Association of Mild to Moderate Aortic Valve Stenosis Progression With Higher Lipoprotein(a) and Oxidized Phospholipid Levels: Secondary Analysis of a Randomized Clinical Trial

Lipoprotein (a) and lipid-lowering treatment from the perspective of a cardiac surgeon. An impact on the prognosis in patients with aortic valve replacement and after heart transplantation

Lipoprotein(a) is a recognized risk factor for ASCVD. There is still no targeted therapy for Lp(a), however, drugs such as pelacarsen, olpasiran, zerlasiran, lepodisiran and muvalaplin are in clinical trials and have been shown to be effective in significantly reducing Lp(a) levels. Moreover, elevated Lp(a) levels significantly affect the prognosis of patients after aortic valve replacement (AVR) and heart transplantation (HTx). Therefore, the assessment of Lp(a) concentration in these patients will allow for a more accurate stratification of their cardiovascular risk, and the possibility of lowering Lp(a) will allow for the optimization of this risk. In this article, we summarized the most important information regarding the role of Lp(a) and lipid-lowering treatment in patients after AVR and HTx.

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.

Genetics and Pathophysiological Mechanisms of Lipoprotein(a)-Associated Cardiovascular Risk

Elevated lipoprotein(a) is a genetically transmitted codominant trait that is an independent risk driver for cardiovascular disease. Lipoprotein(a) concentration is heavily influenced by genetic factors, including LPA kringle IV-2 domain size, single-nucleotide polymorphisms, and interleukin-1 genotypes. Apolipoprotein(a) is encoded by the LPA gene and contains 10 subtypes with a variable number of copies of kringle -2, resulting in >40 different apolipoprotein(a) isoform sizes. Genetic loci beyond LPA, such as APOE and APOH, have been shown to impact lipoprotein(a) levels. Lipoprotein(a) concentrations are generally 5% to 10% higher in women than men, and there is up to a 3-fold difference in median lipoprotein(a) concentrations between racial and ethnic populations. Nongenetic factors, including menopause, diet, and renal function, may also impact lipoprotein(a) concentration. Lipoprotein(a) levels are also influenced by inflammation since the LPA promoter contains an interleukin-6 response element; interleukin-6 released during the inflammatory response results in transient increases in plasma lipoprotein(a) levels. Screening can identify elevated lipoprotein(a) levels and facilitate intensive risk factor management. Several investigational, RNA-targeted agents have shown promising lipoprotein(a)-lowering effects in clinical studies, and large-scale lipoprotein(a) testing will be fundamental to identifying eligible patients should these agents become available. Lipoprotein(a) testing requires routine, nonfasting blood draws, making it convenient for patients. Herein, we discuss the genetic determinants of lipoprotein(a) levels, explore the pathophysiological mechanisms underlying the association between lipoprotein(a) and cardiovascular disease, and provide practical guidance for lipoprotein(a) testing.

Oxidized phospholipids in cardiovascular disease

Prolonged or excessive exposure to oxidized phospholipids (OxPLs) generates chronic inflammation. OxPLs are present in atherosclerotic lesions and can be detected in plasma on apolipoprotein B (apoB)-containing lipoproteins. When initially conceptualized, OxPL-apoB measurement in plasma was expected to reflect the concentration of minimally oxidized LDL, but, surprisingly, it correlated more strongly with plasma lipoprotein(a) (Lp(a)) levels. Indeed, experimental and clinical studies show that Lp(a) particles carry the largest fraction of OxPLs among apoB-containing lipoproteins. Plasma OxPL-apoB levels provide diagnostic information on the presence and extent of atherosclerosis and improve the prognostication of peripheral artery disease and first and recurrent myocardial infarction and stroke. The addition of OxPL-apoB measurements to traditional cardiovascular risk factors improves risk reclassification, particularly in patients in intermediate risk categories, for whom improving decision-making is most impactful. Moreover, plasma OxPL-apoB levels predict cardiovascular events with similar or greater accuracy than plasma Lp(a) levels, probably because this measurement reflects both the genetics of elevated Lp(a) levels and the generalized or localized oxidation that modifies apoB-containing lipoproteins and leads to inflammation. Plasma OxPL-apoB levels are reduced by Lp(a)-lowering therapy with antisense oligonucleotides and by lipoprotein apheresis, niacin therapy and bariatric surgery. In this Review, we discuss the role of role OxPLs in the pathophysiology of atherosclerosis and Lp(a) atherogenicity, and the use of OxPL-apoB measurement for improving prognosis, risk reclassification and therapeutic interventions.

Lipoprotein(a) and calcific aortic valve disease: current evidence and future directions

PURPOSE OF REVIEW

Calcific aortic valve disease (CAVD), the most common cause of aortic stenosis (AS), is characterized by slowly progressive fibrocalcific remodelling of the valve cusps. Once symptomatic, severe AS is associated with poor survival unless surgical or transcatheter valve replacement is performed. Unfortunately, no pharmacological interventions have been demonstrated to alter the natural history of CAVD. Lipoprotein(a) [Lp(a)], a low-density lipoprotein-like particle, has been implicated in the pathophysiology of CAVD.

RECENT FINDINGS

The mechanisms by which Lp(a) results in CAVD are not well understood. However, the oxidized phospholipids carried by Lp(a) are considered a crucial mediator of the disease process. An increasing number of studies demonstrate a causal association between plasma Lp(a) levels and frequency of AS and need for aortic valve replacement, which is independent of inflammation, as measured by plasma C-reactive protein levels. However, not all studies show an association between Lp(a) and increased progression of calcification in individuals with established CAVD.

SUMMARY

Epidemiologic, genetic, and Mendelian randomization studies have collectively suggested that Lp(a) is a causal risk factor for CAVD. Whether Lp(a)-lowering can prevent initiation or slow progression of CAVD remains to be demonstrated.

Lp(a) and risk of cardiovascular disease - A review of existing evidence and emerging concepts

Cardiovascular disease (CVD) remains the leading cause of death among adults in the United States. There has been significant advancement in the diagnosis and treatment of atherosclerotic cardiovascular disease (ASCVD) and its underlying risk factors. In certain populations, there remains a significant residual risk despite adequate lowering of low-density lipoprotein cholesterol (LDL-C) and control of traditional risk factors. This has led to an interest in research to identify additional risk factors that contribute to atherosclerotic cardiovascular disease. Elevated lipoprotein (a) [Lp(a)] has been identified as an independent risk factor contributing to an increased risk for CVD. There are also ethnic and racial disparities in Lp(a) inheritance that need to be understood. This paper reviews the current literature on lipoprotein a, proposed mechanisms of actions for cardiovascular disease, recommendations for testing, and the current and emerging therapies for lowering Lp(a).

Association between remnant cholesterol and progression of bioprosthetic valve degeneration

AIMS

Remnant cholesterol (RC) seems associated with native aortic stenosis. Bioprosthetic valve degeneration may share similar lipid-mediated pathways with aortic stenosis. We aimed to investigate the association of RC with the progression of bioprosthetic aortic valve degeneration and ensuing clinical outcomes.

METHODS AND RESULTS

We enrolled 203 patients with a median of 7.0 years (interquartile range: 5.1-9.2) after surgical aortic valve replacement. RC concentration was dichotomized by the top RC tertile (23.7 mg/dL). At 3-year follow-up, 121 patients underwent follow-up visit for the assessment of annualized change in aortic valve calcium density (AVCd). RC levels showed a curvilinear relationship with an annualized progression rate of AVCd, with increased progression rates when RC >23.7 mg/dL (P = 0.008). There were 99 deaths and 46 aortic valve re-interventions in 133 patients during a median clinical follow-up of 8.8 (8.7-9.6) years. RC >23.7 mg/dL was independently associated with mortality or re-intervention (hazard ratio: 1.98; 95% confidence interval: 1.31-2.99; P = 0.001).

CONCLUSION

Elevated RC is independently associated with faster progression of bioprosthetic valve degeneration and increased risk of all-cause mortality or aortic valve re-intervention.

Lipoprotein(a)-60 Years Later-What Do We Know?

