Dependence of Gorlin formula and continuity equation valve areas on transvalvular volume flow rate in valvular aortic stenosis

Evidence That Anemia Accelerates AS Progression Via Shear-Induced TGF-β1 Activation: Heyde's Syndrome Comes Full Circle

The severity of aortic stenosis (AS) is associated with acquired von Willebrand syndrome (AVWS) and gastrointestinal bleeding, leading to anemia (Heyde's syndrome). We investigated how anemia is linked with AS and AVWS using the LA100 mouse model and patients with AS. Induction of anemia in LA100 mice increased transforming growth factor (TGF)-β1 activation, AVWS, and AS progression. Patients age >75 years with severe AS had higher plasma TGF-β1 levels and more severe anemia than AS patients age <75 years, and there was a correlation between TGF-β1 and anemia. These data are compatible with the hypothesis that the blood loss anemia of Heyde's syndrome contributes to AS progression via WSS-induced activation of platelet TGF-β1 and additional gastrointestinal bleeding via WSS-induced AVWS.

Prognostic value of flow-status in severe aortic stenosis patients undergoing percutaneous intervention

PURPOSE

Low-flow status is a mortality predictor in severe aortic stenosis (SAS) patients, including after transcatheter aortic valve implantation (TAVI) treatment. However, the best parameter to assess flow is unknown. Recent studies suggest that transaortic flow rate (FR) is superior to currently used stroke volume index (SVi) in defining low-flow states. Therefore, we aimed to evaluate the prognostic value of FR and SVi in patients undergoing TAVI.

METHODS

A single-centre retrospective analysis of all consecutive patients treated with TAVI for SAS between 2011 and 2019 was conducted. Low-FR was defined as < 200 mL/s and low-SVi as < 35 mL/m2. Primary endpoint was all-cause five-year mortality, analyzed using Kaplan-Meier curves and Cox regression models. Secondary endpoint was variation of NYHA functional class six months after procedure. Patients were further stratified according to ejection fraction (EF < 50%).

RESULTS

Of 489 cases, 59.5% were low-FR, and 43.1% low-SVi. Low-flow patients had superior surgical risk, worse renal function, and had a higher prevalence of coronary artery disease. Low-FR was associated with mortality (hazard ratio 1.36, p = 0.041), but not after adjustment to EuroSCORE II. Normal-SVi was not associated with survival, despite a significative p-trend for its continuous value. No associations were found for flow-status and NYHA recovery. When stratifying according to preserved and reduced EF, both FR and SVi did not predict all-cause mortality.

CONCLUSION

In patients with SAS undergoing TAVI, a low-FR state was associated with higher mortality, as well as SVi, but not at a 35 mL/m2 cut off.

Improving accuracy in diagnosing aortic stenosis severity: An in-depth analysis of echocardiographic measurement error through literature review and simulation study

AIMS

The present guidelines advise replacing the aortic valve for individuals with severe aortic stenosis (AS) based on various echocardiographic parameters. Accurate measurements are essential to avoid misclassification and unnecessary interventions. The objective of this study was to evaluate the influence of measurement error on the echocardiographic evaluation of the severity of AS.

METHODS AND RESULTS

A systematic review was performed to examine whether measurement errors are reported in studies focusing on the prognostic value of peak aortic jet velocity (Vmax ), mean pressure gradient (MPG), and effective orifice area (EOA) in asymptomatic patients with AS. Out of the 37 studies reviewed, 17 (46%) acknowledged the existence of measurement errors, but none of them utilized methods to address them. Secondly, the magnitude of potential errors was collected from available literature for use in clinical simulations. Interobserver variability ranged between 0.9% and 8.3% for Vmax and MPG but was higher for EOA (range 7.7%-12.7%), indicating lower reliability. Assuming a circular left ventricular outflow tract area led to a median underestimation of EOA by 23% compared to planimetry by other modalities. A clinical simulation resulted in the reclassification of 42% of patients, shifting them from a diagnosis of severe AS to moderate AS.

CONCLUSIONS

Measurement errors are underreported in studies on echocardiographic assessment of AS severity. These errors can lead to misclassification and misdiagnosis. Clinicians and scientists should be aware of the implications for accurate clinical decision-making and assuring research validity.

The Impact of Left Ventricular Performance and Afterload on the Evaluation of Aortic Valve Stenosis: A 1D Mathematical Modeling Approach

