Demonstration of left ventricular outflow tract eccentricity by 64-slice multi-detector CT

Quantification of left ventricular ejection fraction and cardiac output using a novel semi-automated echocardiographic method: a prospective observational study in coronary artery bypass patients

BACKGROUND

Echocardiographic quantification of ejection fraction (EF) by manual endocardial tracing requires training, is time-consuming and potentially user-dependent, whereas determination of cardiac output by pulmonary artery catheterization (PAC) is invasive and carries a risk of complications. Recently, a novel software for semi-automated EF and CO assessment (AutoEF) using transthoracic echocardiography (TTE) has been introduced. We hypothesized that AutoEF would provide EF values different from those obtained by the modified Simpson's method in transoesophageal echocardiography (TOE) and that AutoEF CO measurements would not agree with those obtained via VTI_LVOT in TOE and by thermodilution using PAC.

METHODS

In 167 patients undergoing coronary artery bypass graft surgery (CABG), TTE cine loops of apical 4- and 2-chamber views were recorded after anaesthesia induction under steady-state conditions. Subsequently, TOE was performed following a standardized protocol, and CO was determined by thermodilution. EF and CO were assessed by TTE AutoEF as well as TOE, using the modified Simpson's method, and Doppler measurements via velocity time integral in the LV outflow tract (VTI_LVOT). We determined Pearson's correlation coefficients r and carried out Bland-Altman analyses. The primary endpoints were differences in EF and CO. The secondary endpoints were differences in left ventricular volumes at end diastole (LVEDV) and end systole (LVESV).

RESULTS

AutoEF and the modified Simpson's method in TOE showed moderate EF correlation (r = 0.38, p < 0.01) with a bias of -12.6% (95% limits of agreement (95%LOA): -36.6 - 11.3%). AutoEF CO correlated poorly both with VTI_LVOT in TOE (r = 0.19, p < 0.01) and thermodilution (r = 0.28, p < 0.01). The CO bias between AutoEF and VTI_LVOT was 1.33 l min^-1 (95%LOA: -1.72 - 4.38 l min^-1) and 1.39 l min^-1 (95%LOA -1.34 - 4.12 l min^-1) between AutoEF and thermodilution, respectively. AutoEF yielded both significantly lower EF (EF_AutoEF: 42.0% (IQR 29.0 - 55.0%) vs. EF_{TOE Simpson}: 55.2% (IQR 40.1 - 70.3%), p < 0.01) and CO values than the reference methods (CO_{AutoEF biplane}: 2.30 l min^-1 (IQR 1.30 - 3.30 l min^-1) vs. CO_{VTI LVOT}: 3.64 l min^-1 (IQR 2.05 - 5.23 l min^-1) and CO_PAC: 3.90 l min^-1 (IQR 2.30 - 5.50 l min^-1), p < 0.01)).

CONCLUSIONS

AutoEF correlated moderately with TOE EF determined by the modified Simpson's method but poorly both with VTI_LVOT and thermodilution CO. A systematic bias was detected overestimating LV volumes and underestimating both EF and CO compared to the reference methods.

TRIAL REGISTRATION

German Register for Clinical Trials (DRKS-ID DRKS00010666, date of registration: 08/07/2016).

Two wrongs sometimes do make a right: errors in aortic valve stenosis assessment by same-day Doppler echocardiography and 4D flow MRI

This study aims to systematically verify if the simplified geometry and flow profile of the left ventricular outflow tract (LVOT) assumed in 2D echocardiography is appropriate while examining the utility of 4D flow MRI to assess valvular disease. This prospective study obtained same-day Doppler echocardiography and 4D flow MRI in 37 healthy volunteers (age: 51.9 ± 18.2, 20 females) and 7 aortic stenosis (AS) patients (age: 64.2 ± 9.6, 1 female). Two critical assumptions made in echocardiography for aortic valve area assessment were examined, i.e. the assumption of (1) a circular LVOT shape and (2) a flat velocity profile through the LVOT. 3D velocity and shape information obtained with 4D flow MRI was used as comparison. It was found that the LVOT area was lower (by 26.5% and 24.5%) and the velocity time integral (VTI) was higher (by 28.5% and 30.2%) with echo in the healthy and AS group, respectively. These competing errors largely cancelled out when examining individual and cohort averaged LVOT stroke volume. The LVOT area, VTI and stroke volume measured by echo and 4D flow MRI were 3.6 ± 0.7 vs. 4.9 ± 1.0 cm2 (p < 0.001), 21.2 ± 3.0 vs 15.2 ± 2.8 cm (p < 0.001), and 75.6 ± 15.6 vs 72.8 ± 14.1 ml (p = 0.3376), respectively. In the ensemble average of LVOT area and VTI, under- and over-estimation seem to compensate each other to result in a 'realistic' stroke volume. However, it is important to understand that this compensation may fail. 4D flow MRI provides a unique insight into this phenomenon.

Normal Values of Cardiac Output and Stroke Volume According to Measurement Technique, Age, Sex, and Ethnicity: Results of the World Alliance of Societies of Echocardiography Study

BACKGROUND

Assessment of cardiac output (CO) and stroke volume (SV) is essential to understand cardiac function and hemodynamics. These parameters can be examined using three echocardiographic techniques (pulsed-wave Doppler, two-dimensional [2D], and three-dimensional [3D]). Whether these methods can be used interchangeably is unclear. The influence of age, sex, and ethnicity on CO and SV has also not been examined in depth. In this report from the World Alliance of Societies of Echocardiography Normal Values Study, the authors compare CO and SV in healthy adults according to age, sex, ethnicity, and measurement techniques.

