Ventricular Twisting and Dyssynchrony in Children with Single Left Ventricle Using Three-Dimensional Speckle Tracking Imaging after the Fontan Operation

Longitudinal Changes in Ventricular Mechanics in Adolescents After the Fontan Operation

BACKGROUND

Ventricular dysfunction is a significant clinical challenge in the long-term follow-up of patients with single-ventricle (SV) physiology. Ventricular function and myocardial mechanics can be studied using speckle-tracking echocardiography, which provides information on myocardial deformation. Limited information is available on serial changes in SV myocardial mechanics after the Fontan operation. The aim of this study was to describe serial changes in myocardial mechanics in children after the Fontan operation and the relationship of these changes with myocardial fibrosis markers as obtained by cardiac magnetic resonance and exercise performance parameters.

METHODS

The authors hypothesized that ventricular mechanics decline in patients with SVs over time and are associated with increased myocardial fibrosis and reduced exercise performance. A single-center retrospective cohort study including adolescents after the Fontan operation was conducted. Ventricular strain and torsion were assessed using speckle-tracking echocardiography. Cardiac magnetic resonance and cardiopulmonary exercise testing data closest to the latest echocardiographic examinations were performed. The most recent follow-up echocardiographic and cardiac magnetic resonance data were compared with those from sex- and age-matched control subjects and with individual patients' early post-Fontan data.

RESULTS

Fifty patients with SVs (31 left ventricle, 13 right ventricle [RV], and six codominant) were included. Median time at follow-up echocardiography from the time of Fontan was 12.8 years (interquartile range [IQR], 10.6 to 16.6 years). Compared with early post-Fontan echocardiography, follow-up assessment showed reduced global longitudinal strain (-17.5% [IQR, -14.5% to -19.5%] vs -19.8% [IQR, -16.0% to -21.7%], P = .01], circumferential strain (-15.7% [IQR, -11.4% to -18.7%] vs -18.9% [IQR, -15.2% to -25.0%], P = .009), and torsion (1.28°/cm [IQR, 0.51°/cm to 1.74°/cm] vs 1.72°/cm [IQR, 0.92°/cm to 2.34°/cm], P = .02), with decreased apical rotation but no significant change in basal rotation. Single RVs had lower torsion compared with single left ventricles (1.04°/cm [IQR, 0.12°/cm to 2.20°/cm] vs 1.25°/cm [IQR, 0.25°/cm to 2.51°/cm], P = .01). T1 values were higher in patients with SV compared with control subjects (1,009 ± 36 vs 958 ± 40 msec, P = .004) and in those with single RVs compared with single left ventricles (1,023 ± 19 vs 1,006 ± 17 msec, P = .02). T1 was correlated with circumferential strain (r = 0.59, P = .04) and inversely correlated with O2 saturation (r = -0.67, P < .001) and torsion (r = -0.71, P = .02). Peak oxygen consumption was correlated with torsion (r = 0.52, P = .001) and untwist rates (r = 0.23, P = .03).

CONCLUSIONS

After the Fontan procedures, there is a progressive decrease in myocardial deformation parameters. The progressive decrease in SV torsion is related to a decrease in apical rotation, which is more pronounced in single RVs. Decreased torsion is associated with increased markers of myocardial fibrosis and lower maximal exercise capacity. Torsional mechanics may be an important parameter to monitor after Fontan palliation, but further prognostic information is required.

Myocardial Fibrosis in Congenital Heart Disease and the Role of MRI

Progress in the field of congenital heart surgery over the last century can only be described as revolutionary. Recent improvements in patient outcomes have been achieved through refinements in perioperative care. In the current and future eras, the preservation and restoration of myocardial health, beginning with the monitoring of tissue remodeling, will be central to improving cardiac outcomes. Visualization and quantification of fibrotic myocardial remodeling is one of the greatest assets that cardiac MRI brings to the field of cardiology, and its clinical use within the field of congenital heart disease (CHD) has been an area of particular interest in the last few decades. This review summarizes the physical underpinnings of myocardial tissue characterization in CHD, with an emphasis on T1 parametric mapping and late gadolinium enhancement. It describes methods and suggestions for obtaining images, extracting quantitative and qualitative data, and interpreting the results for children and adults with CHD. The tissue characterization observed in different lesions is used to examine the causes and pathomechanisms of fibrotic remodeling in this population. Similarly, the clinical consequences of elevated imaging biomarkers of fibrosis on patient health and outcomes are explored. Keywords: Pediatrics, MR Imaging, Cardiac, Heart, Congenital, Tissue Characterization, Congenital Heart Disease, Cardiac MRI, Parametric Mapping, Fibrosis, Late Gadolinium Enhancement © RSNA, 2023.

