Significance of aortic valve calcification in patients with low-gradient low-flow aortic stenosis

Diagnostic Value of Aortic Valve Calcification Levels in the Assessment of Low-Gradient Aortic Stenosis

BACKGROUND

In patients with low-gradient aortic stenosis (AS) and low transvalvular flow, dobutamine stress echocardiography (DSE) is recommended to determine AS severity, whereas the degree of aortic valve calcification (AVC) supposedly correlates with AS severity according to current European and American guidelines.

OBJECTIVES

The purpose of this study was to assess the relationship between AVC and AS severity as determined using echocardiography and DSE in patients with aortic valve area <1 cm2 and peak aortic valve velocity <4.0 m/s.

METHODS

All patients underwent DSE to determine AS severity and multislice computed tomography to quantify AVC. Receiver-operating characteristics curve analysis was used to assess the diagnostic value of AVC for AS severity grading as determined using echocardiography and DSE in men and women.

RESULTS

A total of 214 patients were included. Median age was 78 years (25th-75th percentile: 71-84 years) and 25% were women. Left ventricular ejection fraction was reduced (<50%) in 197 (92.1%) patients. Severe AS was diagnosed in 106 patients (49.5%). Moderate AS was diagnosed in 108 patients (50.5%; in 77 based on resting transthoracic echocardiography, in 31 confirmed using DSE). AVC score was high (≥2,000 for men or ≥1,200 for women) in 47 (44.3%) patients with severe AS and in 47 (43.5%) patients with moderate AS. AVC sensitivity was 44.3%, specificity was 56.5%, and positive and negative predictive values for severe AS were 50.0% and 50.8%, respectively. Area under the receiver-operating characteristics curve was 0.508 for men and 0.524 for women.

CONCLUSIONS

Multi-slice computed tomography-derived AVC scores showed poor discrimination between grades of AS severity using DSE and cannot replace DSE in the diagnostic work-up of low-gradient severe AS.

Pre-discharge 18F-Flourodeoxyglucose uptake pattern following transcatheter aortic-valve replacement and adverse prognostic features in aortic stenosis

18F-Flourodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) has been shown to be of utility in transcatheter aortic valve replacement (TAVR) patients with suspected prosthetic valve endocarditis. In the present study, we sought to analyze the relationship between 18F-FDG-PET/CT performed before discharge in TAVR patients and adverse prognostic features of aortic stenosis. We analyzed the association between 18F-FDG-PET/CT uptake pattern and degree of left ventricular mass index, aortic root dilatation, and aortic leaflet calcification extent. This is the first study to demonstrate that pre-discharge 18F-FDG-PET/CT in patients undergoing TAVR shows a significant negative correlation between 18F-FDG uptake pattern and adverse prognostic features.

Native aortic leaflets and permanent pacemaker implantation risk following balloon-expandable transcatheter aortic valve implantation

OBJECTIVE

Permanent pacemaker implantation (PPI) risk is higher following transcatheter aortic valve implantation (TAVI) than surgical valve replacement. Native aortic leaflets are retained in patients undergoing TAVI, unlike in surgical valve replacement. Whether the retained leaflets influence PPI risk because of their proximity to the conduction system is unknown. The study sought to determine the association between infra-annular extension of native right coronary cusp/noncoronary cusp (RCC/NCC) post balloon-expandable TAVI and PPI risk.

METHODS

We performed a retrospective analysis of 190 patients undergoing balloon-expandable TAVI at a single center. Manifestation of infra-annular extension of RCC/NCC was considered to be present when part of leaflet extended below aortic-annular plane on post-implantation aortic-root angiography.

