Development of paradoxical low-flow, low-gradient severe aortic stenosis

Arterial stiffness in aortic stenosis - complex clinical and prognostic implications

Arterial stiffness and degenerative aortic stenosis (AoS) are frequently associated leading to a combined valvular and vascular load imposed on the left ventricle (LV). Vascular load consists of a pulsatile load represented by arterial stiffness and a steady load corresponding to vascular resistance. Increased vascular load in AoS has been associated with LV dysfunction and poor prognosis in pre-intervention state, as well as after aortic valve replacement (AVR), suggesting that the evaluation of arterial load in AoS may have clinical benefits. Nevertheless, studies that investigated arterial stiffness in AoS either before or after AVR used various methods of measurement and their results are conflicting. The aim of the present review was to summarize the main pathophysiological mechanisms which may explain the complex valvulo-arterial interplay in AoS and their consequences on LV structure and function on the patients' outcome. Future larger studies are needed to clarify the complex hemodynamic modifications produced by increased vascular load in AoS and its changes after AVR. Prospective evaluation is needed to confirm the prognostic value of arterial stiffness in patients with AoS. Simple, non-invasive, reliable methods which must be validated in AoS still remain to be established before implementing arterial stiffness measurement in patients with AoS in clinical practice.

Impaired Left Ventricular Circumferential Midwall Systolic Performance Appears Linked to Depressed Preload, but Not Intrinsic Contractile Dysfunction or Excessive Afterload, in Paradoxical Low-Flow/Low-Gradient Severe Aortic Stenosis

Paradoxical low-flow/low-gradient aortic stenosis (P-LFLG-AS) occurs in about one-third of patients with severe AS and preserved left ventricular (LV) ejection fraction (EF). Our aim was to differentiate between altered LV loading conditions and contractility as determinants of subtle LV systolic dysfunction in P-LFLG-AS. We retrospectively analyzed medical records of patients with isolated severe degenerative AS and preserved EF (30 subjects with P-LFLG-AS and 30 patients with normal-flow/high-gradient severe AS (NFHG-AS)), without relevant coexistent diseases (e.g., diabetes, coronary artery disease and chronic kidney disease) or any abnormalities which could account for a low-flow state. Patients with P-LFLG-AS and NFHG-AS did not differ in aortic valve area index and most clinical characteristics. Compared to NFHG-AS, subjects with P-LFLG-AS exhibited smaller LV end-diastolic diameter (LVd) (44 ± 5 vs. 54 ± 5 mm, p < 0.001) (consistent with lower LV preload) with pronounced concentric remodeling, higher valvulo-arterial impedance (3.8 ± 1.1 vs. 2.2 ± 0.5 mmHg per mL/m2, p < 0.001) and diminished systemic arterial compliance (0.45 ± 0.11 vs. 0.76 ± 0.23 mL/m2 per mmHg, p < 0.001), while circumferential end-systolic LV midwall stress (cESS), an estimate of afterload at the LV level, was similar in P-LFLG-AS and NFHG-AS (175 ± 83 vs. 198 ± 69 hPa, p = 0.3). LV midwall fractional shortening (mwFS) was depressed in P-LFLG-AS vs. NFHG-AS (12.3 ± 3.5 vs. 14.7 ± 2.9%, p = 0.006) despite similar EF (61 ± 6 vs. 59 ± 8%, p = 0.4). By multiple regression, the presence of P-LFLG-AS remained a significant predictor of lower mwFS compared to NFHG-AS upon adjustment for cESS (β ± SEM: −2.35 ± 0.67, p < 0.001); however, the significance was lost after further correction for LVd (β = −1.10 ± 0.85, p = 0.21). In conclusion, the association of P-LFLG-AS with a lower cESS-adjusted mwFS, an index of afterload-corrected LV circumferential systolic function at the midwall level, appears secondary to a smaller LV end-diastolic cavity size according to the Frank−Starling law. Thus, low LV preload, not intrinsic contractile dysfunction or excessive afterload, may account for impaired LV circumferential midwall systolic performance in P-LFLG-AS.

Aortic Stenosis: New Insights in Diagnosis, Treatment, and Prevention

There has been an explosion of diagnostic, prognostic, and treatment data in aortic stenosis (AS). Severity of AS should be based not only on valve hemodynamics, but underlying LV dysfunction and comorbidities. Indications for aortic valve replacement continue to evolve, extending to patients with less than severe AS. There are several trials to find a medical therapy to reduce the progression of AS. An application of artificial intelligence and clinical trial results will have a major impact in identifying asymptomatic patients and optimal treatment to the right patient at the right time.