Single Ventricular Torsional Mechanics After Fontan Palliation and Their Impact on Outcomes

Background

Abnormal left ventricular (LV) rotational mechanics in biventricular hearts are associated with adverse outcomes; however, these are less well characterized for hearts with functionally single ventricles.

Objectives

The purpose of this study was to characterize ventricular rotational mechanics in the Fontan circulation and their relationship to outcomes.

Methods

Single-center, retrospective analysis of magnetic resonance examinations for 329 Fontan patients (15 [IQR: 10-21] years) and 42 controls. The ventricular cine short-axis stack was analyzed to derive torsion metrics. Torsion calculated as the difference between apical and basal rotation normalized to ventricular length.

Results

Fontan patients had higher indexed ventricular end-diastolic volume (97 mL/body surface area1.3 vs 72 mL/body surface area1.3), lower ejection fraction (53% vs 60%), and lower proportion of basal clockwise rotation (62% vs 93%), apical counterclockwise rotation (77% vs 95%), and positive torsion (82% vs 100%); P < 0.001 for all. A composite outcome of death or heart transplant-listing occurred in 31 (9%) patients at a median follow-up of 3.9 years. Torsion metrics were associated with the outcome; although, on multivariate analysis only right ventricular (RV) morphology and indexed ventricular end-diastolic volume were independently associated. LVs with negative torsion, and RVs regardless of torsional pattern, had worse outcomes compared to LVs with positive torsion (P = 0.020).

Conclusions

Single ventricles in a Fontan circulation exhibit abnormal torsional mechanics, which are more pronounced for RV morphology. Abnormal torsion is associated with death or need for heart transplantation. Fontan patients with LV morphology and preserved torsion exhibit the highest transplant-free survival and torsion may offer incremental prognostic data in this group of patients.

Comparison of cardiac function between single left ventricle and tricuspid atresia: assessment using echocardiography combined with computational fluid dynamics

Patients with single left ventricle (SLV) and tricuspid atresia (TA) have impaired systolic and diastolic function. However, there are few comparative studies among patients with SLV, TA and children without heart disease. The current study includes 15 children in each group. The parameters measured by two-dimensional echocardiography, three-dimensional speckle tracking echocardiography (3DSTE), and vortexes calculated by computational fluid dynamics were compared among these three groups. Twist is best correlated with ejection fraction measured by 3DSTE. Twist, torsion, apical rotation, average radial strain, peak velocity of systolic wave in left lateral wall by tissue Doppler imaging (sL), and myocardial performance index are better in the TA group than those in the SLV group. sL by tissue Doppler imaging in the TA group are even higher than those in the Control group. In patients with SLV, blood flow spreads out in a fan-shaped manner and forms two small vortices. In the TA group, the main vortex is similar to the one in a normal LV chamber, but smaller. The vortex rings during diastolic phase are incomplete in the SLV and TA groups. In summary, patients with SLV or TA have impaired systolic and diastolic function. Patients with SLV had poorer cardiac function than those with TA due to less compensation and more disordered streamline. Twist may be good indicator for LV function.

Adverse fibrosis remodeling and aortopulmonary collateral flow are associated with poor Fontan outcomes

BACKGROUND

The extent and significance in of cardiac remodeling in Fontan patients are unclear and were the subject of this study.

METHODS

This retrospective cohort study compared cardiovascular magnetic resonance (CMR) imaging markers of cardiac function, myocardial fibrosis, and hemodynamics in young Fontan patients to controls.