The transaortic valvular pressure gradient (TPG) plays a central role in decision-making for patients suffering from severe aortic stenosis. However, the flow-dependence nature of the TPG makes the diagnosis of aortic stenosis challenging since the markers of cardiac performance and afterload present high physiological interdependence and thus, isolated effects cannot be measured directly in vivo. We used a validated 1D mathematical model of the cardiovascular system, coupled with a model of aortic stenosis, to assess and quantify the independent effect of the main left ventricular performance parameters (end-systolic (Ees) and end-diastolic (Eed) elastance) and principal afterload indices (total vascular resistance (TVR) and total arterial compliance (TAC)) on the TPG for different levels of aortic stenosis. In patients with critical aortic stenosis (aortic valve area (AVA) ≤ 0.6 cm2), a 10% increase of Eed from the baseline value was associated with the most important effect on the TPG (-5.6 ± 0.5 mmHg, p < 0.001), followed by a similar increase of Ees (3.4 ± 0.1 mmHg, p < 0.001), in TAC (1.3 ±0.2 mmHg, p < 0.001) and TVR (-0.7 ± 0.04 mmHg, p < 0.001). The interdependence of the TPG left ventricular performance and afterload indices become stronger with increased aortic stenosis severity. Disregarding their effects may lead to an underestimation of stenosis severity and a potential delay in therapeutic intervention. Therefore, a comprehensive evaluation of left ventricular function and afterload should be performed, especially in cases of diagnostic challenge, since it may offer the pathophysiological mechanism that explains the mismatch between aortic severity and the TPG.

Normative values of the aortic valve area and Doppler measurements using two-dimensional transthoracic echocardiography: results from the Multicentre World Alliance of Societies of Echocardiography Study

AIMS

Aortic valve area (AVA) used for echocardiographic assessment of aortic stenosis (AS) has been traditionally interpreted independently of sex, age and race. As differences in normal values might impact clinical decision-making, we aimed to establish sex-, age- and race-specific normative values for AVA and Doppler parameters using data from the World Alliance Societies of Echocardiography (WASE) Study.

METHODS AND RESULTS

Two-dimensional transthoracic echocardiographic studies were obtained from 1903 healthy adult subjects (48% women). Measurements of the left ventricular outflow tract (LVOT) diameter and Doppler parameters, including AV and LVOT velocity time integrals (VTIs), AV mean pressure gradient, peak velocity, were obtained according to ASE/EACVI guidelines. AVA was calculated using the continuity equation. Compared with men, women had smaller LVOT diameters and AVA values, and higher AV peak velocities and mean gradients (all P < 0.05). LVOT and AV VTI were significantly higher in women (P < 0.05), and both parameters increased with age in both sexes. AVA differences persisted after indexing to body surface area. According to the current diagnostic criteria, 13.5% of women would have been considered to have mild AS and 1.4% moderate AS. LVOT diameter and AVA were lower in older subjects, both men and women, and were lower in Asians, compared with whites and blacks.

CONCLUSION

WASE data provide clinically relevant information about significant differences in normal AVA and Doppler parameters according to sex, age, and race. The implementation of this information into clinical practice should involve development of specific normative values for each ethnic group using standardized methodology.

Arterial Wave Reflection and Aortic Valve Stenosis: Diagnostic Challenges and Prognostic Significance

Introduction

Arterial wave reflection is an important component of the left ventricular afterload, affecting both pressure and flow to the aorta. The aim of the present study was to evaluate the impact of wave reflection on transvalvular pressure gradients (TPG), a key parameter for the evaluation of aortic valve stenosis (AS), as well as its prognostic significance in patients with AS undergoing a transcatheter aortic valve replacement (TAVR).

Materials and Methods

The study population consisted of 351 patients with AS (mean age 84 ± 6 years, 43% males) who underwent a complete hemodynamic evaluation before the TAVR. The baseline assessment included right and left heart catheterization, transthoracic echocardiography, and a thorough evaluation of the left ventricular afterload by means of wave separation analysis. The cohort was divided into quartiles according to the transit time of the backward pressure wave (BWTT). Primary endpoint was all-cause mortality at 1 year.

Results

Early arrival of the backward pressure wave was related to lower cardiac output (Q1: 3.7 ± 0.9 lt/min vs Q4: 4.4 ± 1.0 lt/min, p &lt; 0.001) and higher aortic systolic blood pressure (Q1: 132 ± 26 mmHg vs Q4: 117 ± 26 mmHg, p &lt; 0.001). TPG was significantly related to the BWTT, patients in the arrival group exhibiting the lowest TPG (mean TPG, Q1: 37.6 ± 12.7 mmHg vs Q4: 44.8 ± 14.7 mmHg, p = 0.005) for the same aortic valve area (AVA) (Q1: 0.58 ± 0.35 cm2 vs 0.61 ± 0.22 cm2, p = 0.303). In multivariate analysis, BWTT remained an independent determinant of mean TPG (beta 0.3, p = 0.002). Moreover, the prevalence of low-flow, low-gradient AS with preserved ejection fraction was higher in patients with early arterial reflection arrival (Q1: 33.3% vs Q4: 14.9%, p = 0.033). Finally, patients with early arrival of the reflected wave (Q1) exhibited higher all-cause mortality at 1 year after the TAVR (unadjusted HR: 2.33, 95% CI: 1.17–4.65, p = 0.016).

Conclusion

Early reflected wave arrival to the aortic root is associated with poor prognosis and significant aortic hemodynamic alterations in patients undergoing a TAVR for AS. This is related to a significant decrease in TPG for a given AVA, leading to a possible underestimation of the AS severity.

Evaluation of low gradient severe aortic stenosis: should we change our outlook in the analysis of clinical data?