Aortic stenosis (AS) is one of the most common valvular heart diseases and the number of patients with AS is expected to increase globally as the older population is growing fast. Since the majority of patients are elderly, AS is no longer a simple valvular heart disease of left ventricular outflow obstruction but is accompanied by other cardiac and comorbid conditions. Because of the significant variations of the disease, identifying patients at high risk and even earlier detection of patients with AS before developing symptomatic severe AS is becoming increasingly important. With the proven of efficacy and safety of transcatheter aortic valve replacement (TAVR) in the severe AS population, there is a growing interest in applying TAVR in those with less than severe AS. A medical therapy to reduce or prevent the progression in AS is actively investigated by several randomized control trials. In this review, we will summarize the most recent findings in AS and discuss potential future management strategies of patients with AS.

Non-calcific aortic tissue quantified from computed tomography angiography improves diagnosis and prognostication of patients referred for transcatheter aortic valve implantation

AIMS

We aimed to investigate the role of aortic valve tissue composition from quantitative cardiac computed tomography angiography (CTA) in patients with severe aortic stenosis (AS) for the differentiation of disease subtypes and prognostication after transcatheter aortic valve implantation (TAVI).

METHODS AND RESULTS

Our study included 447 consecutive AS patients from six high-volume centres reporting to a prospective nationwide registry of TAVI procedures (POL-TAVI), who underwent cardiac CTA before TAVI, and 224 matched controls with normal aortic valves. Components of aortic valve tissue were identified using semi-automated software as calcific and non-calcific. Volumes of each tissue component and composition [(tissue component volume/total tissue volume) × 100%] were quantified. Relationship of aortic valve composition with clinical outcomes post-TAVI was evaluated using Valve Academic Research Consortium (VARC)-2 definitions.High-gradient (HG) AS patients had significantly higher aortic tissue volume compared to low-flow low-gradient (LFLG)-AS (1672.7 vs. 1395.3 mm3, P < 0.001) as well as controls (509.9 mm3, P < 0.001), but increased non-calcific tissue was observed in LFLG compared to HG patients (1063.6 vs. 860.2 mm3, P < 0.001). Predictive value of aortic valve calcium score [area under the curve (AUC) 0.989, 95% confidence interval (CI): 0.981-0.996] for severe AS was improved after addition of non-calcific tissue volume (AUC 0.995, 95% CI: 0.991-0.999, P = 0.011). In the multivariable analysis of clinical and quantitative computed tomography parameters of aortic valve tissue, non-calcific tissue volume [odds ratio (OR) 5.2, 95% CI 1.8-15.4, P = 0.003] and history of stroke (OR 2.6, 95% CI 1.1-6.5, P = 0.037) were independent predictors of 30-day major adverse cardiovascular event (MACE).

CONCLUSION

Quantitative CTA assessment of aortic valve tissue volume and composition can improve detection of severe AS, differentiation between HG and LFLG-AS in patients referred for TAVI as well as prediction of 30-day MACEs post-TAVI, over the current clinical standard.

The relation of structural valve deterioration to adverse remodelling and outcome in patients with biological heart valve prostheses

AIMS

Native valve aortic stenosis is associated with adverse remodelling of the left ventricle and remodelling is stopped or even reversed with aortic valve replacement (AVR). However, the degeneration of bioprostheses and development of structural valve deterioration (SVD) may affect this.

METHODS AND RESULTS

To assess the association with SVD, remodelling and outcome 451 patients from a single surgical centre who had undergone AVR with a Mitroflow pericardial bioprosthesis were studied. All patients were assessed in 2014 and a subgroup of patients (N = 327) were re-exanimated again after at least 18 months [median time of 27 (interquartile range, IQR 26-33) months] including echocardiography, measurements of N-terminal pro-brain natriuretic peptide, and assessment of functional status. SVD was based on echocardiography. Moderate SVD was present in 63 patients (14%) and severe SVD in 19 (4%), in the subgroup with follow-up echocardiography 48 patients (15%) patients had moderate to severe SVD at first examination. Patients with SVD had significantly greater increase in left ventricular (LV) mass index [21.6 g/m2 (IQR 5.7-48.3 g/m2) vs. 9.1 g/m2 (-8.6 to 27.3 g/m2), P = 0.01]. Further, patients with SVD had lower LV ejection fraction [55% (IQR 51-62%) vs. 60% (IQR 54-63%), P = 0.01] at follow-up. During follow-up, 94 patients (21%) met the composite endpoint of death or reoperation due to SVD and 41 patient readmitted for heart failure. In multivariable Cox regression analysis, severe SVD [hazard ratio (HR) 2.64 (1.37-5.07), P = 0.004] was associated with composite endpoint, and readmission for heart failure [HR 3.82 (1.53-9.51), P = 0.004].

