Imaging aortic valve calcification: significance, approach and implications

Aortic Valve Calcium Score: Applications in Clinical Practice and Scientific Research-A Narrative Review

In this narrative review, we investigate the essential role played by the computed tomography Aortic Valve Calcium Score (AVCS) in the cardiovascular diagnostic landscape, with a special focus on its implications for clinical practice and scientific research. Calcific aortic valve stenosis is the most prevalent type of aortic stenosis (AS) in industrialized countries, and due to the aging population, its prevalence is increasing. While transthoracic echocardiography (TTE) remains the gold standard, AVCS stands out as an essential complementary tool in evaluating patients with AS. The advantage of AVCS is its independence from flow; this allows for a more precise evaluation of patients with discordant findings in TTE. Further clinical applications of AVCS include in the assessment of patients before transcatheter aortic valve replacement (TAVR), as it helps in predicting outcomes and provides prognostic information post-TAVR. Additionally, we describe different AVCS thresholds regarding gender and the anatomical variations of the aortic valve. Finally, we discuss various scientific studies where AVCS was applied. As AVCS has some limitations, due to the pathophysiologies of AS extending beyond calcification and gender differences, scientists strive to validate contrast-enhanced AVCS. Furthermore, research on developing radiation-free methods of measuring calcium content is ongoing.

Osteopontin stabilization and collagen containment slows amorphous calcium phosphate transformation during human aortic valve leaflet calcification

Calcification of aortic valve leaflets is a growing mortality threat for the 18 million human lives claimed globally each year by heart disease. Extensive research has focused on the cellular and molecular pathophysiology associated with calcification, yet the detailed composition, structure, distribution and etiological history of mineral deposition remains unknown. Here transdisciplinary geology, biology and medicine (GeoBioMed) approaches prove that leaflet calcification is driven by amorphous calcium phosphate (ACP), ACP at the threshold of transformation toward hydroxyapatite (HAP) and cholesterol biomineralization. A paragenetic sequence of events is observed that includes: (1) original formation of unaltered leaflet tissues: (2) individual and coalescing 100's nm- to 1 μm-scale ACP spherules and cholesterol crystals biomineralizing collagen fibers and smooth muscle cell myofilaments; (3) osteopontin coatings that stabilize ACP and collagen containment of nodules preventing exposure to the solution chemistry and water content of pumping blood, which combine to slow transformation to HAP; (4) mm-scale nodule growth via ACP spherule coalescence, diagenetic incorporation of altered collagen and aggregation with other ACP nodules; and (5) leaflet diastole and systole flexure causing nodules to twist, fold their encasing collagen fibers and increase stiffness. These in vivo mechanisms combine to slow leaflet calcification and establish previously unexplored hypotheses for testing novel drug therapies and clinical interventions as viable alternatives to current reliance on surgical/percutaneous valve implants.

Aortic valve perivascular adipose tissue computed tomography attenuation in patients with aortic stenosis

OBJECTIVE

Aortic stenosis (AS) shares pathophysiological similarities with atherosclerosis including active inflammation. CT attenuation of perivascular adipose tissue provides a measure of vascular inflammation that is linked to prognosis and has the potential to be applied to the aortic valve. We investigated perivascular adipose tissue attenuation around the aortic valve in patients with AS.

METHODS

CT attenuation was measured in the perivascular adipose tissue extending 3 mm radially and 10 mm longitudinally around the aortic valve in patients with and without AS. Associations between perivascular adipose tissue attenuation and AS disease severity, activity and progression were investigated.

RESULTS

Perivascular adipose tissue attenuation around the aortic valve demonstrated good intraobserver and interobserver repeatability (interobserver: intraclass correlation coefficient 0.977 (95% CI: 0.94, 0.99)) but was similar between patients with AS (n=120) and control subjects (n=80) (-62.4 (-68.7, -56.5) Hounsfield units (HU) vs -61.2 (-65.3, -55.6) HU, p=0.099). There were no differences between perivascular adipose tissue attenuation in patients with mild (-60.2 (-66.9, -55.1) HU), moderate (-62.8 (-69.6, -56.80) HU) or severe (-62.3 (-69.3, -55.4) HU) AS (all p>0.05), and perivascular adipose tissue attenuation did not demonstrate an association with AS severity as assessed by echocardiography or CT calcium scoring, nor with disease activity assessed by 18F-sodium fluoride positron emission tomography. Moreover, there was no association between baseline aortic valve perivascular adipose tissue attenuation and subsequent AS progression (annualised change in peak velocity: r=0.072, p=0.458). Similar results were found using five other image analysis methods.

