Aortic stenosis and CT calcium scoring: is it for everyone?

Influence of cusp morphology and sex on quantitative valve composition in severe aortic stenosis

AIMS

Aortic stenosis is characterized by fibrosis and calcification of the valve, with a higher proportion of fibrosis observed in women. Stenotic bicuspid aortic valves progress more rapidly than tricuspid valves, which may also influence the relative composition of the valve. We aimed to investigate the influence of cusp morphology on quantitative aortic valve composition quantified from contrast-enhanced computed tomography angiography in severe aortic stenosis.

METHODS AND RESULTS

Patients undergoing transcatheter aortic valve implantation with bicuspid and tricuspid valves were propensity matched 1:1 by age, sex, and comorbidities. Computed tomography angiograms were analysed using semi-automated software to quantify the fibrotic and calcific scores (volume/valve annular area) and the fibro-calcific ratio (fibrotic score/calcific score). The study population (n = 140) was elderly (76 ± 10 years, 62% male) and had a peak aortic jet velocity of 4.1 ± 0.7 m/s. Compared with those with tricuspid valves (n = 70), patients with bicuspid valves (n = 70) had higher fibrotic scores [204 (interquartile range 118-267) vs. 144 (99-208) mm3/cm2, P = 0.006] with similar calcific scores (P = 0.614). Women had greater fibrotic scores than men in bicuspid [224 (181-307) vs. 169 (109-247) mm3/cm2, P = 0.042] but not tricuspid valves (P = 0.232). Men had greater calcific scores than women in both bicuspid [203 (124-355) vs. 130 (70-182) mm3/cm2, P = 0.008] and tricuspid [177 (136-249) vs. 100 (62-150) mm3/cm2, P = 0.004] valves. Among both valve types, women had a greater fibro-calcific ratio compared with men [tricuspid 1.86 (0.94-2.56) vs. 0.86 (0.54-1.24), P = 0.001 and bicuspid 1.78 (1.21-2.90) vs. 0.74 (0.44-1.53), P = 0.001].

CONCLUSIONS

In severe aortic stenosis, bicuspid valves have proportionately more fibrosis than tricuspid valves, especially in women.

18F-Sodium Fluoride PET/CT in Assessing Valvular Heart and Atherosclerotic Diseases

Aortic valve stenosis is the most common valvular disease in Western countries, while atherosclerotic cardiovascular disease is the foremost cause of death and disability worldwide. Valve degeneration and atherosclerosis are mediated by inflammation and calcification and inevitably progress over time. Computed tomography can visualise the later stages of macroscopic calcification but fails to assess the early stages of microcalcification and cannot differentiate active from burnt out disease states. Molecular imaging has the ability to provide complementary information related to disease activity, which may allow us to detect disease early, to predict disease progression and to monitor preventive or therapeutic strategies for in both aortic stenosis and atherosclerosis. PET/CT is a non-invasive imaging technique that enables visualization of ongoing molecular processes within small structures, such as the coronary arteries or heart valves. ¹⁸F-sodium fluoride (¹⁸F-NaF) binds hydroxyapatite deposits in the extracellular matrix, with preferential binding to newly developing deposits of microcalcification, which provides an assessment of calcification activity. In recent years, ¹⁸F-NaF has attracted the attention of many research groups and has been evaluated in several pathological cardiovascular processes. Histologic validation of the ¹⁸F-NaF PET signal in valvular disease and atherosclerosis has been reported in multiple independent studies. The selective high-affinity binding of ¹⁸F-NaF to microscopic calcified deposits (beyond the resolution of μCT) has been demonstrated ex vivo, as well as its ability to distinguish between areas of macro- and active microcalcification. In addition, prospective clinical studies have shown that baseline ¹⁸F-NaF uptake in patients with aortic stenosis and mitral annular calcification is correlated with subsequent calcium deposition and valvular dysfunction after a follow-up period of 2 years. In patients with surgical bioprosthetic aortic valves but without morphological criteria for prosthetic degeneration, increased ¹⁸F-NaF uptake at baseline was associated with subsequent bioprosthetic degeneration over time. Similar data were obtained in a cohort of patients with transcatheter aortic valve implantation. Furthermore, several studies have confirmed the association of coronary ¹⁸F-NaF uptake with adverse atherosclerotic plaque features, active disease and future disease progression. ¹⁸F-NaF uptake is also associated with future fatal or nonfatal myocardial infarction in patients with established coronary artery disease. The link between ¹⁸F-NaF uptake and active atherosclerotic disease has not only been demonstrated in the coronary arteries, but also in peripheral arterial disease, abdominal aortic aneurysms and carotid atherosclerosis. It can be assumed that ¹⁸F-NaF PET/CT will strengthen the diagnostic toolbox of practitioners in the coming years. Indeed, there is a strong medical need to diagnose degenerative valvular disease and to detect active atherosclerotic disease states. Finally, the use of ¹⁸F-NaF as a biomarker to monitor the efficacy of drug therapies in preventing these pathological processes is attractive. In this review, we consider the role of ¹⁸F-NaF PET/CT imaging in cardiac valvular diseases and atherosclerosis.