CONCLUSION

SVD in aortic bioprostheses is associated with adverse LV remodelling and adverse outcome.

Left Ventricular Remodeling in Degenerative Aortic Valve Stenosis

Aortic stenosis was once considered a pure isolated valve obstacle challenging left ventricle driving force of contraction and flow generation. Left ventricular (LV) adaptation was merely interpreted as a uniform hypertrophic response to increased afterload. However, in these last 2 decades cardiac imaging research and some histopathology correlation studies brought insight towards the complex interaction between the vasculature, the valve and the myocardium. Verily, LV remodeling in this setting is a complex multidetermined process that goes further beyond myocardial hypertrophy. Ultrastructural changes involving both diffuse and replacement fibrosis of the myocardium take part and might explain the transition of clinical phenotypes with distinct prognosis, from compensated hypertrophy to LV maladaptive dysfunction and heart failure. Presently, the combined appropriate use of echocardiography and cardiac magnetic resonance may better assess the global LV afterload, hypertrophy and geometric remodeling, global and regional LV function, beyond ejection fraction, and structural changes that include the fibrotic burden of the myocardium. As a whole these may not only better stratify individual risk of disease progression but also identify patients benefiting from earlier valve intervention. In this paper, we review the maladaptive response of the LV to chronic pressure overload, describing the different signaling pathways and mechanisms that underly both hypertrophy and remodeling. Histomorphology changes in this setting are described and we try to make sense of the use of new imaging tools for LV characterization.

Transvalvular Flow, Sex, and Survival After Valve Replacement Surgery in Patients With Severe Aortic Stenosis

BACKGROUND

The respective impacts of transvalvular flow, gradient, sex, and their interactions on mortality in patients with severe aortic stenosis undergoing surgical aortic valve replacement (AVR) are unknown.

OBJECTIVES

This study sought to compare the impact of pre-operative flow-gradient patterns on mortality after AVR and to examine whether there are sex differences.

METHODS

This study analyzed clinical, echocardiographic, and outcome data prospectively collected in 1,490 patients (544 women [37%]), with severe aortic stenosis and preserved left ventricular ejection fraction who underwent AVR.

RESULTS

In this cohort, 601 patients (40%) had normal flow (NF) with high gradient (HG), 405 (27%) NF with low gradient (LG), 246 (17%) paradoxical low flow (LF)/HG, and 238 (16%) LF/LG. During a median follow-up of 2.42 years (interquartile range: 1.04 to 4.29 years), 167 patients died. Patients with LF/HG exhibited the highest mortality after AVR (hazard ratio [HR]: 2.01; 95% confidence interval [CI]: 1.33 to 3.03; p < 0.01), which remained significant after multivariate adjustment (HR: 1.96; 95% CI: 1.29 to 2.98; p < 0.01). Both LF/LG and NF/LG patients had comparable outcome to NF/HG (p ≥ 0.47). Optimal thresholds of stroke volume index were obtained for men (40 ml/m²) and women (32 ml/m²). Using these sex-specific cutpoints, paradoxical LF was independently associated with increased mortality in both women (adjusted HR: 2.05; 95% CI: 1.21 to 3.47; p < 0.01) and men (adjusted HR: 1.54; 95% CI: 1.02 to 2.32; p = 0.042), whereas guidelines' threshold (35 ml/m²) does not.

CONCLUSIONS

Paradoxical LF/HG was associated with higher mortality following AVR, suggesting that a reduced flow is a marker of disease severity even in patients with HG aortic stenosis. Early surgical AVR (i.e., before gradient attains 40 mm Hg) might be preferable in these patients. Furthermore, the use of sex-specific thresholds (<40 ml/m² for men and <32 ml/m² for women) to define low-flow outperforms the guidelines' threshold of 35 ml/m² in risk stratification after AVR.

