Dobutamine echocardiography in patients with aortic stenosis and left ventricular dysfunction: predicting outcome as a function of management strategy

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.

Evidence for a sigmoidal flow-to-valve opening relation in low-flow low-gradient aortic stenosis

We analyzed the relationship between flow (Q) and aortic valve opening area (AVA) using a sequence of echocardiographic stress tests of increasing strength. Low-dose dobutamine stress echocardiography (DSE) has been used to differentiate pseudo-severe from true severe aortic stenoses. Because the Q-response to DSE is so variable between individuals, AVA has been projected to a standardized flow (AVA_proj) using linear interpolation. A linear Q-to-AVA relation implies that AVA shows an unconstrained increase. We applied three stress maneuvers of increasing strength to investigate whether AVA shows signs of saturation. We performed an echocardiographic examination at rest, during the passive leg raise maneuver ("PLR"), maximal dobutamine infusion ("Dmax"), and their combination ("Dmax + PLR") in 45 patients with severe low-flow, low-gradient aortic stenosis. We analyzed the effect of the stress maneuver on Q, AVA, valve compliance (VC), and AVA_proj. We also compared the proportion of patients with nonconclusive test (ΔQ < 20%) between stress maneuvers. We computed the Akaike information criterion (AIC) to compare a linear with a saturating function for the Q-AVA relation. Q gradually increased from "PLR" to "Dmax" to "Dmax + PLR" (P < 0.0001), whereas the number of nonconclusive tests concomitantly diminished from n = 35 to n = 3. The stress sequence increased AVA (P < 0.001) but decreased AVA_proj (P = 0.006) and VC (P = 0.005). In the pooled Q-AVA data, the AIC value was lower for the saturating (sigmoidal) model compared with the linear model fitting (-1,593 vs. -1,504). "Dmax + PLR" is capable of reducing the number of nonconclusive DSE tests. With increasing stress strength, the Q-AVA relation progressively flattens, indicating saturation.NEW & NOTEWORTHY The relation between transaortic flow (Q) and aortic valve opening area (AVA) shows a saturation when three different stress maneuvers are used to increase Q as much as possible. This has implications for the assessment of aortic stenosis severity.

Surgical aortic valve replacement for low-gradient aortic stenosis

AIMS

Low-gradient aortic stenosis is a challenging entity that needs accurate preoperative evaluation. For this high-risk patient population, ad hoc predictive scores are not available and profile risk is currently revealed by the EuroSCOREs. Aims of this study are to verify the suitability of the ES II as predictor of mortality in low-gradient aortic stenosis and to analyse the role of surgery as a treatment.

METHODS

From June 2013 to August 2019, 414 patients underwent surgical aortic valve replacement for low-gradient aortic stenosis. Mean age was 75.78 ± 6.77 years and 190 were women. The prognostic value of Logistic EuroSCORE and EuroSCORE II were compared by receiver-operating characteristics (ROC) curve analysis.

RESULTS

In-hospital, 30-day and 1-year mortality rates were respectively 3.4, 2.9 and 4.8% (14, 12 and 20 patients over 414). In-hospital mortality risk calculated by the Additive EuroSCORE was 7.2 ± 2.7%, by the Logistic EuroSCORE was 9 ± 5.2% and by the ES II was 4.13 ± 2.56%. The prognostic values of the EuroSCORE II and of the EuroSCORE were analysed in a ROC curve analysis for the prediction of in-hospital mortality [area under the curve (AUC): 0.62 vs. 0.58], 30-day mortality (AUC: 0.63 vs. 0.64) and 1-year mortality (AUC: 0.79 vs. 0.65). Both scores did not show significant differences with the only exception of 1-year mortality, for which EuroSCORE II had a better predictive ability than the Logistic EuroSCORE (P < 0.05).

CONCLUSION

In low-gradient aortic stenosis undergoing surgery, the EuroSCORE II is a strong predictor of 1-year mortality.

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.

Discordant Echocardiographic Grading in Low Gradient Aortic Stenosis (DEGAS Study) From the Italian Society of Echocardiography and Cardiovascular Imaging Research Network: Rationale and Study Design

Background

Low-gradient aortic stenosis (LG-AS) is characterized by the combination of an aortic valve area compatible with severe stenosis and a low transvalvular mean gradient with low-flow state (i.e., indexed stroke volume <35 mL/m²) in the presence of reduced (classical low-flow AS) or preserved (paradoxical low-flow AS) ejection fraction. Furthermore, the occurrence of a normal-flow LG-AS is still advocated by many authors. Within this diagnostic complexity, the diagnosis of severe AS remains challenging.

