Comparison of simultaneous invasive and noninvasive measurements of pressure gradients in congenital aortic valve stenosis

Standardization in paediatric echocardiographic reporting and critical interpretation of measurements, functional parameters, and prediction scores: a clinical consensus statement of the European Association of Cardiovascular Imaging of the European Society of Cardiology and the Association for European Paediatric and Congenital Cardiology

This document has been developed to provide a guide for basic and advanced reporting in paediatric echocardiography. Furthermore, it aims to help clinicians in the interpretation of echocardiographic measurements and functional data for estimating the severity of disease in different paediatric age groups. The following topics will be reviewed and discussed in the present document: (i) the general principle in constructing a paediatric echocardiographic report, (ii) the basic elements to be included, and (iii) the potential and limitation of currently employed tools used for disease severity quantification during paediatric reporting. A guide for the interpretation of Z-scores will be provided. Use and interpretation of parameters employed for quantification of ventricular systolic function will be discussed. Difficulties in the adoption of adult parameters for the study of diastolic function and valve defects at different ages and pressure and loading conditions will be outlined, with pitfalls for the assessment listed. A guide for careful use of prediction scores for complex congenital heart disease will be provided. Examples of basic and advanced (disease-specific) formats for reporting in paediatric echocardiography will be provided. This document should serve as a comprehensive guide to (i) structure a comprehensive paediatric echocardiographic report; (ii) identify the basic morphological details, measures, and functional parameters to be included during echocardiographic reporting; and (iii) correctly interpret measurements and functional data for estimating disease severity.

Guidelines for Performing a Comprehensive Pediatric Transthoracic Echocardiogram: Recommendations From the American Society of Echocardiography

Echocardiography is a fundamental component of pediatric cardiology, and appropriate indications have been established for its use in the setting of suspected, congenital, or acquired heart disease in children. Since the publication of guidelines for pediatric transthoracic echocardiography in 2006 and 2010, advances in knowledge and technology have expanded the scope of practice beyond the use of traditional modalities such as two-dimensional, M-mode, and Doppler echocardiography to evaluate the cardiac segmental structures and their function. Adjunct modalities such as contrast, three-dimensional, and speckle-tracking echocardiography are now used routinely at many pediatric centers. Guidelines and recommendations for the use of traditional and newer adjunct modalities in children are described in detail in this document. In addition, suggested protocols related to standard operations, infection control, sedation, and quality assurance and improvement are included to provide an organizational structure for centers performing pediatric transthoracic echocardiograms.

Effect of aortic curvature on bioprosthetic aortic valve performance

Transvalvular pressure gradient (ΔP) after aortic valve replacement is an important surrogate of aortic bioprostheses performance. Invasive ΔP is often measured after transcatheter aortic valve replacement to exclude patient-prosthetic mismatch. However, invasive aortic pressures are usually recorded in the pressure recovery (PR) zone downstream of the valve, potentially resulting in ΔP underestimation compared to noninvasive measurements. PR was extensively studied in straight ascending aortas. However, the impact of various aortic arch configurations on ΔP has not been explored. PR was assessed in a pulse duplicating simulator at various cardiac conditions of cardiac output, heart rates and pressures. Three different aortic geometries with identical root dimensions but with different aortic arches were used: (1) curvature 1, (2) curvature 2, and (3) straight aortic models. Instantaneous pressure and peak ΔP measurements were recorded incrementally along the models for each cardiac condition. The models with aortic arches produced two distinct PR zones (after the valve and after the aortic arch), whereas the model without an aortic arch produced only one PR zone (after the valve). The trend of the pressure and ΔP curves for each model was independent of the cardiac condition used, but the individually measured pressure magnitudes did change with different conditions. In this study, we illustrated the differences in PR between distinct aortic curvatures and straight aorta. PR affects pressure and ΔP measurements. These effects are clear when recording aortic pressures by catheterization and echocardiography.