RESULTS

Fifty-five Fontan patients and 44 healthy controls were included (median age 14 years (range 7-17 years) vs 13 years (range 4-14 years), p = 0.057). Fontan patients had a higher indexed end-diastolic ventricular volume (EDVI 129 ml/m2 vs 93 ml/m2, p < 0.001), and lower ejection fraction (EF 45% vs 58%, p < 0.001), circumferential (CS - 23.5% vs - 30.8%, p < 0.001), radial (6.4% vs 8.2%, p < 0.001), and longitudinal strain (- 13.3% vs - 24.8%, p < 0.001). Compared to healthy controls, Fontan patients had higher extracellular volume fraction (ECV) (26.3% vs 20.6%, p < 0.001) and native T1 (1041 ms vs 986 ms, p < 0.001). Patients with a dominant right ventricle demonstrated larger ventricles (EDVI 146 ml/m2 vs 120 ml/m2, p = 0.03), lower EF (41% vs 47%, p = 0.008), worse CS (- 20.1% vs - 25.6%, p = 0.003), and a trend towards higher ECV (28.3% versus 24.1%, p = 0.09). Worse EF and CS correlated with longer cumulative bypass (R = - 0.36, p = 0.003 and R = 0.46, p < 0.001), cross-clamp (R = - 0.41, p = 0.001 and R = 0.40, p = 0.003) and circulatory arrest times (R = - 0.42, p < 0.001 and R = 0.27, p = 0.03). T1 correlated with aortopulmonary collateral (APC) flow (R = 0.36, p = 0.009) which, in the linear regression model, was independent of ventricular morphology (p = 0.9) and EDVI (p = 0.2). The composite outcome (cardiac readmission, cardiac reintervention, Fontan failure or any clinically significant arrhythmia) was associated with increased native T1 (1063 ms vs 1026 ms, p = 0.029) and EDVI (146 ml/m2 vs 118 ml/m2, p = 0.013), as well as decreased EF (42% vs 46%, p = 0.045) and worse CS (- 22% vs - 25%, p = 0.029). APC flow (HR 5.5 CI 1.9-16.2, p = 0.002) was independently associated with the composite outcome, independent of ventricular morphology (HR 0.71 CI 0.30-1.69 p = 0.44) and T1 (HR1.006 CI 1.0-1.13, p = 0.07).

CONCLUSIONS

Pediatric Fontan patients have ventricular dysfunction, altered myocardial mechanics and increased fibrotic remodeling. Cumulative exposure to cardiopulmonary bypass and increased aortopulmonary collateral flow are associated with myocardial dysfunction and fibrosis. Cardiac dysfunction, fibrosis, and collateral flow are associated with adverse outcomes.

Ventricular function and dyssynchrony in children with a functional single right ventricle using real time three-dimensional echocardiography after fontan operation

BACKGROUND

This study aimed to evaluate the feasibility and clinical value of real time three-dimensional echocardiography (RT-3DE) for assessing ventricular systolic dysfunction and dyssynchrony in children with an functional single right ventricle (FSRV) having undergone the Fontan procedure.

METHODS

Twenty-five children with an FSRV and 25 healthy children were enrolled in our study. RV volume analysis was performed compared with magnetic resonance imaging (MRI) as the reference standard in FSRV patients. The patients were divided into wide and narrow QRS interval groups. Global and regional functions of the RV in three compartments (inflow, body, and outflow) were compared between FSRV and control subjects, including RV systolic dyssynchrony indices of maximal difference of time to minimal volume (Tmsv-Dif), standard deviation of time to minimal volume (Tmsv-SD), maximal difference of time to minimal volume corrected by R-R interval (Tmsv-Dif%), and standard deviation of time to minimal volume corrected by R-R interval (Tmsv-SD%).

RESULTS

RT-3DE measurements were significantly lower than MRI measurements for RV-EDV, RV-ESV, RV-SV, and RVEF (p < 0.01).Compared with controls, patients with an FRSV had significantly higher dyssynchrony indices and significantly lower global EF in both narrow QRS interval and wide QRS interval groups. Tmsv-SD% was shown to be most strongly correlated with MRI-RVEF (r = -.570, p = 0.003).

CONCLUSIONS

RT-3DE tended to underestimate RV ventricular volume in children with FSRV. Children with an FSRV and either a wide or narrow QRS interval had reduced ventricular function and higher dyssynchrony than normal subjects. Worsening RV dyssynchrony is associated with overall decline in function after the Fontan operation.

Systemic ventricular strain and torsion are predictive of elevated serum NT-proBNP in Fontan patients: a magnetic resonance study

Background

This study aimed to investigate the associations between cardiac strain, cardiac torsion, ventricular volumes, and ventricular ejection fraction, with N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels in Fontan patients who were age- and gender-matched with healthy control subjects.