RESULTS

Infra-annular extension of RCC/NCC was observed in 33 patients (17.37%). PPI incidence post-TAVI was higher in patients with infra-annular extension of RCC/NCC than in those without (36.36% versus 8.92%, relative-risk: 4.08, p˂0.0001). On logistic-regression analysis, preexisting right bundle-branch block (RBBB) (odds-ratio: 12.73, 95% confidence-interval: 2.16-74.93, p = 0.005), and infra-annular extension of RCC/NCC (odds-ratio: 5.63, 95% confidence-interval: 2.17-14.58, p < 0.0001) were independently associated with PPI risk. Preexisting RBBB (φ = +0.25, p = 0.001) and infra-annular extension of RCC/NCC (φ = +0.30, p < 0.0001) showed a positive-correlation with PPI risk. Infra-annular extension of RCC/NCC was a significant predictor of PPI risk on receiver-operating-characteristic curve analysis (area under-the-curve 0.67; 95% confidence-interval: 0.54-0.79, p = 0.006).

CONCLUSION

The retained native aortic leaflets play a significant role in PPI risk following balloon-expandable TAVI. Infra-annular extension of RCC/NCC is a novel predictor, and is associated with a four-fold higher risk of PPI.

Prognostic value of cardiac magnetic resonance in patients with aortic stenosis: A systematic review and meta-analysis

BACKGROUND

The timing of surgery for aortic stenosis (AS) is imperfect, and the management of moderate AS and asymptomatic severe AS is still challenging. Myocardial fibrosis (MF) is the main pathological basis of cardiac decompensation in patients with AS and can be detected by cardiovascular magnetic resonance (CMR). The aim of this study was to evaluate the prognostic value of MF measured by CMR in patients with AS, which can provide a reference for the timing of aortic valve replacement (AVR).

METHODS

We searched Medline, Embase, and Web of Science to include all studies that investigated the prognostic value of CMR in patients with AS. The search deadline is March 31, 2021. The pooled relative risk (RR) or hazard ratio (HR) and 95% confidence intervals (CI) of the biomarkers including late gadolinium enhancement (LGE), Native T1 or extracellular volume (ECV) were calculated to evaluate the prognostic value.

RESULTS

13 studies and 2,430 patients with AS were included in this study, the mean or medium follow-up duration for each study was ranged from 6 to 67.2 months. Meta-analysis showed the presence of LGE was associated with an increased risk for all-cause mortality (pooled RR: 2.14, 95% CI: 1.67-2.74, P < 0.001), cardiac mortality (pooled RR: 3.50, 95% CI: 2.32-5.30, P < 0.001), and major adverse cardiovascular events (MACEs) (pooled RR: 1.649, 95% CI: 1.23-2.22, P = 0.001). Native T1 was significantly associated with MACEs (pooled RR: 2.23, 95% CI: 1.00-4.95; P = 0.049), and higher ECV was associated with a higher risk of cardiovascular events (pooled HR: 1.69, 95% CI: 1.11-2.58; P = 0.014).

CONCLUSION

The use of CMR to detect MF has a good prognostic value in patients with AS. LGE, Native T1 and ECV measured by CMR can contribute to risk stratification of AS, thereby helping to optimize the timing of AVR.

Imaging Challenges in Patients with Severe Aortic Stenosis and Heart Failure: Did We Find a Way Out of the Labyrinth?

Aortic stenosis (AS) is the most frequent degenerative valvular disease in developed countries. Its incidence has been constantly rising due to population aging. The diagnosis of AS was considered straightforward for a very long time. High gradients and reduced aortic valve area were considered as "sine qua non" in diagnosis of AS until a growing body of evidence showed that patients with low gradients could also have severe AS with the same or even worse outcome. This completely changed the paradigm of AS diagnosis and involved large numbers of parameters that had never been used in the evaluation of AS severity. Low gradient AS patients may present with heart failure (HF) with preserved or reduced left ventricular ejection fraction (LVEF), associated with changes in cardiac output and flow across the aortic valve. These patients with low-flow low-gradient or paradoxical low-flow low-gradient AS are particularly challenging to diagnose, and cardiac output and flow across the aortic valve have become the most relevant parameters in evaluation of AS, besides gradients and aortic valve area. The introduction of other imaging modalities in the diagnosis of AS significantly improved our knowledge about cardiac mechanics, tissue characterization of myocardium, calcium and inflammation burden of the aortic valve, and their impact on severity, progression and prognosis of AS, not only in symptomatic but also in asymptomatic patients. However, a variety of novel parameters also brought uncertainty regarding the clinical relevance of these indices, as well as the necessity for their validation in everyday practice. The aim of this review is to summarize the prevalence of HF in patients with severe AS and elaborate on the diagnostic challenges and advantages of comprehensive multimodality cardiac imaging to identify the patients that may benefit from surgical or transcatheter aortic valve replacement, as well as parameters that may help during follow-up.

