Noninvasive Assessment of Myocardial Work in Children.

The noninvasive assessment of ventricular function is an ongoing challenge with new tools and measurements always being considered and tested. The noninvasive assessment of myocardial work via the pressure-strain relationship is one of the newer tools proposed to evaluate ventricular systolic function. However, prior to using any new tool, one should understand its properties, utility, and limitations. In this commentary we focus on the noninvasive assessment of myocardial work via the pressure-strain relationship from a pediatric point of view. We address the current knowledge, limitations, and propose future directions to better understand this tool.

Hemodynamic assessment of transitioning from parenteral prostacyclin to selexipag in pediatric pulmonary hypertension.

Despite the increase in therapeutic options, parenteral prostacyclins remain the cornerstone in the medical management of pulmonary arterial hypertension (PAH). While the use of parenteral prostacyclins in pediatric patients is well documented, less is known about alternative drug delivery methods such as enteral administration. Given that parenteral routes of prostacyclin administration (IV or SC) are invariably accompanied by complicated logistics and lifestyle compromises, enteral prostacyclin administration represents an attractive treatment option. Selexipag (Uptravi®) was approved for adults PAH in 2015. There is limited data on the hemodynamic efficacy of transitioning from parenteral prostacyclins to selexipag, particularly in the pediatric population. We report 11 pediatric PAH patients who underwent this transition, in which 10 had complete cardiac catheterization data before and following the transition to selexipag. All patients/families reported an improvement in quality of life, and the transitions occurred without adverse effects. However, 3 of the 11 (27%) did not tolerate the transition; two for worsening hemodynamics, and one for acute right ventricular failure in the setting of an intercurrent illness. In addition, the transition to selexipag was associated with a modest increase in pulmonary vascular resistance index (6/10) and decrease in cardiac index (6/10) in some patients. Selexipag use in pediatric PAH represents a significant addition to our therapeutic arsenal, and its use provides a meaningful improvement in quality of life compared with other prostacyclin formulations. However, when goals of care include aggressive disease management, a decision between improved quality of life and possible adverse outcomes must be considered, and its substitution should include cautious, close, long-term follow-up.

Pulmonary artery acceleration time in young children is determined by heart rate and transpulmonary gradient but not by pulmonary blood flow: A simultaneous echocardiography-cardiac catheterization study.

INTRODUCTION: Pulmonary artery acceleration time (PAAT) is considered useful for the non-invasive evaluation of pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). PAAT is dependent on PAP, PVR, pulmonary artery compliance, stroke volume, and heart rate. Its relative dependency on these determinants may differ between young and older children, raising uncertainty regarding its utility in young children. We aim to identify the primary determinants of the PAAT in children less than 36 months undergoing cardiac catheterization and its utility for the diagnosis of elevated PVR. METHODS: We prospectively studied 42 children undergoing cardiac catheterization and simultaneous echocardiography. We determined the correlations of PAAT to the above-mentioned determinants and evaluated receiver operator characteristic (ROC) curves for diagnosis of PVR indexed to body surface area (PVRi) ≥3 Wu*m2 . RESULTS: Median age was 11.5 (IQR 5.2, 21.2) months. Moderate correlations were found between PAAT and mean PAP (R = -.66, p < .001), PVRi (R = -.54, p = .004), pulmonary artery compliance (R = .65, p < .001), transpulmonary gradient (R = -.67, p < .001), stroke volume (R = .61, p = .002), and heart rate (R = -.63, p < .001). In multivariate regression modeling, only transpulmonary gradient and heart rate were independent determinants of PAAT. PAAT ≤77 msec had acceptable utility for diagnosing PVRi ≥ 3 Wu*m2 (AUC .8 [.64, .95], n = 36), low sensitivity (59%), and excellent specificity (94%). CONCLUSION: Transpulmonary gradient and heart rate, but not pulmonary blood flow, are important determinants of PAAT in children <36 months undergoing cardiac catheterization. PAAT has low sensitivity for diagnosing elevated PVRi, therefore, should not be solely relied upon in screening for elevated PVRi in young children.