Progression of Normal Flow Low Gradient "Severe" Aortic Stenosis With Preserved Left Ventricular Ejection Fraction

Normal-flow low-gradient severe aortic stenosis (NF-LG-SAS), defined by an aortic valve area (AVA) <1 cm², mean pressure gradient (MPG) <40 mm Hg and indexed stroke volume ≥35 ml/m², is the most prevalent form of low-gradient aortic stenosis (AS) with preserved ejection fraction (PEF). However, the true severity of AS in these patients is controversial. The aim of this Doppler echocardiographic study was to investigate changes over time in the hemodynamic severity of patients with NF-LG-SAS with PEF. We retrospectively identified 96 patients who had 2 Doppler echocardiographic examinations without an intervening event. After a median follow-up of 25 (interquartile range 15 to 52) months, progression was observed, with increased transaortic MPG (from 28 [25 to 33] to 39 [34 to 50] mm Hg; p<0.001), peak aortic jet velocity (from 3.46 [3.20 to 3.64] to 4.01 [3.70 to 4.39] m/s; p<0.001), and decreased AVA (from 0.87 [0.82 to 0.94] to 0.72 [0.62 to 0.81] cm²; p<0.001). Median annual rates of progression were 4.3 (1.7 to 8.1) mm Hg/year, 0.25 (0.08 to 0.44) m/s/year, and -0.05 (-0.10 to -0.02) cm²/year, respectively. There was no significant change in left ventricular ejection fraction over time (p = 0.74). At follow-up, 46 patients (48%) acquired the features of classical high-gradient severe AS (MPG ≥40 mm Hg). This study shows that most patients with NF-LG-SAS with PEF exhibit significant hemodynamic progression of AS severity without EF impairment. These findings suggest that NF-LG-SAS with PEF is an "intermediate" stage between moderate AS and classical high-gradient severe AS requiring close monitoring.

Coronary Microcirculation in Aortic Stenosis

Aortic stenosis is a heterogeneous disorder. Variations in the pathological and physiological responses to pressure overload are incompletely understood and generate a range of flow and pressure gradient patterns, which ultimately cause varying microvascular effects. The impact of cardiac-coronary coupling depends on these pressure and flow effects. In this article, we explore important concepts concerning cardiac physiology and the coronary microcirculation in aortic stenosis and their impact on myocardial remodeling, aortic valve flow patterns, and clinical progression.

Remodeling classification system considering left ventricular volume in patients with aortic valve stenosis: Association with adverse cardiovascular outcomes

BACKGROUND

To assess prevalence and clinical implications of left ventricular (LV) remodeling considering: LV volume, mass and relative wall thickness at the time of aortic valve stenosis diagnosis.

METHODS AND RESULTS

We retrospectively analyzed 343 patients (age 79.2 ± 9.5 years, 48.1% males) with functional aortic valve area (AVA) ≤ 1.5 cm² . LV geometric patterns and clinical outcomes (combined death, cardiac hospitalization, aortic valve replacement [AVR]) were evaluated. According to the new LV remodeling classification, 4.9% had normal geometry, 7.5% concentric remodeling, 39.3% concentric hypertrophy (LVH), 22.4% mixed LVH, 12.5% dilated LVH, 3.2% eccentric LVH and 4.3% eccentric remodeling, 5.5% had not classifiable LVH. Indexed stroke volume (SVi) was higher in patients with concentric LVH (40.3 ± 11.9 mL/m² ) and mixed LVH (41.6 ± 13.4 mL/m² ) and lower in patients with eccentric LVH (24.9 ± 7.7 mL/m² ), concentric (36.6 ± 12.7 mL/m² ) and eccentric remodeling (34.9 ± 9.5 mL/m² ), P = 0.003. During a median follow-up of 2.2 years, 260 (75.8%) had the combined end point. A significant association between the combined end point and LV dilation (P = 0.010) or LV remodeling patterns (P = 0.0001) was found. After multivariable adjustment for AVR, concentric remodeling (HR 3.12, IC 95% 1.14-8.55; P = 0.02) and dilated LVH (HR 3.48, IC 95% 1.31-9.27; P = 0.01) were strongly associated with death or cardiac hospitalizations.

CONCLUSIONS

In patients with AVA ≤ 1.5 cm² , when the new LV remodeling classification system is applied, only a minority had normal geometry and less than half had "classic" concentric LVH or remodeling. LV volume dilatation is frequent and associated with adverse outcome. Concentric remodeling, eccentric remodeling, dilated LVH had the worst noninvasive hemodynamic profile and prognosis.