Nowadays, technological progress has equipped clinicians with new useful devices for the collection, analysis and presentation of data. As a consequence, many diseases and pathological conditions have been studied in a more detailed way, sometimes with remarkable results. In fact, they are not always validated by the old physiological models. In this respect, we present the case of low gradient severe aortic stenosis, a condition characterised by a small aortic valve area and a low-pressure gradient. According to the mathematical and physical assumptions these readings are contradictory whereas the Doppler-echocardiography shows clearly the existence of such a situation. In this work, we have described the physiological base of this phenomenon and discussed the limitations of the technology used. In this work, we are going to analyse some conditions commonly observed in daily clinical practice in order to prompt a critical outlook in both clinicians and technicians about the instrumentations used and the methods applied.

Echocardiographic assessment of aortic stenosis: a practical guideline from the British Society of Echocardiography

The guideline provides a practical step-by-step guide in order to facilitate high-quality echocardiographic studies of patients with aortic stenosis. In addition, it addresses commonly encountered yet challenging clinical scenarios and covers the use of advanced echocardiographic techniques, including TOE and Dobutamine stress echocardiography in the assessment of aortic stenosis.

Sex differences in transaortic flow rate and association with all-cause mortality in patients with severe aortic stenosis

AIMS

It is not known whether transaortic flow rate (FR) in aortic stenosis (AS) differs between men and women, and whether the commonly used cut-off of 200 mL/s is prognostic in females. We aimed to explore sex differences in the determinants of FR, and determine the best sex-specific cut-offs for prediction of all-cause mortality.

METHODS AND RESULTS

Between 2010 and 2017, a total of 1564 symptomatic patients (mean age 76 ± 13 years, 51% men) with severe AS were prospectively included. Mean follow-up was 35 ± 22 months. The prevalence of cardiovascular disease was significantly higher in men than women (63% vs. 42%, P < 0.001). Men had higher left ventricular mass and lower left ventricular ejection fraction compared to women (both P < 0.001). Men were more likely to undergo an aortic valve intervention (AVI) (54% vs. 45%, P = 0.001), while the death rates were similar (42.0% in men and 40.6% in women, P = 0.580). A total of 779 (49.8%) patients underwent an AVI in which 145 (18.6%) died. In a multivariate Cox regression analysis, each 10 mL/s decrease in FR was associated with a 7% increase in hazard ratio (HR) for all-cause mortality (HR 1.07; 95% CI 1.03-1.11, P < 0.001). The best cut-off value of FR for prediction of all-cause mortality was 179 mL/s in women and 209 mL/s in men.

CONCLUSION

Transaortic FR was lower in women than men. In the group undergoing AVI, lower FR was associated with increased risk of all-cause mortality, and the optimal cut-off for prediction of all-cause mortality was lower in women than men.

Two Barricades in a Row Mixed Lesion of Dynamic Left Ventricular Outflow Tract Obstruction and Aortic Stenosis: Finding the Culprit for Decision Making

Concurrent lesions of dynamic left ventricular outflow tract obstruction (DLVOTO) with aortic stenosis pose a challenge in the measurement of the pressure gradient and severity of each lesion. Determining the true culprit lesion is difficult and challenging. The establishment of true culprit lesion is crucial in deciding the future course of action. We present two cases of concurrent DLVOTO and aortic stenosis. Although the composition of lesions is similar, the severity of each lesion was different and described a variety of technical problems. Finding the culprit through the shape of the stenotic jet from the continuous wave Doppler as well as other different technical approaches is the critical point of this case report. The first patient showed nonsignificant DLVOTO with severe aortic stenosis in which transthoracic echocardiography (TTE) alone was sufficient to find the culprit. Meanwhile, the second patient concluded to have significant DLVOTO with moderate aortic stenosis based on TTE and transesophageal echocardiography examination data. Jet morphology from Doppler examination is a crucial finding to differentiate DLVOTO with aortic stenosis, along with other parameters that might help find the dominant lesion. Multiple modalities with several tailor-made technical considerations might be needed to establish a culprit lesion.

A Pilot Study Comparing Aortic Valve Area Estimates Derived from Fick Cardiac Output with Estimates Based on Cheetah-NICOM Cardiac Output

Cardiac output during cardiac catheterization is often estimated using the modified Fick method (CO_Fick). In this proof-of-concept, prospective non-randomized study carried out in a single academic healthcare centre, we examined whether replacing CO_Fick in the Gorlin formula with Cheetah-NICOM monitor cardiac output (CO_Cheetah) could produce an accurate and precise estimate of aortic valve area in patients with severe aortic stenosis. In twenty-six subjects, CO_Fick and CO_Cheetah were obtained concurrently. A spot and 3-minute running average of CO_Cheetah was used. Bland and Altman analysis was used to derive bias, 95% limits of agreement (LOA) and confidence intervals (CI). The mean difference (bias) between AVA_Cheetah (average) and AVA_Fick was 0.11 cm² and the 95% LOA were ±0.42 cm². The 95% CI of the bias was 0.02–0.2 cm². The bias and 95% LOA of AVA_Cheetah (spot value) were 0.14 ± 0.42cm², with a 95% CI of 0.06–0.23 cm². No proportional bias was present. AVA_Cheetah thus appears to be a reasonably accurate measure of AVA in patients with severe aortic stenosis compared to AVA_Fick measured using a modified Fick CO. However, the limits of agreement were not narrow enough to consider AVA_Cheetah and AVA_Fick interchangeable.