Doppler Echocardiographic Features of Pulmonary Vein Stenosis in Ex-Preterm Children.

BACKGROUND: Echocardiography is used to screen for the presence of pulmonary vein stenosis (PVS) in ex-preterm infants and children. However, there are no standard accepted criteria for screening or diagnosis of PVS by echocardiography. The aim of this study was to identify Doppler waveform features and Doppler systolic and diastolic velocity cutoff values associated with a diagnosis of PVS by cardiac catheterization. METHODS: In this retrospective observational study, the echocardiograms of ex-preterm children <3 years old who underwent cardiac catheterization at a single institution were reviewed. PVS on cardiac catheterization was defined by a mean pressure gradient of >3 mm Hg in the pulmonary vein, with angiographic evidence of stenosis. Pulmonary vein Doppler waveforms, from echocardiograms obtained before catheterization, in children with and without PVS were compared. Nonstenosed veins in patients with PVS were excluded. The systolic and diastolic velocities of blood flow, phasic flow, and return of the Doppler waveform to baseline were analyzed. RESULTS: Forty-seven children were analyzed in the study, 18 children with 25 stenosed pulmonary veins and 29 children with 78 nonstenosed pulmonary veins. Stenosed pulmonary veins had higher peak systolic and diastolic velocities and higher peak and mean pressure gradients as measured by spectral Doppler. Peak systolic and diastolic velocities had areas under the receiver operating characteristic curve of 0.89 (95% CI, 0.79-0.99) and 0.93 (95% CI, 0.85-0.99) for PVS, respectively, and a threshold velocity of 0.7 m/sec had sensitivity of 80% and 84% and specificity of 94%. There was no correlation between Doppler-derived pulmonary vein mean gradient and measured pulmonary vein mean gradient during cardiac catheterization in stenosed pulmonary veins. Presence of phasic flow in the pulmonary vein and return of the Doppler waveform to baseline were associated with a nonstenosed pulmonary vein (sensitivity of 94% and 60% and specificity of 52% and 60%, respectively). CONCLUSIONS: Systolic and diastolic Doppler velocities and features of the waveform can discriminate stenosed pulmonary veins confirmed by cardiac catheterization in ex-preterm children. These results suggest the use of lower systolic and diastolic Doppler velocity cutoff values than currently published to screen for PVS in ex-preterm children. These cutoff values require validation in prospective studies.

Diagnostic value of myocardial deformation pattern in children with noncompaction cardiomyopathy.

The current echocardiographic diagnostic criteria for noncompaction cardiomyopathy (NCC) have variable sensitivity and low specificity. Moreover, there are limited data on the use of myocardial deformation imaging for early detection of myocardial dysfunction in children with NCC. We describe left ventricular (LV) deformation patterns in children with NCC, with the goal of identifying a potential diagnostic pattern. We prospectively enrolled 30 children with NCC (47% male; mean age 7.2 years) and 30 age- and gender-matched controls. Extent and severity of non compaction in each segment were evaluated in LV 16-segment model. Regional (base, mid and apex) and segmental (16 segments) longitudinal strain (LS), circumferential strain (CS) and radial strain (RS) were measured using speckle tracking echocardiography. In all patients with NCC, regional and segmental CS and RS at the apex were significantly decreased compared to controls (CS apex: - 19.2 ± 5.4% vs. - 30.2 ± 6.9%, p < 0.001/RS apex: 23.5 ± 8.6% vs. 44.1 ± 14.5%, p < 0.001). Thirty percent (9/30) of patients had an EF < 50%. In these patients, there was additional decrease in CS in basal segments and in LS in basal, mid-cavity and apical segments (CS base: - 16.4 ± 4.7% vs. - 24.6 ± 3.9%, p < 0.001/LS (average all LV segments): - 13.9 ± 3.1% vs. - 20.7 ± 4.7%, p < 0.001). A cut-off value of CS at the apex of - 24.5% was a strong differentiating feature between patients with NCC and EF > 50% and controls (sensitivity: 87%, specificity 79%, AUC 0.88, p < 0.001). Children with NCC exhibit a deformation pattern characterized by decreased apical circumferential strain, which may serve as a potential diagnostic tool for NCC. The role of decreased global LV longitudinal and basal circumferential strain should be further evaluated as a potential prognostic tool.

