Deep learning based classification of left ventricular function from two-dimensional echocardiographic images

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Philips Healthcare

Background. Echocardiographic quantification of left ventricular function (LVF) is mainly based on ejection fraction (EF) measurements, which relies on either manual or automated identification of endocardial boundaries followed by calculation of model-based end-systolic and end-diastolic LV volumes. Recent developments in artificial intelligence resulted in computer algorithms that allow fully automated detection of endocardial boundaries and measurement of LV volumes and EF. However, this methodology is prone to errors and inter-measurement variability. We hypothesized that a fully automated deep learning algorithm could be developed, which would accurately classify LVF while avoiding volume and EF measurements. This study was designed to test the accuracy of this approach.

Methods. Deep learning algorithm was developed (Philips Research) based on convolutional neural network (CNN) that uses as input dynamic sequences of apical 2- and 4-chamber echocardiographic views obtained without ultrasound enhancing agents. We used for CNN development a database of clinical DICOM studies: a training set of 14,427 studies with normal LV function and 6,135 abnormal, and a validation set of 2,898 normal and 1,081 abnormal studies, based on Philips IntelliSpace Cardiovascular (ISCV) codes found (defined by cardiologists) in the patients’ reports. The CNN was trained to automatically classify LVF into 3 categories: (1) normal, (2) mildly-to-moderately or moderately reduced, and (3) moderately-to-severely or severely reduced. In the validation set, the automated classifications were compared to those in the patients’ reports as a reference standard. Accuracy of the automated classification was tested using contingency tables, from which sensitivity, specificity, and negative and positive predictive values (NPV, PPV) and overall accuracy were calculated for each category of LVF. Additionally, the area under ROC curve (AUC) was calculated to assess the diagnostic accuracy of the automated classification for each LVF category.

Results.  Automated classification of LVF showed high levels of diagnostic accuracy in identifying cases with LVF in all 3 categories, reflected by high AUC values: (1) 0.94, (2) 0.87 and (3) 0.97 (Figure), and overall accuracy of 0.84 (Table). 

Conclusions. Deep learning algorithm based on CNN allowed accurate automated classification of LVF, when tested on ∼4,000 clinical studies and compared to ISCV codes found in the patients’ reports. This novel fully-automated methodology may become a useful aid in the interpretation of echocardiographic images by providing the reader with a preliminary assessment of LVF. Abstract Figure.

Intracardiac device associated interference with tricuspid valve apparatus on echocardiography: What can we learn from pathology?

Funding Acknowledgements

Type of funding sources: None.

Background

 New or worsening tricuspid regurgitation (TR) is associated with right-sided heart failure and worsened outcomes. Cardiac Implantable Electronic Devices (CIEDs), which are being implanted at growing rates worldwide, are increasingly being recognized as associated with TR occurrence related to interference with the tricuspid valve (TV) apparatus. Purpose: We sought to identify echocardiographic features in the right ventricle and TV that differentiate patients who have anatomically demonstrated interference with the TV on direct pathology inspection. 

Methods

 Explanted hearts from 44 consecutive patients undergoing orthotopic heart transplant (55 ±13 yrs, 68% men) with known implanted CIEDs were dissected to assess the presence (n = 18) or absence (n = 26) of CIED interference with the TV (Figure). Echocardiographic measurements performed prior to transplantation, including left and right ventricular (LV, RV) size and performance metrics as well as TR severity, were compared between both groups using non-parametric testing. 

Results

 Echocardiographic features of patients with and without anatomically demonstrated TV interference are shown in the Table. Although overall LV dimensions and volumes were not different between the two groups and LV ejection fraction was severely reduced in both groups, patients demonstrating CIED interference trended towards larger right atrial volumes (Table) and also larger RV and tricuspid annular sizes. Importantly, however, they were more than 4 times likely to have abnormal right ventricular function. Lastly, patients with tricuspid apparatus interference tended to have more significant TR, although these differences have not reached statistical significance (Table). 

Conclusion

 CIED interreference with tricuspid valve apparatus occurs frequently (41%) among patients with CIEDs, who undergo orthotopic heart transplantation. This may be associated with worsening TV function with subsequent changes in right atrial and ventricular geometry and function. In light of prior data showing poor outcomes with CIED associated TR, this study emphasizes the importance of non-invasive assessment of CIED interference with the tricuspid valve, in order to improve device placement and patient outcomes. Abstract Figure  Abstract Table

Performance of artificial intelligence system for prescriptive acquisition guidance of transthoracic echocardiography by novice users combined with automated quantification of ejection fraction

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Caption Health

Background

Artificial intelligence (AI) has the potential to expedite the acquisition of transthoracic echocardiograms (TTE) and provide automated quantitative data including left ventricular ejection fraction (LVEF).  Specifically, AI-based imaging systems may permit less experienced individuals to obtain quantitative measurements of LVEF, with important implications for clinical workflow. 