Impact of Surgical and Transcatheter Aortic Valve Replacement in Low-Gradient Aortic Stenosis: A Meta-Analysis

OBJECTIVES

The aim of this study was to assess the impact of aortic valve replacement (AVR) on survival in patients with each subclass of low-gradient (LG) aortic stenosis (AS) and to compare outcomes following surgical AVR (SAVR) and transcatheter AVR (TAVR).

BACKGROUND

LG severe AS encompasses a wide variety of pathophysiology, including classical low-flow, LG (LF-LG), paradoxical LF-LG, and normal-flow, LG (NF-LG) AS, and uncertainty exists regarding the impact of AVR on each subclass of LG AS.

METHODS

PubMed and Embase were queried through October 2020 to identify studies comparing survival with different management strategies (SAVR, TAVR, and conservative) in patients with LG AS. Pairwise meta-analysis comparing AVR versus conservative management and network meta-analysis comparing SAVR versus TAVR versus conservative management were performed.

RESULTS

Thirty-two studies with a total of 6,515 patients and a median follow-up time of 24.2 months (interquartile range: 36.5 months) were included. AVR was associated with a significant decrease in all-cause mortality in classical LF-LG (hazard ratio [HR]: 0.42; 95% confidence interval [CI]: 0.36 to 0.48), paradoxical LF-LG (HR: 0.41; 95% CI: 0.29 to 0.57), and NF-LG (HR: 0.41; 95% CI: 0.27 to 0.62) AS compared with conservative management. SAVR and TAVR were each associated with a decrease in all-cause mortality in classical LF-LG (HR: 0.46 [95% CI: 0.38 to 0.55] and 0.49 [95% CI: 0.37 to 0.64], respectively), paradoxical LF-LG (HR: 0.42 [95% CI: 0.28 to 0.65] and 0.42 [95% CI: 0.25 to 0.72], respectively), and NF-LG (HR: 0.40 [95% CI: 0.21 to 0.77] and 0.46 [95% CI: 0.26 to 0.84], respectively) AS compared with conservative management. No significant difference was observed between SAVR and TAVR.

CONCLUSIONS

In all subclasses of LG AS, AVR was associated with a significant decrease in all-cause mortality regardless of surgical or transcatheter approach.

Predictors of true-severe classical low-flow low-gradient aortic stenosis at resting echocardiography

BACKGROUND

Classical low-flow, low-gradient (LF/LG) aortic stenosis (AS) is subclassified into a true-severe (TS) and a pseudo-severe (PS) subform using low-dose dobutamine stress echocardiography (DSE). In clinical practice a resting peak jet velocity (Vmax) >3.5 m/s or a mean transvalvular gradient (MPG) >35 mmHg suggests the presence of TS classical LF/LG AS, but there is no data to support this. The aim of this study was therefore to investigate whether a resting Vmax >3.5 m/s or MPG >35 mmHg reliably predicted diagnosis of TS classical LF/LG AS.

METHODS

One hundred (100) consecutive patients with classical LF/LG AS were prospectively recruited. All patients underwent DSE for subcategorization. The impact of Vmax and MPG for the presence of the TS subform were analyzed.