Methods

Cardiovascular magnetic resonance (CMR) studies performed in 22 (15 male, 7 female) patients with single-ventricle physiology (all morphological left ventricles) palliated with Fontan and 17 (10 male, 7 female) age- and gender-matched healthy children volunteers were retrospectively analyzed. Serum NT-proBNP levels were obtained in Fontan subjects. Standard post-processing of CMR images included systemic ventricular end-diastolic and end-systolic volumes, stroke volume, cardiac mass, atrioventricular regurgitation, and ejection fraction. CMR tissue tracking (TT) software was used to quantify global longitudinal strain (GLS), global radial strain (GRS), and global circumferential strain (GCS) and torsion of the systemic ventricle. Pearson and Spearman correlation coefficients were used in comparisons of correlations between NT-proBNP and functional parameters in repair Fontan patients. Intra-observer and inter-observer variability of CMR strain and torsion values were determined from 10 randomly selected Fontan subjects and 10 randomly selected control subjects.

Results

GLS was significantly lower in Fontan patients than in control subjects (-15.19±2.94 vs. -19.97±1.70; P<0.001). GLS was not significantly different between normal NT-proBNP levels and high NT-proBNP levels in Fontan patients (-15.59±2.72 vs. -14.62±3.32; P=0.462). The GCS of repair Fontan patients was not significantly lower than that of the control group (-16.76±3.27 vs. -17.88±2.26; P=0.235). GCS was significantly different between normal and high NT-proBNP levels group in Fontan patients (-17.95±2.43 vs. -15.04±3.67; P=0.036). The peak systolic torsion and peak systolic torsion rates were significantly lower in Fontan patients than in control subjects (0.81±0.41 vs. 1.07±0.36, P=0.044; 7.36±3.41 vs. 9.85±2.61, P=0.017). Peak systolic torsion was significantly lower in Fontan patients with normal NT-proBNP levels than in high NT-proBNP subjects (0.67±0.43 vs. 1.01±0.29; P=0.036). GCS and torsion were more strongly correlated with NT-proBNP in the patient group (r=0.541 for GCS; r=0.588 for torsion, P<0.01). The parameters of strain and torsion could be reproduced with sufficient accuracy by intra-observer agreement(biases =0.04 for GLS; biases =0.66 for GCS; biases =1.03 for GRS; biases =0.04 for torsion) and inter-observer agreement (biases =0.32 for GLS; biases =0.85 for GCS; biases =1.52 for GRS; biases =0.18 for torsion).

Conclusions

GLS is an earlier marker of contractile dysfunction in repair Fontan patients. Peak systolic torsion may be a biomarker for determining subclinical dysfunction, as it is more strongly correlated with serum biomarkers of ventricular function than ventricular size or ejection fraction.

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.

Why Dyssynchrony Matters in Heart Failure?

Cardiac resynchronization therapy (CRT) is an electrical therapy to resolve an electrical problem. Any method to predict CRT response must specifically reflect the electrical substrate. Time-to-peak dyssynchrony is too unspecific for prediction of response because dyssynchrony by this approach may reflect the presence of scar or fibrosis even in the absence of conduction delay. New methods are based on the actual physiology of activation delay-induced heart failure (HF) and are superior to time-to-peak methods in predicting CRT response. Time-to-peak dyssynchrony may be used for prognosis in HF patients without signs of delayed ventricular activation and for monitoring CRT response.

Strain and Rotational Mechanics in Children With Single Left Ventricles After Fontan

BACKGROUND

Left ventricular (LV) mechanics in patients with different single morphologic LV subtypes, including tricuspid atresia, double-inlet left ventricle, and pulmonary atresia with intact ventricular septum, remain poorly studied. Given that histologic studies indicate differences in LV myocardial fiber orientation, we hypothesized that this may result in altered LV mechanics. The aim of this study was to evaluate the influence of LV morphology on LV mechanics.

METHODS

Fifty-two children with single left ventricles after Fontan operation and age-matched control subjects were prospectively enrolled. Using two-dimensional speckle-tracking echocardiography, longitudinal strain was measured in the four-, three-, and two-chamber long-axis planes, and circumferential strain was measured at the basal, mid, and apical short-axis planes. Apical and basal rotation were measured, and twist and torsion were calculated. We compared strain and rotational mechanics in cases versus control subjects and among LV subtypes.