Lipoprotein(a) (Lp(a)) molecule includes two protein components: apolipoprotein(a) and apoB100. The molecule is the main transporter of oxidized phospholipids (OxPL) in plasma. The concentration of this strongly atherogenic lipoprotein is predominantly regulated by the LPA gene expression. Lp(a) is regarded as a risk factor for several cardiovascular diseases. Numerous epidemiological, clinical and in vitro studies showed a strong association between increased Lp(a) and atherosclerotic cardiovascular disease (ASCVD), calcific aortic valve disease/aortic stenosis (CAVD/AS), stroke, heart failure or peripheral arterial disease (PAD). Although there are acknowledged contributions of Lp(a) to the mentioned diseases, clinicians struggle with many inconveniences such as a lack of well-established treatment lowering Lp(a), and common guidelines for diagnosing or assessing cardiovascular risk among both adult and pediatric patients. Lp(a) levels are different with regard to a particular race or ethnicity and might fluctuate during childhood. Furthermore, the lack of standardization of assays is an additional impediment. The review presents the recent knowledge on Lp(a) based on clinical and scientific research, but also highlights relevant aspects of future study directions that would approach more suitable and effective managing risk associated with increased Lp(a), as well as control the Lp(a) levels.

Global, regional, and national incidence, mortality, and disability-adjusted life years of non-rheumatic valvular heart disease and trend analysis from 1990 to 2019: Results from the Global Burden of Disease study 2019

BACKGROUND

In the context of the population growing and aging worldwide, the incidence of non-rheumatic valvular heart disease increased rapidly. This study aimed to describe the burden of non-rheumatic valvular heart disease, providing an up-to-date and comprehensive analysis on the global and regional levels and time trends from 1900 to 2019.

METHODS

The Global Burden of Disease 2019 was used to obtain data for this analysis. Non-rheumatic valvular heart disease in the Global Burden of Disease study includes both non-rheumatic calcific aortic valve disease and non-rheumatic degenerative mitral valve disease. The incidence, mortality, and disability-adjusted life year in 204 countries from 1990 to 2019 were analyzed by location, year, sex, age, and socio-demographic index. Estimated annual percentage change was calculated to represent the temporal trends from 1990 to 2019. Spearman's rank order correlation was used to determine the correlation between socio-demographic index and the incidence and burden of non-rheumatic valvular heart disease.

RESULTS

Globally, there were 1.65 million (95% uncertainty interval, 1.56-1.76 million) incident cases, 0.16 million (95% uncertainty interval, 0.14-0.18 million) death cases, and 2.79 million (95% uncertainty interval, 2.52-3.31 million) disability-adjusted life years of non-rheumatic valvular heart disease. Compared with 1990, the number of incident cases, death cases, and disability-adjusted life years in 2019 increased by 104.58%, 210.60%, and 167.62%, respectively, the age-standardized incidence rate (estimated annual percentage change, 0.39; 95% confidence interval, 0.29 to 0.49) increased due to population growth, and the age-standardized death rates (estimated annual percentage change, -0.32; 95% confidence interval, -0.39 to -0.25) and age-standardized disability-adjusted life year rate (estimated annual percentage change, -0.81; 95% confidence interval, -0.87 to -0.74) decreased during this period. Regarding the socio-demographic index, the highest age-standardized incidence, death, and disability-adjusted life year rates of non-rheumatic valvular heart disease were found in high-socio-demographic index countries in 2019. Meantime, the age-standardized incidence rate remained increased from 1990 to 2019, while significant decreases were found in the age-standardized death rate and age-standardized disability-adjusted life year rate. Females have higher age-standardized incidence rate, while higher age-standardized death rate and age-standardized disability-adjusted life year rate belong to males globally during the period of 1990-2019. Increasing trends were observed for both incidence, death, and disability-adjusted life year rates with age. High systolic blood pressure was the leading cause for non-rheumatic valvular heart disease across all ages.

CONCLUSIONS

From 1990 to 2019, the age-standardized incidence rate of non-rheumatic valvular heart disease remained increased, while age-standardized death rate and age-standardized disability-adjusted life year rate decreased, resulting from the growing population worldwide and improving medical resources. The aged, who has high systolic blood pressure and diet high in sodium, should pay more attention to, especially in high-socio-demographic index regions. With the population aging, the number of patients who require heart valve replacement is estimated to increase significantly in the future. Effective measures are warranted to control and treat the incidence and burden of non-rheumatic valvular heart disease.

Treatment of Lp(a): Is It the Future or Are We Ready Today?

PURPOSE OF REVIEW

The goal of this review is to present the pharmacodynamic effectiveness as well as the clinical efficacy and safety of investigational antisense oligonucleotides (ASOs) and small interference RNAs (siRNAs) drugs that specifically target lipoprotein(a) (Lp(a)). The review will discuss whether the existing lipid-lowering therapies are adequate to treat high Lp(a) levels or whether it is necessary to use the emerging new therapeutic approaches which are based on the current RNA technologies.

RECENT FINDINGS

Lipoprotein(a) (Lp(a)) is a causal risk factor for atherosclerotic cardiovascular disease (ASCVD), independent of other conventional risk factors. High Lp(a) levels are also independently associated with an increased risk of aortic stenosis progression rate. Plasma Lp(a) levels are primarily genetically determined by variation in the LPA gene coding for apo(a). All secondary prevention trials have demonstrated that the existing hypolipidemic therapies are not adequate to reduce Lp(a) levels to such an extent that could lead to a substantial reduction of ASCVD risk. This has led to the development of new drugs that target the mRNA transcript of LPA and efficiently inhibit Lp(a) synthesis leading to potent Lp(a) reduction. These new drugs are the ASO pelacarsen and the siRNAs olpasiran and SLN360. Recent pharmacodynamic studies showed that all these drugs potently reduce Lp(a) up to 98%, in a dose-dependent manner. Ongoing clinical trials will determine the Lp(a)-lowering efficacy, tolerability, and safety of these drugs as well as their potential effectiveness in reducing the ASCVD risk attributed to high plasma Lp(a) levels. We are not ready today to significantly reduce plasma Lp(a). Emerging therapies potently decrease Lp(a) and ongoing clinical trials will determine their effectiveness in reducing ASCVD risk in subjects with high Lp(a) levels.

Epidemiological study of calcified aortic valve stenosis in a Chinese community population

BACKGROUND AND AIMS

Due to the ageing global population, calcified aortic valve disease is currently the most common cardiac valve disorder. This study aimed to investigate the prevalence and the risk factors for calcified aortic valve stenosis (CAVS), and develop a prediction model for predicting CAVS risk.

METHODS AND RESULTS

This study was derived from the cross-sectional baseline survey of the PRECISE study (NCT03178448). The demographic, clinical and laboratory information of each participant was obtained. Univariable and multivariable logistic regression models were used to determine CAVS risk factors. A prediction model for predicting CAVS risk based on risk factors was developed and the result was performed by nomogram. The discrimination of the prediction model was assessed by receiver operating characteristic curve analysis. The degree of fitting for the prediction model was assessed by calibration curve analysis. A total of 3067 participants (1427 men and 1640 women) were included. The prevalence of CAVS among those aged below 60 years old, 60-70 years old and over 70 years old was 4.1%, 10.3% and 21.9%, respectively. Multivariable regression analysis revealed that age (OR: 1.099; 95% CI: 1.076 to 1.123, p<0.001), pulse pressure (OR: 1.020; 95% CI: 1.009 to 1.031, p<0.001), uric acid (OR: 1.003; 95% CI: 1.001 to 1.004, p<0.001), glycosylated haemoglobin (HbA1c) (OR: 1.152; 95% CI: 1.028 to 1.292, p=0.015) and lipoprotein(a) (OR: 1.002; 95% CI: 1.001 to 1.002, p<0.001) were independent risk factors for CAVS. High-density lipoprotein cholesterol (HDL-C) was a protective factor for CAVS (OR: 0.539; 95% CI: 0.349 to 0.831, p=0.005). The prediction model including the above risk factors showed a risk prediction of CAVS with good discrimination. The area under the curve value was found to be 0.743 (95% CI: 0.711 to 0.775).

CONCLUSION

CAVS is currently prevalent in the elderly Chinese population. Age, pulse pressure, HbA1c, lower-level HDL-C, lipoprotein(a) and uric acid are the independent risk factors for CAVS.