Fluid Structure Interaction on Paravalvular Leakage of Transcatheter Aortic Valve Implantation Related to Aortic Stenosis: A Patient-Specific Case

This study investigated the impact of paravalvular leakage (PVL) in relation to the different valve openings of the transcatheter aortic valve implantation (TAVI) valve using the fluid structure interaction (FSI) approach. Limited studies were found on the subject of FSI with regards to TAVI-PVL condition, which involves both fluid and structural responses in coupling interaction. Hence, further FSI simulation with the two-way coupling method is implemented to investigate the effects of hemodynamics blood flow along the patient-specific aorta model subjected to the interrelationship between PVL and the different valve openings using the established FSI software ANSYS 16.1. A 3D patient-specific aorta model is constructed using MIMICS software. The TAVI valve identical to Edward SAPIEN XT 26 (Edwards Lifesciences, Irvine, California), at different Geometrical Orifice Areas (GOAs), is implanted into the patient's aortic annulus. The leaflet opening of the TAVI valve is drawn according to severity of GOA opening represented in terms of 100%, 80%, 60%, and 40% opening, respectively. The result proved that the smallest percentage of GOA opening produced the highest possibility of PVL, increased the recirculatory flow proximally to the inner wall of the ascending aorta, and produced lower backflow velocity streamlines through the side area of PVL region. Overall, 40% GOA produced 89.17% increment of maximum velocity magnitude, 19.97% of pressure drop, 65.70% of maximum WSS magnitude, and a decrement of 33.62% total displacement magnitude with respect to the 100% GOA.

Contemporary Imaging of Aortic Stenosis

Degenerative or fibrocalcific aortic stenosis (AS) is now the most common native valvular heart disease assessed and managed by cardiologists in developed countries. Transthoracic echocardiography remains the quintessential imaging modality for the non-invasive characterisation of AS due to its widespread availability, superior assessment of flow haemodynamics, and a wealth of prognostic data accumulated over decades of clinical utility and research applications. With expanding technologies and increasing availability of treatment options such as transcatheter aortic valve replacements, in addition to conventional surgical approaches, accurate and precise assessment of AS severity is critical to guide decisions for and timing of interventions. Despite clear guideline echocardiographic parameters demarcating severe AS, discrepancies between transvalvular velocities, gradients, and calculated valve areas are commonly encountered in clinical practice. This often results in diagnostically challenging cases with significant implications. Greater emphasis must be placed on the quality of performance of basic two dimensional (2D) and Doppler measurements (attention to detail ensuring accuracy and precision), incorporating ancillary haemodynamic surrogates, understanding study- or patient-specific confounders, and recognising the role and limitations of stress echocardiography in the subgroups of low-flow low-gradient AS. A multiparametric approach, along with the incorporation of multimodality imaging (cardiac computed tomography or magnetic resonance imaging) in certain scenarios, is now mandatory to avoid incorrect misclassification of severe AS. This is essential to ensure appropriate selection of patients who would most benefit from interventions on the aortic valve to relieve the afterload mismatch resulting from truly severe valvular stenosis.

Comparison of grading of aortic stenosis between transthoracic and transesophageal echocardiography in adult patients undergoing elective aortic valve replacement surgeries: A prospective observational study

Introduction:

Intraoperative trans-esophageal echocardiography (TEE) has been found to underestimate severity of aortic stenosis (AS) compared to trans-thoracic echo (TTE). We conducted a prospective study comparing pre induction TTE and intra operative TEE grading of AS in patients posted for aortic valve replacement surgeries.

Methods:

Sixty patients with isolated AS who were undergoing aortic valve replacement were enrolled in our study. Baseline TTE was done and after induction of anesthesia, TEE was done. Mean gradient across aortic valve, peak jet velocity, aortic valve area (AVA) by continuity equation and dimensionless index (DI) were assessed in both.

Results:

Mean gradient decreased from 56.4 in TTE to 39.8 mm Hg in TEE leading to underestimation of AS in 74.5% of patients (P < 0.0). Mean of peak jet velocity also decreased from 500 in TTE to 386cm/s in TEE (P < 0.01). In 76 % of patients this led to reduction of AS grade from severe to moderate. Mean AVA was 0.67 cm² in TTE and 0.69 cm² in TEE. Though there was 0.02 cm² increase, it was not statistically significant (P = 0.07). All the patients remained as severe AS in TEE. DI mean was 0.19 in both TTE and TEE (P = 0.14).It led to underestimation of severity in 6% of patients in TEE.

Conclusion:

Our study shows that AVA measurement by continuity equation and DI are reliable in grading aortic stenosis while performing intraoperative TEE. Mean gradient and jet velocity can be significantly reduced.