RESULTS

TS classical LF/LG AS was diagnosed in 72 patients. Resting Vmax and resting MPG predicted true-severity with an ROC-AUC of 0.737 (95%CI: 0.635-0.838; p < 0.001) and 0.725 (95%CI: 0.615-0.834; p < 0.001), respectively. The optimal positive predictive values (PPV) for the diagnosis of TS classical LF/LG AS were obtained with a resting Vmax >3.5 m/s or resting MPG >35 mmHg. In a multivariate logistic regression analysis, Vmax >3.5 m/s was independently associated with a 5.33-fold odds-ratio of TS classical LF/LG AS (OR 5.33; 95%CI: 1.34-21.18, p = 0.018).

CONCLUSIONS

TS classical LF/LG AS can be reliably predicted by a resting Vmax >3.5 m/s or a resting MPG >35 mmHg. Further imaging for subclassification is not needed in this situation.

Reclassification of aortic stenosis by fusion of echocardiography and computed tomography in low-gradient aortic stenosis

Background

The integration of computed tomography (CT)-derived left ventricular outflow tract area into the echocardiography-derived continuity equation results in the reclassification of a significant proportion of patients with severe aortic stenosis (AS) into moderate AS based on aortic valve area indexed to body surface area determined by fusion imaging (fusion AVA_i). The aim of this study was to evaluate AS severity by a fusion imaging technique in patients with low-gradient AS and to compare the clinical impact of reclassified moderate AS versus severe AS.

Methods

We included 359 consecutive patients who underwent transcatheter aortic valve implantation for low-gradient, severe AS at two academic institutions and created a joint database. The primary endpoint was a composite of all-cause mortality and rehospitalisations for heart failure at 1 year.

Results

Overall, 35% of the population (n = 126) were reclassified to moderate AS [median fusion AVAi 0.70 (interquartile range, IQR 0.65–0.80) cm²/m²] and severe AS was retained as the classification in 65% [median fusion AVAi 0.49 (IQR 0.43–0.54) cm²/m²]. Lower body mass index, higher logistic EuroSCORE and larger aortic dimensions characterised patients reclassified to moderate AS. Overall, 57% of patients had a left ventricular ejection fraction (LVEF) <50%. Clinical outcome was similar in patients with reclassified moderate or severe AS. Among patients reclassified to moderate AS, non-cardiac mortality was higher in those with LVEF <50% than in those with LVEF ≥50% (log-rank p = 0.029).

Conclusions

The integration of CT and transthoracic echocardiography to obtain fusion AVAi led to the reclassification of one third of patients with low-gradient AS to moderate AS. Reclassification did not affect clinical outcome, although patients reclassified to moderate AS with a LVEF <50% had worse outcomes owing to excess non-cardiac mortality.

Association of Time Between Left Ventricular and Aortic Systolic Pressure Peaks With Severity of Aortic Stenosis and Calcification of Aortic Valve

Importance

Diagnosis of low-gradient severe aortic stenosis (AS) is challenging. We hypothesized that the time between left ventricular (LV) and aortic systolic pressure peaks (TLV-Ao) is associated with aortic stenosis (AS) severity and may have additive value in diagnosing severe AS, especially in patients with low-gradient AS.

Objective

To investigate the diagnostic utility of measuring catheter-based TLV-Ao in patients with severe AS.

Design, Setting, and Participants

We studied 123 patients with severe AS at the Cleveland Clinic Foundation, a tertiary referral center, who underwent transcatheter aortic valve replacement (TAVR) via femoral access and had pre-TAVR cardiac computed tomography assessment and hemodynamic measurements recorded during a TAVR procedure. All patients received hemodynamic evaluation, echocardiographic assessment, and quantification of aortic valve calcification (AVC) by multidetector computed tomography. Hemodynamic data were collected via left heart catheterization done just before TAVR, and TLV-Ao was calculated offline. Data were analyzed between October 5, 2015, and July 20, 2016.

Main Outcomes and Measures

The association between TLV-Ao and AVC or other conventional imaging parameters was analyzed.

