Multimodality Imaging of the Anatomy of the Aortic Root

Anatomical characteristics of aortic valve diseases: Implications for transcatheter aortic valve replacement

Background

The etiology of aortic stenosis (AS) significantly impacts transcatheter heart valve (THV) implantation, with rheumatic etiology posing challenges. The concept of valve anchoring during transcatheter aortic valve replacement (TAVR) for patients with aortic regurgitation (AR) remains unclear.

Objective

This study aims to investigate the clinical and CT anatomical characteristics of various aortic valve diseases.

Methods

A retrospective analysis was conducted on consecutive patients who underwent CT for severe aortic diseases between April 2019 and February 2023. CT analysis was performed in eight anatomical landmarks: left ventricular outflow tract (LVOT), aortic annulus, sinus of Valsalva (SOV), sinotubular junction (STJ), ascending aorta (AAO), coronary height, aortic angle, and aortic valve calcification volume.

Results

121 patients with severe aortic valve disease were included, divided into AS (71 cases, 59%) and AR (50 cases, 41%) groups. In patients with AR, the absolute diameters of the annulus, LVOT, SOV, STJ, and AAO, as well as the heights of SOV and STJ and the cardiac angle, are larger than those in patients with AS (all P < 0.05). In normalized aortic root dimensions, the AR group had a higher SOV and STJ diameter-to-annulus ratio than the AS group (STJ-SOV-annulus: 1.51-1.44-1.00 vs 1.33-1.28-1.00). The bicuspid and rheumatic AS groups had smaller sinuses (STJ-SOV-annulus:1.27-1.35-1.00, 1.17-1.30-1.00, respectively), necessitating the downsizing of the THV. For 74% of AR patients, the sinotubular junction could not be used as a second anchoring zone, and anchoring relied primarily on the annulus.

Conclusions

Patients with rheumatic etiology require smaller valves, and anchoring in AR patients depends on the valve annulus. These structural characteristics will influence TAVR selection.

Role of Runx2 in Calcific Aortic Valve Disease in Mouse Models

Background: Calcific aortic valve disease is common in the aging population and is characterized by the histological changes of the aortic valves including extracellular matrix remodeling, osteochondrogenic differentiation, and calcification. Combined, these changes lead to aortic sclerosis, aortic stenosis (AS), and eventually to heart failure. Runt-related transcription factor 2 (Runx2) is a transcription factor highly expressed in the calcified aortic valves. However, its definitive role in the progression of calcific aortic valve disease (CAVD) has not been determined. In this study, we utilized constitutive and transient conditional knockout mouse models to assess the molecular, histological, and functional changes in the aortic valve due to Runx2 depletion. Methods: Lineage tracing studies were performed to determine the provenance of the cells giving rise to Runx2+ osteochondrogenic cells in the aortic valves of LDLr^-/- mice. Hyperlipidemic mice with a constitutive or temporal depletion of Runx2 in the activated valvular interstitial cells (aVICs) and sinus wall cells were further investigated. Following feeding with a diabetogenic diet, the mice were examined for changes in gene expression, blood flow dynamics, calcification, and histology. Results: The aVICs and sinus wall cells gave rise to Runx2+ osteochondrogenic cells in diseased mouse aortic valves. The conditional depletion of Runx2 in the SM22α+ aVICs and sinus wall cells led to the decreased osteochondrogenic gene expression in diabetic LDLr^-/- mice. The transient conditional depletion of Runx2 in the aVICs and sinus wall cells of LDLr^-/-ApoB¹⁰⁰ CAVD mice early in disease led to a significant reduction in the aortic peak velocity, mean velocity, and mean gradient, suggesting the causal role of Runx2 on the progression of AS. Finally, the leaflet hinge and sinus wall calcification were significantly decreased in the aortic valve following the conditional and temporal Runx2 depletion, but no significant effect on the valve cusp calcification or thickness was observed. Conclusions: In the aortic valve disease, Runx2 was expressed early and was required for the osteochondrogenic differentiation of the aVICs and sinus wall cells. The transient depletion of Runx2 in the aVICs and sinus wall cells in a mouse model of CAVD with a high prevalence of hemodynamic valve dysfunction led to an improved aortic valve function. Our studies also suggest that leaflet hinge and sinus wall calcification, even in the absence of significant leaflet cusp calcification, may be sufficient to cause significant valve dysfunctions in mice.

Multimodality Imaging of the Anatomy of Tricuspid Valve

Even though the tricuspid valve is no longer “forgotten”, it still remains poorly understood. In this review, we focus on some controversial and still unclear aspects of tricuspid anatomy as illustrated by noninvasive imaging techniques. In particular, we discuss the anatomical architecture of the so-called tricuspid annulus with its two components (i.e., the mural and the septal annulus), emphasizing the absence of any fibrous “ring” around the right atrioventricular junction. Then we discussed the extreme variability in number and size of leaflets (from two to six), highlighting the peculiarities of the septal leaflet as part of the septal atrioventricular junction (crux cordis). Finally, we describe the similarities and differences between the tricuspid and mitral valve, suggesting a novel terminology for tricuspid leaflets.