Lipoprotein(a) and calcific aortic valve disease initiation and progression: a systematic review and meta-analysis

Although evidence indicates the association of lipoprotein(a) [Lp(a)] with atherosclerosis, the link with calcific aortic valve disease (CAVD) is unclear. This systematic review and meta-analysis explores the connection between Lp(a) and aortic valve calcification and stenosis (AVS). We included all relevant studies, indexed in eight databases, up to February 2023. A total of 44 studies (163 139 subjects) were included, with 16 of them being further meta-analysed. Despite considerable heterogeneity, most studies support the relationship between Lp(a) and CAVD, especially in younger populations, with evidence of early aortic valve micro-calcification in elevated-Lp(a) populations. The quantitative synthesis showed higher Lp(a) levels, by 22.63 nmol/L (95% CI: 9.98-35.27), for patients with AVS, while meta-regressing the data revealed smaller Lp(a) differences for older populations with a higher proportion of females. The meta-analysis of eight studies providing genetic data, revealed that the minor alleles of both rs10455872 and rs3798220 LPA gene loci were associated with higher risk for AVS (pooled odds ratio 1.42; 95% CI: 1.34-1.50 and 1.27; 95% CI: 1.09-1.48, respectively). Importantly, high-Lp(a) individuals displayed not only faster AVS progression, by a mean difference of 0.09 m/s/year (95% CI: 0.09-0.09), but also a higher risk of serious adverse outcomes, including death (pooled hazard ratio 1.39; 95% CI: 1.01-1.90). These summary findings highlight the effect of Lp(a) on CAVD initiation, progression and outcomes, and support the early onset of Lp(a)-related subclinical lesions before clinical evidence.

Serum lipoprotein(a) and bioprosthetic aortic valve degeneration

AIMS

Bioprosthetic aortic valve degeneration demonstrates pathological similarities to aortic stenosis. Lipoprotein(a) [Lp(a)] is a well-recognized risk factor for incident aortic stenosis and disease progression. The aim of this study is to investigate whether serum Lp(a) concentrations are associated with bioprosthetic aortic valve degeneration.

METHODS AND RESULTS

In a post hoc analysis of a prospective multimodality imaging study (NCT02304276), serum Lp(a) concentrations, echocardiography, contrast-enhanced computed tomography (CT) angiography, and 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) were assessed in patients with bioprosthetic aortic valves. Patients were also followed up for 2 years with serial echocardiography. Serum Lp(a) concentrations [median 19.9 (8.4-76.4) mg/dL] were available in 97 participants (mean age 75 ± 7 years, 54% men). There were no baseline differences across the tertiles of serum Lp(a) concentrations for disease severity assessed by echocardiography [median peak aortic valve velocity: highest tertile 2.5 (2.3-2.9) m/s vs. lower tertiles 2.7 (2.4-3.0) m/s, P = 0.204], or valve degeneration on CT angiography (highest tertile n = 8 vs. lower tertiles n = 12, P = 0.552) and 18F-NaF PET (median tissue-to-background ratio: highest tertile 1.13 (1.05-1.41) vs. lower tertiles 1.17 (1.06-1.53), P = 0.889]. After 2 years of follow-up, there were no differences in annualized change in bioprosthetic hemodynamic progression [change in peak aortic valve velocity: highest tertile [0.0 (-0.1-0.2) m/s/year vs. lower tertiles 0.1 (0.0-0.2) m/s/year, P = 0.528] or the development of structural valve degeneration.

CONCLUSION

Serum lipoprotein(a) concentrations do not appear to be a major determinant or mediator of bioprosthetic aortic valve degeneration.

Lipoprotein(a) As a Risk Factor in a Cohort of Hospitalised Cardiovascular Patients: A Retrospective Clinical Routine Data Analysis

INTRODUCTION

Lipoprotein(a) (Lp(a)) is a well-recognised risk factor for ischemic heart disease (IHD) and calcific aortic valve stenosis (AVS).

METHODS

A retrospective observational study of Lp(a) levels (mg/dL) in patients hospitalised for cardiovascular diseases (CVD) in our clinical routine was performed. The Lp(a)-associated risk of hospitalisation for IHD, AVS, and concomitant IHD/AVS versus other non-ischemic CVDs (oCVD group) was assessed by means of logistic regression.

RESULTS

In total of 11,767 adult patients, the association with Lp(a) was strongest in the IHD/AVS group (e^β = 1.010, p < 0.001), followed by the IHD (e^β = 1.008, p < 0.001) and AVS group (e^β = 1.004, p < 0.001). With increasing Lp(a) levels, the risk of IHD hospitalisation was higher compared with oCVD in women across all ages and in men aged ≤75 years. The risk of AVS hospitalisation was higher only in women aged ≤75 years (e^β = 1.010 in age < 60 years, e^β = 1.005 in age 60-75 years, p < 0.05).

CONCLUSIONS

The Lp(a)-associated risk was highest for concomitant IHD/AVS hospitalisations. The differential impact of sex and age was most pronounced in the AVS group with an increased risk only in women aged ≤75 years.

Association of aortic valve calcification and high levels of lipoprotein (a): Systematic review and Meta-analysis

AIM

This study aimed to assess the association between aortic valve calcification and lipoprotein (a).

METHODS

We searched PUBMED, WOS, and SCOPUS databases. Inclusion criteria were any controlled clinical trials or observational studies that reported the level of Lipoprotein A in patients with aortic valve calcifications, excluding case reports, editorials and animal studies. RevMan software (5.4) was used to perform the meta-analysis.

RESULTS

After complete screening, 7 studies were included with a total number of 446179 patients included in the analysis. The pooled analysis showed a statistically significant association between the incidence of aortic valve calcium and increased levels of lipoprotein (a) compared with controls (SMD = 1.71, 95% CI = 1.04 to 2.38, p-value < 0.00001).

CONCLUSION

This meta-analysis showed a statistically significant association between the incidence of aortic valve calcium and increased levels of lipoprotein (a) compared with controls. Patients with high levels of lipoprotein (a) are at increased risk of developing aortic valve calcification. Medications targeting lipoprotein (a) in future clinical trials may be useful in primary prevention of aortic valve calcification in high risk patients.

Pathophysiology, emerging techniques for the assessment and novel treatment of aortic stenosis

Our perspectives on aortic stenosis (AS) are changing. Evolving from the traditional thought of a passive degenerative disease, developing a greater understanding of the condition's mechanistic underpinning has shifted the paradigm to an active disease process. This advancement from the 'wear and tear' model is a result of the growing economic and health burden of AS, particularly within industrialised countries, prompting further research. The pathophysiology of calcific AS (CAS) is complex, yet can be characterised similarly to that of atherosclerosis. Progressive remodelling involves lipid-protein complexes, with lipoprotein(a) being of particular interest for diagnostics and potential future treatment options.There is an unmet clinical need for asymptomatic patient management; no pharmacotherapies are proven to slow progression and intervention timing varies. Novel approaches are developing to address this through: (1) screening with circulating biomarkers; (2) development of drugs to slow disease progression and (3) early valve intervention guided by medical imaging. Existing biomarkers (troponin and brain natriuretic peptide) are non-specific, but cost-effective predictors of ventricular dysfunction. In addition, their integration with cardiovascular MRI can provide accurate risk stratification, aiding aortic valve replacement decision making. Currently, invasive intervention is the only treatment for AS. In comparison, the development of lipoprotein(a) lowering therapies could provide an alternative; slowing progression of CAS, preventing left ventricular dysfunction and reducing reliance on surgical intervention.The landscape of AS management is rapidly evolving. This review outlines current understanding of the pathophysiology of AS, its management and future perspectives for the condition's assessment and treatment.

Impact of C-reactive protein levels on lipoprotein(a)-associated aortic stenosis incidence and progression

Aims

Elevated lipoprotein(a) [Lp(a)] levels are associated with the risk of coronary artery disease (CAD) and calcific aortic valve stenosis (CAVS). Observational studies revealed that Lp(a) and C-reactive protein (CRP) levels, a biomarker of systemic inflammation, may jointly predict CAD risk. Whether Lp(a) and CRP levels also jointly predict CAVS incidence and progression is unknown.