Purpose

We sought to evaluate the accuracy of an AI-based imaging system for the evaluation of LVEF in a spectrum of novice TTE imagers in a real-world clinical setting, and hypothesized that after appropriate training, it can perform as well as experienced sonographers. 

Methods

Consecutive exams (N = 102; BMI 29 ± 7; most common indications for TTE: heart failure, arrhythmia, valve assessment) were performed by a cohort of physician trainees (MD) and nurses (RN) with no prior TTE experience, using an AI-guided imaging system equipped with real-time prescriptive guidance software that automatically measures LVEF. Guided imaging included 3 views: parasternal long-axis (PLAX), apical 4-and apical 2-chamber (AP4, AP2), with the software recognizing when a satisfactory imaging window is obtained and then auto-capturing and automatically generating an AI based LVEF. AI-EF measurements were compared against the reference standard EF (Ref EF) measured by 2 expert sonographers according to ASE chamber quantification guidelines. Bland-Altman analysis was performed to determine inter-technique agreement.

Results

Feasibility was 80%. AI-EF and Ref EF demonstrated strong correlation when all 3 views were obtained, with a small bias (Table). In cases when <3 views were available, the combination of PLAX and AP4 views achieved comparable results, with a slight increase in bias and limits of agreement. When results were stratified by cohort (MD vs RN), MD AI-EF attempts showed greater feasibility (100%, n = 51) with stronger correlation (r = 0.93) and smaller bias (-1.9%) compared to RN (feasibility of 61%; n = 31 and r= 0.85, bias -2.1%). 

Conclusions

Use of an AI-assisted imaging system for limited TTE imaging by novices is feasible in a real-world setting, with the AI based EF in good agreement with reference standard. Acquisition of all 3 views provided optimal results, but the combination of AP4/PLAX views performed reasonably well, without the AP2 view that is more difficult to acquire for less skilled users. Untrained MD were more successful when compared to RN, suggesting additional training may be needed for specific user groups. Abstract Figure.

Normal Values of Left Ventricular Size and Function on 3D Echocardiography: Results of the World Alliance of Societies of Echocardiography Study

BACKGROUND

Echocardiography remains the most widely used modality to assess left ventricular (LV) chamber size and function. Currently this assessment is most frequently performed using 2D echocardiography (2DE). Yet, 3D echocardiography (3DE) has been shown to be more accurate and reproducible than 2DE. Current normative reference values for 3D LV analysis are predominantly based on data from North America and Europe. The World Alliance of Societies of Echocardiography (WASE) study was a designed to sample normal subjects from around the world to provide more universal global reference ranges. In this study we sought to assess the world-wide feasibility of LV 3DE and report on size and function measurements.

METHODS

2262 healthy subjects were prospectively enrolled from 19 centers in 15 countries. 3D LV full-volume datasets were obtained and analyzed offline with vendor-neutral software. Measurements included end-diastolic and end-systolic volumes (EDV, ESV), ejection fraction (EF), global longitudinal and circumferential strain (GLS and GCS). Results were categorized by age (18-40, 41-65 and >65 years), sex and race.

RESULTS

1589 subjects (feasibility 70%) had adequate LV datasets for analysis. Mean normal values for indexed EDV, ESV and EF in men and women were 70 ± 15 and 65 ± 12 mL, 28 ± 7 and 25 ± 6 mL and 60 ± 5, 62 ± 5% respectively. Men had larger LV volumes and lower EF than women. GLS and GCS were higher in magnitude in women. In both sexes, LV volumes were lower and EF tended to be higher with increasing age, especially considering the differences between the youngest and oldest age groups. While GLS was similar across age groups in men, in women, the youngest and middle-age cohorts revealed higher magnitudes of GLS when compared to the oldest age group. GCS was higher in magnitude at older age in both men and women. Finally, Asians had smaller chamber sizes and higher EF and absolute strain values than both blacks and whites.

CONCLUSIONS

Age, sex, and race should be considered when defining normal reference values for LV dimension and function parameters obtained by 3DE.

Ventricular Changes in Patients with Acute COVID-19 Infection: Follow-Up of The World Alliance Societies of Echocardiography (WASE-COVID) Study

Background

COVID-19 infection is known to cause a wide array of clinical chronic sequelae, but little is known regarding the long-term cardiac complications. We aim to report echocardiographic follow-up findings and describe the changes in left (LV) and right ventricular (RV) function that occur following acute infection.