Value of ejection fraction/velocity ratio in the prognostic stratification of patients with asymptomatic aortic valve stenosis

BACKGROUND

The ejection fraction/velocity ratio (EFVR) is a simple function-corrected index of aortic stenosis severity with a good correlation with aortic valve area measured using the Gorlin formula at cardiac catheterization. It is calculated by dividing left ventricular ejection fraction (LVEF) to 4 × (peak jet velocity)² .

OBJECTIVE

Our aim was to evaluate the value of EFVR in predicting adverse events in patients with asymptomatic aortic stenosis.

METHODS

We analyzed the clinical and echocardiographic data of 216 asymptomatic patients with at least moderate aortic stenosis (AVA ≤ 1.5 cm² ). The primary end-point was cardiovascular death or aortic valve replacement.

RESULTS

There were 119 (55%) men and mean age was 68 ± 10 years. The mean follow-up time was 4.2 ± 1.6 years (median 4.3 years). During follow-up, the composite end-point of death or aortic valve replacement was reached in 105 patients (49%). Using multivariate Cox regression analysis, EFVR and valvulo-arterial impedance emerged as independent variables associated with outcome (P < 0.001 and P = 0.001, respectively). In the subgroup of patients with severe aortic stenosis (AVA < 1 cm² ), EFVR ≤ 0.9 was associated with an increased hazard ratio for the composite end-point of mortality and aortic valve replacement (HR 2.14, 95% CI: 1.15-4.0, P = 0.017), even after adjusting for aortic valve area.

CONCLUSIONS

In patients with asymptomatic moderate to severe aortic stenosis, EFVR is useful for risk stratification. Our results suggest that incorporating EFVR in the evaluation of patients with asymptomatic aortic stenosis might help identify those who are most likely to benefit from early elective aortic replacement.

The Utility of Flow Rate Compared with Left Ventricular Stroke Volume Index in the Hemodynamic Classification of Severe Aortic Stenosis with Preserved Ejection Fraction

OBJECTIVES

To substitute the stroke volume index (SVi) with flow rate (FR) in the hemodynamic classification of severe aortic stenosis (AS) with preserved ejection fraction (EF), in order to evaluate its prognostic value.

METHODS

A total of 529 patients (78.8 ± 9.8 years old, 44.1% males) with isolated severe AS (aortic valve area, AVA < 1 cm2), EF ≥50%, in sinus rhythm, who underwent transthoracic echocardiography, were stratified by FR (≥/< 200 mL/s) and mean pressure gradient (MG) (≥/< 40 mm Hg): FRnormal/MGhigh, FRlow/MGhigh, FRnormal/MGlow, and FRlow/MGlow.

RESULTS

Aortic valve replacement was more frequently performed in the FRnormal/MGhigh than in the FRlow/MGlow group (69.3 vs. 47%, respectively, p < 0.0001), yielding a similar survival benefit across all four groups. Over a median follow-up of 51 ± 29 months, there were 249 deaths. In highly adjusted models, the FRlow/MGlow group had a higher all-cause mortality (HR = 1.7, 95% CI: 1.1-2.6, p = 0.02) than patients with FRnormal/MGhigh. FR had a stronger association with AVA than SVi (r = 0.51 vs. 0.41, respectively, p = 0.0002), and a similar predictive value for death (AUC = 0.57 and 0.58, respectively, p = 0.88).

CONCLUSIONS

The FRlow/MGlow subset of AS is associated with the worst prognosis, and FR is not superior to SVi in the hemodynamic classification of severe AS.

Discongruence Index - Simple Indicator to Predict Prosthesis-Patient Mismatch After Transcatheter Aortic Valve Replacement

BACKGROUND

Prosthesis-patient mismatch (PPM) after transcatheter aortic valve replacement (TAVR) remains an important issue. The aim of this study was to assess the value of a new discongruence index, to predict PPM after TAVR.Methods and Results: A total of 185 patients with severe aortic stenosis who underwent TAVR with the Edwards Sapien prosthesis or CoreValve Revalving system were included (Edwards valve, n=119; Core Valve Revalving system, n=66). Discongruence index was calculated pre-procedurally as the ratio of selected transcatheter valve size (mm) to body surface area (cm²). PPM was defined as effective orifice area (EOA) ≤0.85 cm²/m² on transthoracic echocardiography before hospital discharge. Mean age was 82±5 years and 72 patients (38.9%) were men. The overall incidence of post-TAVR PPM was 35.1% (n=65). Discongruence index correlated with post-TAVR indexed EOA (y=0.18+0.057x; P<0.001). On multivariate logistic regression analysis, discongruence index was the only independent predictor of post-TAVR PPM (OR, 0.15; 95% CI: 0.03-0.66; P=0.012), and the area under the receiver operating characteristic curve was 0.62 (95% CI: 0.54-0.70, P=0.003), with an optimal cut-off point of 15.02 (sensitivity, 86.2%; specificity, 72.5%; positive predictive value, 74.3%; negative predictive value, 83.4%).

CONCLUSIONS

The new discongruence index may be useful tool to predict PPM after TAVR.