First-Phase Ejection Fraction Is a Powerful Predictor of Adverse Events in Asymptomatic Patients With Aortic Stenosis and Preserved Total Ejection Fraction

OBJECTIVES

This study investigated the prognostic value of first-phase ejection fraction (EF1) in patients with aortic stenosis (AS), a condition in which left ventricular dysfunction as measured by conventional indices is an indication for valve replacement.

BACKGROUND

EF1, the ejection fraction up to the time of maximal ventricular contraction may be more sensitive than existing markers in detecting early systolic dysfunction.

METHODS

The predictive value of EF1 compared to that of conventional echocardiographic indices for outcomes was assessed in 218 asymptomatic patients with at least moderate AS, including 73 with moderate, 50 with severe, and 96 with "discordant" (aortic area <1.0 cm² and gradient <40 mm Hg) AS, all with preserved EF, followed for at least 2 years. EF1 was measured retrospectively from archived echocardiographic images by wall tracking of the endocardium. The primary outcome was a combination of aortic valve intervention, hospitalization for heart failure, and death from any cause.

RESULTS

EF1 was the most powerful predictor of events in the total population and all subgroups. A cutoff value of 25% (or EF1 of <25% compared to ≥25%) gave hazard ratios of 27.7 (95% confidence interval [CI]: 13.1 to 58.7; p < 0.001) unadjusted and 24.4 (95% CI: 11.3 to 52.7; p < 0.001) adjusted for other echocardiographic measurements including global longitudinal strain, for events at 2 years in all patients with asymptomatic AS. Corresponding hazard ratios for all-cause mortality in the total population were 17.5 (95% CI: 5.7 to 53.3) and 17.4 (95% CI: 5.5 to 55.2) unadjusted and adjusted, respectively.

CONCLUSIONS

EF1 may be potentially valuable in the clinical management of patients with AS and other conditions in which there is progression from early to late systolic dysfunction.

Outcomes after transcatheter aortic valve replacement in patients with low versus high gradient severe aortic stenosis in the setting of preserved left ventricular ejection fraction

BACKGROUND

Transcatheter aortic valve replacement (TAVR) for low gradient (LG) severe aortic stenosis (AS) with preserved left ventricular ejection fraction (LVEF) remains an area of clinical uncertainty.

METHODS

Retrospective review identified 422 patients who underwent TAVR between September 4, 2014 and July 1, 2016. Procedural indication other than severe AS (n = 22) or LVEF <50% (n = 98) were excluded. Outcomes were defined by valve academic research consortium two criteria when applicable and compared between LG (peak velocity <4.0 m/s and mean gradient <40 mmHg; n = 73) and high gradient (HG) (n = 229) groups. The LG group was further categorized as low stroke volume index (SVI) (n = 41) or normal SVI (n = 32). Median follow-up was 747 days [interquartile range 220-1013].

RESULTS

Baseline thirty-day mortality risk (LG 6.2% [3.8-8.1] vs HG 5.7% [4.1-7.4], P = 0.43) did not differ between groups. Short-term outcomes, including procedural success rate (86.1% vs 88.8%, P = 0.53), peri-procedural complications (intra-procedural heart block: 6.8% vs 7.9%, P = 0.99; permanent pacemaker placement: 11.0% vs 13.6%, P = 0.69; moderate paravalvular regurgitation: 2.7% vs 1.3%, P = 0.60), and all-cause in-hospital mortality (2.7% vs 0.9%, P = 0.25) did not differ between LG and HG groups. On long-term follow-up, all-cause mortality also did not differ between LG and HG groups (6.8% vs 10.0%, p_log-rank  = 0.33) or between the LG low SVI (9.8%), LG normal SVI (3.1%), and HG (10.0%) groups (p_log-rank  = 0.39).

CONCLUSION

Patients with preserved LVEF undergoing TAVR for severe AS with LG, including LG with low SVI, have no significant difference in adverse outcomes when compared to patients with HG.