Objective

The general objective of the Discordant Echocardiographic Grading in Low-gradient AS (DEGAS Study) study will be to assess the prevalence of true severe AS in this population and validate new parameters to improve the assessment and the clinical decision-making in patients with LG-AS.

Methods and Analyses

The DEGAS Study of the Italian Society of Echocardiography and Cardiovascular Imaging is a prospective, multicenter, observational diagnostic study that will enroll consecutively adult patients with LG-AS over 2 years. AS severity will be ideally confirmed by a multimodality approach, but only the quantification of calcium score by multidetector computed tomography will be mandatory. The primary clinical outcome variable will be 12-month all-cause mortality. The secondary outcome variables will be (i) 30-day mortality (for patients treated by Surgical aortic valve replacement or TAVR); (ii) 12-month cardiovascular mortality; (iii) 12-month new major cardiovascular events such as myocardial infarction, stroke, vascular complications, and rehospitalization for heart failure; and (iv) composite endpoint of cardiovascular mortality and hospitalization for heart failure. Data collection will take place through a web platform (REDCap), absolutely secure based on current standards concerning the ethical requirements and data integrity.

"Pure" severe aortic stenosis without concomitant valvular heart diseases: echocardiographic and pathophysiological features

Purpose

In echocardiography the severity of aortic stenosis (AS) is defined by effective orifice area (EOA), mean pressure gradient (mPG_AV) and transvalvular flow velocity (maxV_AV). The hypothesis of the present study was to confirm the pathophysiological presence of combined left ventricular hypertrophy (LVH), diastolic dysfunction (DD) and pulmonary artery hypertension (PAH) in patients with “pure” severe AS.

Methods and Results

Patients (n = 306) with asymptomatic (n = 133) and symptomatic (n = 173) “pure” severe AS (mean age 78 ± 9.5 years) defined by indexed EOA < 0.6 cm² were enrolled between 2014 and 2016. AS patients were divided into 4 subgroups according to mPG_AV and indexed left ventricular stroke volume: low flow (LF) low gradient (LG)-AS (n = 133), normal flow (NF) LG-AS (n = 91), LF high gradient (HG)-AS (n = 21) and NFHG-AS (n = 61). Patients with “pure” severe AS showed mean mPG_AV of 31.7 ± 9.1 mmHg and mean maxV_AV of 3.8 ± 0.6 m/s. Only 131 of 306 patients (43%) exhibited mPG_AV > 40 mmHg and maxV_AV > 4 m/s documenting incongruencies of the AS severity assessment by Doppler echocardiography. LVH was documented in 81%, DD in 76% and PAH in 80% of AS patients. 54% of “pure” AS patients exhibited all three alterations. Ranges of mPG_AV and maxV_AV were higher in patients with all three alterations compared to patients with less than three. 224 (73%) patients presented LG-conditions and 82 (27%) HG-conditions. LVH was predominant in NF-AS (p = 0.014) and PAH in LFHG-AS (p = 0.014). Patients’ treatment was retrospectively assessed (surgery: n = 100, TAVI: n = 48, optimal medical treatment: n = 156).

Conclusion

In patients with “pure” AS according to current guidelines the presence of combined LVH, DD and PAH as accepted pathophysiological sequelae of severe AS cannot be confirmed. Probably, the detection of these secondary cardiac alterations might improve the diagnostic algorithm to avoid overestimation of AS severity.

Self-Expanding Transcatheter Aortic Valve Replacement in Patients With Low-Gradient Aortic Stenosis

OBJECTIVES

The authors sought to compare clinical and hemodynamic outcomes in patients receiving transcatheter aortic valve replacement (TAVR) for low-gradient (LG) aortic stenosis in the CoreValve EUS (Expanded Use Study) versus those with high-gradient (HG) aortic stenosis from the CoreValve U.S. Pivotal Extreme Risk Trial and CAS (Continued Access Study).

BACKGROUND

The EUS examined the impact of TAVR in patients unsuitable for surgical aortic valve replacement who were excluded from the U.S. Pivotal Extreme Risk Trial due to LG aortic stenosis.