METHODS

A total of 1,450 adult subjects (53% men) free of heart, lung, and kidney disease were prospectively enrolled in 15 countries, with even distributions among age groups and sex. Subjects were divided into three age groups (young, 18-40 years; middle aged, 41-65 years; and old, >65 years) and three main racial groups (whites, blacks, and Asians). CO and SV were indexed (cardiac index [CI] and SV index [SVI], respectively) to body surface area and height and measured using three echocardiographic methods: Doppler, 2D, and 3D. Images were analyzed at two core laboratories (one each for 2D and 3D).

RESULTS

CI and SVI were significantly lower by 2D compared with both Doppler and 3D methods in both sexes. SVI was significantly lower in women than men by all three methods, while CI differed only by 2D. SVI decreased with aging by all three techniques, whereas CI declined only with 2D and 3D. CO and SV were smallest in Asians and largest in whites, and the differences persisted after normalization for body surface area.

CONCLUSIONS

The present results provide normal reference values for CO and SV, which differ by age, sex, and race. Furthermore, CI and SVI measurements by the different echocardiographic techniques are not interchangeable. All these factors need to be taken into account when evaluating cardiac function and hemodynamics in individual patients.

Comparison of the effective orifice area of prosthetic mitral valves using two-dimensional versus three-dimensional transesophageal echocardiography

Objective

This study compared the continuity equation-based effective orifice area (EOA) of prosthetic mitral valves between two-dimensional (2D) and 3D transesophageal echocardiography (TEE).

Methods

Thirty-four patients without major aortic valve abnormalities underwent mitral valve replacement surgery. The EOAs of prosthetic mitral valves were calculated using the continuity equation with 2D and 3D TEE. For 18/34 patients using a biological valve prosthesis, the EOA of the prosthesis was obtained from commercial records.

Results

The EOA of prosthetic mitral valves significantly varied between the 2D and 3D methods (2.22 ± 0.71 vs 2.35 ± 0.70 cm², n = 34). The area of the diameter of the left ventricular outflow tract as determined by the 3D method was significantly higher than that by the 2D method (mean difference: −0.14 ± 0.20 cm²), with 95% coherence boundaries of −0.53 and 0.25 cm². The regression equation for the EOA by 3D and 2D TEE was y = 0.27 + 0.94x, with a good correlation.

Conclusions

The EOA of prosthetic mitral valves is underestimated using the 2D TEE method compared with the 3D TEE method. The 3D-TEE method has the advantage of higher precision over the 2D TEE method, and it may be helpful for better assessment of prosthetic mitral valves intraoperatively.

Association between multimodality measures of aortic stenosis severity and quality-of-life improvement outcomes after transcatheter aortic valve replacement

AIMS

Up to 40% of patients with aortic stenosis (AS) present with discordant grading of AS severity based on common transthoracic echocardiography (TTE) measures. Our aim was to evaluate the utility of TTE and multi-detector computed tomography (MDCT) measures in predicting symptomatic improvement in patients with AS undergoing transcatheter aortic valve replacement (TAVR).

METHODS AND RESULTS

A retrospective review of 201 TAVR patients from January 2017 to November 2018 was performed. Pre- and post-intervention quality-of-life was measured using the Kansas City Cardiomyopathy Questionnaire (KCCQ-12). Pre-intervention measures including dimensionless index (DI), stroke volume index (SVI), mean transaortic gradient, peak transaortic velocity, indexed aortic valve area (AVA), aortic valve calcium score, and AVA based on hybrid MDCT-Doppler calculations were obtained and correlated with change in KCCQ-12 at 30-day follow-up. Among the 201 patients studied, median KCCQ-12 improved from 54.2 pre-intervention to 85.9 post-intervention. In multivariable analysis, patients with a mean gradient >40 mmHg experienced significantly greater improvement in KCCQ-12 at follow-up than those with mean gradient ≤40 mmHg (28.1 vs. 16.4, P = 0.015). Patients with MDCT-Doppler-calculated AVA of ≤1.2 cm2 had greater improvements in KCCQ-12 scores than those with computed tomography-measured AVA of >1.2 cm2 (23.4 vs. 14.1, P = 0.049) on univariate but not multivariable analysis. No association was detected between DI, SVI, peak velocity, calcium score, or AVA index and change in KCCQ-12.

CONCLUSION

Mean transaortic gradient is predictive of improvement in quality-of-life after TAVR. This measure of AS severity may warrant greater relative consideration when selecting the appropriateness of patients for TAVR.

Assessment of left ventricular outflow tract and aortic root: comparison of 2D and 3D transthoracic echocardiography with multidetector computed tomography

AIMS

Accurate echocardiographic assessment of left ventricular outflow tract (LVOT) and the aortic root is necessary for risk stratification and choice of appropriate treatment in patients with pathologies of the aortic valve and aortic root. Conventional 2D transthoracic echocardiographic (TTE) assessment is based on the assumption of a circular shaped LVOT and aortic root, although previous studies have indicated a more ellipsoid shape. 3D TTE and multidetector computed tomography (MDCT) applies planimetry and are not dependent on geometrical assumptions. The aim was to test accuracy, feasibility, and reproducibility of 3D TTE compared to 2D TTE assessment of LVOT and aortic root areas, with MDCT as reference.