Flow-related right ventricular to pulmonary arterial pressure gradients during exercise

Aims

The assumption of equivalence between right ventricular (RV) and pulmonary arterial systolic pressure is fundamental to several assessments of RV or pulmonary vascular haemodynamic function. Our aims were to (i) determine whether systolic pressure gradients develop across the RV outflow tract in healthy adults during exercise, (ii) examine the potential correlates of such gradients, and (iii) consider the effect of such gradients on calculated indices of RV function.

Methods and results

Healthy untrained and endurance-trained adult volunteers were studied using right-heart catheterization at rest and during submaximal cycle ergometry. RV and pulmonary artery (PA) pressures were simultaneously transduced, and the cardiac output was determined by thermodilution. Systolic pressures, peak and mean gradients, and indices of chamber, vascular, and valve function were analysed offline. Summary data are reported as mean ± standard deviation or median (interquartile range). No significant RV outflow tract gradients were observed at rest [mean gradient = 4 (3–5) mmHg], and the calculated effective orifice area was 3.6 ± 1.0 cm2. The increase in right ventricular systolic pressure during exercise was greater than the PA systolic pressure. Accordingly, mean gradients were developed during light exercise [8 (7–9) mmHg] and increased during moderate exercise [12 (9–14) mmHg, P < 0.001]. The magnitude of the mean gradient was linearly related to the cardiac output (r2 = 0.70, P < 0.001).

Conclusions

In healthy adults without pulmonic stenosis, systolic pressure gradients develop during exercise, and the magnitude is related to the blood flow rate.

Recommendations on the echocardiographic assessment of aortic valve stenosis: a focused update from the European Association of Cardiovascular Imaging and the American Society of Echocardiography

Echocardiography is the key tool for the diagnosis and evaluation of aortic stenosis. Because clinical decision-making is based on the echocardiographic assessment of its severity, it is essential that standards are adopted to maintain accuracy and consistency across echocardiographic laboratories. Detailed recommendations for the echocardiographic assessment of valve stenosis were published by the European Association of Echocardiography and the American Society of Echocardiography in 2009. In the meantime, numerous new studies on aortic stenosis have been published with particular new insights into the difficult subgroup of low gradient aortic stenosis making an update of recommendations necessary. The document focuses in particular on the optimization of left ventricular outflow tract assessment, low flow, low gradient aortic stenosis with preserved ejection fraction, a new classification of aortic stenosis by gradient, flow and ejection fraction, and a grading algorithm for an integrated and stepwise approach of artic stenosis assessment in clinical practice.

Characteristics and outcome following transcatheter aortic valve replacement in patients with severe aortic stenosis with low flow

AIMS

Only a few studies have examined the respective impact of low flow (LF), low gradient (LG) and low ejection fraction (LEF) on outcomes following transcatheter aortic valve replacement (TAVR). The purpose of this study was to assess the impact of preprocedural stroke volume index, aortic valve gradient, left ventricular ejection fraction (LVEF) and different flow/gradient/LVEF patterns on the clinical outcomes of patients with severe aortic stenosis (AS) who undergo TAVR.

METHODS AND RESULTS

We analysed the clinical, echocardiographic, and outcome data collected in 770 patients with AS who underwent TAVR. Overall, 357 patients had normal flow (NF) AS and 413 had LF AS. Patients with NF had similar one-year mortality (12.0% vs. 15.0%, p=0.23) compared with those in the LF group. Overall, patients with NF and/or HG had lower one-year mortality rates (11.7 to 13%) compared to those with paradoxical LF-LG with NEF (19%) and those with classical LF-LG with LEF (27.3%). Low mean gradient was an independent predictor of all-cause mortality (hazard ratio: 1.14, per 10 mmHg decrease, p=0.02). Despite significant association in univariable analyses, LF and LEF were not found to be predictors of outcomes in multivariable analyses.

CONCLUSIONS

Patients with HG and those with NF-LG have low one-year mortality rates following TAVR, whereas those with classical LF-LG and LEF and those with paradoxical LF-LG and NEF have high and intermediate risk of mortality, respectively. In contradiction to previous reports, LG but not LF or LEF is an independent predictor of late mortality in high-risk patients with severe AS undergoing TAVR.

[Low-flow low-gradient aortic valve stenosis : Current evidence]

Many patients with severe aortic stenosis have a "low-flow, low-gradient" aortic stenosis. The management of these patients can be quite difficult, as these patients often show impairment of the left ventricle, which can lead to false measurements of the severity of stenosis and also leads to a higher risk during aortic valve replacement. More diagnostic tools than only standard echocardiography are needed to correctly differentiate true severe aortic stenosis from pseudo severe aortic stenosis.

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.

Nifedipine increases fetoplacental perfusion

AIM

Our aim is to evaluate the effect of nifedipine on fetoplacental hemodynamic parameters.