METHODS

EUS patients were stratified by left ventricular ejection fraction: normal (≥50%, LG-normal ejection fraction), and low (<50%, did not respond to dobutamine by generating a mean gradient >40 mm Hg and/or velocity >4.0 m/s, "nonresponders"), and compared with extreme-risk patients from U.S. Pivotal and CAS that had either low resting gradient and responded to dobutamine ("responders"), or a high resting gradient (HG) or velocity. The primary endpoint was all-cause mortality or major stroke at 1 year. Hemodynamics and quality of life are reported at 30 days and 1 year.

RESULTS

At 30 days, patients with LG/low left ventricular ejection fraction (nonresponders and responders) had significantly higher rates of all-cause mortality or major stroke, all-cause mortality, and cardiovascular mortality than both HG and LG-normal ejection fraction patients. At 1 year, only the responders had higher rates of these outcomes in comparison to the other 3 groups. Mean gradient and effective orifice area improved significantly in all patients and were maintained through 1 year. New York Heart Association functional classification and Kansas City Cardiomyopathy Questionnaire overall summary scores improved (p < 0.05) in all cohorts through 1 year. When all 4 subgroups were pooled, both decreasing mean gradient and stroke volume index were associated with increased mortality. Pre-procedural mean gradient was the only hemodynamic independent predictor of 1-year mortality by multivariate analysis.

CONCLUSIONS

In this study, TAVR provided EUS patients significant hemodynamic relief with both 1-year survival and quality of life outcomes comparable to Pivotal and CAS patients (Safety & Efficacy Study of the Medtronic CoreValve System-Treatment of Symptomatic Severe Aortic Stenosis With Significant Comorbidities in Extreme Risk Subjects Who Need Aortic Valve Replacement, NCT01675440; Safety and Efficacy Study of the Medtronic CoreValve System in the Treatment of Symptomatic Severe Aortic Stenosis in High Risk and Very High Risk Subjects Who Need Aortic Valve Replacement, NCT01240902; Safety and Efficacy Continued Access Study of the Medtronic CoreValve System in the Treatment of Symptomatic Severe Aortic Stenosis in Very High Risk Subjects and High Risk Subjects Who Need Aortic Valve Replacement, NCT01531374).

Dilemma in the therapeutic management of low-gradient aortic stenosis

PURPOSE OF REVIEW

Grading of aortic stenosis is essential in aortic stenosis management patients. However, despite clear thresholds provided in the guidelines, up to 30% of patients have discordant grading of aortic stenosis. The management of patients with low gradients/velocity despite tight aortic valve area is challenging.

RECENT FINDINGS

Recent studies demonstrated that patients with or without low flow may have a severe aortic stenosis despite a low gradient. Moreover, aortic valve replacement has been shown to improve outcome in low-gradient aortic stenosis patients with or without low flow. Finally, measurement of aortic valve calcification by multidetector computed tomography is an important tool to assess aortic stenosis severity in these patients.

SUMMARY

The presence of a low gradient/velocity despite a tight aortic valve area could be linked to low ejection fraction or low flow with preserved ejection fraction but also with normal flow and normal ejection fraction. In each situation, aortic stenosis could be truly severe or pseudosevere, and the severity of aortic stenosis has to be accurately evaluated for clinical decision-making. Nowadays, two types of interventions are available: surgical and transcatheter aortic valve replacement, whereas conservative management should be considered as a palliative treatment in patients with proven severe aortic stenosis and symptoms or left ventricle dysfunction.

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.

Cardiac amyloidosis mimicking severe aortic valve stenosis - a case report demonstrating diagnostic pitfalls and role of dobutamine stress echocardiography

Background

Aortic valve stenosis is a common finding diagnosed with high sensitivity in transthoracic echocardiography, but the examiner often finds himself confronted with uncertain results in patients with moderate pressure gradients and concomitant systolic heart failure. While patients with true-severe low-gradient aortic valve stenosis with either reduced or preserved left ventricular systolic function are primarily candidates for valve replacement, there is a relevant proportion of patients with pseudo-severe aortic valve stenosis anticipated not to benefit but actually rather deteriorate by interventional therapy or surgery.

