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

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.

Multimodality Imaging of Aortic Valve Calcification and Function in a Murine Model of Calcific Aortic Valve Disease and Bicuspid Aortic Valve

Calcific aortic valve disease (CAVD) is a prevailing disease with increasing occurrence and no known medical therapy. Dcbld2-/- mice have a high prevalence of bicuspid aortic valve (BAV), spontaneous aortic valve calcification, and aortic stenosis (AS). 18F-NaF PET/CT can detect the aortic valve calcification process in humans. However, its feasibility in preclinical models of CAVD remains to be determined. Here, we sought to validate 18F-NaF PET/CT for tracking murine aortic valve calcification and leveraged it to examine the development of calcification with aging and its interdependence with BAV and AS in Dcbld2-/- mice. Methods: Dcbld2-/- mice at 3-4 mo, 10-16 mo, and 18-24 mo underwent echocardiography, 18F-NaF PET/CT (n = 34, or autoradiography (n = 45)), and tissue analysis. A subset of mice underwent both PET/CT and autoradiography (n = 12). The aortic valve signal was quantified as SUVmax on PET/CT and as percentage injected dose per square centimeter on autoradiography. The valve tissue sections were analyzed by microscopy to identify tricuspid and bicuspid aortic valves. Results: The aortic valve 18F-NaF signal on PET/CT was significantly higher at 18-24 mo (P < 0.0001) and 10-16 mo (P < 0.05) than at 3-4 mo. Additionally, at 18-24 mo BAV had a higher 18F-NaF signal than tricuspid aortic valves (P < 0.05). These findings were confirmed by autoradiography, with BAV having significantly higher 18F-NaF uptake in each age group. A significant correlation between PET and autoradiography data (Pearson r = 0.79, P < 0.01) established the accuracy of PET quantification. The rate of calcification with aging was significantly faster for BAV (P < 0.05). Transaortic valve flow velocity was significantly higher in animals with BAV at all ages. Finally, there was a significant correlation between transaortic valve flow velocity and aortic valve calcification by both PET/CT (r = 0.55, P < 0.001) and autoradiography (r = 0.45, P < 0.01). Conclusion: 18F-NaF PET/CT links valvular calcification to BAV and aging in Dcbld2-/- mice and suggests that AS may promote calcification. In addition to addressing the pathobiology of valvular calcification, 18F-NaF PET/CT may be a valuable tool for evaluation of emerging therapeutic interventions in CAVD.

Daring to dream: Targeting lipoprotein(a) as a causal and risk-enhancing factor

Lipoprotein(a) [Lp(a)], a distinct lipoprotein class, has become a major focus for cardiovascular research. This review is written in light of the recent guideline and consensus statements on Lp(a) and focuses on 1) the causal association between Lp(a) and cardiovascular outcomes, 2) the potential mechanisms by which elevated Lp(a) contributes to cardiovascular diseases, 3) the metabolic insights on the production and clearance of Lp(a) and 4) the current and future therapeutic approaches to lower Lp(a) concentrations. The concentrations of Lp(a) are under strict genetic control. There exists a continuous relationship between the Lp(a) concentrations and risk for various endpoints of atherosclerotic cardiovascular disease (ASCVD). One in five people in the Caucasian population is considered to have increased Lp(a) concentrations; the prevalence of elevated Lp(a) is even higher in black populations. This makes Lp(a) a cardiovascular risk factor of major public health relevance. Besides the association between Lp(a) and myocardial infarction, the relationship with aortic valve stenosis has become a major focus of research during the last decade. Genetic studies provided strong support for a causal association between Lp(a) and cardiovascular outcomes: carriers of genetic variants associated with lifelong increased Lp(a) concentration are significantly more frequent in patients with ASCVD. This has triggered the development of drugs that can specifically lower Lp(a) concentrations: mRNA-targeting therapies such as anti-sense oligonucleotide (ASO) therapies and short interfering RNA (siRNA) therapies have opened new avenues to lower Lp(a) concentrations more than 95%. Ongoing Phase II and III clinical trials of these compounds are discussed in this review.

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.

Calcific aortic valve disease: mechanisms, prevention and treatment

Calcific aortic valve disease (CAVD) is the most common disorder affecting heart valves and is characterized by thickening, fibrosis and mineralization of the aortic valve leaflets. Analyses of surgically explanted aortic valve leaflets have shown that dystrophic mineralization and osteogenic transition of valve interstitial cells co-occur with neovascularization, microhaemorrhage and abnormal production of extracellular matrix. Age and congenital bicuspid aortic valve morphology are important and unalterable risk factors for CAVD, whereas additional risk is conferred by elevated blood pressure and plasma lipoprotein(a) levels and the presence of obesity and diabetes mellitus, which are modifiable factors. Genetic and molecular studies have identified that the NOTCH, WNT-β-catenin and myocardin signalling pathways are involved in the control and commitment of valvular cells to a fibrocalcific lineage. Complex interactions between valve endothelial and interstitial cells and immune cells promote the remodelling of aortic valve leaflets and the development of CAVD. Although no medical therapy is effective for reducing or preventing the progression of CAVD, studies have started to identify actionable targets.

The nonlinear correlation between lipoprotein (a) and the prevalence of aortic valve calcification in patients with new-onset acute myocardial infarction

BACKGROUND

Growing studies show that lipoprotein (a) [Lp(a)] is related to calcified aortic valve diseases in general population, while the relationship between Lp(a) and aortic valve calcification (AVC) in patients with new-onset acute myocardial infarction (AMI) remains unclear. Therefore, this study was to evaluate the correlation between Lp(a) and AVC in patients with new-onset AMI.

