Artificial intelligence in the pediatric echocardiography laboratory: Automation, physiology, and outcomes

Artificial intelligence (AI) is frequently used in non-medical fields to assist with automation and decision-making. The potential for AI in pediatric cardiology, especially in the echocardiography laboratory, is very high. There are multiple tasks AI is designed to do that could improve the quality, interpretation, and clinical application of echocardiographic data at the level of the sonographer, echocardiographer, and clinician. In this state-of-the-art review, we highlight the pertinent literature on machine learning in echocardiography and discuss its applications in the pediatric echocardiography lab with a focus on automation of the pediatric echocardiogram and the use of echo data to better understand physiology and outcomes in pediatric cardiology. We also discuss next steps in utilizing AI in pediatric echocardiography.

Comprehensive evaluation of left ventricular deformation using speckle tracking echocardiography in normal children: comparison of three-dimensional and two-dimensional approaches

Background

Three-dimensional (3D) speckle tracking echocardiography (STE) can overcome some of the inherent limitations of two-dimensional (2D) STE; however, clinical experience is lacking. We aimed to assess and compare the feasibility, agreement, and reproducibility of left ventricular (LV) global longitudinal (GLS), and regional strain by 3D vs 2D STE in normal children.

Methods

Healthy pediatric subjects (n = 105, age mean = 11.2 ± 5.5 years) were prospectively enrolled. Three-dimensional and 2D LV GLS, as well as regional strain in 16 myocardial segments were quantified. Bland Altman analysis, intra- class correlation coefficients (ICC), percent error and linear regression were used for agreement and correlation between the two techniques. Analysis and acquisition times were compared. Inter- and intra-observer reproducibility was assessed in 20 studies.

Results

There was good to excellent agreement for 2D and 3D global longitudinal strain (ICC =0.82) and modest agreement for regional strain (ICC range 0.43–0.71). Both methods had high feasibility (88.6% for 2D vs 85.7% for 3D, p = 0.21), although 3D STE required significantly shorter acquisition and analysis time than 2D STE (acquisition time 1 ± 1.2 mins vs 2.4 ± 1 mins; p = 0.03, analysis time = 3.3 ± 1 mins vs 8.2 ± 2.5 mins; p = 0.001, respectively). Inter and intra-observer reproducibility was excellent for GLS by the two techniques (ICC = 0.78–0.93) but moderate to poor for regional strain (ICC = 0.21–0.64).

Conclusion

Three-dimensional global LV strain is as feasible and reproducible as 2D strain, with good agreement yet significantly more efficient acquisition and analysis. Regional strain is less concordant and 2D and 3D values should not be used interchangeably. 3D LV GLS may represent a viable alternative in evaluation of LV deformation in pediatric subjects.

1. Adequate feasibility of 3D STE in pediatrics; comparable to 2D STE.

2. Significantly shorter acquisition and analysis time for 3D GLS compared to 2D GLS.

3. Excellent agreement between 3D and 2D LV GLS and moderate to poor agreement between regional strain values.

4. Excellent inter and intra-observer reproducibility for GLS by the two techniques, and fair to poor reproducibility for regional strain (higher for apical than basal regions).

Left Ventricular Systolic Impairment after Pediatric Cardiac Surgery Assessed by STE Analysis

Background: Speckle-tracking echocardiography (STE) has gained increasing value in the evaluation of congenital heart diseases (CHD); however, its use in pediatric cardiac surgery is limited. Aim: To evaluate left ventricular (LV) systolic impairment after biventricular pediatric cardiac surgery by STE strain (ε) analysis. Methods: We prospectively enrolled 117 children undergoing cardiac surgery for CHD. Echocardiography was performed at four different times: pre-operatively, 12–36 h (Time 1), 3–5 days (Time 2), and 6–8 days (Time 3). Images were obtained in the 4-2-and 3 apical chamber’s views to derive LV global and regional (basal/mid/apical) ε values. Results: At different postoperative times, we performed 320 examinations in 117 children (mean age: 2.4 ± 3.9, range: 0–16 years); 117 age-matched healthy children served as controls. All global, basal, and mid LVε values decreased after surgery; the lowest values being at Time 1 (p < 0.0001), which increased thereafter. At discharge, all global, basal, and mid LVε values remained lower than in pre-operative and healthy children (p < 0.05). Instead, apical segments (lowest at baseline) increased after surgery (p < 0.0001) but remained lower compared to controls. LV ejection fraction (LVEF) decreased at Time 1 (p = 0.0004) but promptly recovered to Time 2 and normalized at Time 3. Conclusions: STE ε analysis revealed a significant LV systolic impairment after surgery with amelioration thereafter but incomplete normalization at discharge. Base-apex differences emerged with apical segments that, contrary to all the other regions, showed relative hypercontractility after surgery. The slower recovery of LVε values compared to LVEF suggests that STE ε analysis may be more accurate for the follow-up of mild LV post-surgical impairment.