Methods and results

We investigated the association of Lp(a) with CAVS according to CRP levels in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study (n = 18 226, 406 incident cases) and the UK Biobank (n = 438 260, 4582 incident cases), as well as in the ASTRONOMER study (n = 220), which assessed the haemodynamic progression rate of pre-existing mild-to-moderate aortic stenosis. In EPIC-Norfolk, in comparison to individuals with low Lp(a) levels (<50 mg/dL) and low CRP levels (<2.0 mg/L), those with elevated Lp(a) (>50 mg/dL) and low CRP levels (<2.0 mg/L) and those with elevated Lp(a) (>50 mg/dL) and elevated CRP levels (>2.0 mg/L) had a higher CAVS risk [hazard ratio (HR) = 1.86 (95% confidence intervals, 1.30-2.67) and 2.08 (1.44-2.99), respectively]. A comparable predictive value of Lp(a) in patients with vs. without elevated CRP levels was also noted in the UK Biobank. In ASTRONOMER, CAVS progression was comparable in patients with elevated Lp(a) levels with or without elevated CRP levels.

Conclusion

Lp(a) predicts the incidence and possibly progression of CAVS regardless of plasma CRP levels. Lowering Lp(a) levels may warrant further investigation in the prevention and treatment of CAVS, regardless of systemic inflammation.

Lipoprotein(a): Its Association with Calcific Aortic Valve Stenosis, the Emerging RNA-Related Treatments and the Hope for a New Era in “Treating” Aortic Valve Calcification

The treatment of patients with aortic valve calcification (AVC) and calcific aortic valve stenosis (CAVS) remains challenging as, until today, all non-invasive interventions have proven fruitless in preventing the disease’s onset and progression. Despite the similarities in the pathogenesis of AVC and atherosclerosis, statins failed to show a favorable effect in preventing AVC progression. The recognition of lipoprotein(a) [Lp(a)] as a strong and potentially modifiable risk factor for the development and, perhaps, the progression of AVC and CAVS and the evolution of novel agents leading in a robust Lp(a) reduction, have rekindled hope for a promising future in the treatment of those patients. Lp(a) seems to promote AVC via a ‘three hit’ mechanism including lipid deposition, inflammation and autotaxin transportation. All of these lead to valve interstitial cells transition into osteoblast-like cells and, thus, to parenchymal calcification. Currently available lipid-lowering therapies have shown a neutral or mild effect on Lp(a), which was proven insufficient to contribute to clinical benefits. The short-term safety and the efficacy of the emerging agents in reducing Lp(a) have been proven; nevertheless, their effect on cardiovascular risk is currently under investigation in phase 3 clinical trials. A positive result of these trials will probably be the spark to test the hypothesis of the modification of AVC’s natural history with the novel Lp(a)-lowering agents.

New Horizons: Revival of Lipoprotein (a) as a Risk Factor for Cardiovascular Disease

The status of lipoprotein (a) [Lp(a)] as a cardiovascular risk factor has been resurrected by advances in genetics. Mendelian randomization studies show a causal link of Lp(a) with coronary artery disease (CAD), peripheral artery disease (PAD), and calcific aortic valve stenosis (CAVS). The genetics of Lp(a) is complex and extends beyond the kringle-IV type 2, as it is also dependent on ancestry. The plasma concentration of Lp(a) is determined by the hepatic production of apolipoprotein(a) [apo(a)] component of Lp(a), supporting the use of nucleic acids that inhibit the messenger RNA (mRNA) gene transcript for apo(a). Analytical barriers to measurement of Lp(a) are being addressed using isoform independent assays and a traceable standard. The association of Lp(a) and atherosclerotic cardiovascular disease is higher for myocardial infarction than PAD and CAVS. Increased risk of type 2 diabetes mellitus associated with low Lp(a) levels is perplexing and requires further investigation. The greatest advancement in Lp(a)-lowering therapies is based on using RNA therapeutics that are now being investigated in clinical trials. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition lowers Lp(a) modestly, but whether cardiovascular benefit is independent of low-density lipoprotein lowering remains unclear. Opportunistic and selective testing for Lp(a) is supported by moderate evidence, with the case for universal screening premature. Modification of behavioral and clinical risk factors may be targeted to mitigate Lp(a)-mediated risk of cardiovascular disease. Clinical practice guidelines have been developed to address gaps in care of high Lp(a), but full implementation awaits the findings of clinical outcome trials using RNA-directed therapies currently underway.

Oxidized phospholipids and lipoprotein-associated phospholipase A2 (Lp-PLA2 ) in atherosclerotic cardiovascular disease: An update

Inflammation and oxidative stress conditions lead to a variety of oxidative modifications of lipoprotein phospholipids implicated in the occurrence and development of atherosclerotic lesions. Lipoprotein-associated phospholipase A2 (Lp-PLA₂ ) is established as an independent risk biomarker of atherosclerosis-related cardiovascular disease (ASCVD) and mediates vascular inflammation through the regulation of lipid metabolism in the blood and in atherosclerotic lesions. Lp-PLA₂ is associated with low- and high-density lipoproteins and Lipoprotein (a) in human plasma and specifically hydrolyzes oxidized phospholipids involved in oxidative stress modification. Several oxidized phospholipids (OxPLs) subspecies can be detoxified through enzymatic degradation by Lp-PLA₂ activation, forming lysophospholipids and oxidized non-esterified fatty acids (OxNEFAs). Lysophospholipids promote the expression of adhesion molecules, stimulate cytokines production (TNF-α, IL-6), and attract macrophages to the arterial intima. The present review article discusses new data on the functional roles of OxPLs and Lp-PLA₂ associated with lipoproteins.

Lipoprotein(a) and Cardiovascular Disease in Chinese Population: A Beijing Heart Society Expert Scientific Statement

Elevated concentration of lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerotic cardiovascular disease, including coronary artery disease, stroke, peripheral artery disease, and so on. Emerging data suggest that Lp(a) contributes to the increased risk for cardiovascular events even in the setting of effective reduction of plasma low-density lipoprotein cholesterol. Nevertheless, puzzling issues exist covering potential genetic factors, Lp(a) assay, possible individuals for analysis, a cutoff point of increased risk, and clinical interventions. In the Chinese population, Lp(a) exhibited a distinctive prevalence and regulated various cardiovascular diseases in specific ways. Hence, it is valuable to clarify the role of Lp(a) in cardiovascular diseases and explore prevention and control measures for the increase in Lp(a) prevalence in the Chinese population. This Beijing Heart Society experts' scientific statement will present the detailed knowledge concerning Lp(a)-related studies combined with Chinese population observations to provide the key points of reference.

Lipoprotein(a): Evidence for Role as a Causal Risk Factor in Cardiovascular Disease and Emerging Therapies

Lipoprotein(a) (Lp(a)) is an established risk factor for multiple cardiovascular diseases. Several lines of evidence including mechanistic, epidemiologic, and genetic studies support the role of Lp(a) as a causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and aortic stenosis/calcific aortic valve disease (AS/CAVD). Limited therapies currently exist for the management of risk associated with elevated Lp(a), but several targeted therapies are currently in various stages of clinical development. In this review, we detail evidence supporting Lp(a) as a causal risk factor for ASCVD and AS/CAVD, and discuss approaches to managing Lp(a)-associated risk.

Contribution of Oxidative Stress (OS) in Calcific Aortic Valve Disease (CAVD): From Pathophysiology to Therapeutic Targets

Calcific aortic valve disease (CAVD) is a major cause of cardiovascular mortality and morbidity, with increased prevalence and incidence. The underlying mechanisms behind CAVD are complex, and are mainly illustrated by inflammation, mechanical stress (which induces prolonged aortic valve endothelial dysfunction), increased oxidative stress (OS) (which trigger fibrosis), and calcification of valve leaflets. To date, besides aortic valve replacement, there are no specific pharmacological treatments for CAVD. In this review, we describe the mechanisms behind aortic valvular disease, the involvement of OS as a fundamental element in disease progression with predilection in AS, and its two most frequent etiologies (calcific aortic valve disease and bicuspid aortic valve); moreover, we highlight the potential of OS as a future therapeutic target.

Determinants of Aortic Stenosis Progression in Bicuspid and Tricuspid Aortic Valves

Background

Bicuspid aortic valve (BAV) is associated with a faster progression of aortic stenosis (AS). Whether the determinants of AS progression are the same or different in patients with BAV vs tricuspid aortic valve (TAV) is unknown. The aim of this study was to identify the factors associated with the progression of AS in patients with BAV vs patients with TAV.

Methods

Patients with AS were prospectively recruited in the Metabolic Determinants of the Progression of Aortic Stenosis (PROGRESSA) study (ClinicalTrials.gov Identifier: NCT01679431). The haemodynamic progression rate of AS was assessed by the annualized progression rate of peak aortic jet velocity (Vpeak). Univariable and multivariable linear regression analyses were used to identify the factors associated with a faster progression of AS in patients with BAV vs patients with TAV.