Results

Of the included patients, the mean (SD) age was 81 (9) years, and 65 (54%) were men (54%). Among 123 patients, 48 patients (39%) had low-gradient AS (<40 mm Hg) and mean (SD) TLV-Ao was 69 (39) milliseconds. In multivariable logistic regression analyses, higher TLV-Ao (odds ratio [OR], 1.02; 95% CI, 1.01-1.04; P = .002) and higher peak aortic valve (AV) velocity (OR, 1.01; 95% CI, 1.00-1.02; P = .008) were independently associated with severe AVC (AVC >1000 AU). Adding TLV-Ao to the peak AV velocity and AV area showed significant incremental value to be associated with AVC, with a net reclassification improvement of 0.61 (95% CI, 0.23-0.99; P = .002) and integrated discriminatory improvement of 0.09 (95% CI, 0.03-0.16; P = .003). In a subgroup of patients with low-grade AS, higher TLV-Ao was the only parameter associated with severe AVC (OR, 1.02; 95% CI, 1.001-1.04; P = .03).

Conclusions and Relevance

Prolonged TLV-Ao was associated with severe AVC. This catheter-based hemodynamic index may be an additional surrogate to differentiate low-gradient true severe AS. Larger, prospective studies investigating the role of TLV-Ao as a marker of clinical outcomes in patients undergoing TAVR are required.

Predicting Disease Progression and Mortality in Aortic Stenosis: A Systematic Review of Imaging Biomarkers and Meta-Analysis

Background: Detecting among patients with aortic stenosis (AS) those who are likely to rapidly progress, yet potentially benefiting from prophylactic aortic valve replacement, is needed for improved patient care. The objective of this study was to evaluate the role of imaging biomarkers in predicting the progression to clinical symptoms and death in patients with AS. Methods: We searched the Pubmed and the International Clinical Trials Registry Platform databases for studies including patients with AS, and investigating imaging techniques, published in any language until Jan 1, 2018. Eligible sets of data include effect of imaging biomarkers relative to: (1) Overall mortality, (2) Cardiac mortality, and (3) Overall events (Symptom onset and Major Adverse Cardiovascular Events). Meta-analysis was used to examine associations between the imaging biomarkers and outcomes of AS using Random Effect models. Results: Eight studies and 1,639 patients were included after systematic review. Four studies investigated aortic valve calcification (AVC) whereas the remaining investigated biomarkers provided by cardiac magnetic resonance (CMR). Four articles investigated the presence of midwall fibrosis on late-gadolinium enhancement imaging, three reported its extent (LGE%) and two, the myocardial extracellular volume (ECV). By decreasing strength of association, there were significant associations between cardiac mortality and LGE% [Relative Risk (RR) = 1.05, 95% Confidence Interval (CI) 1.01-1.10]; overall mortality and AVC (RR = 1.19, 95%CI: 1.05-1.36); overall events and ECV (RR = 1.68, 95%CI: 1.17-2.41); cardiac mortality and midwall fibrosis (RR = 2.88, 95%CI: 1.12-7.39). Conclusion: AVC and myocardial fibrosis imaging biomarkers predict the outcomes in AS, and help understanding AS pathophysiology and setting therapeutic targets.

Calcific Aortic Valve Disease: a Developmental Biology Perspective

PURPOSE OF REVIEW

This review aims to highlight the past and more current literature related to the multifaceted pathogenic programs that contribute to calcific aortic valve disease (CAVD) with a focus on the contribution of developmental programs.

RECENT FINDINGS

Calcification of the aortic valve is an active process characterized by calcific nodule formation on the aortic surface leading to a less supple and more stiffened cusp, thereby limiting movement and causing clinical stenosis. The mechanisms underlying these pathogenic changes are largely unknown, but emerging studies have suggested that signaling pathways common to valvulogenesis and bone development play significant roles and include Transforming Growth Factor-β (TGF-β), bone morphogenetic protein (BMP), Wnt, Notch, and Sox9. This comprehensive review of the literature highlights the complex nature of CAVD but concurrently identifies key regulators that can be targeted in the development of mechanistic-based therapies beyond surgical intervention to improve patient outcome.