MicroRNAs distribution in different phenotypes of Aortic Stenosis

Aortic valve stenosis (AVS) represents a cluster of different phenotypes, considering gradient and flow pattern. Circulating micro RNAs may reflect specific pathophysiological processes and could be useful biomarkers to identify disease. We assessed 80 patients (81, 76.7–84 years; 46, 57.5%females) with severe AVS. We performed bio-humoral evaluation (including circulating miRNA-1, 21, 29, 133) and 2D-echocardiography. Patients were classified according to ACC/AHA groups (D1-D3) and flow-gradient classification, considering normal/low flow, (NF/LF) and normal/high gradient, (NG/HG). Patients with reduced ejection fractionwere characterized by higher levels of miRNA1 (p = 0.003) and miRNA 133 (p = 0.03). LF condition was associated with higher levels of miRNA1 (p = 0.02) and miRNA21 (p = 0.02). Levels of miRNA21 were increased in patients with reduced Global longitudinal strain (p = 0.03). LF-HG and LF-LG showed higher levels of miRNA1 expression (p = 0.005). At one-year follow-up miRNA21 and miRNA29 levels resulted significant independent predictors of reverse remodeling and systolic function increase, respectively. Different phenotypes of AVS may express differential levels and types of miRNAs, which may retain a pathophysiological role in pro-hypertrophic and pro-fibrotic processes.

Postoperative Reverse Remodeling and Symptomatic Improvement in Normal-Flow Low-Gradient Aortic Stenosis After Aortic Valve Replacement

Background—

Severe aortic stenosis (AS) most often presents with reduced aortic valve area (<1 cm 2 ), normal stroke volume index (≥35 mL/m 2 ), and either high mean gradient (≥40 mm Hg; normal-flow high-gradient AS) or low mean gradient (normal-flow low-gradient [NFLG] AS). The benefit of aortic valve replacement (AVR) among NFLG patients is controversial. We compared the impact of NFLG condition on preoperative left ventricular (LV) remodeling and myocardial fibrosis and postoperative remodeling and symptomatic benefit.

Methods and Results—

Eighty-seven consecutive patients with reduced aortic valve area and normal stroke volume index undergoing AVR underwent echocardiography, magnetic resonance imaging, a 6-minute walk test, and measurement of natriuretic peptides before and 1 year after AVR. Myocardial fibrosis was assessed from magnetic resonance imaging. Patients were stratified as NFLG or normal-flow high-gradient. In total, 33 patients (38%) had NFLG. Before AVR, they were characterized by similar symptom burden but less severe AS measured by aortic valve area index (0.50±0.09 versus 0.40±0.08 cm 2 /m 2 ; P <0.0001), lower LV mass index (74±18 versus 90±26 g/m 2 ; P =0.01), but the same degree of myocardial fibrosis. After AVR, NFLG had a smaller reduction in LV mass index (−3±10 versus −±18 g/m 2 ; P <0.0001) and a smaller reduction in natriuretic peptides. Both groups experienced similar symptomatic improvement. Normal-flow high-gradient condition independently predicted change in LV mass index.

Conclusions—

Patients with NFLG had less severe AS and LV remodeling than patients with normal-flow high-gradient. Furthermore, NFLG patients experienced less reverse remodeling but the same symptomatic benefit.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT02316587.

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.

Low-flow/low-gradient aortic stenosis-Still a diagnostic and therapeutic challenge

Aortic stenosis (AS) is the most frequently observed valvular heart disease. During the symptomatic stage, the rate of death increases dramatically, so that a precise diagnostic approach is taken to guide therapeutic options. Of patients with severe AS, 30% to 50% present with low-flow/low-gradient AS (LF/LGAS) status. This review focuses on LF/LGAS and the best diagnostic and therapeutic management in either classic LF/LGAS with reduced left ventricular ejection fraction (LVEF) or paradoxical LF/LGAS with preserved LVEF. Current literature demonstrates that in classic LF/LGAS it is crucial to rule out a pseudo-severe AS, because reduced LVEF may result in an incomplete opening of the valve. This can be done by low-dose dobutamine stress echocardiography. Classic LF/LGAS has poor clinical outcomes when managed conservatively; therefore, surgical or interventional aortic valve replacement should be performed. In paradoxical LF/LGAS, the LVEF is preserved (>50%), but impaired filling of the concentric hypertrophied ventricle leads to reduced stroke volume. Therefore, diagnostic and therapeutic decisions in paradoxical LF/LGAS are even more challenging. It is a heterogeneous disease entity, and it is crucial to rule out any diagnostic errors because numerous potential confounders might lead to misdiagnosis. As in classic stenosis, pseudo-severe stenosis must be ruled out as well. Evaluation via multidetector computed tomography or transesophageal echocardiography can help to evaluate the morphologic alterations of the valve (eg, calcification). Further studies are necessary to understand this disease entity and to evaluate the optimal diagnostic and therapeutic approach for these patients.