Results

There were 79 patients with BAV and 208 patients with TAV. The baseline severity of AS was similar between the 2 groups of patients as well as the annualized progression rate of AS. In patients with BAV, obesity (β = 0.25, P = 0.04), diabetes (β = 0.26, P = 0.02), and BAV with right-noncoronary cusp fusion (β = 0.29, P = 0.01) were found to be independently associated with a faster progression of AS, whereas in patients with TAV, AS baseline severity (baseline Vpeak, β = 0.14, P = 0.04) and chronic kidney disease (β = 0.16, P = 0.02) were significantly associated with AS progression.

Conclusion

Factors associated with progression rate of AS are different in BAV and TAV. The main factors associated with a faster progression of AS appear to be obesity, diabetes, right-noncoronary cusp fusion in patients with BAV vs chronic kidney disease in patients with TAV.

Lipoprotein(a): Insights for the Practicing Clinician

Following the discovery of the Lipoprotein(a) (Lp(a)) molecule by Kare Berg in 1963, many physiological and pathological properties of this particle remain to be fully understood. Multiple population-based studies have demonstrated a correlation between elevated Lp(a) levels and the incidence of cardiovascular disease. Data extrapolated from the Copenhagen City Heart and ASTRONOMER studies also demonstrated the link between Lp(a) levels and the incidence and rate of progression of calcific aortic stenosis. Interest in Lp(a) has increased in recent years, partly due to new emerging therapies that can specifically reduce serum Lp(a) concentrations. Given the strong correlation between Lp(a) and CV disease from epidemiological studies, several international guidelines have also been updated to advocate Lp(a) testing in specific population groups. This review aims to highlight the importance of the role of Lp(a) in cardiovascular disease and discusses the potential of novel therapies in patients with elevated Lp(a) levels.

Implication of Lipids in Calcified Aortic Valve Pathogenesis: Why Did Statins Fail?

Calcific Aortic Valve Disease (CAVD) is a fibrocalcific disease. Lipoproteins and oxidized phospholipids play a substantial role in CAVD; the level of Lp(a) has been shown to accelerate the progression of valve calcification. Indeed, oxidized phospholipids carried by Lp(a) into the aortic valve stimulate endothelial dysfunction and promote inflammation. Inflammation and growth factors actively promote the synthesis of the extracellular matrix (ECM) and trigger an osteogenic program. The accumulation of ECM proteins promotes lipid adhesion to valve tissue, which could initiate the osteogenic program in interstitial valve cells. Statin treatment has been shown to have the ability to diminish the death rate in subjects with atherosclerotic impediments by decreasing the serum LDL cholesterol levels. However, the use of HMG-CoA inhibitors (statins) as cholesterol-lowering therapy did not significantly reduce the progression or the severity of aortic valve calcification. However, new clinical trials targeting Lp(a) or PCSK9 are showing promising results in reducing the severity of aortic stenosis. In this review, we discuss the implication of lipids in aortic valve calcification and the current findings on the effect of lipid-lowering therapy in aortic stenosis.

Oxidized phospholipids and lipoprotein(a): An update

Over the past few years, there has been an undiminished interest in lipoprotein(a) [Lp(a)] and oxidized phospholipids (OxPLs), mainly carried on this lipoprotein. Elevated Lp(a) has been established as an independent causal risk factor for cardiovascular disease. OxPLs play an important role in atherosclerosis. The main questions that remain to be answered, however, is to what extent OxPLs contribute to the atherogenicity of Lp(a), what effect hypolipidaemic medications may have on their levels and the potential clinical benefit of their reduction. This narrative review aimed to summarize currently available data on OxPLs and cardiovascular risk, as well as the effect of established and emerging hypolipidaemic medications on Lp(a)-OxPLs.

Latest Advances in Multimodality Imaging of Aortic Stenosis

Aortic stenosis is a common condition associated with major morbidity, mortality, and health-care costs. Nevertheless, we currently lack any effective medical therapies that can treat or prevent disease development or progression. Modern advances in echocardiography and CT have helped improve the assessment of aortic stenosis severity and monitoring of disease progression, whereas cardiac MRI informs on myocardial health and the development of fibrosis. In a series of recent studies, 18F-NaF PET/CT has been shown to assess valvular disease activity and progression, providing mechanistic insights that can inform potential novel therapeutic approaches. This review will examine the latest advances in the imaging of aortic stenosis and bioprosthetic valve degeneration and explore how these techniques can assist patient management and potentially accelerate novel therapeutic developments.

Lipoprotein(a) and aortic valve stenosis: A casual or causal association?

AIMS

This review aims to provide an update of available methods for imaging calcification activity and potential therapeutic options.

DATA SYNTHESIS

Aortic valve calcification represents the most common heart valve condition requiring treatment among adults in Western societies. No medical therapies are proven to be effective in treating symptoms or reducing disease progression. Therefore, surgical or transcatheter aortic valve replacement remains the only available treatment option. Elevated circulating concentrations of lipoprotein(a) is strongly associated with degenerative aortic stenosis. This relationship was first observed in prospective observational studies, and the causal relationship was confirmed in genetic studies.

CONCLUSIONS

New therapeutic targets have been identified and new imaging techniques could be used to test the effectiveness of new agents and further clarify the pathophysiology of AVS. No therapy that specifically lowers Lp (a) levels has been approved for clinical use.

Lipoprotein(a), a Lethal Player in Calcific Aortic Valve Disease

Calcified aortic valve disease (CAVD) is the most common valvular cardiovascular disease with increasing incidence and mortality. The primary treatment for CAVD is surgical or transcatheter aortic valve replacement and there remains a lack of effective drug treatment. Recently, lipoprotein (a) (Lp(a)) has been considered to play a crucial role in CAVD pathophysiology. Multiple studies have shown that Lp(a) represents an independent risk factor for CAVD. Moreover, Lp(a) mediates the occurrence and development of CAVD by affecting aortic valve endothelial dysfunction, indirectly promoting foam cell formation through oxidized phospholipids (OxPL), inflammation, oxidative stress, and directly promotes valve calcification. However, there is a lack of clinical trials with Lp(a) reduction as a primary endpoint. This review aims to explore the relationship and mechanism between Lp(a) and CAVD, and focuses on the current drugs that can be used as potential therapeutic targets for CAVD.

Innate immune cells in the pathophysiology of calcific aortic valve disease: lessons to be learned from atherosclerotic cardiovascular disease?

Calcific aortic valve disease (CAVD) is the most common valvular disease in the developed world with currently no effective pharmacological treatment available. CAVD results from a complex, multifactorial process, in which valvular inflammation and fibro-calcific remodelling lead to valve thickening and cardiac outflow obstruction. The exact underlying pathophysiology of CAVD is still not fully understood, yet the development of CAVD shows many similarities with the pathophysiology of atherosclerotic cardiovascular disease (ASCVD), such as coronary artery disease. Innate immune cells play a crucial role in ASCVD and might also play a pivotal role in the development of CAVD. This review summarizes the current knowledge on the role of innate immune cells, both in the circulation and in the aortic valve, in the development of CAVD and the similarities and differences with ASCVD. Trained immunity and clonal haematopoiesis of indeterminate potential are proposed as novel immunological mechanisms that possibly contribute to the pathophysiology of CAVD and new possible treatment targets are discussed.

Trends in testing and prevalence of elevated Lp(a) among patients with aortic valve stenosis

Background and aims:

Lipoprotein(a) [Lp(a)] is causally associated with aortic valve stenosis (AS) but Lp(a) testing among AS patients is not broadly incorporated into clinical practice. We evaluated trends in Lp(a) testing in an academic medical center.

Methods:

Educational efforts and adding Lp(a) to the lipid panel on the electronic medical record (EMR) and preprocedure order sets were used to increase awareness of Lp(a) as a risk factor in AS. Medical records at University of California San Diego Health (UCSDH) were analyzed from 2010 to 2020 to define the yearly frequency of first time Lp(a) testing in patients with diagnosis codes for AS or undergoing transcatheter aortic valve replacement (TAVR).