METHODS AND RESULTS

We examined 51 patients with 2D/3D TTE and MDCT at the same day. All patients were re-examined with 2D/3D TTE on a different day to evaluate 2D and 3D re-test variability. Areas of LVOT, aortic annulus, and sinus were assessed using 2D, 3D TTE, and MDCT. Both 2D/3D TTE underestimated the areas compared to MDCT; however, 3D TTE areas were significantly closer to MDCT-areas. 2D vs. 3D mean MDCT-differences: LVOT 1.61 vs. 1.15 cm2, P = 0.019; aortic annulus 1.96 vs. 1.06 cm2, P < 0.001; aortic sinus 1.66 vs. 1.08 cm2, P = 0.015. Feasibility was 3D 76-79% and 2D 88-90%. LVOT and aortic annulus areas by 3D TTE had lowest variabilities; intraobserver coefficient of variation (CV) 9%, re-test variation CV 18-20%.

CONCLUSION

Estimation of LVOT and aortic root areas using 3D TTE is feasible, more precise and more accurate than 2D TTE.

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

Background

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

Methods

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

Results

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

Conclusions

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

Role of computed tomography in transcatheter aortic valve implantation and valve-in-valve implantation: complete review of preprocedural and postprocedural imaging

: Since 2002, transcatheter aortic valve implantation (TAVI) has revolutionized the treatment and prognosis of patients with aortic stenosis. A preprocedural assessment of the patient is vital for achieving optimal outcomes from the procedure. Retrospective ECG-gated cardiac computed tomography (CT) today it is the gold-standard imaging technique that provides three-dimensional images of the heart, thus allowing a rapid and complete evaluation of the morphology of the valve, ascending aorta, coronary arteries, peripheral access vessels, and prognostic factors, and also provides preprocedural coplanar fluoroscopic angle prediction to obtain complete assessment of the patient. The most relevant dimension in preprocedural planning of TAVI is the aortic annulus, which can determine the choice of prosthesis size. CT is also essential to identify patients with increased anatomical risk for coronary artery occlusion in Valve in Valve (ViV) procedures.Moreover, CT is very useful in the evaluation of late complications, such as leakage, thrombosis and displacements. At present, CT is the cornerstone imaging modality for the extensive and thorough work-up required for planning and performing each TAVI procedure, to achieve optimal outcomes. Both the CT procedure and analysis should be performed by trained and experienced personnel, with a radiological background and a deep understanding of the TAVI procedure, in close collaboration with the implantation team. An accurate pre-TAVI CT and post-processing for the evaluation of all the points recommended in this review allow a complete planning for the choice of the valve dimensions and type (balloon or self-expandable) and of the best percutaneous access.

Direct Planimetry of Left Ventricular Outflow Tract Area by Simultaneous Biplane Imaging: Challenging the Need for a Circular Assumption of the Left Ventricular Outflow Tract in the Assessment of Aortic Stenosis

BACKGROUND

Evaluation of aortic stenosis (AS) requires calculation of aortic valve area (AVA), which relies on the assumption of a circular-shaped left ventricular outflow tract (LVOT). However, the LVOT is often elliptical, and the circular assumption underestimates the true LVOT area (LVOTA). Biplane imaging using transthoracic echocardiography allows direct planimetry of LVOTA. The aim of this study was to assess the feasibility of obtaining LVOTA using this technique and its impact on the discordance between AVA and gradient criteria in AS grading.

METHODS

We prospectively studied 134 patients (median age, 80 years; interquartile range, 73-87 years; 39% women) with AS, including 82 (61%) with severe AS and 52 (39%) with mild or moderate AS. LVOTA was traced using direct planimetry (LVOTA_biplane) and compared with LVOTA calculated using the circular assumption (LVOTA_circ). In a subset of patients who underwent cardiac computed tomography, direct planimetry of LVOTA was used as a reference standard.

RESULTS

LVOTA_biplane was significantly larger than LVOTA_circ (4.20 cm² [interquartile range, 3.66-4.90 cm²] vs 3.73 cm² [interquartile range, 3.14-4.15 cm²], P < .001). Among 30 patients who underwent cardiac computed tomography, LVOTA_biplane had better agreement with LVOTA by direct planimetry than LVOTA_circ (mean bias, -0.45 ± 0.63 vs -1.02 ± 0.63 cm²; P < .0001). Of 82 patients with severe AS (AVA ≤ 1 cm² using LVOTA_circ), 40 (49%) had discordant mean gradient (<40 mm Hg). By using LVOTA_biplane, patients with discordant AVA and mean gradient decreased from 49% to 27% (P = .004), and 29% of patients with severe AS were reclassified with moderate AS, with the highest percentage of reclassification in the group with low-gradient AS with preserved left ventricular ejection fraction.

CONCLUSIONS

Direct planimetry using biplane imaging avoids the inherent underestimation of LVOTA using the circular assumption. LVOTA obtained by biplane planimetry can lead to better concordance between AVA and mean gradient and classification of AS severity.

Hemodynamic and Imaging Assessment of Transcatheter Aortic Valve Replacement with the Inovare® Proseal using Multislice Computed Tomography

Objective

To evaluate the hemodynamic performance (i.e., gradients and paravalvular leakage [PVL]) of the new and experimental Braile Inovare^® Proseal. Additionally, we aimed to assess pre and postoperatively the aortic annulus and the transcatheter prosthesis using multislice computed tomography (MSCT).

