Relationship Between Proximal Aorta Morphology and Progression Rate of Aortic Stenosis

Regional wall stress differences on tricuspid aortic valve-associated ascending aortic aneurysms

OBJECTIVES

Ascending thoracic aortic aneurysms (aTAAs) carry a risk of acute type A dissection. Elective repair guidelines are based on diameter, but complications often occur below diameter threshold. Biomechanically, dissection can occur when wall stress exceeds wall strength. Aneurysm wall stresses may better capture dissection risk. Our aim was to investigate patient-specific aTAA wall stresses associated with a tricuspid aortic valve (TAV) by anatomic region.

METHODS

Patients with aneurysm diameter ≥4.0 cm underwent computed tomography angiography. Aneurysm geometries were reconstructed and loaded to systemic pressure while taking prestress into account. Finite element analyses were conducted to obtain wall stress distributions. The 99th percentile longitudinal and circumferential stresses were determined at systole. Wall stresses between regions were compared using one-way analysis of variance with post hoc Tukey HSD for pairwise comparisons.

RESULTS

Peak longitudinal wall stresses on aneurysms (n = 204) were 326 [standard deviation (SD): 61.7], 246 (SD: 63.4) and 195 (SD: 38.7) kPa in sinuses of Valsalva, sinotubular junction (STJ) and ascending aorta (AscAo), respectively, with significant differences between AscAo and both sinuses (P < 0.001) and STJ (P < 0.001). Peak circumferential wall stresses were 416 (SD: 85.1), 501 (SD: 119) and 340 (SD: 57.6) kPa for sinuses, STJ and AscAo, respectively, with significant differences between AscAo and both sinuses (P < 0.001) and STJ (P < 0.001).

CONCLUSIONS

Circumferential and longitudinal wall stresses were greater in the aortic root than AscAo on aneurysm patients with a TAV. Aneurysm wall stress magnitudes and distribution relative to respective regional wall strength could improve understanding of aortic regions at greater risk of dissection in a particular patient.

Ascending aortic elongation and correlative change in overall configuration of the proximal aorta in elderly patients with severe aortic stenosis

BACKGROUND

Configurational changes in the proximal aorta are relevant to the procedural difficulty of transcatheter aortic valve implantation (TAVI). Among several morphological changes involving the ascending aorta, elongation is characteristics of elderly patients with aortic stenosis and can compromise the success and safety of TAVI. However, the effect of ascending aortic elongation on the overall morphology of the proximal aorta has not been established.

AIMS

Our primary purpose was to investigate the effect of ascending aortic elongation on structural changes in the proximal aorta in TAVI candidates.

MATERIALS & METHODS

In total, 121 consecutive patients with severe aortic stenosis (mean age, 84.5 ± 5.3 years; 69% women) who had undergone preprocedural computed tomography before TAVI were enrolled. We examined the structural anatomy of the proximal aorta in detail, focusing on its elongation, dilatation, tilting, rotation, and wedging.

RESULTS

The mean length of the ascending aorta was 68.0 ± 9.2 mm, and the length was significantly correlated with dilatation (R = .278, p = .002), rightward tilting (R = .437, p < .001), clockwise rotation (R = .228, p = .018), and deep wedging (R = -.366, p < .001) of the proximal aorta. Elongation of the ascending aorta was correlated with dilatation, rightward tilting, clockwise rotation, and deep wedging of the proximal aorta in an elderly population with severe aortic stenosis.

DISCUSSION

Appreciation of the clinical anatomy around the proximal aorta is required for clinicians involved in TAVI to estimate the procedural difficulty.

CONCLUSION

Elongation of the ascending aorta was associated with dilatation, rightward tilting, clockwise rotation, and deep wedging of the proximal aorta.