METHODS

This cross-sectional study included 410 patients with new-onset AMI who were hospitalised in Zhongda Hospital affiliated to Southeast University from January 1, 2020 to December 31, 2021. Multivariable logistic regression, subgroup analysis, generalised additive model, threshold and saturation effect and receiver operator characteristic (ROC) curve were used to explore the association between Lp(a) and AVC.

RESULTS

Patients with AVC had higher levels of Lp(a) than those without AVC. Multivariable logistic regression analysis showed that higher Lp(a) was still associated with higher risk of AVC after adjusting for confounding factors, and this correlation was robust in most subgroups and sensitivity analyses (p < 0.05). Additionally, the generalised additive model showed that there was a nonlinear correlation between Lp(a) and AVC (P for nonlinearity = 0.037). Threshold and saturation effect analysis indicated that when Lp(a) < 840 mg/L, it was positively correlated with the prevalence of AVC (p < 0.05), but when Lp(a) ≥ 840 mg/L, this correlation no longer existed. Besides, ROC curve analysis demonstrated that Lp(a) had a good diagnostic performance for AVC.

CONCLUSION

Lp(a) was independently associated with the prevalence of AVC in patients with new-onset AMI.

Lipoprotein(a) in atherosclerotic cardiovascular disease and aortic stenosis: a European Atherosclerosis Society consensus statement

This 2022 European Atherosclerosis Society lipoprotein(a) [Lp(a)] consensus statement updates evidence for the role of Lp(a) in atherosclerotic cardiovascular disease (ASCVD) and aortic valve stenosis, provides clinical guidance for testing and treating elevated Lp(a) levels, and considers its inclusion in global risk estimation. Epidemiologic and genetic studies involving hundreds of thousands of individuals strongly support a causal and continuous association between Lp(a) concentration and cardiovascular outcomes in different ethnicities; elevated Lp(a) is a risk factor even at very low levels of low-density lipoprotein cholesterol. High Lp(a) is associated with both microcalcification and macrocalcification of the aortic valve. Current findings do not support Lp(a) as a risk factor for venous thrombotic events and impaired fibrinolysis. Very low Lp(a) levels may associate with increased risk of diabetes mellitus meriting further study. Lp(a) has pro-inflammatory and pro-atherosclerotic properties, which may partly relate to the oxidized phospholipids carried by Lp(a). This panel recommends testing Lp(a) concentration at least once in adults; cascade testing has potential value in familial hypercholesterolaemia, or with family or personal history of (very) high Lp(a) or premature ASCVD. Without specific Lp(a)-lowering therapies, early intensive risk factor management is recommended, targeted according to global cardiovascular risk and Lp(a) level. Lipoprotein apheresis is an option for very high Lp(a) with progressive cardiovascular disease despite optimal management of risk factors. In conclusion, this statement reinforces evidence for Lp(a) as a causal risk factor for cardiovascular outcomes. Trials of specific Lp(a)-lowering treatments are critical to confirm clinical benefit for cardiovascular disease and aortic valve stenosis.

Lipoprotein(a) is associated with the onset but not the progression of aortic valve calcification

AIM

Lipoprotein(a) [Lp(a)] is a potential causal factor in the pathogenesis of aortic valve disease. However, the relationship of Lp(a) with new onset and progression of aortic valve calcium (AVC) has not been studied. The purpose of the study was to assess whether high serum levels of Lp(a) are associated with AVC incidence and progression.

METHODS AND RESULTS

A total of 922 individuals from the population-based Rotterdam Study (mean age 66.0±4.2 years, 47.7% men), whose Lp(a) measurements were available, underwent non-enhanced cardiac computed tomography imaging at baseline and after a median follow-up of 14.0 [interquartile range (IQR) 13.9-14.2] years. New-onset AVC was defined as an AVC score >0 on the follow-up scan in the absence of AVC on the first scan. Progression was defined as the absolute difference in AVC score between the baseline and follow-up scan. Logistic and linear regression analyses were performed to evaluate the relationship of Lp(a) with baseline, new onset, and progression of AVC. All analyses were corrected for age, sex, body mass index, smoking, hypertension, dyslipidaemia, and creatinine. AVC progression was analysed conditional on baseline AVC score expressed as restricted cubic splines. Of the 702 individuals without AVC at baseline, 415 (59.1%) developed new-onset AVC on the follow-up scan. In those with baseline AVC, median annual progression was 13.5 (IQR = 5.2-37.8) Agatston units (AU). Lipoprotein(a) concentration was independently associated with baseline AVC [odds ratio (OR) 1.43 for each 50 mg/dL higher Lp(a); 95% confidence interval (CI) 1.15-1.79] and new-onset AVC (OR 1.30 for each 50 mg/dL higher Lp(a); 95% CI 1.02-1.65), but not with AVC progression (β: -71 AU for each 50 mg/dL higher Lp(a); 95% CI -117; 35). Only baseline AVC score was significantly associated with AVC progression (P < 0.001).

CONCLUSION

In the population-based Rotterdam Study, Lp(a) is robustly associated with baseline and new-onset AVC but not with AVC progression, suggesting that Lp(a)-lowering interventions may be most effective in pre-calcific stages of aortic valve disease.

Molecular Imaging of Aortic Valve Stenosis with Positron Emission Tomography

Aortic valve stenosis (AVS) is an increasingly prevalent disease in our aging population. Although multiple risk factors for AVS have been elucidated, medical therapies capable of slowing down disease progression remain unavailable. Molecular imaging technologies are opening up avenues for the non-invasive assessment of disease progression, allowing the assessment of (early) medical interventions. This review will focus on the role of positron emission tomography of the aortic valve with 18F-fluorodeoxyglucose and 18F-sodium fluoride but will also shed light on novel tracers which have potential in AVS, ranging from the healthy aortic valve to end-stage valvular disease.