Role of cardiac magnetic resonance strain analysis in patients with hypoplastic left heart syndrome in evaluating right ventricular (dys)function: a systematic review

OBJECTIVES

Right ventricular dysfunction predicts death in patients with hypoplastic left heart syndrome (HLHS), but differences in morphology and loading conditions make calculation of the ejection fraction (EF), a challenging measure of its function. Our goal was to evaluate how strain measurements with cardiac magnetic resonance feature tracking could be used to evaluate right ventricular function in patients with HLHS.

METHODS

A systematic search of the literature was performed by 2 independent researchers using the terms 'population', 'intervention', 'comparison', 'outcome' and 'time criteria'. PubMed and the Ovid database were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Our review included 8 studies with 608 participants with ventricular strain values obtained using cardiac magnetic resonance feature tracking. After stage I palliation, global strain was reduced in patients after a hybrid procedure and a right ventricle-to-pulmonary artery conduit compared with a modified Blalock-Taussig shunt despite similar EFs. Global longitudinal strain did not differ between stage II and stage III (Fontan) palliation. Fontan patients had significantly impaired global longitudinal and circumferential strain compared to the left ventricular strain of the controls. Studies of Fontan patients that included patients with HLHS who were part of a cohort with a single right ventricle showed impaired global circumferential strain compared with the cohort with a single left ventricle, with controls, and over time. In this group, impaired global circumferential strain was associated with major adverse cardiac events.

CONCLUSIONS

Cardiac magnetic resonance feature tracking can be used in patients with HLHS to evaluate RV strain and demonstrate differences between surgical strategies, over time and compared with controls. It could be used alongside clinical symptoms and EF values to detect ventricular dysfunction.

Echocardiography vs cardiac magnetic resonance imaging assessment of the systemic right ventricle for patients with d-transposition of the great arteries status post atrial switch

OBJECTIVE

Patients with Dextro-transposition of the great arteries status post atrial switch (dTGA s/p atrial switch) are "at-risk" for systemic right ventricular (RV) dysfunction. Due to complex RV geometry, echocardiography (Echo) does not allow accurate determination of ejection fraction (EF), but cardiac magnetic resonance imaging (CMR) allows quantitative right ventricular assessment. Measures of ventricular deformation may be precursors to global ventricular dysfunction. The primary aim of this study was to characterize imaging and clinical findings for adult patients with dTGA s/p atrial switch.

DESIGN

This was a retrospective cohort study of patients with dTGA s/p atrial switch operation (February 1966 to August 1988) with CMR performed at Children's Hospital of Wisconsin (from September 2005 to May 2015). Eligible patients had clinic visit, Echo, and exercise stress test within 1 year of CMR.

RESULTS

This study enrolled twenty-seven patients (16 males, 11 females) with dTGA s/p atrial switch (18 with Mustard operation and 9 with Senning operation; median age 30 years; 74% New York Heart Association class 1 and 26% class 2). Seventy-four percentage had normal RV systolic function (RV EF >45% by CMR). No correlation was observed between Echo strain data and clinical status (EF, exercise endurance, VO₂ max, or New York Heart Association class). Cardiac magnetic resonance imaging RV global circumferential strain GCS and RV EF had moderate negative correlation (r = -0.65, P < .001). Global circumferential strain was significantly different for those with RV EF above and below 45%, while global peak longitudinal strain (GLS) was not. Patients had reduced CMR myocardial strain values compared with healthy controls.

CONCLUSIONS

Reduced RV CMR GCS (for those with RV EF <45%) suggests that CMR evaluation may enhance early detection of detrimental changes in the systemic RV myocardium.