Congenital Aortic Valve Stenosis

Aortic valve stenosis in children is a congenital heart defect that causes fixed form of hemodynamically significant left ventricular outflow tract obstruction with progressive course. Neonates and young infants who have aortic valve stenosis, usually develop congestive heart failure. Children and adolescents who have aortic valve stenosis, are mostly asymptomatic, although they may carry a small but significant risk of sudden death. Transcatheter or surgical intervention is indicated for symptomatic patients or those with moderate to severe left ventricular outflow tract obstruction. Many may need reintervention.

Hemodynamic characterization of aortic stenosis states

Aortic stenosis (AS) has become an increasingly prevalent clinical condition, as a result of the "greying of the population", the widespread application of sophisticated diagnostic tools including non-invasive imaging and invasive techniques, and the advent of minimally invasive surgical and percutaneous valve therapies. The diagnosis of severe AS traditionally has relied on the assessment of the mean transvalvular gradient (ΔP_mean ) and aortic valve area (AVA) by either echocardiography or catheterization. However, other hemodynamic variables as flow, pressure recovery, and jet eccentricity also play a major role in determining the final hemodynamic state of AS. Moreover, mismatch between ΔP_mean and AVA as in low flow low gradient AS and discordance between catheterization and echocardiographic studies in grading severity of AS have increased the complexity of AS diagnosis. The present case-based treatise emphasizes a multi-modality approach to delineation of the hemodynamic pathophysiology of different AS states. KEY POINTS: Reduction in the aortic valve area, flow across the aortic valve, and direction of the aortic stenosis jet determine the pressure gradient generated across the aortic valve in patients with aortic stenosis. Discordance between echo and catheterization maximum gradients is related to the inherent temporal differences between the times of their acquisition. Discordance between echo and catheterization mean gradients is related to pressure recovery and assumptions in the application of Bernoulli equation to estimate the aortic valve gradient. Pressure recovery relates to the ratio of the aortic valve area and ascending aortic diameter as well as the jet direction. Mismatch between area and gradient criteria for aortic stenosis severity may occur with or without concordance between echocardiographic and catheterization data. Errors of measurement should be excluded prior to assuming any mismatch or discordance between the data. Area gradient mismatch occurs when the aortic valve area is in the severe range, while the gradient is in the non-severe range as in low flow low gradient aortic stenosis. Reverse area gradient mismatch occurs when the gradient is in the severe range, while the aortic valve area is in the non-severe range as in congenital aortic stenosis with an eccentric jet.

Echocardiographic Follow-Up of Congenital Aortic Valvular Stenosis II

We evaluated the natural course of congenital aortic valvular stenosis (AVS) and factors affecting AVS progression during long-term follow-up with echocardiography. Medical records of 388 patients with AVS were reviewed; patients with concomitant lesions other than aortic regurgitation (AR) were excluded. Trivial AVS was defined as a transvalvular Doppler peak systolic instantaneous gradient of < 25 mmHg; mild stenosis, 25-49 mmHg; moderate stenosis, 50-75 mmHg; and severe stenosis, > 75 mmHg. Median age of the patients was 3 years (range 0 day to 21 years), and 287 (74%) were male. A total of 355 patients were followed with medical treatment alone for a median of 4.6 years (range 1 month to 20.6 years), and the degree of AVS increased in 75 (21%) patients. The risk of AVS progression was higher when AVS was diagnosed in neonates (OR 4.29, CI 1.81-10.18, p = 0.001) and infants (OR 3.79, CI 2.21-6.49, p = 0.001). After the infancy period, bicuspid valve morphology increased AVS progression risk (OR 2.4, CI 1.2-4.6, p = 0.034). Patients with moderate AVS were more likely to have AVS progression (OR 2.59, CI 1.3-5.1, p = 0.006). Bicuspid valve morphology increased risk of AR development/progression (OR 1.77, CI 1.1-2.7, p = 0.017). The patients with mild and moderate AVS were more likely to have AR development/progression (p = 0.001). The risk of AR development/progression was higher in patients with AVS progression (OR 2.25, CI 1.33-3.81, p = 0.002). Newborn babies and infants should be followed more frequently than older patients according to disease severity. Bicuspid aortic valve morphology and moderate stenosis are risk factors for the progression of AVS and AR.