A Preliminary Study of Left Ventricular Rotational Mechanics in Children with Noncompaction Cardiomyopathy: Do They Influence Ventricular Function?

BACKGROUND: Current diagnostic criteria for noncompaction cardiomyopathy (NCC) lack specificity, and the disease lacks prognostic indicators. Reverse apical rotation (RAR) with abnormal rotation of the cardiac apex in the same clockwise direction as the base has been described in adults with NCC. The aim of this study was to test the hypothesis that RAR might differentiate between symptomatic NCC and benign hypertrabeculations and might be associated with ventricular dysfunction. METHODS: Echocardiograms from 28 children with NCC without cardiac malformations were prospectively compared with those from 29 age-matched normal control subjects. A chart review was performed to identify the patients' histories and clinical characteristics. Speckle-tracking was used to measure longitudinal strain, circumferential strain, and rotation. RESULTS: RAR occurred in 39% of patients with NCC. History of left ventricular (LV) dysfunction or arrhythmia was universal in, but not exclusive to, patients with RAR. Patients with RAR had lower LV longitudinal strain but similar ejection fractions compared with patients without RAR (median, -15.6% [interquartile range, -12.9% to -19.3%] vs -19% [interquartile range, -14.5% to -21.9%], P < .01; 53% [interquartile range, 43% to 68%] vs 61% [interquartile range, 58% to 67%], P = .08). Only a pattern of contraction with RAR, early arrest of twisting by mid-systole, and premature untwisting was associated with lower ejection fraction (46%; interquartile range, 43% to 52%; P = .006). CONCLUSIONS: RAR is not a sensitive but is a specific indicator of complications in children with NCC. Therefore, RAR may have prognostic rather than diagnostic value. Premature untwisting of the left ventricle during ejection may be an even more worrisome indicator of LV dysfunction.

Intraoperative transesophageal echocardiographic predictors of recurrent left ventricular outflow tract obstruction in children undergoing subaortic stenosis resection.

BACKGROUND: Intraoperative transesophageal echocardiography (iTEE) is used to assess for residual left ventricular outflow tract obstruction (LVOTO) after surgical resection of subaortic membrane causing subaortic stenosis (sub-AS). We aimed to identify the iTEE features associated with recurrence of LVOTO. METHODS: We conducted a retrospective study of children undergoing sub-AS resection from June 2006 to June 2014. Doppler assessment of the flow velocity and the anatomical features of the left ventricular outflow tract were analyzed from stored echocardiograms. Recurrent LVOTO was defined as an increase in the mean pressure gradient across the left ventricular outflow tract of > 15 mm Hg on the most recent follow-up echocardiogram from the mean pressure gradient on the predischarge echocardiogram or as doubling of the mean pressure gradient to a value ≥20 mm Hg. RESULTS: Thirty-five patients were included, with median age at surgery was 8.1 years (range: 0.7-29 years) and median follow-up was 47 months (2-91 months). Ten patients (29%) had recurrent LVOTO, which was associated with a shorter distance between the narrowest diameter of the outflow tract and the aortic valve on iTEE [median 0.59 cm (range 0.39-0.74) vs 0.98 cm (0.75-1.5), P = .03]. No patients with more than mild residual LVOTO on iTEE regressed to mild or no LVOTO on follow-up echocardiograms. CONCLUSIONS: LVOTO recurrence after sub-AS resection is common, and residual LVOTO remains the same or increases over time. Proximity of the LVOTO to the aortic valve is a risk factor for recurrent LVOTO. These findings may be useful in counseling patients and to guide the frequency of postoperative follow-up.

Left Ventricular Rotational Mechanics in Children After Heart Transplantation.