Methods

Patients were selected by a multidisciplinary heart team and referred for transcatheter aortic valve replacement (TAVR). MSCT was performed before and after surgery. Measurements of the aortic valve and prosthesis were conducted and correlated with the valve gradient and residual PVL.

Results

Twenty-one patients were selected for the protocol. Patients had a mean age of 79 years and 38% of them were of female sex. The mean EuroSCORE II value was 12.5%±10.8. Mean gradient was reduced from 45.8±11.04 mmHg to 5.59±2.61 mmHg and there were no instances of PVL worse than mild. There were no cases of coronary obstruction or procedural death. Circularity was present in all prostheses evaluated. Circularity indexes for the prostheses were: inflow 0.05±0.03, middle third 0.04±0.02, and outflow 0.04±0.02 (P=0.08). The mean distance between the prosthesis and the left and right coronary ostia were 14.8 mm±3.3 and 17.3 mm±3, respectively. Oversizing was appropriate with a mean of 22.14%±6%.

Conclusion

Braile Inovare^® Proseal transcatheter device has demonstrated low gradients with low rates of PVL. Oversizing by annular measurements was adequate. MSCT was adequate to evaluate device sizing and has demonstrated preserved expansibility and circularity in the evaluated cases.

Aortic valve area using computed tomography-derived correction factor to improve the validity of left ventricular outflow tract measurements

AIMS

Given the inherent inaccuracies stemming from the assumption that the left ventricular outflow tract (LVOT) is circular, this study aimed to improve the accuracy of transthoracic echocardiography (TTE)-based aortic valve area (AVA) calculation using continuity equation (CE) by introducing a correction factor (CF) derived from multidetector computed tomography angiography (MDCTA) images and validate it in aortic stenosis (AS) patients.

METHODS AND RESULTS

This retrospective study used MDCTA images of 400 patients for modeling and 403 TTE dataset for validation. Echocardiographic parasternal long-axis view was modeled using MDCTA, and LVOT diameter (D1) was measured. Direct planimetry of LVOT area was performed and subsequently converted into a theoretical circle. The assumed circle (D2) diameter was derived, and D2/D1 was calculated and termed as the CF. The CF was 1.13, and it improved the agreement between MDCTA- and TTE-derived LVOT areas and correlation between AVA and peak velocity, mean pressure gradient, and velocity ratio. In discordant subgroups of severe AS, the CF reclassified patients to moderate AS in 40% in the low flow (LF), low gradient (LG), and low ejection fraction (EF) group; 53% in the LF, LG, and normal EF group; and 68% in the LF, high gradient, and normal EF group.

CONCLUSIONS

CF of 1.13 derived from MDCTA improved the accuracy of TTE-derived LVOT area and AVA and improved correlation with hemodynamic variables in AS patients. Reclassification of AS patients using CF may have clinical applicability for patient selection for early intervention.

Outcome of Normal-Flow Low-Gradient Severe Aortic Stenosis With Preserved Left Ventricular Ejection Fraction: A Propensity-Matched Study

Background

Normal‐flow, low‐gradient severe aortic stenosis (NF‐LG‐SAS), defined by aortic valve area <1 cm², mean gradient <40 mm Hg, and indexed stroke volume >35 mL/m², is the most prevalent form of low‐gradient aortic stenosis (AS). However, the true severity of AS and the management of NF‐LG‐SAS are controversial. The aim of this study was to evaluate the outcome of patients with NF‐LG‐SAS compared with moderate AS (MAS) and with high‐gradient severe‐AS (HG‐SAS).

Methods and Results

A total of 154 patients with NF‐LG‐SAS, 366 with MAS (aortic valve area between 1.0 and 1.3 cm²), and 1055 with HG‐SAS were included. On multivariate analysis, after adjustment for covariates of prognostic importance, NF‐LG‐SAS patients did not exhibit an excess risk of mortality compared with MAS patients under medical management (hazard ratio=1.13 [95% CI, 0.82‐1.56]; P=0.45) and under medical and surgical management (hazard ratio 1.06 [95% CI, 0.79‐1.43]; P=0.70), even after further adjustment for aortic valve replacement (hazard ratio=1.09 [95% CI, 0.81‐1.48]; P=0.56). The 6‐year cumulative incidence of aortic valve replacement (performed in accordance with guidelines) was comparable between the 2 groups (39±4% for NF‐LG‐SAS and 35±3% for MAS, P=0.10). After propensity score matching (n=226), NF‐LG‐SAS and MAS patients also had comparable outcomes under medical (P=0.41) and under medical and surgical management (P=0.52). NF‐LG‐SAS had better outcomes than HG‐SAS patients (adjusted hazard ratio 1.84 [95% CI, 1.18‐2.88]; P<0.001).

Conclusions

This study shows that patients with NF‐LG‐SAS have a comparable outcome to those with MAS when aortic valve replacement is performed during follow‐up according to guidelines, mostly at the stage of HG‐SAS. Rigorous echocardiographic assessment to rule out measurement errors and close follow‐up are essential to detect progression to true severe AS in NF‐LG‐SAS.

Reliability of three-dimensional color flow Doppler and two-dimensional pulse wave Doppler transthoracic echocardiography for estimating cardiac output after cardiac surgery

BACKGROUND

Three-dimensional color flow Doppler (3DCF) is a new convenient technique for cardiac output (CO) measurement. However, to date, no one has evaluated the accuracy of 3DCF echocardiography for CO measurement after cardiac surgery. Therefore, this single-center, prospective study was designed to evaluate the reliability of three-dimensional color flow and two-dimensional pulse wave Doppler (2D-PWD) transthoracic echocardiography for estimating cardiac output after cardiac surgery.