Emerging clinical applications of strain imaging and three-dimensional echocardiography for the assessment of ventricular function in adult congenital heart disease

Management of congenital heart disease (CHD) in adults (ACHD) remains an ongoing challenge due to the presence of residual hemodynamic lesions and development of ventricular dysfunction in a large number of patients. Echocardiographic imaging plays a central role in clinical decision-making and selection of patients who will benefit most from catheter interventions or cardiac surgery.. Recent advances in both strain imaging and three-dimensional (3D)-echocardiography have significantly contributed to a greater understanding of the complex pathophysiological mechanisms involved in CHD. The aim of this paper is to provide an overview of emerging clinical applications of speckle-tracking imaging and 3D-echocardiography in ACHD with focus on functional assessment, ventriculo-ventricular interdependency, mechanisms of electromechanical delay, and twist abnormalities in adults with tetralogy of Fallot (TOF), a systemic RV after atrial switch repair or in double discordance ventricles, and in those with a Fontan circulation.

Racial differences in myocardial deformation in obese children: Significance of inflammatory state

BACKGROUND AND AIMS

The association between racial differences in myocardial deformation and cardiometabolic risk factors is unknown in obese children. Our objective was to: 1) investigate for racial differences in myocardial deformation between white and black obese children and 2) identify biomarkers associated with these observed racial differences. We hypothesized that decreased myocardial deformation observed in black obese children could be accounted for by the differences in the markers of metabolic syndrome between the groups.

METHODS AND RESULTS

Obese children were recruited prospectively. All clinical and laboratory tests for the metabolic syndrome were conducted during a single assessment using a standardized protocol. Speckle-tracking echocardiography was performed to obtain longitudinal and circumferential measures of deformation. 310 patients were included in the analysis; 158 (51%) white and 152 (49%) black. The median age was 11.3 years (IQR 5.9). Blacks demonstrated worse longitudinal strain (-14.7 ± 2.7% vs. -15.4 ± 2.9%, p = 0.04). There was no difference in circumferential strain between the groups. Multivariable linear regression showed a significant relationship between longitudinal strain and hsCRP (β = 0.16, p = 0.03) and HOMA-IR (β = 0.15, p = 0.04); there was no independent association between longitudinal strain and race.

CONCLUSION

Black subjects demonstrated worse longitudinal strain than whites. Only hsCRP and HOMA-IR levels, not race, had an independent association with longitudinal strain, suggesting that the observed racial differences in longitudinal strain may be secondary to differences in inflammation and insulin resistance between the groups.

The Relationship Between Pre-operative Left Ventricular Longitudinal Strain and Post-operative Length of Stay in Patients Undergoing Arterial Switch Operation Is Age Dependent

INTRODUCTION

Post-operative length of stay (LOS) after the arterial switch operation (ASO) is variable. The association between pre-operative non-invasive measures of ventricular function and post-operative course has not been well established. The aims of this study were to (1) evaluate the relationship between pre-operative non-invasive measures of ventricular function and post-operative LOS and (2) evaluate the change in ventricular function after ASO.

METHODS

Data were reviewed in consecutive ASO patients between 2010 and 2016. The primary outcome was post-operative LOS. Echocardiograms obtained during the pre-operative period and at the time of discharge were retrospectively analyzed using speckle-tracking echocardiography. Pearson's correlation between patient-specific, pre-operative, and echocardiographic data versus post-operative LOS was assessed.

RESULTS

Fifty-two patients were included in analyses, 39 neonates and 13 infants. Left ventricular (LV) longitudinal strain correlated with post-operative LOS for infants age > 28 days (r = 0.62, p = 0.03), but not for neonates (r = 0.14, p = 0.40). Operative age (r = - 0.42, p = 0.003), weight at surgery (r = - 0.48, p ≤ 0.001), and cardiopulmonary bypass time (r = 0.30, p = 0.045) also correlated with post-operative LOS. Standard 2D measures of ventricular function did not correlate with post-operative LOS. LV ejection fraction and longitudinal strain worsened post-operatively.

CONCLUSION

Higher pre-operative LV longitudinal strain (representing worse LV function) is associated with increased post-operative LOS after ASO in infants > 28 days, but not in neonates. LV ejection fraction and longitudinal strain worsened after ASO. Future studies should assess the utility of performing STE in risk stratifying patients prior to ASO.

Changes in global strain of puborectalis muscle during pregnancy and postpartum

OBJECTIVE

One of the functional parameters that can be assessed by ultrasound is muscle strain, which represents the extent of deformation of the muscle from its original shape when forces are applied to the tissue under study. The aim of this study was to evaluate the effect of pregnancy and delivery on the puborectalis muscle, by assessing changes in global strain of the muscle during and after pregnancy.