METHODS

A retrospective study was conducted at a tertiary center with 30 patients for whom nifedipine treatment was used as a tocolytic therapy for preterm labor. Initiation of this treatment was at 31.6±2.5 weeks of gestation. We combined the pulse Doppler imaging parameters with grayscale imaging via the Bernoulli theorem, which is called the "continuity equation", to get the fetoplacental perfusion (FPP). Evaluated parameters were the resistance index (RI), the pulsatility index (PI), systole/diastole ratios (S/D), the velocity-time integral of the umbilical artery (VTI), the radius of the umbilical artery, the peak systolic velocity and the mean pressure gradient in the umbilical artery. From these parameters, the FPP was acquired.

RESULTS

We found that the RI, the PI and the S/D ratio did not change after treatment with nifedipine. The mean pressure gradient, the VTI and the peak systolic velocity increased after treatment with nifedipine. Nifedipine increases FPP from 166±73.81 beat.cm3/min to 220±83.3 beat.cm3/min.

DISCUSSION

Although nifedipine had no effect on the PI, the RI or the S/D, it increased the mean pressure gradient, the VTI and FPP.

Improving the accuracy of effective orifice area assessment after transcatheter aortic valve replacement: validation of left ventricular outflow tract diameter and pulsed-wave Doppler location and impact of three-dimensional measurements

BACKGROUND

Echocardiographic calculation of effective orifice area (EOA) after transcatheter aortic valve replacement is integral to the assessment of transcatheter heart valve (THV) function. The aim of this study was to determine the most accurate method for calculating the EOA of the Edwards SAPIEN and SAPIEN XT THVs.

METHODS

One hundred intraprocedural transesophageal echocardiograms were analyzed. To calculate the post-transcatheter aortic valve replacement left ventricular outflow tract (LVOT) stroke volume (SV), four diameters were measured using two-dimensional echocardiography: (1) baseline LVOT diameter (LVOTd_PRE), (2) postimplantation LVOT diameter, (3) native aortic annular diameter, and (4) THV in-stent diameter. Four corresponding areas were planimetered by three-dimensional echocardiography. Two LVOT velocity-time integrals (VTI) were measured with the pulsed-wave Doppler sample volume at (1) the proximal (apical) edge of the valve stent or (2) within the valve stent at the level of the THV cusps. LVOT velocity-time integral with the sample volume at the proximal edge of the valve stent was used with the LVOT and aortic annular measurements above, whereas in-stent VTI was paired with the in-stent THV diameter to yield eight different SVs. Right ventricular outflow tract (RVOT) SV was calculated using RVOT diameter and RVOT VTI and was used as the primary comparator. Transaortic VTI was obtained by continuous-wave Doppler, and EOA calculations using each SV measurement were compared with (1) EOA calculated using RVOTSV and (2) planimetered aortic valve area using three-dimensional echocardiography (AVAplanimetry3D).

RESULTS

Post-transcatheter aortic valve replacement EOA calculated using LVOTd_PRE was not significantly different from EOA calculated using RVOTSV (1.88 ± 0.33 vs 1.86 ± 0.39 cm(2), P = .36) or from AVAplanimetry3D (1.85 ± 0.28, P = .38, n = 34). All other two-dimensional EOA calculations were statistically larger than EOA calculated using RVOTSV. All three-dimensional echocardiography-based EOA calculations were statistically different from AVAplanimetry3D.

CONCLUSIONS

The most accurate EOA after implantation of a balloon-expandable THV is calculated using preimplantation LVOT diameter and VTI.

Echocardiographic Evaluation of Aortic Stenosis - Normal Flow and Low Flow Scenarios

The echocardiographic evaluation of the patient with aortic stenosis (AS) has evolved in recent years, beyond confirming the diagnosis and measuring the resting mean pressure gradient or valve area. New echocardiographic approaches have developed to address the clinical dilemmas related to discordant haemodynamic data, asymptomatic haemodynamically severe AS and low-flow, low-gradient AS in order to better evaluate the disease severity, enhance the risk stratification of patients and provide important prognostic information. This article reviews the echocardiographic evaluation of the AS patient and focuses on the echocardiographic assessment of the haemodynamic severity, the prediction of clinical outcome and the use of echocardiography to guide patient management in the presence of normal flow and low flow scenarios.

Non-invasive and invasive evaluation of aortic valve area in 100 patients with severe aortic valve stenosis: comparison of cardiac computed tomography with ECHO (transesophageal/transthoracic) and catheter examination

BACKGROUND

Current guidelines place emphasis on the determination of aortic valve area (AVA) for defining an appropriate treatment strategy. Invasive and non-invasive modalities are used to perform planimetric [transesophageal echocardiography (TEE) and cardiac multidetector computed tomography (MDCT)] and calculated [catheter examination (CE), transthoracic echocardiography (TTE)] AVA measurements.

PURPOSE AND METHODS

We investigated 100 patients admitted to evaluate the AVA using cardiac MDCT (CT), TEE/TTE as well as invasive CE.