Results:

Lp(a) testing for any indication increased over 5-fold from 2010 to 2020. A total of 3808 patients had a diagnosis of AS and 417 patients had TAVR. Lp(a) levels >30 mg/dL were present in 37% of AS and 35% of TAVR patients. The rates of Lp(a) testing in AS and TAVR were 14.0% and 65.7%, respectively. In AS, Lp(a) testing increased over time from 8.5% in 2010, peaking at 24.2% in 2017, and declining to 13.9% in 2020 (p < 0.001 for trend). Following implementation of EMR order-sets in 2016, Lp(a) testing in TAVR cases increased to a peak of 88.5% in 2018.

Conclusions:

Elevated Lp(a) is prevalent in AS and TAVR patients. Implementation of educational efforts and practice pathways resulted in increased Lp(a) testing in patients with AS. This study represents a paradigm that may allow increased global awareness of Lp(a) as a risk factor for AS.

Lipoprotein(a) has no major impact on calcification activity in patients with mild to moderate aortic valve stenosis

OBJECTIVE

To assess whether patients with aortic valve stenosis (AS) with elevated lipoprotein(a) (Lp(a)) are characterised by increased valvular calcification activity compared with those with low Lp(a).

METHODS

We performed 18F-sodium fluoride (18F-NaF) positron emission tomography/CT in patients with mild to moderate AS (peak aortic jet velocity between 2 and 4 m/s) and high versus low Lp(a) (>50 mg/dL vs <50 mg/dL, respectively). Subjects were matched according to age, gender, peak aortic jet velocity and valve morphology. We used a target to background ratio with the most diseased segment approach to compare 18F-NaF uptake.

RESULTS

52 individuals (26 matched pairs) were included in the analysis. The mean age was 66.4±5.5 years, 44 (84.6%) were men, and the mean aortic valve velocity was 2.80±0.49 m/s. The median Lp(a) was 79 (64-117) mg/dL and 7 (5-11) mg/dL in the high and low Lp(a) groups, respectively. Systolic blood pressure and low-density-lipoprotein cholesterol (corrected for Lp(a)) were significantly higher in the low Lp(a) group (141±12 mm Hg vs 128±12 mm Hg, 2.5±1.1 mmol/L vs 1.9±0.8 mmol/L). We found no difference in valvular 18F-NaF uptake between the high and low Lp(a) groups (3.02±1.26 vs 3.05±0.96, p=0.902). Linear regression analysis showed valvular calcium score to be the only significant determinant of valvular 18F-NaF uptake (β=0.63; 95% CI 0.38 to 0.88 per 1000 Agatston unit increase, p<0.001). Lp(a) was not associated with 18F-NaF uptake (β=0.17; 95% CI -0.44 to 0.88, p=0.305 for the high Lp(a) group).

CONCLUSION

Among patients with mild to moderate AS, calcification activity is predominantly determined by established calcium burden. The results do not support our hypothesis that Lp(a) is associated with valvular 18F-NaF uptake.

Towards Personalized Therapy of Aortic Stenosis

Calcific aortic stenosis (CAS) is the most common cause of acquired valvular heart disease in adults with no available pharmacological treatment to inhibit the disease progression to date. This review provides an up-to-date overview of current knowledge of molecular mechanisms underlying CAS pathobiology and the related treatment pathways. Particular attention is paid to current randomized trials investigating medical treatment of CAS, including strategies based on lipid-lowering and antihypertensive therapies, phosphate and calcium metabolism, and novel therapeutic targets such as valvular oxidative stress, coagulation proteins, matrix metalloproteinases, and accumulation of advanced glycation end products.

Lipoprotein(a): Pathophysiology, measurement, indication and treatment in cardiovascular disease. A consensus statement from the Nouvelle Société Francophone d'Athérosclérose (NSFA)

Lipoprotein(a) is an apolipoprotein B100-containing low-density lipoprotein-like particle that is rich in cholesterol, and is associated with a second major protein, apolipoprotein(a). Apolipoprotein(a) possesses structural similarity to plasminogen but lacks fibrinolytic activity. As a consequence of its composite structure, lipoprotein(a) may: (1) elicit a prothrombotic/antifibrinolytic action favouring clot stability; and (2) enhance atherosclerosis progression via its propensity for retention in the arterial intima, with deposition of its cholesterol load at sites of plaque formation. Equally, lipoprotein(a) may induce inflammation and calcification in the aortic leaflet valve interstitium, leading to calcific aortic valve stenosis. Experimental, epidemiological and genetic evidence support the contention that elevated concentrations of lipoprotein(a) are causally related to atherothrombotic risk and equally to calcific aortic valve stenosis. The plasma concentration of lipoprotein(a) is principally determined by genetic factors, is not influenced by dietary habits, remains essentially constant over the lifetime of a given individual and is the most powerful variable for prediction of lipoprotein(a)-associated cardiovascular risk. However, major interindividual variations (up to 1000-fold) are characteristic of lipoprotein(a) concentrations. In this context, lipoprotein(a) assays, although currently insufficiently standardized, are of considerable interest, not only in stratifying cardiovascular risk, but equally in the clinical follow-up of patients treated with novel lipid-lowering therapies targeted at lipoprotein(a) (e.g. antiapolipoprotein(a) antisense oligonucleotides and small interfering ribonucleic acids) that markedly reduce circulating lipoprotein(a) concentrations. We recommend that lipoprotein(a) be measured once in subjects at high cardiovascular risk with premature coronary heart disease, in familial hypercholesterolaemia, in those with a family history of coronary heart disease and in those with recurrent coronary heart disease despite lipid-lowering treatment. Because of its clinical relevance, the cost of lipoprotein(a) testing should be covered by social security and health authorities.

Calcific aortic valve disease: from molecular and cellular mechanisms to medical therapy

Calcific aortic valve disease (CAVD) is a highly prevalent condition that comprises a disease continuum, ranging from microscopic changes to profound fibro-calcific leaflet remodelling, culminating in aortic stenosis, heart failure, and ultimately premature death. Traditional risk factors, such as hypercholesterolaemia and (systolic) hypertension, are shared among atherosclerotic cardiovascular disease and CAVD, yet the molecular and cellular mechanisms differ markedly. Statin-induced low-density lipoprotein cholesterol lowering, a remedy highly effective for secondary prevention of atherosclerotic cardiovascular disease, consistently failed to impact CAVD progression or to improve patient outcomes. However, recently completed phase II trials provide hope that pharmaceutical tactics directed at other targets implicated in CAVD pathogenesis offer an avenue to alter the course of the disease non-invasively. Herein, we delineate key players of CAVD pathobiology, outline mechanisms that entail compromised endothelial barrier function, and promote lipid homing, immune-cell infiltration, and deranged phospho-calcium metabolism that collectively perpetuate a pro-inflammatory/pro-osteogenic milieu in which valvular interstitial cells increasingly adopt myofibro-/osteoblast-like properties, thereby fostering fibro-calcific leaflet remodelling and eventually resulting in left ventricular outflow obstruction. We provide a glimpse into the most promising targets on the horizon, including lipoprotein(a), mineral-binding matrix Gla protein, soluble guanylate cyclase, dipeptidyl peptidase-4 as well as candidates involved in regulating phospho-calcium metabolism and valvular angiotensin II synthesis and ultimately discuss their potential for a future therapy of this insidious disease.

The current landscape of lipoprotein(a) in calcific aortic valvular disease

PURPOSE OF REVIEW

Calcific aortic stenosis (CAVS) is the most common form of valvular heart disease in developed countries, increasing in prevalence with the aging population. Surgical or transcatheter aortic valve replacement is the only treatment available for CAVS. However, these interventions are typically reserved for severe symptomatic aortic stenosis (AS). The purpose of this review is to summarize the recent literature in uncovering the underlying pathophysiology of CAVS in the setting of lipoprotein (a) [Lp(a)] and emerging therapies targeting Lp(a) which may help halt disease progression in CAVS.

RECENT FINDINGS

Pathophysiologic, epidemiological, and genetic studies over the past two decades have provided strong evidence that Lp(a) is an important mediator of calcific aortic valvular disease (CAVD). Studies suggest that Lp(a) is a key carrier of pro-calcifying oxidized phospholipids (OxPL). The metabolism of OxPL results in a pro-inflammatory state and subsequent valvular thickening and mineralization through pro-osteogenic signaling. The identification of Lp(a) as a causal mediator of CAVD has allowed for opportunities for emerging therapeutic agents which may slow the progression of CAVD (Fig. 1JOURNAL/cocar/04.03/00001573-202109000-00007/figure1/v/2021-08-04T080204Z/r/image-jpeg).