Methods

Patients enrolled in the World Alliance Societies of Echocardiography-COVID study with acute COVID-19 infection were asked to return for a follow-up transthoracic echocardiogram. Overall, 198 returned at a mean of 129 days of follow-up, of which 153 had paired baseline and follow-up images that were analyzable, including LV volumes, ejection fraction (LVEF), and longitudinal strain (LVLS). Right-sided echocardiographic parameters included RV global longitudinal strain, RV free wall strain, and RV basal diameter. Paired echocardiographic parameters at baseline and follow-up were compared for the entire cohort and for subgroups based on the baseline LV and RV function.

Results

For the entire cohort, echocardiographic markers of LV and RV function at follow-up were not significantly different from baseline (all P > .05). Patients with hyperdynamic LVEF at baseline (>70%), had a significant reduction of LVEF at follow-up (74.3% ± 3.1% vs 64.4% ± 8.1%, P < .001), while patients with reduced LVEF at baseline (<50%) had a significant increase (42.5% ± 5.9% vs 49.3% ± 13.4%, P = .02), and those with normal LVEF had no change. Patients with normal LVLS (<−18%) at baseline had a significant reduction of LVLS at follow-up (−21.6% ± 2.6% vs −20.3% ± 4.0%, P = .006), while patients with impaired LVLS at baseline had a significant improvement at follow-up (−14.5% ± 2.9% vs −16.7% ± 5.2%, P < .001). Patients with abnormal RV global longitudinal strain (>−20%) at baseline had significant improvement at follow-up (−15.2% ± 3.4% vs −17.4% ± 4.9%, P = .004). Patients with abnormal RV basal diameter (>4.5 cm) at baseline had significant improvement at follow-up (4.9 ± 0.7 cm vs 4.6 ± 0.6 cm, P = .019).

Conclusions

Overall, there were no significant changes over time in the LV and RV function of patients recovering from COVID-19 infection. However, differences were observed according to baseline LV and RV function, which may reflect recovery from the acute myocardial injury occurring in the acutely ill. Left ventricular and RV function tends to improve in those with impaired baseline function, while it tends to decrease in those with hyperdynamic LV or normal RV function.

Feasibility and Accuracy of the Automated Software for Dynamic Quantification of Left Ventricular and Atrial Volumes and Function in a Large Unselected Population

We aimed to evaluate the feasibility and accuracy of machine learning-based automated dynamic quantification of left ventricular (LV) and left atrial (LA) volumes in an unselected population. We enrolled 600 unselected patients (12% in atrial fibrillation) clinically referred for transthoracic echocardiography (2DTTE), who also underwent 3D echocardiography (3DE) imaging. LV ejection fraction (EF), LV, and LA volumes were obtained from 2D images; 3D images were analyzed using dynamic heart model (DHM) software (Philips) resulting in LV and LA volume–time curves. A subgroup of 140 patients also underwent cardiac magnetic resonance (CMR) imaging. Average time of analysis, feasibility, and image quality were recorded, and results were compared between 2DTTE, DHM, and CMR. The use of DHM was feasible in 522/600 cases (87%). When feasible, the boundary position was considered accurate in 335/522 patients (64%), while major (n = 38) or minor (n = 149) border corrections were needed. The overall time required for DHM datasets was approximately 40 seconds. As expected, DHM LV volumes were larger than 2D ones (end-diastolic volume: 173 ± 64 vs. 142 ± 58 mL, respectively), while no differences were found for LV EF and LA volumes (EF: 55% ± 12 vs. 56% ± 14; LA volume 89 ± 36 vs. 89 ± 38 mL, respectively). The comparison between DHM and CMR values showed a high correlation for LV volumes (r = 0.70 and r = 0.82, p < 0.001 for end-diastolic and end-systolic volume, respectively) and an excellent correlation for EF (r = 0.82, p < 0.001) and LA volumes. The DHM software is feasible, accurate, and quick in a large series of unselected patients, including those with suboptimal 2D images or in atrial fibrillation.

Impact of physiological pacing on functional mitral regurgitation in systolic dysfunction: Initial echocardiographic remodeling findings after His bundle pacing

Background

Although His bundle pacing (HBP) has been shown to improve left ventricular ejection fraction (LVEF), its impact on mitral regurgitation (MR) remains uncertain.

Objectives

The aim of this study was to evaluate change in functional MR after HBP in patients with left ventricular (LV) systolic dysfunction.