RESULTS

Compared with control subjects, subjects with single left ventricles had similar LV end-diastolic dimensions but significantly decreased ejection fractions. The single left ventricle cohort had normal global longitudinal strain (P = .20) but lower basal mean circumferential strain (P < .0001). Single left ventricle subjects had higher apical rotation (P = .0001) but decreased basal rotation (P = .0007); there was no difference in twist but increased torsion (P = .001). LV subtypes had different four-chamber (P = .01), two-chamber (P = .006), and global longitudinal strain (P = .01), lowest in the pulmonary atresia with intact ventricular septum subtype.

CONCLUSIONS

Longitudinal LV strain was preserved in children with single left ventricles after Fontan. A pattern of reduced basal circumferential strain and rotation with an increase in apical rotation and torsion in the single left ventricle cohort may be related to differences in myofiber orientation, increased fibrosis, and the impact of altered loading conditions throughout palliation. Decreased longitudinal strain in the pulmonary atresia with intact ventricular septum group may also reflect detrimental interventricular interactions.

Ventricular Torsion in Young Patients With Single-Ventricle Anatomy

BACKGROUND

In normal left ventricles, clockwise basal rotation and counterclockwise apical rotation result in systolic torsion. Torsion is important for contractile efficiency and may be especially important in single-ventricle (SV) physiology. However, little is known about torsion in patients with SVs. The aim of this study was to measure torsion in SVs and to determine its relationship with other measures of ventricular function. The hypothesis was that torsion would be decreased in all SVs, most significantly in single right ventricles, and that it would correlate with other measures of ventricular function.

METHODS

A prospective cross-sectional study was performed in 61 patients with SVs undergoing pre- or post-Fontan cardiac catheterization and 30 matched control subjects. Echocardiography, catheterization, and cardiac magnetic resonance imaging were performed under the same anesthetic. Torsion and strain were measured using speckle-tracking echocardiography. Intracardiac pressures, pulmonary vascular resistance, and cardiac magnetic resonance imaging-derived ventricular volume and ejection fraction were measured.

RESULTS

Thirty-five patients were left ventricular dominant, 15 were right ventricular dominant, 10 were codominant, and one had indeterminate morphology. Thirty-seven patients were pre-Fontan and 24 were post-Fontan. Patients with SVs had similar overall torsion as control subjects (median, 1.7°/cm vs 1.65°/cm; P = NS); however, they had decreased or reversed basal rotation (-0.32°/cm vs -0.93°/cm, P < .0001) and increased apical rotation (1.45°/cm vs 1.06°/cm, P = .0065). There were no differences on the basis of ventricular dominance or palliative stage. Torsion did not significantly correlate with other echocardiographic, catheter-based, or cardiac magnetic resonance imaging measures of cardiac function.

CONCLUSIONS

Single left and right ventricles exhibit preserved torsion, mainly because of preserved or increased apical rotation. Possible mechanisms of torsion in single right ventricles include myofiber remodeling and altered ventricular-ventricular interactions. Understanding myocardial deformation in SVs will improve the ability to interpret ventricular function in this precarious population.

Three-dimensional echocardiography in adult congenital heart disease

Congenital heart disease (CHD) is now more common in adults than in children due to improvements in fetal echo, neonatal and pediatric care, and surgical techniques leading to dramatically increased survivability into adulthood. Adult patients with CHD, regardless of prior cardiac surgery, experience further cardiac problems or therapeutic challenges; therefore, a non-invasive, easily accessible echocardiographic examination is an essential follow-up tool. Among echocardiographic modalities, three-dimensional (3D) echocardiography provides better delineation of spatial relationships in complex cardiac geometries and more accurate volumetric information without geometric assumptions. For atrial septal defects, an en face view of the tissue defect allows better decisions on device closure. For tricuspid valve malformations, an en face view provides diagnostic information that is difficult to obtain from routine 2D tomography. In repaired tetralogy of fallot with pulmonary regurgitation, preoperative 3D echocardiography- based right ventricular volume may be used to determine the timing of a pulmonary valve replacement in conjunction with cardiovascular magnetic imaging. For optimal adult CHD care, 3D echocardiography is an important complement to routine 2D echocardiography.