Simplified Bernoulli's method significantly underestimates pulmonary transvalvular pressure drop

PURPOSE

To determine whether neglecting the flow unsteadiness in simplified Bernoulli's equation significantly affects the pulmonary transvalvular pressure drop estimation.

MATERIALS AND METHODS

3.0T magnetic resonance imaging (MRI) 4D velocity mapping was performed on four healthy volunteers, seven patients with repaired tetralogy of Fallot, and thirteen patients with transposition of the great arteries repaired by arterial switch. Pulmonary transvalvular pressure drop was estimated based on two methods: General Bernoulli's Equation (GBE), ie, the most complete form; and Simplified Bernoulli's Equation (SBE), known as 4V(2) . More than 2300 individual pressure drop measurements were used to compare the simplified and the general Bernoulli's methods. A linear mixed-effects model was employed for statistical analyses, fully accounting for clustering of observations among the methods and systolic phases.

RESULTS

The simplified Bernoulli's method systematically underestimated the pressure drop compared to general Bernoulli's method during the entire systolic phase (P < 0.05), including the peak systole, where on average ΔpSBE/ΔpGBE=78%.

CONCLUSION

The simplified Bernoulli method underestimated the pressure drop during all systolic phases in all the studied subjects. Therefore, it is necessary to take into account the flow unsteadiness for more accurate estimation of the pressure drop. J. Magn. Reson. Imaging 2016;43:1313-1319.

Comparison of invasive and non-invasive pressure gradients in aortic arch obstruction

BACKGROUND

Aortic arch obstruction can be evaluated by catheter peak-to-peak gradient or by Doppler peak instantaneous pressure gradient. Previous studies have shown moderate correlation in discrete coarctation, but few have assessed correlation in patients with more complex aortic reconstruction.

METHODS

We carried out retrospective comparison of cardiac catheterisations and pre- and post-catheterisation echocardiograms in 60 patients with native/recurrent coarctation or aortic reconstruction. Aortic arch obstruction was defined as peak-to-peak gradient ⩾25 mmHg in patients with native/recurrent coarctation and ⩾10 mmHg in aortic reconstruction.

RESULTS

Diastolic continuation of flow was not associated with aortic arch obstruction in either group. Doppler peak instantaneous pressure gradient, with and without the expanded Bernoulli equation, weakly correlated with peak-to-peak gradient even in patients with a normal cardiac index (r=0.36, p=0.016, and r=0.49, p=0.001, respectively). Receiver operating characteristic curve analysis identified an area under the curve of 0.61 for patients with all types of obstruction, with a cut-off point of 45 mmHg correctly classifying 64% of patients with arch obstruction (sensitivity 39%, specificity 89%). In patients with aortic arch reconstruction who had a cardiac index ⩾3 L/min/m², a cut-off point of 23 mmHg correctly classified 69% of patients (71% sensitivity, 50% specificity) with an area under the curve of 0.82.

CONCLUSION

The non-invasive assessment of aortic obstruction remains challenging. The greatest correlation of Doppler indices was noted in patients with aortic reconstruction and a normal cardiac index.

Clinical utility of Doppler echocardiography in assessing aortic stenosis severity and predicting need for intervention in children