SUMMARY

This review summarizes the current knowledge on the association of Lp(a) with CAVD and ongoing studies of potential Lp(a)-lowering therapies. Based on the rate-limiting and causal role of Lp(a) in progression of CAVS, these therapies may represent novel pharmacotherapies in AS and inform the developing role of Lp(a) in the clinical management of CAVD.

Lipoprotein(a): Knowns, unknowns and uncertainties

Over the last 10 years, there have been advances on several aspects of lipoprotein(a) which are reviewed in the present article. Since the standard immunoassays for measuring lipoprotein(a) are not fully apo(a) isoform-insensitive, the application of an LC-MS/MS method for assaying molar concentrations of lipoprotein(a) has been advocated. Genome wide association, epidemiological, and clinical studies have established high lipoprotein(a) as a causal risk factor for atherosclerotic cardiovascular diseases (ASCVD). However, the relative importance of molar concentration, apo(a) isoform size or variants within the LPA gene is still controversial. Lipoprotein(a)-raising single nucleotide polymorphisms has not been shown to add on value in predicting ASCVD beyond lipoprotein(a) concentrations. Although hyperlipoproteinemia(a) represents an important confounder in the diagnosis of familial hypercholesterolemia (FH), it enhances the risk of ASCVD in these patients. Thus, identification of new cases of hyperlipoproteinemia(a) during cascade testing can increase the identification of high-risk individuals. However, it remains unclear whether FH itself increases lipoprotein(a). The ASCVD risk associated with lipoprotein(a) seems to follow a linear gradient across the distribution, regardless of racial subgroups and other risk factors. The inverse association with the risk of developing type 2 diabetes needs consideration as effective lipoprotein(a) lowering therapies are progressing towards the market. Considering that Mendelian randomization analyses have identified the degree of lipoprotein(a)-lowering that is required to achieve ASCVD benefit, the findings of the ongoing outcome trial with pelacarsen will clarify whether dramatically lowering lipoprotein(a) levels can reduce the risk of ASCVD.

Neutralization of oxidized phospholipids attenuates age-associated bone loss in mice

Oxidized phospholipids (OxPLs) are pro‐inflammatory molecules that affect bone remodeling under physiological conditions. Transgenic expression of a single‐chain variable fragment (scFv) of the antigen‐binding domain of E06, an IgM natural antibody that recognizes the phosphocholine (PC) moiety of OxPLs, increases trabecular and cortical bone in adult male and female mice by increasing bone formation. OxPLs increase with age, while natural antibodies decrease. Age‐related bone loss is associated with increased oxidative stress and lipid peroxidation and is characterized by a decline in osteoblast number and bone formation, raising the possibility that increased OxPLs, together with the decline of natural antibodies, contribute to age‐related bone loss. We show here that transgenic expression of E06‐scFv attenuated the age‐associated loss of spinal, femoral, and total bone mineral density in both female and male mice aged up to 22 and 24 months, respectively. E06‐scFv attenuated the age‐associated decline in trabecular bone, but not cortical bone, and this effect was associated with an increase in osteoblasts and a decrease in osteoclasts. Furthermore, RNA‐seq analysis showed that E06‐scFv increased Wnt10b expression in vertebral bone in aged mice, indicating that blocking OxPLs increases Wnt signaling. Unlike age‐related bone loss, E06‐scFv did not attenuate the bone loss caused by estrogen deficiency or unloading in adult mice. These results demonstrate that OxPLs contribute to age‐associated bone loss. Neutralization of OxPLs, therefore, is a promising therapeutic target for senile osteoporosis, as well as atherosclerosis and non‐alcoholic steatohepatitis (NASH), two other conditions shown to be attenuated by E06‐scFv in mice.

Lipoprotein (a): When to Measure and How to Treat?

PURPOSE OF REVIEW

The purpose of this article is to review current evidence for lipoprotein (a) (Lp(a)) as a risk factor for multiple cardiovascular (CV) disease phenotypes, provide a rationale for Lp(a) lowering to reduce CV risk, identify therapies that lower Lp(a) levels that are available clinically and under investigation, and discuss future directions.

RECENT FINDINGS

Mendelian randomization and epidemiological studies have shown that elevated Lp(a) is an independent and causal risk factor for atherosclerosis and major CV events. Lp(a) is also associated with non-atherosclerotic endpoints such as venous thromboembolism and calcific aortic valve disease. It contributes to residual CV risk in patients receiving standard-of-care LDL-lowering therapy. Plasma Lp(a) levels present a skewed distribution towards higher values and vary widely between individuals and according to ethnic background due to genetic variants in the LPA gene, but remain relatively constant throughout a person's life. Thus, elevated Lp(a) (≥50 mg/dL) is a prevalent condition affecting >20% of the population but is still underdiagnosed. Treatment guidelines have begun to advocate measurement of Lp(a) to identify patients with very high levels that have a family history of premature CVD or elevated Lp(a). Lipoprotein apheresis (LA) efficiently lowers Lp(a) and was recently associated with a reduction of incident CV events. Statins have neutral or detrimental effects on Lp(a), while PCSK9 inhibitors significantly reduce its level by up to 30%. Specific lowering of Lp(a) with antisense oligonucleotides (ASO) shows good safety and strong efficacy with up to 90% reductions. The ongoing CV outcomes study Lp(a)HORIZON will provide a first answer as to whether selective Lp(a) lowering with ASO reduces the risk of major CV events. Given the recently established association between Lp(a) level and CV risk, guidelines now recommend Lp(a) measurement in specific clinical conditions. Accordingly, Lp(a) is a current target for drug development to reduce CV risk in patients with elevated levels, and lowering Lp(a) with ASO represents a promising avenue.

Lipoprotein(a)

Lipoprotein(a) [Lp(a)] is an atherogenic lipoprotein with a strong genetic regulation. Up to 90% of the concentrations are explained by a single gene, the LPA gene. The concentrations show a several-hundred-fold interindividual variability ranging from less than 0.1 mg/dL to more than 300 mg/dL. Lp(a) plasma concentrations above 30 mg/dL and even more above 50 mg/dL are associated with an increased risk for cardiovascular disease including myocardial infarction, stroke, aortic valve stenosis, heart failure, peripheral arterial disease, and all-cause mortality. Since concentrations above 50 mg/dL are observed in roughly 20% of the Caucasian population and in an even higher frequency in African-American and Asian-Indian ethnicities, it can be assumed that Lp(a) is one of the most important genetically determined risk factors for cardiovascular disease.Carriers of genetic variants that are associated with high Lp(a) concentrations have a markedly increased risk for cardiovascular events. Studies that used these genetic variants as a genetic instrument to support a causal role for Lp(a) as a cardiovascular risk factor are called Mendelian randomization studies. The principle of this type of studies has been introduced and tested for the first time ever with Lp(a) and its genetic determinants.There are currently no approved pharmacologic therapies that specifically target Lp(a) concentrations. However, some therapies that target primarily LDL cholesterol have also an influence on Lp(a) concentrations. These are mainly PCSK9 inhibitors that lower LDL cholesterol by 60% and Lp(a) by 25-30%. Furthermore, lipoprotein apheresis lowers both, Lp(a) and LDL cholesterol, by about 60-70%. Some sophisticated study designs and statistical analyses provided support that lowering Lp(a) by these therapies also lowers cardiovascular events on top of the effect caused by lowering LDL cholesterol, although this was not the main target of the therapy. Currently, new therapies targeting RNA such as antisense oligonucleotides (ASO) or small interfering RNA (siRNA) against apolipoprotein(a), the main protein of the Lp(a) particle, are under examination and lower Lp(a) concentrations up to 90%. Since these therapies specifically lower Lp(a) concentrations without influencing other lipoproteins, they will serve the last piece of the puzzle whether a decrease of Lp(a) results also in a decrease of cardiovascular events.

Aortic valvular stenosis: Novel therapeutic strategies

BACKGROUND

Aortic stenosis (AS) prevalence is estimated to reach 4.5 million cases worldwide by the year 2030. AS is a progressive disease without a pharmacological treatment. In the current review, we aimed to investigate novel therapeutic approaches for non-surgical AS treatment, at least in patients with mild-to-moderate AS.