METHODS

Post-cardiac surgical patients with a good acoustic window and a low dose or no dose of vasoactive drugs (norepinephrine < 0.05 μg/kg/min) were enrolled for CO estimation. Three different methods (third generation FloTrac/Vigileo™ [FT/V] system as the reference method, 3DCF, and 2D-PWD) were used to estimate CO before and after interventions (baseline, after volume expansion, and after a dobutamine test).

RESULTS

A total of 20 patients were enrolled in this study, and 59 pairs of CO measurements were collected (one pair was not included because of increasing drainage after the dobutamine test). Pearson's coefficients were 0.260 between the CO-FT/V and CO-PWD measurements and 0.729 between the CO-FT/V and CO-3DCF measurements. Bland-Altman analysis showed the bias between the absolute values of CO-FT/V and CO-PWD measurements was - 0.6 L/min with limits of agreement between - 3.3 L/min and 2.2 L/min, with a percentage error (PE) of 61.3%. The bias between CO-FT/V and CO-3DCF was - 0.14 L/min with limits of agreement between - 1.42 L /min and 1.14 L/min, with a PE of 29.9%. Four-quadrant plot analysis showed the concordance rate between ΔCO-PWD and ΔCO-3FT/V was 93.3%.

CONCLUSIONS

In a comparison with the FT/V system, 3DCF transthoracic echocardiography could accurately estimate CO in post-cardiac surgical patients, and the two methods could be considered interchangeable. Although 2D-PWD echocardiography was not as accurate as the 3D technique, its ability to track directional changes was reliable.

Clinical utility of intraprocedural three-dimensional integrated image guided transcatheter aortic valve implantation using novel automated computed tomography software: A single-center preliminary experience

OBJECTIVES

Novel automated computed tomography (CT) software (Valve ASSIST 2) has been developed for transcatheter aortic valve implantation (TAVI), which not only provides three-dimensional (3D) reconstruction of multidetector (MD) CT images, but also enables intraprocedural real-time fusion of fluoroscopic and MDCT images. We aimed to clarify the reproducibility and accuracy of this software in the aortic annulus assessment and verify the potential of intraprocedural integrated MDCT imaging for TAVI.

METHODS AND RESULTS

We examined 50 patients with severe aortic stenosis undergoing transfemoral TAVI. Aortic annulus measurements were performed using 3mensio and the novel planning software. For intraprocedural imaging, preoperative CT dataset was overlaid onto fluoroscopy with the fusion software. The two images were aligned using the aortic root anatomy visible on both modalities. Novel planning software provided excellent reproducibility for the measurement of aortic annulus area (intraobserver intraclass correlation coefficients [ICC] 0.959, interobserver ICC 0.941), and perimeter (intraobserver ICC 0.915, interobserver ICC 0.912). Excellent correlation was found between novel planning software and 3mensio (ICC 0.952 for aortic annulus area, and 0.923 for perimeter). Intraprocedural fusion image of CT aortography and fluoroscopic aortic root aortography generated by this novel software identified coronary orifices and the distribution of aortic valve calcification during the device positioning. Fusion image displayed coronary orifices after device implantation.

CONCLUSIONS

Novel planning software showed excellent reproducibility and accuracy in the assessment of aortic root anatomy. Furthermore, the integrated 3D fusion image might have a potential as an intraprocedural imaging modality to contribute to the development of a safer TAVI procedure.

Validation of "left ventricular early inflow-outflow index": A novel echocardiographic method for quantification of mitral regurgitation in an Indian population with special focus on rheumatic etiology

BACKGROUND

Quantification of mitral regurgitation (MR) has always required an "integrated approach" as there is no single gold-standard method. We investigated a new Doppler-derived parameter "left ventricular early inflow-outflow index (LVEIO)" for the quantification of MR and its likelihood to predict severe MR in correlation with already established parameters in an Indian population including a large subset of patients with rheumatic etiology.

METHODS

A prospective study was performed at a major tertiary care center in western India over a 5-month period. Five hundred patients diagnosed with isolated MR including 260 (52%) patients with rheumatic etiology were included in the study after applying exclusion criteria. We analyzed MR using color flow jet, effective regurgitant orifice area (EROA), and vena contracta (VC) width. LVEIO is a simplification of the regurgitant volume (RV) method, which was calculated as "E velocity divided by LV outflow velocity integrated over the systolic ejection period left ventricular outflow tract velocity time integral" and compared with the established parameters.

RESULTS

LVEIO was 4.65 ± 1.45, 6.56 ± 1.52, and 9.91 ± 3.70 among patients diagnosed with mild, moderate, and severe MR, respectively (p < 0.001). Those with LVEIO ≥8 were the most likely to have severe MR (positive likelihood ratio: 10.42). LVEIO had specificity of 93.25% for diagnosis of severe MR with positive predictive value of 86.36%. There was positive correlation observed between LVEIO and VC width (r = 0.591), RV (r = 0.410), and EROA (r = 0.778) (all p < 0.001) in the Pearson correlation test. The specificity of LVEIO remained consistent in diagnosing severe MR in patients with rheumatic etiology.

CONCLUSION

LVEIO is a simple yet specific Doppler echocardiographic parameter for estimation of severity of MR including that of rheumatic etiology.