The optimal echocardiographic methodology for predicting need for intervention in children with valvar aortic stenosis (VAS) is not known. We reviewed echocardiograms and catheterization reports of 79 children (aged 9.5 +/- 5.9 years) with isolated VAS. The maximum and mean Doppler-predicted gradients from the apical (MIGAP), MEGAP)) and the suprasternal or right parasternal (MIGHP), MEGHP)) windows were measured. The peak-to-peak catheterization gradient and the intervention (if any) were recorded. All sites and methods of Doppler estimation of VAS gradient correlated in a linear fashion with the invasive gradient (R2 = 0.34-0.50) and with one another (R2 = 0.48-0.86). MIGAP and MIGHP overestimated the invasive gradient in 60% and 86% of patients, whereas MEGAP and MEGHP underestimated the invasive gradient in 94% and 83% of patients, respectively. Age and diameter of the ascending aorta had small but significant effects on the level of agreement. A MIGHP < or = 55 mm Hg predicted no intervention with 100% accuracy, whereas the specificities of a MIGHP > 90 mm Hg, a MEGAP > 50 mm Hg, and a (MIGAP + MIGHP)/2 > 70 mm Hg for intervention were 94%, 100%, and 92%, respectively. The magnitude of overestimation was significantly lower from the apical window. In children with VAS, the best prediction of the catheterization gradient could be based on the average of MIGAP and MIGHP.

Echocardiographic follow-up of congenital aortic valvular stenosis

We investigated the morphology of the stenotic aortic valve, the progression of the stenosis, and the onset and progression of aortic regurgitation (AR) in patients with congenital aortic valvular stenosis (AVS). The medical records of 278 patients with AVS were reviewed, with the patients with concomitant lesions besides AR excluded. Very mild aortic stenosis was defined as a transvalvular Doppler peak systolic instantaneous gradient (PSIG) less than 25 mmHg, mild stenosis as 25-49 mmHg, moderate stenosis as 50-75 mmHg, and severe stenosis as more than 75 mmHg. The mean age of the patients was 4.9 +/- 4.3 years (range, 3 days to 15 years), and 203 (73%) were male. The number of the cusps was determined with two-dimensional echocardiography in 266 patients (95%): unicuspid in 3 patients (1%), bicuspid in 127 patients (48%), and tricuspid in 136 patients (51%). A total of 192 of all patients were followed for 2 months to 14.6 years (mean 4.2 +/- 3.3 years) with medical treatment alone. Among 72 patients with very mild stenosis at initial echocardiographic examination, 20% had mild, 3% moderate, and 1% severe stenosis after a mean period of 3.7 years. In 70 patients with mild stenosis at initial echocardiographic examination, 28% had moderate and 9% severe stenosis after a mean period of 5 years. Among 44 patients with moderate stenosis at initial echocardiographic examination, 36% had severe stenosis after a mean period of 3.7 years. Among 192 patients, 40% had AR (3% trivial, 28% mild, and 9% moderate) at initial echocardiographic examination. After a mean period of 4.2 years, 58% of the patients had AR (13 % trivial, 25% mild, 16% moderate, and 4% severe). There was not statistically significant difference between catheterization peak systolic gradients (47 +/- 16 mmHg) and Doppler estimated mean gradients (45 +/- 9 mmHg) (p = 0.53), whereas Doppler PSIGs (74.9 +/- 15.7 mmHg) were higher than catheterization peak systolic gradients (p < 0.0001) in 25 patients who were studied in the catheterization lab. Patients with very mild stenosis may be followed with a noninvasive approach every 1 or 2 years, and an annual follow-up is suggested for patients with mild stenosis. Nearly one-third of patients with moderate stenosis at initial echocardiographic examination had severe stenosis after a mean period of 3.7 years. Therefore, we recommend, that patients with moderate stenosis undergo noninvasive evaluation every 6 months. Doppler estimated mean gradient is very useful in predicting the need for intervention in children with AVS.

Pediatric Echocardiography

When evaluating congenital heart disease, echocardiography is a powerful diagnostic tool. The availability, mobility, diagnostic accuracy, and noninvasive nature of echocardiography provide distinct advantages over other diagnostic modalities such as cardiac catheterization. Pediatric echocardiography has distinct differences from echocardiography performed on adults. First, the scanning techniques employed are tailored to the smaller size and younger age of the pediatric age group. Second, the types of diseases for which echocardiography is employed are necessarily different and usually consist of complex congenital lesions.