Aortic Stenosis, a Left Ventricular Disease: Insights from Advanced Imaging

Aortic stenosis (AS) is the most common primary valve disorder in the elderly with an increasing prevalence. It is increasingly clear that it is also a disease of the left ventricle (LV) rather than purely the aortic valve. The transition from left ventricular hypertrophy to fibrosis results in the eventual adverse effects on systolic and diastolic function. Appropriate selection of patients for aortic valve intervention is crucial, and current guidelines recommend aortic valve replacement in severe AS with symptoms or in asymptomatic patients with left ventricular ejection fraction (LVEF) <50 %. LVEF is not a sensitive marker and there are other parameters used in multimodality imaging techniques, including longitudinal strain, exercise stress echo and cardiac MRI that may assist in detecting subclinical and subtle LV dysfunction. These findings offer potentially better ways to evaluate patients, time surgery, predict recovery and potentially offer targets for specific therapies. This article outlines the pathophysiology behind the LV response to aortic stenosis and the role of advanced multimodality imaging in describing it.

Cardiac Computed Tomography: Before and After Cardiac Surgery

Cardiac computed tomography angiography (CCTA) is a noninvasive imaging technique that has been rapidly adopted into clinical practice. Over the past decade, technological advances have improved CCTA accuracy, and there is an increasing amount of data supporting its prognostic value in the assessment of coronary artery disease. Recently, "appropriate use criteria" has been used as a tool to minimize inappropriate testing and reduce patient exposure to unnecessary risk and inconclusive studies. This review will summarize the appropriate uses of CCTA in patients before and after cardiac surgery. Although the most common indication for CCTA is assessment of patency of native coronary arteries, other potential perioperative uses (eg, assessment of congenital heart disease, valvular heart disease, pericardial disease, myocardial disease, cardiac anatomy, bypass grafts, aortic disease, and cardiac masses) will be reviewed.

New considerations in the assessment of aortic stenosis

Calcific aortic stenosis (AS) is one of the most common acquired valvular heart diseases in industrialized nations. It is a slowly progressive disease and with the aging population, the prevalence of AS is expected to increase. Doppler echocardiography is used to classify patients based on severity of stenosis. Research efforts on how to better identify and risk-assess these patients are currently underway using advanced imaging modalities and serum biomarkers. Thus far, medications for AS prevention have been unsuccessful. As technology progresses, the assessment of AS will transition from one heavily weighed on echocardiographic gradients to one of active surveillances with multimodality imaging, serum biomarkers and genetic assessment.

The Role of Imaging in Aortic Valve Disease

PURPOSE OF REVIEW

Aortic valve disease is the most common form of heart valve disease in developed countries. Imaging remains central to the diagnosis and risk stratification of patients with both aortic stenosis and regurgitation and has traditionally been performed with echocardiography. Indeed, echocardiography remains the cornerstone of aortic valve imaging as it is cheap, widely available and provides critical information concerning valve hemodynamics and ventricular function.

RECENT FINDINGS

Whilst diagnostic in the vast majority of patients, echocardiography has certain limitations including operator variability, potential for measurement errors and internal inconsistencies in severity grading. In particular, low-gradient severe aortic stenosis is common and challenging to diagnose. Aortic valve imaging may therefore be improved with alternative and complimentary multimodality approaches.

SUMMARY

This review investigates established and novel techniques for imaging both the aortic valve and the myocardial remodelling response including echocardiography, computed tomography, cardiovascular magnetic resonance and positron emission tomography. Moreover, we examine how the complementary information provided by each modality may be used in both future clinical practice and the research arena.