Case presentation

In this article we present a case report of a male patient with pseudo-severe aortic valve stenosis due to cardiac amyloidosis highlighting the diagnostic schedule. The patient underwent stress echocardiography because of discrepant findings in transthoracic echocardiography and cardiac catheterization regarding the severity of aortic valve stenosis. After evaluation of the results, it became clear that he had a need for optimum heart failure medication and implantation of a cardiac resynchronization therapy defibrillator.

Conclusion

Due to the pitfalls in conventional as well as invasive diagnostics at rest, Stress echocardiography should be considered part of the standard optimum diagnostic spectrum in all unclear or borderline cases in order to confirm the correct diagnosis and constitute optimal therapy.

Aortic valve surgery and survival in patients with moderate or severe aortic stenosis and left ventricular dysfunction

AIMS

We aimed to determine the frequency of aortic valve surgery (AVR) with or without coronary artery bypass grafting (CABG), among patients with moderate/severe aortic stenosis (AS) and left ventricular systolic dysfunction (LVSD), and its relationship with survival.

METHODS AND RESULTS

The Duke Echocardiographic Database (N = 132 804) was queried for patients with mean gradient ≥25 mmHg and/or peak velocity ≥3 m/s and LVSD (left ventricular ejection fraction ≤50%) from 1 January 1995-28 February 2014. For analyses purposes, AS was defined both by mean gradient and calculated aortic valve area (AVA) criteria. Time-dependent indicators of AVR in multivariable Cox models were used to assess the relationship of AVR and all-cause mortality. A total of 1634 patients had moderate (N = 1090, 67%) or severe (N = 544, 33%) AS by mean gradient criteria. Overall, 287 (26%) patients with moderate AS and 263 (48%) patients with severe AS underwent AVR within 5 years of the qualifying echo. There were 863 (53%) deaths observed up to 5 years following index echo. After multivariable adjustment in an inverse probability weighted regression model, AVR was associated with higher 5-year survival amongst patients with moderate AS and severe AS whether classified by AVA or mean gradient criteria. Over all, AVR ± CABG compared with medical therapy was associated with significantly lower mortality [hazard ratio, HR = 0.49 (0.38, 0.62), P < 0.0001]. Compared with CABG alone, CABG + AVR was associated with better survival [HR = 0.18 (0.12, 0.27), P < 0.0001].

CONCLUSIONS

In patients with moderate/severe AS and LVSD, mortality is substantial and amongst those selected for surgery, AVR with or without CABG is associated with higher survival. Research is required to understand factors contributing to current practice patterns and the possible utility of transcatheter approaches in this high-risk cohort.

Evaluation of aortic stenosis: an update--including low-flow States, myocardial mechanics, and stress testing

Degenerative aortic stenosis (AS) is one of the most frequent valvular heart diseases in Western countries. Echocardiography plays a central role in the evaluation and management of patients with AS. To overcome the inherent inconsistencies between the echocardiographic parameters defining severe AS and to unify concepts, a new classification based on the interplay between flow and gradients has recently been adopted. Outcome studies of asymptomatic patients with preserved left ventricular ejection fraction (LVEF), as classified by this new approach, have shown that low-flow (LF) states are associated with poor outcome, that the classical normal-flow/high-gradient pattern has an intermediate outcome, while normal-flow/low-gradient severe AS seems to have an outcome comparable to moderate AS and such patients do not benefit from aortic valve replacement. Patients with LF/low-gradient severe AS with preserved LVEF, also known as "paradoxical LF/low-gradient AS," have the worst outcome and benefit greatly from surgical or percutaneous valve replacement, provided that severity is proven. In patients with LF/low-gradient and depressed LVEF, dobutamine stress echocardiography has an important role to distinguish severe from pseudo-severe AS and to assess surgical risk. Assessment of aortic valve calcium score, as well as computation of projected effective orifice aortic area at normal trans-valvular flow rates, has proved to be very useful to distinguish severe from pseudo-severe AS in LF/low-gradient AS with both reduced and preserved LVEF. Asymptomatic patients with normal flow/gradient should be submitted to an exercise test; exercise echocardiography can identify patients at increased risk when mean gradient increases by >18-20 mmHg and/or pulmonary arterial hypertension develops during exercise.

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 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.