MATERIALS AND METHODS

The most recent and relevant papers concerned with novel molecular pathways that have potential as therapeutic targets in AS were selected from searches of PubMed and Web of Science up to February 2021.

RESULTS

Growing evidence indicates that therapies using proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, simvastatin/ezetimibe combination, cholesteryl ester transfer protein inhibitors or antisense oligonucleotides targeting apolipoprotein(a) reduce the risk of AS progression. It has been shown that enhanced valvular lipid oxidation may drive AS development by leading to the activation of valvular interstitial cells (VICs), the most abundant valvular cells having a major contribution to valve calcification. Since VICs are able to release pro-inflammatory cytokines, clotting factors and proteins involved in calcification, strategies targeting these cell activations seem promising as therapeutic interventions. Recently, non-vitamin K antagonist oral anticoagulants (NOACs) have been shown to inhibit activation of VICs.

CONCLUSION

Several novel molecular pathways of AS development have been identified over the past few years. Therapies using PCSK9 inhibitors, simvastatin/ezetimibe combination, lipoprotein(a)-lowering therapy are highly promising candidates as therapeutics in the prevention of mild AS progression, while preclinical studies show that NOACs may inhibit valvular inflammation and coagulation activation and slower the rate of AS progression.

Genetics of Lipoprotein(a): Cardiovascular Disease and Future Therapy

PURPOSE OF REVIEW

Lipoprotein(a) levels are determined 80-90% by genetics and differ by up to 1000-fold between individuals. This review discusses the most recent literature on lipoprotein(a) as a risk factor for cardiovascular disease, as well as future lipoprotein(a)lowering therapies.

RECENT FINDINGS

Over the past few decades, numerous studies have observed that high lipoprotein(a) levels are associated observationally and causally through human genetics with increased risk of cardiovascular disease. Also, the development of safe and effective therapies to lower lipoprotein(a) is ongoing, most importantly using antisense oligonucleotides to prevent production of lipoprotein(a). Finally, both observational and genetic studies have estimated the extent to which lowering of lipoprotein(a) is needed to obtain a clinically meaningful reduction in the risk of cardiovascular disease. Lipoprotein(a) is a causal risk factor for cardiovascular disease; however, currently no approved safe and effective therapy is available to lower lipoprotein(a) levels. That said, promising randomized studies using antisense oligonucleotides show up to 80% reductions in lipoprotein(a), reductions that hopefully will result in lowering the risk of cardiovascular disease as presently tested in the ongoing HORIZON phase 3 trial.

The Association of Lipoprotein(a) and Circulating Monocyte Subsets with Severe Coronary Atherosclerosis

Background and aims: Chronic inflammation associated with the uncontrolled activation of innate and acquired immunity plays a fundamental role in all stages of atherogenesis. Monocytes are a heterogeneous population and each subset contributes differently to the inflammatory process. A high level of lipoprotein(a) (Lp(a)) is a proven cardiovascular risk factor. The aim of the study was to investigate the association between the increased concentration of Lp(a) and monocyte subpopulations in patients with a different severity of coronary atherosclerosis. Methods: 150 patients (124 males) with a median age of 60 years undergoing a coronary angiography were enrolled. Lipids, Lp(a), autoantibodies, blood cell counts and monocyte subpopulations (classical, intermediate, non-classical) were analyzed. Results: The patients were divided into two groups depending on the Lp(a) concentration: normal Lp(a) < 30 mg/dL (n = 82) and hyperLp(a) ≥ 30 mg/dL (n = 68). Patients of both groups were comparable by risk factors, autoantibody levels and blood cell counts. In patients with hyperlipoproteinemia(a) the content (absolute and relative) of non-classical monocytes was higher (71.0 (56.6; 105.7) vs. 62.2 (45.7; 82.4) 10³/mL and 17.7 (13.0; 23.3) vs. 15.1 (11.4; 19.4) %, respectively, p < 0.05). The association of the relative content of non-classical monocytes with the Lp(a) concentration retained a statistical significance when adjusted for gender and age (r = 0.18, p = 0.03). The severity of coronary atherosclerosis was associated with the Lp(a) concentration as well as the relative and absolute (p < 0.05) content of classical monocytes. The high content of non-classical monocytes (OR = 3.5, 95% CI 1.2–10.8) as well as intermediate monocytes (OR = 8.7, 2.5–30.6) in patients with hyperlipoproteinemia(a) were associated with triple-vessel coronary disease compared with patients with a normal Lp(a) level and a low content of monocytes. Conclusion: Hyperlipoproteinemia(a) and a decreased quantity of classical monocytes were associated with the severity of coronary atherosclerosis. The expansion of CD16+ monocytes (intermediate and non-classical) in the presence of hyperlipoproteinemia(a) significantly increased the risk of triple-vessel coronary disease.

Lipoprotein(a) is robustly associated with aortic valve calcium

Objectives

To investigate the prevalence and quantity of aortic valve calcium (AVC) in two large cohorts, stratified according to age and lipoprotein(a) (Lp(a)), and to assess the association between Lp(a) and AVC.

Methods

We included 2412 participants from the population-based Rotterdam Study (52% women, mean age=69.6±6.3 years) and 859 apparently healthy individuals from the Amsterdam University Medical Centers (UMC) outpatient clinic (57% women, mean age=45.9±11.6 years). All individuals underwent blood sampling to determine Lp(a) concentration and non-enhanced cardiac CT to assess AVC. Logistic and linear regression analyses were performed to investigate the associations of Lp(a) with the presence and amount of AVC.

Results

The prevalence of AVC was 33.1% in the Rotterdam Study and 5.4% in the Amsterdam UMC cohort. Higher Lp(a) concentrations were independently associated with presence of AVC in both cohorts (OR per 50 mg/dL increase in Lp(a): 1.54 (95% CI 1.36 to 1.75) in the Rotterdam Study cohort and 2.02 (95% CI 1.19 to 3.44) in the Amsterdam UMC cohort). In the Rotterdam Study cohort, higher Lp(a) concentrations were also associated with increase in aortic valve Agatston score (β 0.19, 95% CI 0.06 to 0.32 per 50 mg/dL increase).

Conclusions

Lp(a) is robustly associated with presence of AVC in a wide age range of individuals. These results provide further rationale to assess the effect of Lp(a) lowering interventions in individuals with early AVC to prevent end-stage aortic valve stenosis.

Prevalence and influence of LPA gene variants and isoform size on the Lp(a)-lowering effect of pelacarsen

BACKGROUND AND AIMS

Antisense oligonucleotides (ASOs) targeting LPA to lower lipoprotein(a) [Lp(a]] are in clinical trials. Patients have been recruited according to various Lp(a) thresholds, but the prevalence of LPA genetic variants and their effect on efficacy of these ASOs are not well described.

METHODS

We analyzed data from 4 clinical trials of the ASO pelacarsen targeting apolipoprotein(a) that included 455 patients. Common LPA genetic variants rs10455872 and rs3798220, major and minor isoform size, and changes in Lp(a), LDL-C, apoB, OxPL-apoB and OxPL-apo(a) were analyzed according to categories of baseline Lp(a).

RESULTS

The prevalence of carrier status for rs10455872 and rs3798220 combined ranged from 25.9% in patients with Lp(a) in the 75 - <125 nmol/L range to 77.1% at Lp(a) ≥375 nmol/L. The prevalence of homozygosity for rs3798220, rs10455872 and for double heterozygosity in category of Lp(a) ≥375 nmol/L was 6.3%, 14.6% and 12.5%, respectively. Isoform size decreased with increasing Lp(a) plasma levels, with 99.3% of patients with Lp(a) ≥175 nmol/L having ≤20 KIV repeats in the major isoform. The mean percent reduction from baseline in Lp(a), OxPL-apoB and OxPL-apo(a) in response to pelacarsen was not affected by the presence of rs10455872 and rs3798220, isoform size or baseline Lp(a) at all doses studied.

CONCLUSIONS

In patients randomized to Lp(a) lowering trials, LPA genetic variants are common, but a sizable proportion do not carry common variants associated with elevated Lp(a). In contrast, the major isoform size was almost uniformly ≤20 KIV repeats in patients with Lp(a) ≥175 nmol/L. The Lp(a) and OxPL lowering effects of pelacarsen were independent of both LPA genetic variants and isoform size.