Eccentric Enlargement of the Aortic Sinuses in Pediatric and Adult Patients with Bicuspid Aortic Valves: A Cardiac MRI Study

Aortic root size and cusp fusion pattern have been related to disease outcomes in bicuspid aortic valve (BAV). This study seeks to characterize symmetry of the aortic sinuses in adult and pediatric BAV patients and its relationship to valvulopathy and root aortopathy. Aortic sinus-to-commissure (S-C) lengths were measured on cardiac MRI of adult and pediatric BAV patients with right-and-left coronary (RL) or right-and-non-coronary (RN) leaflet fusion and tricuspid aortic valve (TAV) controls. Coefficient of variance (CoV) of S-C lengths was calculated to quantify sinus asymmetry, or eccentricity. BAV cohort included 149 adults (48 ± 15 years) and 51 children (15 ± 5 years). TAV cohort included 40 adults (60 ± 13 years) and 20 children (15 ± 5 years). In adult and pediatric BAV patients, the non-fused aortic sinus was larger than either fused sinus. In RL fusion, the non-coronary S-C distance was larger than right or left S-C distances in adults (n = 121, p < 0.001) and larger than the right S-C distance in children (n = 41, p = 0.013). Sinus eccentricity (CoV) in BAV patients was higher than in TAV patients (p < 0.001) and did not correlate with age (p = 0.12). CoV trended higher in RL adults with aortic regurgitation (AR) compared to those without AR (p = 0.081), but was lower in RN adults with AR than without AR (p = 0.006). CoV did not correlate to root Z scores (p = 0.06-0.55) or ascending aortic (AAo) Z scores in adults (p = 0.45-0.55) but correlated negatively to AAo Z score in children (p = 0.005-0.03). Most adult and pediatric BAV patients with RL and RN leaflet fusion demonstrate eccentric dominance of the non-fused aortic sinus irrespective of age. The degree of eccentricity varies with valve dysfunction and BAV phenotype but does not relate to the degree of aortic root dilatation, nor does eccentricity correlate with ascending aorta dilatation in adults.

Genetic Association Analyses Highlight IL6, ALPL, and NAV1 As 3 New Susceptibility Genes Underlying Calcific Aortic Valve Stenosis

BACKGROUND

Calcific aortic valve stenosis (CAVS) is a frequent and life-threatening cardiovascular disease for which there is currently no medical treatment available. To date, only 2 genes, LPA and PALMD, have been identified as causal for CAVS. We aimed to identify additional susceptibility genes for CAVS.

METHODS

A GWAS (genome-wide association study) meta-analysis of 4 cohorts, totaling 5115 cases and 354 072 controls of European descent, was performed. A TWAS (transcriptome-wide association study) was completed to integrate transcriptomic data from 233 human aortic valves. A series of post-GWAS analyses were performed, including fine-mapping, colocalization, phenome-wide association studies, pathway, and tissue enrichment as well as genetic correlation with cardiovascular traits.

RESULTS

In the GWAS meta-analysis, 4 loci achieved genome-wide significance, including 2 new loci: IL6 (interleukin 6) on 7p15.3 and ALPL (alkaline phosphatase) on 1p36.12. A TWAS integrating gene expression from 233 human aortic valves identified NAV1 (neuron navigator 1) on 1q32.1 as a new candidate causal gene. The CAVS risk alleles were associated with higher mRNA expression of NAV1 in valve tissues. Fine-mapping identified rs1800795 as the most likely causal variant in the IL6 locus. The signal identified colocalizes with the expression of the IL6 RNA antisense in various tissues. Phenome-wide association analyses in the UK Biobank showed colocalized associations between the risk allele at the IL6 lead variant and higher eosinophil count, pulse pressure, systolic blood pressure, and carotid artery procedures, implicating modulation of the IL6 pathways. The risk allele at the NAV1 lead variant colocalized with higher pulse pressure and higher prevalence of carotid artery stenosis. Association results at the genome-wide scale indicated genetic correlation between CAVS, coronary artery disease, and cardiovascular risk factors.

CONCLUSIONS

Our study implicates 3 new genetic loci in CAVS pathogenesis, which constitute novel targets for the development of therapeutic agents.