Low flow low gradient aortic stenosis: clinical pathways

Aortic stenosis patients with severe LV dysfunction and low cardiac output present with relatively low transvalvular gradients. It is difficult to distinguish them from aortic sclerosis and LV dysfunction with low cardiac output. The former condition is severe AS with LV dysfunction and latter is primarily a contractile dysfunction. Dobutamine stress echocardiogram is key to diagnosis. AS with LV dysfunction associated with preserved contractile reserve benefit from valve replacement and those without contractile reserve needs critical evaluation on a case to case basis. Patients of AS with LV dysfunction with associated coronary artery disease need coronary angiograms to decide regarding need for valve replacement with bypass surgery. A subset of AS patients have low flow, low mean gradients with preserved ejection fraction in whom one must evaluate global hemodynamic load to assess ventriculo-arterial impedence. In this review an approach to the clinical pathways for assessment of low flow, low gradient aortic stenosis has been discussed.

Prognostic value of low-dose dobutamine stress echocardiography in patients with aortic stenosis and impaired left ventricular function

INTRODUCTION

The aim of this multicenter, prospective study was to evaluate the long-term prognostic value of low-dose dobutamine stress echocardiography (LDDSE) in patients with aortic stenosis (AS) and depressed left ventricular (LV) function.

MATERIAL AND METHODS

The study group comprised 39 patients (34 male, mean age 59 ±13 years) with AS (peak gradient > 25 mm Hg), LV ejection fraction (LVEF) ≤ 45% and low transaortic gradient (peak gradient ≤ 45 mm Hg, mean gradient ≤ 35 mm Hg). The qualification for subsequent therapeutic procedures was based on generally accepted indications. All patients underwent LDDSE and coronary angiography. Twelve months after LDDSE patients underwent control resting echocardiography and clinical evaluation.

RESULTS

Twenty-seven (69.2%) patients had preserved contractile reserve. In this subgroup, true-severe AS was diagnosed in 12 patients, whereas pseudo-severe AS was found in 15 patients. Nine patients with true-severe AS, 2 patients with pseudo-severe AS and 7 patients without contractile reserve were referred for surgical treatment. The independent risk factors of death during follow-up were: aortic valve area (AVA) at peak stress < 0.8 cm(2) (OR 1.4; p = 0.003) and LVEF at rest < 35% (OR 6.8; p = 0.05). The independent risk factors of composite end-point (death or myocardial infarctions or pulmonary edema) were: AVA at stress < 0.8 cm(2) (OR 4.0; p = 0.03), absence of AVA increase during LDDSE (OR 5.7; p = 0.005), absence of contractile reserve (OR 4.5; p = 0.01) and presence of significant CAD (OR 6.9; p = 0.02).

CONCLUSIONS

In patients with AS and depressed LVEF, LDDSE is a useful tool for long-term risk stratification.

Aortic valve and ascending aorta guidelines for management and quality measures: executive summary

The Society of Thoracic Surgeons Clinical Practice Guidelines are intended to assist physicians and other health care providers in clinical decision making by describing a range of generally acceptable approaches for the diagnosis, management, or prevention of specific diseases or conditions. These guidelines should not be considered inclusive of all proper methods of care or exclusive of other methods of care reasonably directed at obtaining the same results. Moreover, these guidelines are subject to change over time, without notice. The ultimate judgment regarding the care of a particular patient must be made by the physician in light of the individual circumstances presented by the patient.

Low-flow, low-gradient aortic stenosis with normal and depressed left ventricular ejection fraction

Low-flow, low-gradient (LF-LG) aortic stenosis (AS) may occur with depressed or preserved left ventricular ejection fraction (LVEF), and both situations are among the most challenging encountered in patients with valvular heart disease. In both cases, the decrease in gradient relative to AS severity is due to a reduction in transvalvular flow. The main challenge in patients with depressed LVEF is to distinguish between true severe versus pseudosevere stenosis and to accurately assess the severity of myocardial impairment. Paradoxical LF-LG severe AS despite a normal LVEF is a recently described entity that is characterized by pronounced LV concentric remodeling, small LV cavity size, and a restrictive physiology leading to impaired LV filling, altered myocardial function, and worse prognosis. Until recently, this entity was often misdiagnosed, thereby causing underestimation of AS severity and inappropriate delays for surgery. Hence, the main challenge in these patients is proper diagnosis, often requiring diagnostic tests other than Doppler echocardiography. The present paper proposes to review the diagnostic and therapeutic management specificities of LF-LG AS with and without depressed LV function.