Calcific Aortic Valve Disease: Part 1--Molecular Pathogenetic Aspects, Hemodynamics, and Adaptive Feedbacks

Aortic valvular stenosis (AVS), produced by calcific aortic valve disease (CAVD) causing reduced cusp opening, afflicts mostly older persons eventually requiring valve replacement. CAVD had been considered "degenerative," but newer investigations implicate active mechanisms similar to atherogenesis--genetic predisposition and signaling pathways, lipoprotein deposits, chronic inflammation, and calcification/osteogenesis. Consequently, CAVD may eventually be controlled/reversed by lifestyle and pharmacogenomics remedies. Its management should be comprehensive, embracing not only the valve but also the left ventricle and the arterial system with their interdependent morphomechanics/hemodynamics, which underlie the ensuing diastolic and systolic LV dysfunction. Compared to even a couple of decades ago, we now have an increased appreciation of genomic and cytomolecular pathogenetic mechanisms underlying CAVD. Future pluridisciplinary studies will characterize better and more completely its pathobiology, evolution, and overall dynamics, encompassing intricate feedback processes involving specific signaling molecules and gene network cascades. They will herald more effective, personalized medicine treatments of CAVD/AVS.

Quantification of Calcium Amount in a New Experimental Model: A Comparison between Ultrasound and Computed Tomography

Purpose

Calcification is an important prognostic factor in aortic valve stenosis. However, there is no ultrasound (US) method available to accurately quantify calcification in this setting to date. We aimed to validate a new US method for measuring the amount of calcium in an in vitro model, and compare it to computed tomography (CT), the current imaging gold standard.

Materials and Methods

An agar phantom (2% agar) was made, containing 9 different amounts of calcium-hydroxyapatite Ca₅(PO₄)₃OH (2 to 50mg). The phantoms were imaged with micro-CT and US (10 MHz probe). The calcium area (area_calcium) and its maximum pixel value (PV_max) were obtained. These values were summed to calculate CT and US calcium scores (∑(area_calcium × PV_max)) and volumes (∑area_calcium). Both US- and CT-calcium scores were compared with the calcium amounts, and with each other.

Results

Both calcium scores correlated significantly with the calcium amount (R² = 0.9788, p<0.0001 and R² = 0.8154, p<0.0001 for CT and US respectively). Furthermore, there was a significant correlation between US and CT for calcium volumes (R² = 0.7392, p<0.0001) and scores (R² = 0.7391, p<0.0001).

Conclusion

We developed a new US method that accurately quantifies the amount of calcium in an in vitro model. Moreover it is strongly correlated with CT.

Calcification Characteristics of Low-Flow Low-Gradient Severe Aortic Stenosis in Patients Undergoing Transcatheter Aortic Valve Replacement

Low-flow low-gradient severe aortic stenosis (LFLGAS) is associated with worse outcomes. Aortic valve calcification patterns of LFLGAS as compared to non-LFLGAS have not yet been thoroughly assessed. 137 patients undergoing transcatheter aortic valve replacement (TAVR) with preprocedural multidetector computed tomography (MDCT) and postprocedural transthoracic echocardiography were enrolled. Calcification characteristics were assessed by MDCT both for the total aortic valve and separately for each leaflet. 34 patients had LFLGAS and 103 non-LFLGAS. Total aortic valve calcification volume (p < 0.001), mass (p < 0.001), and density (p = 0.004) were lower in LFLGAS as compared to non-LFLGAS patients. At 30-day follow-up, mean transaortic pressure gradients and more than mild paravalvular regurgitation did not differ between groups. In conclusion, LFLGAS and non-LFLGAS express different calcification patterns which, however, did not impact on device success after TAVR.