Evolving new concepts in the assessment of aortic stenosis

Echocardiography has been pivotal in evaluating aortic stenosis (AS) over the past several decades. Recent experience has shown a wide spectrum in the clinical presentation of AS. A better understanding of the underlying hemodynamic principles has resulted in emergence of new subtypes of AS. New treatment modalities have also been introduced, requiring precise evaluation of aortic valve (AV) pathology for implementation of these therapies. This review will discuss new concepts and indices in the use of echocardiography in patients with AS. Specifically, we will address the hemodynamic characteristics, clinical presentation, and management of normal-flow, high-gradient; paradoxical low-flow, low-gradient; and classical low-flow, low-gradient aortic stenoses.

Impact of left ventricular outflow tract ellipticity on the grading of aortic stenosis in patients with normal ejection fraction

BACKGROUND

The pathophysiology of paradoxical low-gradient (LG) severe aortic stenosis (SAS) remains controversial. As low transvalvular flow has been implicated, we sought to investigate the impact of left ventricular outflow tract (LVOT) ellipticity on the estimation of the LV stroke volume, the calculation of the aortic valve area (AVA) by use of the continuity equation and on AS severity grading.

METHODS

We studied 190 consecutive patients (mean age: 72 ± 13 years; male: 57%) with SAS (indexed AVA < 0.6 cm2/m2) and preserved LV ejection fraction, including 120 patients with severe high gradient (HG) AS and 70 with severe paradoxical LG-AS. AS severity, LV volumes and LVOT ellipticity were assessed by 2D-Doppler echocardiography and cardiac magnetic resonance (CMR).

RESULTS

The LVOT exhibited an elliptical shape on CMR images, with a shorter anterior-posterior than median-lateral diameter (2.2 ± 0.2 vs 2.8 ± 0.3 cm, p < 0.01). Accordingly, the LVOT area measured by planimetry was larger than by 2D-echocardiography, assuming a circular orifice (4.9 ± 0.9 cm2 vs 3.7 ± 0.8 cm2, p < 0.01). Inputting the elliptical LVOT area into the continuity equation resulted in a 29% increase in the indexed AVA (from 0.41 ± 0.09 cm2 to 0.54 ± 0.10 cm2). Accordingly, 30 (43%) patients with severe paradoxical LG-SAS were reclassified as having moderate AS. Similar results were obtained when considering 3D-echo for direct planimetry of the LVOT in a subset of 75 patients.

CONCLUSIONS

Our results confirm that the LVOT is elliptical in shape and that taking this parameter into account in the calculation of the AVA results in reclassification of 43% of patients with severe paradoxical LG-AS into moderate AS.

Severe low-gradient aortic stenosis, with preserved ventricular function: should it be treated?

Exists a group of patients with small AVA (<0,6 cm/m), and normal LVEF (≥50%) who display a low transvalvular flow (LF) [index stroke volume (SVi)<35 ml/m2] and/or low transvalvular gradient (LG). This condition is called severe paradoxical aortic stenosis (SAO) LFLG. In many studies this condition was associated to increased mortality both with medical therapy and with surgical intervention. Crucial is define correctly the diagnostical criteria of this condition. Indeed there are several specific anatomical and functional characteristics useful in differentiating paradoxical severe aortic stenosis from the other forms of aortic stenosis. In case of doubt in the diagnostical process, the Multidetector Computed Tomography (MDCT) could be useful in quantifying calcificazions of the aortic valve. The guidelines European Society of Cardiology (ESC) and American College of Cardiology (ACC) recomended aortic valve replacement for symptomatic patients with paradoxical LFLG severe aortic stenosis, recommending to accurately measure the flow in these patients as to differentiate them from those with NFLG and better prognosis.

Multimodality imaging for the diagnosis and assessment of aortic stenosis severity

INTRODUCTION

Aortic stenosis (AS) is the most common cause of valvular heart disease. Imaging plays a major role in the diagnosis and evaluation of AS severity.

AREAS COVERED

The present review focuses on new emerging concepts in AS by stressing the substantial value of imaging into the understanding of the complex pathophysiology and management of AS. Expert commentary: Though, standard 2D echocardiography is often diagnostic multi-modality imaging can be required in patients with doubtful results or to refine the evaluation of AS.