The emerging role of exercise testing and stress echocardiography in valvular heart disease

Exercise testing has an established role in the evaluation of patients with valvular heart disease and can aid clinical decision making. Because symptoms may develop slowly and indolently in chronic valve diseases and are often not recognized by patients and their physicians, the symptomatic, blood pressure, and electrocardiographic responses to exercise can help identify patients who would benefit from early valve repair or replacement. In addition, stress echocardiography has emerged as an important component of stress testing in patients with valvular heart disease, with relevant established and potential applications. Stress echocardiography has the advantages of its wide availability, low cost, and versatility for the assessment of disease severity. The versatile applications of stress echocardiography can be tailored to the individual patient with aortic or mitral valve disease, both before and after valve replacement or repair. Hence, exercise-induced changes in valve hemodynamics, ventricular function, and pulmonary artery pressure, together with exercise capacity and symptomatic responses to exercise, provide the clinician with diagnostic and prognostic information that can contribute to subsequent clinical decisions. Nevertheless, there is a lack of convincing evidence that the results of stress echocardiography lead to clinical decisions that result in better outcomes, and therefore large-scale prospective randomized studies focusing on patient outcomes are needed in the future.

New concepts in valvular hemodynamics: implications for diagnosis and treatment of aortic stenosis

Aortic valve stenosis (AS) is the third-most frequent heart disease after coronary artery disease and arterial hypertension, and it is associated with a high incidence of adverse outcomes. Recent data support the notion that AS is not an isolated disease uniquely limited to the valve. Indeed, AS is frequently associated with abnormalities of the systemic arterial system, and, in particular, with reduced arterial compliance, which may have important consequences for the pathophysiology and clinical outcome of this disease. Moreover, AS may also be associated with left ventricular systolic dysfunction and reduced transvalvular flow rate, which pose important challenges with regards to diagnostic evaluation and clinical decision making in AS patients. Hence, the assessment of AS severity, as well as its therapeutic management, should be conducted with the use of a comprehensive evaluation that includes not only the aortic valve, but also the systemic arterial system and the left ventricle because these three entities are tightly coupled from both a pathophysiological and a hemodynamic standpoint.

Predictors of Outcomes in Low-Flow, Low-Gradient Aortic Stenosis

Background— Patients with low-flow, low-gradient aortic stenosis have a poor prognosis with conservative therapy but a high operative mortality if treated surgically. Recently, we proposed a new index of aortic stenosis severity derived from dobutamine stress echocardiography, the projected aortic valve area at a normal transvalvular flow rate, as superior to other conventional indices to differentiate true-severe from pseudosevere aortic stenosis. The objective of this study was to identify the determinants of survival, functional status, and change in left ventricular ejection fraction during follow-up of patients with low-flow, low-gradient aortic stenosis.

Methods and Results— One hundred one patients with low-flow, low-gradient aortic stenosis (aortic valve area ≤1.2 cm 2 , left ventricular ejection fraction ≤40%, and mean gradient ≤40 mm Hg) underwent dobutamine stress echocardiography and an assessment of functional capacity using the Duke Activity Status Index. A subset of 72 patients also underwent a 6-minute walk test. Overall survival was 70±5% at 1 year and 57±6% at 3 years. After adjusting for age, gender, and the type of treatment (aortic valve replacement versus no aortic valve replacement), significant predictors of mortality during follow-up were a Duke Activity Status Index ≤20 ( P =0.0005) or 6-minute walk test distance ≤320 m ( P <0.0001, in the subset of 72 patients), projected aortic valve area at a normal transvalvular flow rate ≤1.2 cm 2 ( P =0.03), and peak dobutamine stress echocardiography left ventricular ejection fraction ≤35% ( P =0.03). More severe stenosis, defined as projected aortic valve area ≤1.2 cm 2 , was a predictor of mortality only in the no aortic valve replacement group. The Duke Activity Status Index, 6-minute walk test, and left ventricular ejection fraction improved significantly during follow-up in the aortic valve replacement group, but remained unchanged or decreased in the no aortic valve replacement group.