Geometry of the left ventricular outflow tract assessed by 3D TEE in patients with aortic stenosis: impact of upper septal hypertrophy on measurements of Doppler-derived left ventricular stroke volume

BACKGROUND

It is unclear how upper septal hypertrophy (USH) affects Doppler-derived left ventricular stroke volume (SV) in patients with AS. The aims of this study were to: (1) validate the accuracy of 3D transesophageal echocardiography (TEE) measurements of the left ventricular outflow tract (LVOT), (2) evaluate the differences in LVOT geometry between AS patients with and without USH, and (3) assess the impact of USH on measurement of SV.

METHODS

In protocol 1, both 3D TEE and multi-detector computed tomography were performed in 20 patients with AS [aortic valve area (AVA) ≤ 1.5 cm²]. Multiplanar reconstruction was used to measure the LVOT short and long diameters in four parts from the tip of the septum to the annulus. In protocol 2, the same 3D TEE measurements were performed in AS patients (AVA ≤ 1.5 cm², n = 129) and controls (n = 30). We also performed 2D and 3D transthoracic echocardiography in all patients.

RESULTS

In protocol 1, excellent correlations of LVOT parameters were found between the two modalities. In protocol 2, the USH group had smaller LVOT short and long diameters than the non-USH group. Although no differences in mean pressure gradient, or SV calculated with the 3D method existed between the two groups, the USH group had greater SV calculated with the Doppler method (73 ± 15 vs. 66 ± 15 ml) and aortic valve area (0.89 ± 0.26 vs. 0.73 ± 0.24 cm²) than the non-USH group.

CONCLUSIONS

3D TEE can provide a precise assessment of the LVOT in AS. USH affects the LVOT geometry in patients with AS, which might lead to inaccurate assessments of disease severity.

Resolving Apparent Inconsistencies Between Area, Flow, and Gradient Measurements in Patients With Aortic Valve Stenosis and Preserved Left Ventricular Ejection Fraction

Inconsistencies between area (aortic valve area [AVA])-flow-gradient are common during the echocardiographic assessment of aortic stenosis (AS). This study was conducted to investigate the importance of these inconsistencies and the impact of 3 methods to resolve these inconsistencies. The study population consisted of 327 patients (age: 76.3 ± 8.6 years, 49.5% males) with severe AS (SAS) (AVA ≤ 1 cm²) and preserved left ventricular ejection fraction (≥50%). Inconsistent findings between AVA, flow, and mean gradient (MG) were observed in 78 (23.9%) patients with low flow and a high MG, 52 (15.9%) patients with normal flow and a low MG, and 37 (11.3%) patients with a low flow and a low MG. Using stroke volume index by catheterization for AVA recalculation showed the greatest effect to resolve inconsistencies in the low flow and a high MG group (85%). Decreasing the AVA cut-off values for SAS to ≤0.8 cm² resulted in a shift from SAS to moderate AS in 36 patients (69%) in the normal flow and a low MG. Indexing AVA to body surface area had only a minor impact on reclassification. In conclusion, in patients with SAS and preserved left ventricular ejection fraction, the majority of area-flow-gradient inconsistencies at echocardiography can be resolved by correcting errors in stroke volume index measurements by alternative techniques and by redefining the cut-off value for SAS to ≤0.8 cm².

Anatomic estimation of aortic stenosis severity vs "fusion" of data from computed tomography and Doppler echocardiography

AIM

Two-dimensional, transthoracic echocardiography does not account for the noncircular anatomy of the left ventricular outflow tract (LVOT) and may therefore underestimate LVOT area. Fusion of computed tomography (CT)-derived LVOT area and Doppler-derived flow data has been proposed to improve assessment of aortic valve area (AVA) and classification of aortic stenosis severity. For hemodynamic reasons, effective AVA has to be smaller than anatomic AVA. The aim of the study was to test the "fusion approach" by comparing effective CT-derived AVA with anatomic AVA from CT planimetry.

METHODS AND RESULTS

Data of 244 consecutive patients (mean age 81 ± 5 years, 61% female) with aortic stenosis were retrospectively analyzed comparing effective AVA (calculated from the continuity equation using CT-LVOT and transthoracic Doppler measurements) with anatomic AVA based on CT planimetry. Substituting the LVOT area from transthoracic echocardiography (TTE) by the CT-LVOT resulted in an increase in AVA from 0.74 ± 0.15 to 0.92 ± 0.18cm² (P < .01), which was larger than anatomic AVA (0.82 ± 0.15cm²). Similar results were obtained based on planimetry from transesophageal echocardiography (TEE; AVA 0.79 ± 0.14cm², P < .01 vs CT-LVOT) and in the subgroup presenting with low-gradient severe aortic stenosis and preserved ejection fraction (n = 67, AVA from TTE 0.76 ± 0.09; from CT-LVOT 0.97 ± 0.14; CT planimetry 0.86 ± 0.12; TEE planimetry 0.82 ± 0.13cm²).

CONCLUSION

Fusion of CT-derived LVOT area with Doppler echocardiography results in a calculated effective AVA that is larger than the corresponding anatomic AVA. Therefore, adjustment of partition values may be warranted when using this approach.

The mystery of defining aortic valve area: what have we learnt from three-dimensional imaging modalities?