BACKGROUND: Left ventricular (LV) dysfunction after orthotopic heart transplantation (OHT) is multifactorial and can be an indicator of graft rejection or coronary artery vasculopathy. Analysis of rotational mechanics may help in the early diagnosis of ventricular dysfunction. Studies describing the left ventricular rotational strain in children after OHT are lacking. It is important to establish the baseline rotational mechanics in pediatric OHT to pursue further studies in this population. METHODS AND RESULTS: Rotational strain measured by speckle tracking was compared in 32 children after OHT, with no evidence of active rejection or coronary artery vasculopathy with 35 age-matched normal controls. Twelve OHT patients and 13 controls underwent moderate exercise with pre- and postexercise echocardiography. Torsion, slope of the systolic limb of the torsion-radial displacement loop, and the untwist rate were significantly higher in OHT patients (torsion: median 2.7°/cm [Q1-Q3, 2.3-3.2] versus 2.3°/cm [Q1-Q3, 1.9-2.7]; P=0.03, torsion-radial displacement loop: 2.7°/mm [Q1-Q3, 2.1-3.6] versus 2.0°/mm [Q1-Q3, 1.6-2.7]; P=0.008, indexed peak untwist rate: -21.6°/s/cm [Q1-Q3, -24.3 to -15.7] versus -17.1°/s/cm [Q1-Q3, -19.6 to -13.3]; P=0.01). Contrary to controls, OHT recipients were unable to increase torsion with exercise (OHT: 2.8°/cm [2.7-3.2] versus 3°/cm [2.4-3.5]; P=0.81, controls: 2.2°/cm [2-2.6] versus 3°/cm [2.4-3.7]; P=0.01, pre and post exercise, respectively). The systolic slope of the torsion-radial displacement loop relationship decreased with exercise in most OHT patients. CONCLUSIONS: Baseline rotational strain in OHT patients is higher than normal with a blunted response to exercise. The slope of torsion-radial displacement loop, and its response to exercise, may serve as a marker of left ventricular dysfunction in OHT patients.

Right Ventricular Systolic-to-Diastolic Time Index: Hypoplastic Left Heart Fetuses Differ Significantly from Normal Fetuses.

BACKGROUND: A growing body of evidence indicates that right ventricular dysfunction in patients with palliated hypoplastic left heart syndrome (HLHS) originates in fetal life. In this study, the systolic-to-diastolic time index (SDI) was used to study the presence of ventricular dysfunction in single right ventricles in fetuses with HLHS or evolving HLHS and to assess whether this dysfunction is related to increase preload, myocardial performance, or interventricular interaction. METHODS: Echocardiograms from 78 fetuses with HLHS and 10 with evolving HLHS were retrospectively compared with those of 78 normal control fetuses. Fetuses with HLHS were further grouped according to morphology of the left ventricle (LV): not visible (n = 35) or visible (n = 43). Spectral Doppler signals obtained from right ventricular inflow (blood pool) and tissue Doppler from the tricuspid lateral annulus were analyzed. The SDI was calculated as the ratio of the ejection time plus isovolumic contraction and relaxation times to the diastolic filling time. E/A and E/e' ratios, cardiac output, preload index, and Tei index were also calculated. RESULTS: Fetuses with HLHS demonstrated significantly elevated right ventricular SDI values by both blood pool Doppler and Doppler tissue imaging compared with control subjects (1.89 ± 0.33 vs 1.58 ± 0.29 [P < .001] and 2.1 ± 0.57 vs 1.66 ± 0.31 [P < .001], respectively). Changes in filling time rather than ejection time predominated. Fetuses with HLHS with visible LVs and those with evolving HLHS had significantly higher SDI values than fetuses with HLHS without visible LVs (no visible LV, 1.75 ± 0.22; visible LV, 2 ± 0.36; P = .001; evolving HLHS, 2.19 ± 0.68; P < .001). SDI was correlated with the Tei index (R = 0.58) and was more sensitive than the Tei index in identifying differences between the HLHS subgroups. CONCLUSIONS: Fetuses with evolving and overt HLHS exhibit abnormally increased SDI values in utero. This difference is likely related to inherently pathologic interventricular interactions and/or diastolic dysfunction of the right ventricle in fetuses with HLHS.