Conclusion— In patients with low-flow, low-gradient aortic stenosis, the most significant risk factors for poor outcome were (1) impaired functional capacity as measured by Duke Activity Status Index or 6-minute walk test distance; (2) more severe valve stenosis as measured by projected aortic valve area at a normal transvalvular flow rate; and (3) reduced peak stress left ventricular ejection fraction, a composite measure accounting for both resting left ventricular function and contractile reserve.

Paradoxical low-flow, low-gradient severe aortic stenosis despite preserved ejection fraction is associated with higher afterload and reduced survival

BACKGROUND

Recent studies and current clinical observations suggest that some patients with severe aortic stenosis on the basis of aortic valve area may paradoxically have a relatively low gradient despite the presence of a preserved left ventricular (LV) ejection fraction. The objective of the present study was to document the prevalence, potential mechanisms, and clinical relevance of this phenomenon.

METHODS AND RESULTS

We retrospectively studied the clinical and Doppler echocardiographic data of 512 consecutive patients with severe aortic stenosis (indexed aortic valve area < or = 0.6 cm2 x m(-2)) and preserved LV ejection fraction (> or = 50%). Of these patients, 331 (65%) had normal LV flow output defined as a stroke volume index > 35 mL x m2, and 181 (35%) had paradoxically low-flow output defined as stroke volume index < or = 35 mL x m(-2). When compared with normal flow patients, low-flow patients had a higher prevalence of female gender (P<0.05), a lower transvalvular gradient (32+/-17 versus 40+/-15 mm Hg; P<0.001), a lower LV diastolic volume index (52+/-12 versus 59+/-13 mL x m(-2); P<0.001), lower LV ejection fraction (62+/-8% versus 68+/-7%; P<0.001), a higher level of LV global afterload reflected by a higher valvulo-arterial impedance (5.3+/-1.3 versus 4.1+/-0.7 mm Hg x mL(-1) x m(-2); P<0.001) and a lower overall 3-year survival (76% versus 86%; P=0.006). Only age (hazard ratio, 1.04; 95% CI, 1.01 to 1.08; P=0.025), valvulo-arterial impedance > 5.5 mm Hg x mL(-1) x m(-2) (hazard ratio, 2.6; 95% CI, 1.2 to 5.7; P=0.017), and medical treatment (hazard ratio, 3.3; 95% CI, 1.8 to 6.7; P=0.0003) were independently associated with increased mortality.

CONCLUSION

Patients with severe aortic stenosis may have low transvalvular flow and low gradients despite normal LV ejection fraction. A comprehensive evaluation shows that this pattern is in fact consistent with a more advanced stage of the disease and has a poorer prognosis. Such findings are clinically relevant because this condition may often be misdiagnosed, which leads to a neglect and/or an underestimation of symptoms and an inappropriate delay of aortic valve replacement surgery.

Indications for aortic valve replacement in aortic stenosis

Aortic stenosis is a common condition, particularly in the elderly. The treatment is surgical, and any patient with symptomatic severe aortic stenosis should be considered for aortic valve replacement. Aortic stenosis causes an increase in afterload to the left ventricle, which when severe can lead to hemodynamic instability. Although the therapy of aortic stenosis is valve replacement, determining whether a patient has symptoms and accurately assessing the severity of stenosis can be difficult. The management of patients with severe aortic stenosis in the intensive care unit setting can be very challenging, particularly when comorbid medical conditions make aortic valve replacement difficult. This article reviews the diagnosis of aortic stenosis, methods of assessing symptoms and severity, and management of severe symptomatic stenosis, particularly in the intensive care unit setting. Components of the history that suggest symptomatic aortic stenosis are presented. The role of physical examination is discussed, as are the echocardiographic means of determining stenosis severity. Other means of assessing severity are addressed, as are circumstances in which there can be difficulty in interpretation, such as severe aortic stenosis and left ventricular dysfunction. Management of patients, focusing on the intensive care unit setting, is reviewed, with a focus on the timing of aortic valve replacement.

Low-flow, low-gradient aortic stenosis: from evaluation to treatment

PURPOSE OF REVIEW

Valve replacement improves symptoms and survival in symptomatic severe aortic stenosis. Low-flow, low-gradient aortic stenosis, however, is an especially challenging subset as valve replacement has a significant risk, and may fail to alleviate symptoms or improve left ventricular function. This article reviews the potential problems in evaluating aortic stenosis severity in low-flow, low-gradient aortic stenosis, the utility of dobutamine challenge to identify patients most likely to benefit from surgery, and the factors predicting patient outcome.