Aortic valve area is one of the main criteria used by echocardiography to determine the degree of valvular aortic stenosis, and it is calculated using the continuity equation which assumes that the flow volume of blood is equal at two points, the aortic valve area and the left ventricular outflow tract (LVOT). The main fallacy of this equation is the assumption that the LVOT area which is used to calculate the flow volume at the LVOT level is circular, where it is often an ellipse and sometimes irregular. The aim of this review is to explain the physiology of the continuity equation, the different sources of errors, the added benefits of using three-dimensional imaging modalities to measure LVOT area, the latest recommendations related to valvular aortic stenosis, and to introduce future perspectives. A literature review of studies comparing aortic valve area and LVOT area, after using three-dimensional data, has shown underestimation of both measurements when using the continuity equation. This has more impact on patients with discordant echocardiographic measurements when aortic valve area is disproportionate to haemodynamic measurements in assessing the degree of aortic stenosis. Although fusion imaging modalities of LVOT area can help in certain group of patients to address the issue of aortic valve area underestimation, further research on introducing a correction factor to the conventional continuity equation might be more rewarding, saving patients additional tests and potential radiation, with no clear evidence of cost-effectiveness.

Maximum Aortic Valve Opening Phase for Annulus Sizing in Pre-TAVR CTA

RATIONALE AND OBJECTIVES

The optimal phase for the measurement of the aortic annular area for transcatheter aortic valve replacement (TAVR) is not standardized, although most agree that systolic measurements are preferred, when the annulus is larger. We hypothesized that the maximum annular area occurs at the cardiac phase of the maximum aortic valve opening (MAVO) and that this phase can be accurately and reproducibly assessed by visual inspection only.

MATERIALS AND METHODS

The aortic valve opening area was inspected visually by two readers to determine the MAVO phase. The annular area was measured at the MAVO phase and the typical systolic phase (35% of the R-R interval). Differences in the annular area that would change valve sizing for prostheses were noted.

RESULTS

Fifty patients (mean age 81) were studied. Ninety percent had the MAVO at the 15%-25% R-R interval. There was high interobserver correlation (0.89) for determining the MAVO phase by visual inspection. For 49 out of 50 patients, the annular area was maximal at the MAVO phase. The mean difference in the annular area between the MAVO phase and 35% was 22.3 (±4.57) mm². In 12% of the patients, the difference in the annular area changed the recommended size of a self-expanding prosthesis and would have altered the procedure in 32% for balloon-expandable prostheses.

CONCLUSIONS

Visually assessed MAVO occurs in early systole for most patients and is almost always the cardiac phase of the maximal aortic annular area. This method allows rapid and reproducible determination of the appropriate phase for TAVR planning measurements. Consideration should be given to optimizing pre-TAVR computed tomography acquisitions for early systolic reconstruction and visual determination of the MAVO.

Modified continuity equation using left ventricular outflow tract three-dimensional imaging for aortic valve area estimation

PURPOSE

Aortic valve area (AVA) is usually estimated by the continuity equation (CE) in which the left ventricular outflow tract (LVOT) area is calculated assuming a circular shape. This study aimed to compare measurements of LVOT area using standard 2D transthoracic echocardiography (2DTTE), 3D transesophageal echocardiography (3DTEE), and multidetector computed tomography (MDCT) and assess their relative impact on AVA estimated by the CE.

METHODS AND RESULTS

We prospectively enrolled 60 patients with severe aortic stenosis (AS) referred for transcatheter aortic valve replacement (TAVR) who systematically underwent 2DTTE, 3DTEE, and MDCT. Mean LVOT areas obtained by 2DTTE (3.28±0.66 cm² ) and 3DTEE (3.95±0.90 cm² ) were significantly underestimated when compared to the mean MDCT LVOT area (4.31±0.99 cm² ). LVOT was rather elliptical than round, with a mean eccentricity index of 1.47 (ratio of maximum to minimum LVOT diameters) assessed by MDCT. Mean TTE AVA estimated by the CE was 0.62±0.20 cm² . Substitution of 2DTTE LVOT area by 3DTEE LVOT area in the CE resulted in AVA of 0.74±0.24 cm² , while using MDCT LVOT area held an AVA of 0.80±0.24 cm² . MDCT-derived AVA was similar to MDCT planimetric AVA and allowed 24% of patients to be reclassified from severe to moderate AS.

CONCLUSIONS

2DTTE and 3DTEE underestimate LVOT area when compared to MDCT with significant impact on AVA estimation. Assessment through MDCT fusion AVA may be of incremental value in patients with discrepant severity criteria for AS.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Left ventricular early inflow-outflow index: a novel echocardiographic indicator of mitral regurgitation severity

BACKGROUND

No gold standard currently exists for quantification of mitral regurgitation (MR) severity. Classification by echocardiography is based on integrative criteria using color and spectral Doppler and anatomic measurements. We hypothesized that a simple Doppler left ventricular early inflow-outflow index (LVEIO), based on flow velocity into the left ventricle (LV) in diastole and ejected from the LV in systole, would add incrementally to current diagnostic criteria. LVEIO was calculated by dividing the mitral E-wave velocity by the LV outflow velocity time integral.

METHODS AND RESULTS

Transthoracic echocardiography reports from Montefiore Medical Center and its referring clinics from July 1, 2011, to December 31, 2011 (n=11 235) were reviewed. The MR severity reported by a cardiologist certified by the National Board of Echocardiography was used as a reference standard. Studies reporting moderate or severe MR (n=550) were reanalyzed to measure effective regurgitant orifice area by the proximal isovelocity surface area method, vena contracta width, MR jet area, and left-sided chamber volumes. LVEIO was 9.3±3.9, 7.0±3.2, and 4.2±1.7 among those with severe, moderate, and insignificant MR, respectively (ANOVA P<0.001). By receiver operating characteristic analysis, area under the curve for LVEIO was 0.92 for severe MR. Those with LVEIO ≥8 were likely to have severe MR (likelihood ratio 26.5), whereas those with LVEIO ≤4 were unlikely to have severe MR (likelihood ratio 0.11). LVEIO performed better in those with normal LV ejection fraction (≥50%) compared with those with reduced LV ejection fraction (<50%) (area under the curve 0.92 versus 0.80, P<0.001). By multivariate logistic regression analysis, LVEIO was independently associated with severe MR when compared with vena contracta width, MR jet area, and effective regurgitant orifice area measured by the proximal isovelocity surface area method.