Methods

Paired echocardiograms were retrospectively assessed in patients with reduced LVEF (<50%) undergoing HBP for pacing or resynchronization. The primary outcomes assessed were change in MR, LVEF, LV volumes, and valve geometry pre- and post-HBP. MR reduction was characterized as a decline in ≥1 MR grade post-HBP in patients with ≥grade 3 MR at baseline.

Results

Thirty patients were analyzed: age 68 ± 15 years, 73% male, LVEF 32% ± 10%, 38% coronary artery disease, 33% history of atrial fibrillation. Baseline QRS was 162 ± 31 ms: 33% left bundle branch block, 37% right bundle branch block, 17% paced, and 13% narrow QRS. Significant reductions in LV end-systolic volume (122 mL [73–152 mL] to 89 mL [71–122 mL], P = .006) and increase in LV ejection fraction (31% [25%–37%] to 39% [30%–49%], P < .001) were observed after HBP. Ten patients had grade 3 or 4 MR at baseline, with reduction in MR observed in 7. In patients with at least grade 3 MR at baseline, reduction in LV volumes, improved mitral valve geometry, and greater LV contractility were associated with MR reduction. Greater reduction in paced QRS width was present in MR responders compared to non-MR responders (-40% vs -25%, P = .04).

Conclusions

In this initial detailed echocardiographic analysis in patients with LV systolic dysfunction, HBP reduced functional MR through favorable ventricular remodeling.

Utility of transillumination and transparency renderings in 3D transthoracic imaging

Transillumination (TI) is a new 3D rendering tool that uses a freely movable virtual light source to enhance depth, contours, and image detail. The TI model was recently modified to allow the operator adjust the degree of transparency of both cardiac and extra-cardiac structures. While the addition of transparency was shown to significantly improve quality in 3D transesophageal imaging, this has not yet been shown for transthoracic (TTE) imaging. We prospectively studied 35 patients who underwent clinically indicated TTE with standard 3D acquisition, as well as TI with and without transparency. Six experienced echocardiographers were shown images of all three display types in random order. Each image was scored independently using a Likert Scale while assessing each of the following aspects: ability to identify anatomy or pathology, depth perception, degree of anatomic detail, and border delineation. All experts perceived an incremental value of the transparency mode, compared to TI without transparency and standard 3D rendering, in terms of ability to identify anatomy or pathology (4.15 ± 0.97 vs. 3.88 ± 0.99 vs. 2.52 ± 1.41, p < 0.01), depth perception (4.33 ± 0.78 vs. 3.88 ± 0.82 vs. 2.29 ± 1.07, p < 0.01), degree of anatomic detail (4.08 ± 1.0 vs. 3.89 ± 0.79 vs. 2.31 ± 1.08, p < 0.01), and border delineation (4.44 ± 0.80 vs. 3.90 ± 0.78 vs. 2.42 ± 1.13, p < 0.01). Compared to standard 3D and TI renderings of TTE images, the addition of transparency significantly improves both image quality and diagnostic confidence.

Normal Values of Left Atrial Size and Function and the Impact of Age: Results of the World Alliance Societies of Echocardiography Study

BACKGROUND

Left atrial (LA) evaluation includes volumetric and functional parameters with an abundance of diagnostic and prognostic implications. Solid normal reference ranges are compulsory for accurate interpretation in individual patients, but previous studies have yielded mixed conclusions regarding the effects of age, sex, and/or race. The present report from the World Alliance Societies of Echocardiography study focuses on two-dimensional (2D) and three-dimensional (3D) measures of LA structure and function, with subgroup analysis by age, sex, and race.

METHODS

Transthoracic 2D and 3D echocardiographic images were obtained in 1,765 healthy individuals (901 men, 864 women) evenly distributed among age subgroups: 18 to 40 years (n = 745), 41 to 65 years (n = 618), and >65 years (n = 402); the racial distribution was 38.4% white, 39.9% Asian, and 9.7% black. Images were analyzed using dedicated LA analysis software to measure LA volumes and phasic function from 3D volume and 2D strain curves.

RESULTS

Three-dimensional maximum and minimum LA volumes adjusted for body surface area were nearly identical for men and women, but women demonstrated higher 3D total and passive emptying fractions (EFs). Two-dimensional reservoir strain was similar for both sexes. Age was associated with an incremental rise in LA volumes alongside characteristic shifts in functional indices. Total 2D EF and reservoir and conduit strain varied inversely with age, counteracted by higher booster strain, with a greater magnitude of effect in women. Active 3D EF was significantly higher, while total and passive EFs decreased with age. Interracial differences were noted in LA volumes, without substantial differences in functional indices.