Prevalence, clinical and echocardiographic characteristics of various flow and gradient patterns in mild or moderate aortic stenosis with normal left ventricular ejection fraction

BACKGROUND/OBJECTIVES

Paradoxical low-flow aortic stenosis (AS) with preserved left ventricular ejection fraction (LVEF) has only been described in severe AS. Controversy surrounds prognosis and management but no studies have reported this phenomenon in mild or moderate AS. We investigated the prevalence of flow and gradient patterns in this population, characterising their clinical and echocardiographic profile.

METHODS

Consecutive subjects (n=1362) with isolated AS: mild (n=462, aortic valve area≥1.5cm(2), 2.5m/s<aortic jet velocity≤3m/s) or moderate (n=900, 1cm(2)≤aortic valve area<1.5cm(2)) and normal LVEF (≥50%) were studied. Subjects with low-flow (stroke volume index<35ml/m(2)) were identified. Univariate and multivariate analyses were employed to compare the flow and gradient patterns.

RESULTS

In mild AS, 130 (28%) had low-flow. Lower left ventricular mass index (LVMI) (97.0±28.5vs116.4±2.3g/m(2),p<0.001), higher percentage of concentric remodelling (40%vs6%,p<0.001) and hypertrophy (43%vs40%,p<0.001) and lower end-systolic wall stress (ESWS) (57.6±1.60vs67.7±19.6dyn/cm(2),p=0.014) were independently associated with low-flow. Similarly, in moderate AS, 297 (33%) had low-flow. Older age (73.4±14.8vs69.5±16.5,p=0.027), lower LVMI (88.6±25.9vs118.0±36.5,p<0.001), higher percentage of concentric remodelling (46%vs8%,p<0.001) and lower ESWS (59.9±18.3vs70.5±19.7,p<0.001) were independently associated with low-flow. Despite moderate AS, most had lower mean pressure gradients, especially subjects with concentric remodelling. In the entire cohort, low-flow patients had more concentric remodelling (43%vs7%,p<0.001) and less eccentric hypertrophy (2%vs27%,p<0.001) compared to normal flow.

CONCLUSIONS

Low-flow AS with normal LVEF is observed in mild or moderate AS, in up to a third of the cases. These patients had different LV structure compared to normal-flow, with more concentric remodelling. Further studies are warranted.

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.

The spectrum of low-output low-gradient aortic stenosis with normal ejection fraction

Low-flow, low-gradient (LF/LG) severe aortic stenosis (AS) with preserved ejection fraction refers to the condition of AS with aortic valve area ≤1 cm(2), stroke volume index <35 mL/m(2), mean aortic valve gradient <40 mm Hg and left ventricular ejection fraction ≥50%. This mismatch of aortic valve area suggesting severe stenosis and 'low' gradient in some patients has led to confusion as to the severity of stenosis. Conditions previously labelled as LF/LG severe AS include a spectrum, with measurement error probably being the most common cause of marked inconsistency between gradient, valve area and patient presentation. The presence of LG severe AS may be overestimated in petite patients, who may have aortic valve area slightly less than 1 cm(2)with only moderate AS. Concomitant cardiac conditions besides AS, including significant mitral and tricuspid regurgitation, intracardiac shunts and constrictive pericarditis, may contribute to reduced stroke volume, and evidence for these must be sought at the time of echocardiography. True LF/LG severe AS is associated with a unique and probably maladaptive remodelling pattern with smaller ventricles, increasing relative wall thickness, progressive worsening of diastolic function and higher afterload, as demonstrated by lower systemic arterial compliance, higher systemic vascular resistance and higher valvuloarterial impedance. Control of hypertension is essential to the appropriate management of patients with AS. Aortic valve replacement should be considered in patients with compelling evidence of severe AS who remain symptomatic despite optimal treatment of hypertension.

2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines

Aortic stenosis is the most frequent valvular heart disease. In aortic stenosis, therapeutic decision essentially depends on symptomatic status, stenosis severity, and status of left ventricular systolic function. Surgical aortic valve replacement or transcatheter aortic valve implantation is the sole effective therapy in symptomatic patients with severe aortic stenosis, whereas the management of asymptomatic patients remains controversial and is mainly based on individual risk stratification. Imaging is fundamental for the initial diagnostic work-up, follow-up, and selection of the optimal timing and type of intervention. The present review provides specific recommendations for utilization of multimodality imaging to optimize risk stratification and therapeutic decision-making processes in aortic stenosis.