METHODS

This was a secondary analysis of a prospective observational study on the association between stress urinary incontinence and levator ani muscle avulsion after delivery. Two-hundred and eighty nulliparous pregnant women underwent four-dimensional transperineal ultrasound assessments at 12 and 36  weeks of gestation, and 6 months postpartum. Tomographic ultrasound images were constructed and the puborectalis muscle was delineated by hand using programming software. After delineation, the length of the midline of the puborectalis muscle was measured at rest and during maximum pelvic floor muscle contraction, and global strain was expressed as percentile difference. Postpartum results were analyzed separately for vaginal, operative (vacuum) vaginal and Cesarean delivery. Differences in global strain of the puborectalis muscle according to mode of delivery were compared using a paired-sample t-test. The effect of partial or complete avulsion of the puborectalis muscle on postpartum strain was evaluated by ANOVA.

RESULTS

In total, 254 datasets were analyzed. Global strain of the puborectalis muscle did not change during pregnancy, but after spontaneous or operative vaginal delivery the global strain diminished significantly. No significant change was observed in strain of the puborectalis muscle after Cesarean delivery. Women who suffered complete bilateral avulsion had significantly lower strain compared with women with an intact puborectalis muscle.

CONCLUSION

Spontaneous or operative vacuum vaginal birth and complete bilateral avulsion of the puborectalis muscle influence negatively the strain of the puborectalis muscle. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Evaluation of myocardial deformation in patients with Kawasaki disease using speckle-tracking echocardiography during mid-term follow-up

Speckle-tracking echocardiography is a recently developed technique for the evaluation of myocardial deformation or strain. Our objective was to examine strain through a mid-term follow-up of patients with Kawasaki disease.

METHODS

We explored left ventricular mechanics using speckle-tracking echocardiography in 35 patients with a history of Kawasaki disease at least 6 months after the acute phase. We also included 30 healthy children as controls. Strain data sets were acquired for the quantification of left ventricular global strain, segmental strain, and left ventricular ejection fraction.

RESULTS

The mean age of our patients was 25.6±15.4 months. At a median follow-up of 57.5 months (16.5-98.2), although both values were in the normal range, the mean left ventricular ejection proportion of patients (57.3%) was a little lower than that of controls (p⩽0.05). Patient strain values at the basal inferoseptal (20.0), basal anterolateral (19.5), apical septal (23.3), and apical inferior (24.0) segments were lower compared with controls. In all, seven patients had coronary aneurysms during follow-up. Kawasaki disease patients with pyuria had lower left ventricular strain at the mid anterior, mid anteroseptal, apical anterior, and apical inferior segments and global longitudinal strain compared with patients with no pyuria (p⩽0.05).

CONCLUSION

In children with a history of Kawasaki disease, impairment of left ventricular mechanics occurs especially within the left anterior descending artery territories.

Speckle-Tracking Echocardiography Improves Pre-operative Risk Stratification Before the Total Cavopulmonary Connection

INTRODUCTION

Single-ventricle patients with elevated pulmonary vascular resistance (PVR) or end-diastolic pressure (EDP) are excluded from undergoing total cavopulmonary connection (TCPC). However, a subset of patients deemed to be at acceptable risk experience prolonged length of stay (LOS) after TCPC. Routine assessment of ventricular function has been inadequate in identifying these high-risk patients. Speckle-tracking echocardiography (STE) is a novel method for assessment of myocardial deformation that may be useful in single-ventricle patients. The aim of this study was to perform a contemporary preoperative risk assessment for prolonged LOS to determine whether STE improves risk stratification before TCPC.

METHODS

Our single institution's perioperative data were retrospectively collected. The primary outcome was postoperative LOS >14 days. Longitudinal and circumferential STE deformation measures were analyzed on echocardiograms obtained during preoperative catheterization. Patient-specific, echocardiographic, and catheterization data were included in multivariable logistic regression. Receiver operating characteristic area under the curves (AUC) were analyzed.

RESULTS

From 2007 to 2014, 135 patients who underwent TCPC were included in the analysis. The median LOS was 11 (IQR 9-14) days. The PVR (P < .01) and circumferential strain rate (CSR) (P < .01) were the only variables independently associated with LOS >14 days. For every 0.1 s-1 CSR increased, there was a 20% increased odds of prolonged LOS. The AUC for CSR was 0.70. The AUC for PVR and EDP combined was 0.68. The AUC for PVR, EDP, and CSR combined was 0.73.

CONCLUSION

Preoperative CSR is independently associated with LOS >14 days and improves preoperative risk stratification in patients undergoing TCPC.