CONCLUSION

Although similar normal values for LA volumes and strain can be applied to both sexes, meaningful differences in LA size occur with aging. Indices of function also shift with age, with a compensatory rise in booster function, which may serve to counteract observed lower total and passive EFs. Defining age-associated normal values may help differentiate age-associated "healthy" LA aging from pathologic processes.

Right atrial volume is a major determinant of tricuspid annulus area in functional tricuspid regurgitation: a three-dimensional echocardiographic study

AIMS

The aim of this study is to explore the relationships of tricuspid annulus area (TAA) with right atrial maximal volume (RAVmax) and right ventricular end-diastolic volume (RVEDV) in healthy subjects and patients with functional tricuspid regurgitation (FTR) of different aetiologies and severities.

METHODS AND RESULTS

We enrolled 280 patients (median age 66 years, 59% women) with FTR due to left heart disease (LHD), pulmonary hypertension (PH), corrected tetralogy of Fallot (TOF), chronic atrial fibrillation (AF), and 210 healthy volunteers (45 years, 53% women). We measured TAA at mid-systole and end-diastole, tenting volume of tricuspid leaflets, RAVmax, and RVEDV by 3D echocardiography. Irrespective of TA measurement timing, TAA correlated more closely with RAVmax than with RVEDV in both controls and FTR patients. On multivariable analysis, RAVmax was the most important determinant of TAA, accounting for 41% (normals) and 56% (FTR) of TAA variance. In FTR patients, age, RVEDV, and left ventricular ejection fraction were also independently correlated with TAA. RAVmax (AUC = 0.81) and TAA (AUC = 0.78) had a greater ability than RVEDV (AUC = 0.72) to predict severe FTR (P < 0.05). Among FTR patients, those with AF had the largest RAVmax and smallest RVEDV. RAVmax and TA were significantly dilated in all FTR groups, except in TOF. PH and TOF had largest RVEDV, yet tenting volume was increased only in PH and LHD.

CONCLUSION

RA volume is a major determinant of TAA, and RA enlargement is an important mechanism of TA dilation in FTR irrespective of cardiac rhythm and RV loading conditions.

Two-Dimensional Echocardiographic Right Ventricular Size and Systolic Function Measurements Stratified by Sex, Age, and Ethnicity: Results of the World Alliance of Societies of Echocardiography Study

BACKGROUND

Echocardiographic assessment of right ventricular (RV) systolic function is an important component of clinical decision making. Although professional societies have worked to define normal ranges of RV size and function, their guidelines have not included the impacts of age, sex, and ethnicity on these parameters, as they have for the left ventricle. The World Alliance of Societies of Echocardiography study was designed to investigate the effects of age, sex, and ethnicity on all cardiac chambers. The aim of this study was to explore whether these differences exist for RV systolic parameters.

METHODS

Adequate two-dimensional RV-focused views for the measurement of systolic parameters, including fractional area change and global and free wall longitudinal strain, were available in 1,913 subjects (mean age, 47 ± 17 years; 51% men). Basal and mid-RV dimensions, length, tricuspid annular peak systolic excursion, tissue Doppler S' velocity, and myocardial performance index were also measured. Subjects were grouped by age (<40, 41-65, and >65 years), with results also stratified by sex and ethnicity (Asian, black, or white) and analyzed using vendor-independent software. Differences among groups were evaluated using analysis of variance.

RESULTS

Women had smaller absolute and indexed RV areas and absolute RV dimensions and higher magnitudes of fractional area change, free wall strain, and global longitudinal strain compared to men. With respect to age, most of the statistically significant differences were noted between the <40- and >65-year age groups, with RV areas and lengths smaller in older age groups and RV functional parameters (S', fractional area change, tricuspid annular plane systolic excursion, global longitudinal strain, free wall strain, and myocardial performance index) showing minimal decreases or no changes with age. Although there were no meaningful differences in functional parameters among ethnic groups, RV size was smallest in Asians.

CONCLUSIONS

These findings suggest that although two-dimensional RV parameters are age and sex dependent, association with race is less apparent, excepting that the Asian population appears to have smaller chamber sizes compared with whites and blacks.

Biventricular Pacing Versus Right Ventricular Pacing in Patients Supported With LVAD

OBJECTIVES

This study sought to evaluate the effects of right ventricular (RV) pacing versus biventricular (BiV) pacing on quality of life, functional status, and arrhythmias in LVAD patients.