Let there be light! The meteoric rise of cardiac imaging

Imaging plays a central role in modern cardiovascular practice. It is a field characterised by exciting technological advances that have shaped our understanding of pathology and led to major improvements in patient diagnosis and care. The UK has played a key international role in the development of this subspecialty and is the current home to many of the leading global centres in multimodality cardiovascular imaging. In this short review, we will outline some of the key contributions of the British Cardiovascular Society and its members to this rapidly evolving field and look at how this relationship may continue to shape future cardiovascular practice.

Futility in Transcatheter Aortic Valve Implantation: A Search for Clarity

Although transcatheter aortic valve implantation (TAVI) has revolutionised the landscape of treatment for aortic stenosis, there exists a cohort of patients where TAVI is deemed futile. Among the pivotal high-risk trials, one-third to half of patients either died or received no symptomatic benefit from the procedure at 1 year. Futility of TAVI results in the unnecessary exposure of risk for patients and inefficient resource utilisation for healthcare services. Several cardiac and extra-cardiac conditions and frailty increase the risk of mortality despite TAVI. Among the survivors, these comorbidities can inhibit improvements in symptoms and quality of life. However, certain conditions are reversible with TAVI (e.g. functional mitral regurgitation), attenuating the risk and improving outcomes. Quantification of disease severity, identification of reversible factors and a systematic evaluation of frailty can substantially improve risk stratification and outcomes. This review examines the contribution of pre-existing comorbidities towards futility in TAVI and suggests a systematic approach to guide patient evaluation.

Estimating the Haemodynamic Streamline Vena Contracta as the Effective Orifice Area Measured from Reconstructed Multislice Phase-contrast MR Images for Patients with Moderately Accelerated Aortic Stenosis

PURPOSE

In aortic stenosis (AS), the discrepancy between moderately accelerated flow and effective orifice area (EOA) continues to pose a challenge. We developed a method of measuring the vena contracta area as hemodynamic EOA using cardiac MRI focusing on AS patients with a moderately accelerated flow to solve the problem that AS severity can currently be determined only by echocardiography.

METHODS

We investigated 40 patients with a peak transvalvular velocity > 3.0 m/s on transthoracic echocardiography (TTE). The patients were divided into highly accelerated and moderately accelerated AS groups according to whether or not the peak transvalvular velocity was ≥ 4.0 m/s. From the multislice 2D cine phase-contrast MRI data, the cross-sectional area of the vena contracta of the reconstructed streamline in the Valsalva sinus was defined as MRI-EOAs. Patient symptoms and echocardiography data, including EOA (defined as TTE-EOA), were derived from the continuity equation using TTE.

RESULTS

All participants in the highly accelerated AS group (n = 19) showed a peak velocity ≥ 4.0 m/s in MRI. Eleven patients in the moderately accelerated AS group (n = 21) had a TTE-EOA < 1.00 cm². In the moderately accelerated AS group, MRI-EOAs demonstrated a strong correlation with TTE-EOAs (r = 0.76, P < 0.01). Meanwhile, in the highly accelerated AS group, MRI-EOAs demonstrated positivity but a moderate correlation with TTE-EOAs (r = 0.63, P = 0.004). MRI-EOAs were overestimated compared to TTE-EOAs. In terms of the moderately accelerated AS group, the best cut-off value for MRI-EOAs was < 1.23 cm², compatible with TTE-EOAs < 1.00 cm², with an excellent prediction of the New York Heart Association classification ≥ III (sensitivity 87.5%, specificity 76.9%).

CONCLUSION

MRI-EOAs may be an alternative to conventional echocardiography for patients with moderately accelerated AS, especially those with discordant echocardiographic parameters.

18F-Sodium Fluoride (18F-NaF) for Imaging Microcalcification Activity in the Cardiovascular System

Accumulating preclinical and clinical evidence suggests that calcification is one of the body's primary responses to injury and a key pathological feature of cardiovascular disease. Calcification activity can now be imaged using 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) in combination with either computed tomography or magnetic resonance. These techniques allow visualization of calcification activity and, therefore, provide different information to the established macroscopic calcium imaged with computed tomography. Indeed, 18F-NaF PET has been used to investigate a wide range of valvular conditions, including aortic stenosis, mitral annular calcification, and bioprosthetic valve disease, as well as vascular conditions, including abdominal aortic aneurysm disease, coronary, and carotid atherosclerosis, peripheral vascular disease, and erectile dysfunction. In this brief review, we will focus on how 18F-NaF PET has improved our pathophysiological understanding of cardiovascular calcification and how it can be used as a marker of vascular calcification, providing a useful tool that can be utilized in clinical trials investigating the prediction of both disease progression and clinical events. Finally, we will discuss how 18F-NaF might be employed clinically to improve patient assessment and to guide decision-making.