.1459C >T) of transforming growth factor β receptor 1 (TGFBR1) was confirmed, which result in the amino acid substitution p.R487W. Fourteen TGFBR1 mutation carriers were detected among 39 tested members in this family. The average age at diagnosis of aortic root dilatation or aneurysm was 23.2 ± 12.6 years (range 3-37 years). Early onset of aortic root dilatation was significant in this family without reported phenotypes. The David procedure was performed prophylactically in 3 carriers of this family.

CONCLUSIONS

Familial TAAD caused by TGFBR1 mutation (c.1459C >T) was confirmed in a large Chinese Han ethnic family using exome sequencing. Aggressively prophylactic David procedure may be not necessary at a smaller aortic size in familial TAAD patients with TGFBR1 mutation and further observation is warranted.

Selection of reference genes for quantitative real time PCR (qPCR) assays in tissue from human ascending aorta

Dilatation of the ascending aorta (AAD) is a prevalent aortopathy that occurs frequently associated with bicuspid aortic valve (BAV), the most common human congenital cardiac malformation. The molecular mechanisms leading to AAD associated with BAV are still poorly understood. The search for differentially expressed genes in diseased tissue by quantitative real-time PCR (qPCR) is an invaluable tool to fill this gap. However, studies dedicated to identify reference genes necessary for normalization of mRNA expression in aortic tissue are scarce. In this report, we evaluate the qPCR expression of six candidate reference genes in tissue from the ascending aorta of 52 patients with a variety of clinical and demographic characteristics, normal and dilated aortas, and different morphologies of the aortic valve (normal aorta and normal valve n = 30; dilated aorta and normal valve n = 10; normal aorta and BAV n = 4; dilated aorta and BAV n = 8). The expression stability of the candidate reference genes was determined with three statistical algorithms, GeNorm, NormFinder and Bestkeeper. The expression analyses showed that the most stable genes for the three algorithms employed were CDKN1β, POLR2A and CASC3, independently of the structure of the aorta and the valve morphology. In conclusion, we propose the use of these three genes as reference genes for mRNA expression analysis in human ascending aorta. However, we suggest searching for specific reference genes when conducting qPCR experiments with new cohort of samples.

Genetics of thoracic aortic aneurysm: at the crossroad of transforming growth factor-β signaling and vascular smooth muscle cell contractility

Aortic aneurysm, including both abdominal aortic aneurysm and thoracic aortic aneurysm, is the cause of death of 1% to 2% of the Western population. This review focuses only on thoracic aortic aneurysms and dissections. During the past decade, the genetic contribution to the pathogenesis of thoracic aortic aneurysms and dissections has revealed perturbed extracellular matrix signaling cascade interactions and deficient intracellular components of the smooth muscle contractile apparatus as the key mechanisms. Based on the study of different Marfan mouse models and the discovery of several novel thoracic aortic aneurysm genes, the involvement of the transforming growth factor-β signaling pathway has opened unexpected new avenues. Overall, these discoveries have 3 important consequences. First, the pathogenesis of thoracic aortic aneurysms and dissections is better understood, although some controversy still exists. Second, the management strategies for the medical and surgical treatment of thoracic aortic aneurysms and dissections are becoming increasingly gene-tailored. Third, the pathogenetic insights have delivered new treatment options that are currently being investigated in large clinical trials.

[Anaesthetic management of patients with bicuspid aortic valve for delivery. About two consecutive cases]

Cardiac diseases are the second cause of non-obstetrical death during pregnancy in France. Bicuspid aortic valve is the most frequent congenital cardiac disease but its characteristics are little known. We report two consecutive cases of pregnant patients with aortic bicuspidy, one with a severe aortic stenosis and one with a severe dilatation of the ascending aorta. We describe the anaesthetic management of delivery for these two cases and summarize the current recommendations for management of this condition during pregnancy.