BACKGROUND

Cardiac resynchronization therapy (CRT) and left ventricular assist devices (LVADs) independently improve outcomes in heart failure patients, but the effects of combining these therapies remains unknown. We present the first prospective randomized study evaluating the effects of RV versus BiV pacing on quality of life, functional status, and arrhythmias in LVAD patients.

METHODS

In this prospective randomized crossover study, LVAD patients with prior CRT devices were alternated on RV and BiV pacing for planned 7-14-day periods. Ambulatory step count, 6-minute walk test distance, Kansas City Cardiomyopathy Questionnaire scores, arrhythmia burden, CRT lead function, and echocardiographic data were collected with each pacing mode.

RESULTS

Thirty patients were enrolled, with a median age of 65 years, 67% male, and mean duration of LVAD support of 309 days. Compared with BiV pacing, RV-only pacing resulted in 29% higher mean daily step count, 11% higher 6-minute walk test distance, and 7% improved KCCQ-12 score (all p < 0.03). LV end-diastolic volume was significantly lower with RV pacing (220 vs. 250 mL; p = 0.03). Fewer patients had ventricular tachyarrhythmia episodes during RV pacing (p = 0.03). RV lead impedance was lower with RV pacing (p = 0.047), but no significant differences were observed in impedance across other CRT leads.

CONCLUSIONS

In the first prospective randomized study comparing variable pacing in LVAD patients, RV pacing was associated with significantly improved functional status, quality of life, fewer ventricular tachyarrhythmias, and stable lead impedance compared with BiV pacing. This study supports turning off LV lead pacing in LVAD patients with CRT.

Progression of aortic stenosis and echocardiographic criteria for its severity

AIMS

Guidelines-recommended criteria for identifying severe aortic stenosis (AS) are based on small, homogenous cohorts of patients, leading to potentially inconsistent or missed diagnosis. We used a large cohort of patients with varying degrees of AS to (i) characterize its progression; (ii) evaluate the influence of demographic and echocardiographic variables; and (iii) derive haemodynamically consistent cut-off values.

METHODS AND RESULTS

We identified 916 patients with mild to severe AS who had undergone >1 echocardiographic study (N = 2547). For each study, aortic valve area (AVA), peak transaortic velocity (Vmax), and mean pressure gradient (ΔP) were extracted. Annual rates of AVA change were determined by a linear mixed-effects model. To determine the prevalence of inconsistent diagnosis of severe AS, AVA was plotted against ΔP and Vmax, with quadrants defined using guidelines-recommended cut-offs. The rate of AVA change was -0.070 ± 0.003 cm2/year and was more rapid in men than women and in Whites than African Americans. AVA = 1 cm2 corresponded to ΔP = 32 mmHg and Vmax = 3.7 m/s, causing discrepancies in defining severe AS in 480 (19%) and 458 (18%) studies, respectively. Conversely, ΔP = 40 mmHg corresponded to AVA = 0.89 cm2 and Vmax = 4.0 m/s corresponded to AVA = 0.92 cm2, confirming the inconsistency of the guidelines. Notably, discrepancy rate was higher in 206 patients with low flow (SVi < 35 mL/m2): 40% vs. 16% in the remaining patients.

CONCLUSION

Our findings demonstrated gender- and race-related differences in AS progression and underscored the need to refine the multiparametric criteria for diagnosis of severe AS to minimize internal inconsistencies, which are high with the current cut-offs and amplified in patients with low stroke volumes.

Correlation between non-invasive myocardial work indices and main parameters of systolic and diastolic function: results from the EACVI NORRE study

AIMS

The present study sought to evaluate the correlation between indices of non-invasive myocardial work (MW) and left ventricle (LV) size, traditional and advanced parameters of LV systolic and diastolic function by 2D echocardiography (2DE).

METHODS AND RESULTS

A total of 226 (85 men, mean age: 45 ± 13 years) healthy subjects were enrolled at 22 collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study. Global work index (GWI), global constructive work (GCW), global work waste (GWW), and global work efficiency (GWE) were estimated from LV pressure-strain loops using custom software. Peak LV pressure was estimated non-invasively from brachial artery cuff pressure. LV size, parameters of systolic and diastolic function and ventricular-arterial coupling were measured by echocardiography. As advanced indices of myocardial performance, global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) were obtained. On multivariable analysis, GWI was significantly correlated with GLS (standardized beta-coefficient = -0.23, P < 0.001), ejection fraction (EF) (standardized beta-coefficient = 0.15, P = 0.02), systolic blood pressure (SBP) (standardized beta-coefficient = 0.56, P < 0.001) and GRS (standardized beta-coefficient = 0.19, P = 0.004), while GCW was correlated with GLS (standardized beta-coefficient = -0.55, P < 0.001), SBP (standardized beta-coefficient = 0.71, P < 0.001), GRS (standardized beta-coefficient = 0.11, P = 0.02), and GCS (standardized beta-coefficient = -0.10, P = 0.01). GWE was directly correlated with EF and inversely correlated with Tei index (standardized beta-coefficient = 0.18, P = 0.009 and standardized beta-coefficient = -0.20, P = 0.004, respectively), the opposite occurred for GWW (standardized beta-coefficient =--0.14, P = 0.03 and standardized beta-coefficient = 0.17, P = 0.01, respectively).