CONCLUSIONS

CT-derived aortic valve perivascular adipose tissue attenuation is not associated with AS disease severity, activity or progression suggesting that it has no value in the investigation and management of patients with AS.

Association of Red Blood Cell Life Span with Abnormal Changes in Cardiac Structure and Function in Non-Dialysis Patients with Chronic Kidney Disease Stages 3-5

Introduction: With the invention and improvement of the carbon monoxide (CO) breath test, the role of shortened red blood cell life span (RBCLS) in renal anemia, an independent risk factor for cardiovascular events in patients with chronic kidney disease (CKD), is gradually attracting attention. Considering that heart failure is the leading cause of morbidity and mortality in patients with CKD, this study investigated the correlation between the RBCLS and the cardiac structure and function in non-dialysis patients with CKD stages 3−5, aiming to provide new ideas to improve the long-term prognosis of CKD patients. Methods: One hundred thirty-three non-dialysis patients with CKD stages 3−5 were tested for RBCLS. We compared the serological data, cardiac ultrasound results, and follow-up prognosis of patients with different RBCLS. Results: As the RBCLS shortened, the patients’ blood pressure, BNP, and CRP gradually increased, most significantly in patients with an RBCLS < 50 d. Patients with an RBCLS < 50 d had substantially lower hemoglobin (Hb), hematocrit, and albumin levels than those with an RBCLS ≥ 50 d. The cardiac ultrasound results show that patients with an RBCLS < 50 d had significantly larger atrial diameters than those with an RBCLS ≥ 50 d and were associated with more severe diastolic dysfunction. Patients with an RBCLS < 50 d had a 3.06 times greater risk of combined heart failure at baseline than those with an RBCLS ≥ 70 d and a higher risk of heart failure at follow-up. CKD stage 5 patients with an RBCLS < 50 d were more likely to develop heart failure and require renal replacement therapy earlier than patients with an RBCLS ≥ 50 d. Conclusions: In non-dialysis patients with CKD stages 3−5, there is a correlation between the red blood cell life span and cardiac structure and function. The RBCLS may also impact the renal prognosis of CKD patients.

Models and Techniques to Study Aortic Valve Calcification in Vitro, ex Vivo and in Vivo. An Overview

Aortic valve stenosis secondary to aortic valve calcification is the most common valve disease in the Western world. Calcification is a result of pathological proliferation and osteogenic differentiation of resident valve interstitial cells. To develop non-surgical treatments, the molecular and cellular mechanisms of pathological calcification must be revealed. In the current overview, we present methods for evaluation of calcification in different ex vivo, in vitro and in vivo situations including imaging in patients. The latter include echocardiography, scanning with computed tomography and magnetic resonance imaging. Particular emphasis is on translational studies of calcific aortic valve stenosis with a special focus on cell culture using human primary cell cultures. Such models are widely used and suitable for screening of drugs against calcification. Animal models are presented, but there is no animal model that faithfully mimics human calcific aortic valve disease. A model of experimentally induced calcification in whole porcine aortic valve leaflets ex vivo is also included. Finally, miscellaneous methods and aspects of aortic valve calcification, such as, for instance, biomarkers are presented.

Detecting native and bioprosthetic aortic valve disease using 18F-sodium fluoride: Clinical implications

Calcific aortic valve disease is the most common valvular disease and confers significant morbidity and mortality. There are currently no medical therapies that successfully halt or reverse the disease progression, making surgical replacement the only treatment currently available. The majority of patients will receive a bioprosthetic valve, which themselves are prone to degeneration and may also need replaced, adding to the already substantial healthcare burden of aortic stenosis. Echocardiography and computed tomography can identify late-stage manifestations of the disease process affecting native and bioprosthetic aortic valves but cannot detect or quantify early molecular changes. 18F-fluoride positron emission tomography, on the other hand, can non-invasively and sensitively assess disease activity in the valves. The current review outlines the pivotal role this novel molecular imaging technique has played in improving our understanding of native and bioprosthetic aortic valve disease, as well as providing insights into its feasibility as an important future research and clinical tool.