RESULTS

In all 100 patients we calculated a mean AVA of 0.79±0.29cm(2) (female 50/100, 0.70±0.19cm(2), male 0.9±0.21cm(2)) determined by all investigated examinations (mean±SEM). AVA measurements determined by CT were significantly greater (0.86±0.25cm(2)) than those determined by CE: 0.75±0.18cm(2), p=0.01. Echocardiographically determined AVA was comparable to CE (statistically not significant). Similar results were seen in all patients regardless of gender, presence of atrial fibrillation, and heart rate. We calculated a mean AVA for each patient and evaluated the variance of the AVA determined through investigated specific examinations as the bias. Overall, we found for CT 0.13±0.1cm(2), CE 0.13±0.11cm(2), TEE 0.16±0.09cm(2), and for TTE 0.16±0.08cm(2) a specific statistical non-significant variance. On subgroups: sinus rhythm, atrial fibrillation, females, males or combination, we found no further significant relevance for the specific variance.

CONCLUSION

Our data suggest the feasibility of cardiac MDCT to evaluate the correct AVA regardless of rhythm, heart rate, and sex. The planimetric concept to determine the AVA with CT displaces the "gold-standard" CE with respect to elucidating the potencies for complications, i.e. cerebral stroke. Regardless of CT's accessing of AVA measurement the TTE examination should remain the primary method of screening for aortic valve pathologies.

[Low flow/low gradient aortic valve stenosis : clinical and diagnostic management]

Low gradient aortic stenoses (AS) represent a special challenge for physicians with respect to an exact diagnosis and optimal therapy. The difficulty lies in the estimation of the severity of AS which is decisive for subsequent treatment and the prognosis. Low flow and low gradient can be due to systolic or diastolic dysfunction by high-grade as well as by medium-grade AS and be of non-valvular origin. The latter group is to be interpreted as pseudoaortic stenosis as long as the low flow can successfully be raised by interventional means. However, only patients in the first group can be expected to profit from valve replacement and for patients in the second group the accompanying diseases must be the focus of therapeutic treatment. Therefore, according to recent European surveys up to 30% of patients with severe AS are undertreated due to false estimation of the severity of stenosis and perioperative risk stratification. Furthermore, follow-up investigations have shown that patients with low flow/low gradient stenosis and borderline-normal ejection fraction (EF) are in an advanced stage of the disease because they have often developed a severe reduction in longitudinal myocardial function and in addition have pronounced myocardial replacement fibrosis due to cardiac remodelling despite a preserved EF. Therefore, aortic valve area, mean pressure gradient and EF alone cannot be taken into consideration for the management of patients with severe AS but a comprehensive assessment of the hemodynamics, such as stroke volume, special functional parameters as well as individual clinical appearance is essential for precise diagnostic and therapeutic decision making.

The role of echocardiography in the evaluation and management of aortic stenosis in the older adult

Aortic stenosis is currently the most predominant valvular pathology in older adults. Signs and symptoms of aortic stenosis in this age-group may be difficult to recognize due to the decreased activity associated with aging and attribution of symptoms to other conditions. Echocardiography can be very helpful in the assessment of valvular structure and real time hemodynamic evaluation as well as in the progression of the disease over time. Unprecedented advances in echocardiography, including real time three-dimensional echocardiography, facilitate a comprehensive assessment of this condition and help in the decision-making process. Recent innovations in the percutaneous treatment of valvular diseases promise a revolution in the treatment of aortic stenosis especially in older adults.

Ejection fraction/velocity ratio identifies prosthesis-patient mismatches in patients with aortic bioprosthetic valves and left ventricular dysfunction

OBJECTIVES

Recently, a new echocardiographic nonflow corrected index (ejection fraction/velocity ratio [EFVR] = percent left ventricular ejection fraction [EF]/maximum aortic gradient) has been introduced and has shown excellent accuracy in quantifying the effective orifice area (EOA) in native aortic valves and bio-prostheses. The objective of this study was to assess the utility of the EFVR to quantify the indexed EOA in patients with an aortic bioprosthesis and left ventricular dysfunction considering an indexed EOA value of 0.85 cm(2)/m(2) or less to be indicative of a prosthesis-patient mismatch (PPM), defined as an EOA of the inserted prosthetic valve of less than that of the normal human valve.

METHODS

We studied 100 patients (62 men and 38 women; mean age +/- SD, 71 +/- 8.6 years) with an aortic bioprosthesis and left ventricular dysfunction (EF < or =49%), and we evaluated the indexed EOA by both the continuity equation (CE) and EFVR.

RESULTS

We found a significant linear correlation between the CE and EFVR (r = 0.85; P < .0001) and good agreement between the two methods in identifying patients with an indexed EOA of 0.85 cm(2)/m(2) or less; the correlation began to become nonlinear for patients with an indexed EOA of greater than 1.2 cm(2)/m(2), which was not clinically relevant. Notably, all 11 patients with a discrepancy between the indexed EOA and EFVR (ie, EFVR < or =1.0 and indexed EOA >0.85 cm(2)/m(2)) also showed an indexed EOA of greater than 0.85 but less than or equal to 1.0 cm(2)/m(2) (meaning the presence of a mild PPM).

CONCLUSIONS

The EFVR can be considered a reliable echocardiographic alternative to the CE, especially in conditions in which that is technically difficult, allowing identification of a PPM (indexed EOA < or =0.85 cm(2)/m(2)) with excellent sensitivity and specificity.