RECENT FINDINGS

Low-flow, low-gradient aortic stenosis consists of a heterogeneous group of patients with 'true' severe aortic stenosis, in whom afterload mismatch results from a severely stenotic valve; and 'pseudo-severe' aortic stenosis, where the valve is only mildly or moderately stenotic, but appears severe due to limitations in determining disease severity under low-flow conditions. Valve replacement is likely to benefit the former group, but may have little benefit to the latter. Dobutamine challenge can distinguish 'true' and 'pseudo-severe' aortic stenosis, and can evaluate contractile reserve, one of the strongest predictors of patient outcome. Strategies to avoid prosthesis-patient mismatch should be considered to optimize postoperative outcome.

SUMMARY

Dobutamine challenge can identify low-flow, low-gradient aortic stenosis patients most likely to benefit from valve replacement and provides important prognostic information on the operative risks and long-term outcome.

Surgery for severe aortic stenosis with low transvalvular gradient and poor left ventricular function -- a single centre experience and review of the literature

Background

A retrospective comparative study was designed to determine whether the transvalvular gradient has a predictive value in the assessment of operative outcome in patients with severe aortic stenosis and poor left ventricular function.

Methods

From a surgical database, a series of 30 consecutive patients, who underwent isolated aortic valve replacement for severe aortic stenosis with depressed left ventricular (LV) function (EF < 40%), were enrolled in the study and divided into two groups according to the mean transvalvular gradient (TVG): LG(low gradient)-Group < 40 mmHg (n = 13), and HG(high gradient)-Group > 40 mmHg (n = 17). Both groups were then comparatively assessed with respect to perioperative organ functions and mortality.

Results

Both groups were well matched with respect to the preoperative clinical status. LG-Group had a larger aortic valve area, higher LVEDP, larger LVESD and LVEDD, and higher mean pulmonary pressures. The immediate postoperative outcome, hospital morbidity and mortality did not differ significantly among the groups.

Conclusion

In patients with severe aortic stenosis and poor LV function, the mean transvalvular gradient, although corresponds to reduced LV performance, has a limited prognostic value in the assessment of surgical outcome. Generally, operating on this select group of patients is safe.

Aortic Valve Replacement in True Severe Aortic Stenosis with Low Gradient and Low Ejection Fraction

OBJECTIVE

The results of aortic valve replacement are uncertain among patients with severe aortic stenosis, reduced left ventricular ejection fraction, and low mean transvalvular gradient. The aim of the present study was to report on 27 patients who underwent surgery for aortic stenosis with left ventricular ejection fraction <or=30% and mean transvalvular gradient <30 mmHg.

METHODS

The study was performed between January 2000 and December 2005. Twenty-seven patients with aortic stenosis with a calculated valve area <1.0 cm2, aortic mean transvalvular gradient <30 mmHg, and ejection fraction <or=30% were studied. Exclusion criteria were coronary artery disease, concomitant valvular operation, previous aortic valve replacement, or more than moderate aortic valve regurgitation. Preoperative clinical, echocardiography and dobutamine echocardiography, cardiac catheterization and coronary angiography, and operative data were recorded in all patients. Patients who were diagnosed with true aortic stenosis were divided into 2 groups according to left ventricular ejection fraction changes during dobutamine echocardiography, 16 with recruitable myocardium (group 1) versus 11 without (group 2).

RESULTS

One patient from group 2 died. The functional capacities of all of the patients in group 1 significantly improved in the postoperative period (P = .001). All of the patients except for 1 in group 1 had improved left ventricular ejection fraction after the operation (P <.001). The comparison of the preoperative and postoperative functional status of these patients in group 2 was also statistically significant (P = .001). The 10 of the 11 patients in group 2 who were alive had left ventricular ejection fraction value changes that were not significant statistically (P = .096). The comparison of the improvement of functional capacities of the groups revealed a significant difference; that is, the improvement was higher in group 1 (P = .039).

CONCLUSION

Left ventricular ejection fraction and functional capacity improved after aortic valve replacement in patients with left ventricular dysfunction, low mean transvalvular gradient, and aortic valve replacement in these patients has acceptable mortality rates with significantly improved functional status.