CONCLUSION

LVEIO is a simple-to-use echocardiographic parameter that accurately identifies severe MR, particularly in patients with normal LV ejection fraction.

Low gradient severe aortic stenosis with preserved ejection fraction: reclassification of severity by fusion of Doppler and computed tomographic data

AIMS

Low gradient severe aortic stenosis (AS) with preserved left ventricular ejection fraction (LVEF) may be attributed to aortic valve area index (AVAi) underestimation due to the assumption of a circular shape of the left ventricular outflow tract (LVOT) with 2-dimensional echocardiography. The current study evaluated whether fusing Doppler and multidetector computed tomography (MDCT) data to calculate AVAi results in significant reclassification of inconsistently graded severe AS.

METHODS AND RESULTS

In total, 191 patients with AVAi < 0.6 cm²/m² and LVEF ≥ 50% (mean age 80 ± 7 years, 48% male) were included in the current analysis. Patients were classified according to flow (stroke volume index <35 or ≥35 mL/m²) and gradient (mean transaortic pressure gradient ≤40 or >40 mmHg) into four groups: normal flow-high gradient (n = 72), low flow-high gradient (n = 31), normal flow-low gradient (n = 46), and low flow-low gradient (n = 42). Left ventricular outflow tract area was measured by planimetry on MDCT and combined with Doppler haemodynamics on continuity equation to obtain the fusion AVAi. The group of patients with normal flow-low gradient had significantly larger AVAi and LVOT area index compared with the other groups. Although MDCT-derived LVOT area index was comparable among the four groups, the fusion AVAi was significantly larger in the normal flow-low gradient group. By using the fusion AVAi, 52% (n = 24) of patients with normal flow-low gradient and 12% (n = 5) of patients with low flow-low gradient would have been reclassified into moderate AS due to AVAi ≥ 0.6 cm²/m².

CONCLUSION

The fusion AVAi reclassifies 52% of normal flow-low gradient and 12% of low flow-low gradient severe AS into true moderate AS, by providing true cross-sectional LVOT area.

Moderate Aortic Stenosis and Coronary Artery Bypass Grafting: Clinical Update for the Perioperative Echocardiographer

Incidental aortic stenosis in the setting of coronary artery bypass surgery may be a perioperative challenge. The accurate assessment of the degree of aortic stenosis remains an important determinant. Although severe aortic stenosis is an indication for valve replacement, current guidelines advise a balanced approach to the management of moderate aortic stenosis in this setting. Multiple factors should be considered in a team discussion to balance risks versus benefits for the various management options in the given patient. The rapid progress in aortic valve technologies also offer alternatives for definitive management of moderate aortic stenosis in this setting that will likely become even safer in the near future.

ECG-gated MDCT after aortic and mitral valve surgery

OBJECTIVE

The purpose of this article is to review the utility of ECG-gated MDCT in evaluating postsurgical findings in aortic and mitral valves. Normal and pathologic findings after aortic and mitral valve corrective surgery are shown in correlation with the findings of the traditionally used imaging modalities echocardiography and fluoroscopy to assist in accurate noninvasive anatomic and dynamic evaluation of postsurgical valvular abnormalities.

CONCLUSION

Because of its superior spatial and adequate temporal resolution, ECG-gated MDCT has emerged as a robust diagnostic tool in the evaluation and treatment of patients with postsurgical valvular abnormalities.

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.

Aortic valve and aortic root features in CT angiography in patients considered for aortic valve repair

BACKGROUND

The underlying mechanism of aortic regurgitation and aortic valve and root characteristics are associated with the durability of surgical repair.

OBJECTIVE

We investigated whether multidetector CT (MDCT) identifies the characteristics of the aortic valve and root that may be associated with the ability to perform successful surgical repair.

METHODS

Sixty-one patients with aortic regurgitation and/or aortic root pathology who were evaluated for aortic valve or root repair and underwent clinically indicated gated or nongated MDCT of the aortic valve and aortic root were included in the present analysis. Patients with endocarditis were excluded. MDCT data of aortic valve anatomy and calcification and thoracic aorta dimensions were analyzed.

RESULTS

The aortic valve and root was successfully repaired in 36 patients (55 ± 13 years; 61% male; median EuroSCORE II, 3.8%) whereas in 25 patients (56 ± 15 years; 52% male; median EuroSCORE II, 2.5%) repair was not attempted (n = 20) or valve repair was converted to aortic valve replacement during surgery (n = 5). In patients in whom repair was considered not possible or failed, there was a higher percentage of bicuspid aortic valves (48% vs 17%; P = .019), more severe commissural calcification, and more severe annular calcification.

CONCLUSION

The degree of commissural and annular calcification of the aortic valve determined by MDCT is inversely related to the ability to perform surgical valve repair instead of replacement. Similarly, bicuspid valve anatomy predicts failure to perform repair.