Vascular Calcification and Stone Disease: A New Look towards the Mechanism

Calcium phosphate (CaP) crystals are formed in pathological calcification as well as during stone formation. Although there are several theories as to how these crystals can develop through the combined interactions of biochemical and biophysical factors, the exact mechanism of such mineralization is largely unknown. Based on the published scientific literature, we found that common factors can link the initial stages of stone formation and calcification in anatomically distal tissues and organs. For example, changes to the spatiotemporal conditions of the fluid flow in tubular structures may provide initial condition(s) for CaP crystal generation needed for stone formation. Additionally, recent evidence has provided a meaningful association between the active participation of proteins and transcription factors found in the bone forming (ossification) mechanism that are also involved in the early stages of kidney stone formation and arterial calcification. Our review will focus on three topics of discussion (physiological influences-calcium and phosphate concentration-and similarities to ossification, or bone formation) that may elucidate some commonality in the mechanisms of stone formation and calcification, and pave the way towards opening new avenues for further research.

Low gradient aortic stenosis

OPINION STATEMENT

Severe low-gradient (LG) aortic stenosis (AS) [aortic valve area (AVA) ≤ 1.0 cm(2), mean pressure gradient (MG) < 40 mmHg] represents a frequently encountered and challenging clinical dilemma. A systematic approach, which often requires several imaging modalities, should be undertaken to confirm the hemodynamic findings and rule out measurement error. Low-flow conditions often account for the discrepancy and can be present whether the left ventricular ejection fraction (LVEF) is depressed or normal. In patients with classical low-flow (LF), LG AS in which LVEF is reduced (<40-50 %), dobutamine stress echocardiography (DSE) should be used to distinguish patients with true severe AS and pseudo-severe AS, as well as to evaluate for the presence of left ventricular contractile or flow reserve. Surgical or transcatheter aortic valve replacement (AVR) should likely be reserved for those patients with true severe AS. Patient outcome with medical or surgical management generally relates to patient functional capacity, stenosis severity, and left ventricular functional reserve. Patients with severe LG AS with preserved LVEF can have a stroke volume that is either normal (>35 mL/m(2)) or low (<35 mL/m(2)). New data suggest that DSE can identify pseudo-severe AS in up to 30 % of patients with severe LF-LG AS with preserved LVEF. AVR should likely be restricted to those patients with true severe AS, although there is currently little data to support this strategy. Symptomatic patients with severe LG AS with preserved LVEF, whether they have normal or low flow, should be offered AVR. Transcatheter AVR provides an alternative therapeutic option in the high-risk patient.

Echocardiographic integrated backscatter for the differentiation between aortic valve calcification and valvular myxoid degeneration in rats

AIMS

Calcification is an independent predictor of mortality in aortic valve (AV) stenosis. Echocardiographic calibrated integrated backscatter (cIB) is a promising parameter for quantifying AV calcification. However, the ability of cIB to differentiate between calcification and valvular thickening has been questioned. Therefore, we aimed to use cIB to study AV calcification compared with non-calcified AV thickening in rats, with histology as reference.

METHODS AND RESULTS

Twenty male Wistar rats were studied. Group 1 (N = 6) received subcutaneous (SC) serotonin injections (60 mg/kg/day) for 12 weeks to induce myxoid non-calcified AV thickening. Group 2 (N = 7) received vitamin D3 (25,000 UI/kg/day) SC to induce AV calcification, and Group 3 (N = 7) received only vehicle SC for 10 weeks. cIB of the AV was calculated at the end of the study, followed by measurement of the percentage of the histological AV calcification. At the end of the study, cIB values and calcification percentages were significantly higher in vitamin D3-injected rats compared with serotonin-injected rats and controls. There was no significant difference in cIB values between serotonin-injected rats and controls (vitamin D3: 21.5 ± 3.0 dB*; serotonin: 11.8 ± 3.1 dB; control: 10.3 ± 3.4 dB; *P < 0.05). The percentage of histological calcification was significantly higher in the vitamin D3 group compared with the other groups. Serotonin-injected rats developed significant AV thickening.

CONCLUSION

Increased cIB values of the AV are related to increased calcification at histology and not to myxoid non-calcified valvular thickening. Therefore, cIB may be considered as a sensitive technique to quantify calcification of AV rather than for detecting non-calcified valvular thickening.