CONCLUSION

The non-invasive MW indices show a good correlation with traditional 2DE parameters of myocardial systolic function and myocardial strain.

Echocardiographic predictors of new-onset atrial arrhythmias in patients undergoing hematopoietic stem cell transplantation

BACKGROUND

Atrial arrhythmias following hematopoietic stem cell transplantation (HSCT) have been associated with increased length of stay, need for intensive care, and increased mortality within one-year post-transplant. We sought to identify echocardiographic parameters that may predict the development of new atrial arrhythmias post-HSCT.

METHODS

We performed a retrospective chart review of 753 consecutive patients who underwent HSCT at the University of Chicago from January 2015 through December 2019. Patients with baseline echocardiogram within 6 months prior to transplantation were included. Those with prior transplants, history of atrial arrhythmias, or unavailable echocardiographic images were excluded, resulting in 187 patients included for final analysis. Baseline clinical and demographic variables, as well as echocardiographic parameters, were compared between patients who developed new atrial arrhythmias post-HSCT versus those who did not.

RESULTS

Of the 187 patients included for analysis, 25 (13%) developed new atrial arrhythmias, with 13 of these occurring within 30 days of transplantation. Despite no significant difference in left atrial (LA) end-systolic volume between those with and without new arrhythmia following HSCT (OR 1.04; 95% CI 0.91-1.09, p = 0.233), univariable analysis demonstrated that patients who developed atrial arrhythmias had reduced LA function, as reflected by lower LA emptying fraction (OR 0.94; 95% CI 0.91-0.98, p = 0.003) and lower LA reservoir strain (OR 0.95; 95% CI 0.92-0.99, p = 0.009).

CONCLUSIONS

Echocardiographic indices of LA function, namely LA emptying fraction and LA reservoir strain, can identify patients at risk for developing new atrial arrhythmias post-HSCT, prior to the development of morphologic changes in the LA.

Deep Learning-Based Automated Echocardiographic Quantification of Left Ventricular Ejection Fraction: A Point-of-Care Solution

BACKGROUND

We have recently tested an automated machine-learning algorithm that quantifies left ventricular (LV) ejection fraction (EF) from guidelines-recommended apical views. However, in the point-of-care (POC) setting, apical 2-chamber views are often difficult to obtain, limiting the usefulness of this approach. Since most POC physicians often rely on visual assessment of apical 4-chamber and parasternal long-axis views, our algorithm was adapted to use either one of these 3 views or any combination. This study aimed to (1) test the accuracy of these automated estimates; (2) determine whether they could be used to accurately classify LV function.

METHODS

Reference EF was obtained using conventional biplane measurements by experienced echocardiographers. In protocol 1, we used echocardiographic images from 166 clinical examinations. Both automated and reference EF values were used to categorize LV function as hyperdynamic (EF>73%), normal (53%-73%), mildly-to-moderately (30%-52%), or severely reduced (<30%). Additionally, LV function was visually estimated for each view by 10 experienced physicians. Accuracy of the detection of reduced LV function (EF<53%) by the automated classification and physicians' interpretation was assessed against the reference classification. In protocol 2, we tested the new machine-learning algorithm in the POC setting on images acquired by nurses using a portable imaging system.

RESULTS

Protocol 1: the agreement with the reference EF values was good (intraclass correlation, 0.86-0.95), with biases <2%. Machine-learning classification of LV function showed similar accuracy to that by physicians in most views, with only 10% to 15% cases where it was less accurate. Protocol 2: the agreement with the reference values was excellent (intraclass correlation=0.84) with a minimal bias of 2.5±6.4%.

CONCLUSIONS

The new machine-learning algorithm allows accurate automated evaluation of LV function from echocardiographic views commonly used in the POC setting. This approach will enable more POC personnel to accurately assess LV function.

Utility of a Deep-Learning Algorithm to Guide Novices to Acquire Echocardiograms for Limited Diagnostic Use

Importance

Artificial intelligence (AI) has been applied to analysis of medical imaging in recent years, but AI to guide the acquisition of ultrasonography images is a novel area of investigation. A novel deep-learning (DL) algorithm, trained on more than 5 million examples of the outcome of ultrasonographic probe movement on image quality, can provide real-time prescriptive guidance for novice operators to obtain limited diagnostic transthoracic echocardiographic images.

Objective

To test whether novice users could obtain 10-view transthoracic echocardiographic studies of diagnostic quality using this DL-based software.

Design, Setting, and Participants

This prospective, multicenter diagnostic study was conducted in 2 academic hospitals. A cohort of 8 nurses who had not previously conducted echocardiograms was recruited and trained with AI. Each nurse scanned 30 patients aged at least 18 years who were scheduled to undergo a clinically indicated echocardiogram at Northwestern Memorial Hospital or Minneapolis Heart Institute between March and May 2019. These scans were compared with those of sonographers using the same echocardiographic hardware but without AI guidance.

Interventions

Each patient underwent paired limited echocardiograms: one from a nurse without prior echocardiography experience using the DL algorithm and the other from a sonographer without the DL algorithm. Five level 3-trained echocardiographers independently and blindly evaluated each acquisition.

Main Outcomes and Measures

Four primary end points were sequentially assessed: qualitative judgement about left ventricular size and function, right ventricular size, and the presence of a pericardial effusion. Secondary end points included 6 other clinical parameters and comparison of scans by nurses vs sonographers.

Results

A total of 240 patients (mean [SD] age, 61 [16] years old; 139 men [57.9%]; 79 [32.9%] with body mass indexes >30) completed the study. Eight nurses each scanned 30 patients using the DL algorithm, producing studies judged to be of diagnostic quality for left ventricular size, function, and pericardial effusion in 237 of 240 cases (98.8%) and right ventricular size in 222 of 240 cases (92.5%). For the secondary end points, nurse and sonographer scans were not significantly different for most parameters.

Conclusions and Relevance

This DL algorithm allows novices without experience in ultrasonography to obtain diagnostic transthoracic echocardiographic studies for evaluation of left ventricular size and function, right ventricular size, and presence of a nontrivial pericardial effusion, expanding the reach of echocardiography to clinical settings in which immediate interrogation of anatomy and cardiac function is needed and settings with limited resources.

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.

Echocardiographic Correlates of In-Hospital Death in Patients with Acute COVID-19 Infection: The World Alliance Societies of Echocardiography (WASE-COVID) Study

Background

The novel severe acute respiratory syndrome coronavirus-2 virus, which has led to the global coronavirus disease-2019 (COVID-19) pandemic is known to adversely affect the cardiovascular system through multiple mechanisms. In this international, multicenter study conducted by the World Alliance Societies of Echocardiography, we aim to determine the clinical and echocardiographic phenotype of acute cardiac disease in COVID-19 patients, to explore phenotypic differences in different geographic regions across the world, and to identify parameters associated with in-hospital mortality.

Methods

We studied 870 patients with acute COVID-19 infection from 13 medical centers in four world regions (Asia, Europe, United States, Latin America) who had undergone transthoracic echocardiograms. Clinical and laboratory data were collected, including patient outcomes. Anonymized echocardiograms were analyzed with automated, machine learning–derived algorithms to calculate left ventricular (LV) volumes, ejection fraction, and LV longitudinal strain (LS). Right-sided echocardiographic parameters that were measured included right ventricular (RV) LS, RV free-wall strain (FWS), and RV basal diameter. Multivariate regression analysis was performed to identify clinical and echocardiographic parameters associated with in-hospital mortality.

Results

Significant regional differences were noted in terms of patient comorbidities, severity of illness, clinical biomarkers, and LV and RV echocardiographic metrics. Overall in-hospital mortality was 21.6%. Parameters associated with mortality in a multivariate analysis were age (odds ratio [OR] = 1.12 [1.05, 1.22], P = .003), previous lung disease (OR = 7.32 [1.56, 42.2], P = .015), LVLS (OR = 1.18 [1.05, 1.36], P = .012), lactic dehydrogenase (OR = 6.17 [1.74, 28.7], P = .009), and RVFWS (OR = 1.14 [1.04, 1.26], P = .007).

Conclusions

Left ventricular dysfunction is noted in approximately 20% and RV dysfunction in approximately 30% of patients with acute COVID-19 illness and portend a poor prognosis. Age at presentation, previous lung disease, lactic dehydrogenase, LVLS, and RVFWS were independently associated with in-hospital mortality. Regional differences in cardiac phenotype highlight the significant differences in patient acuity as well as echocardiographic utilization in different parts of the world.