Speckle Tracking Echocardiography Improves Ventricular Function Assessment in Complex Single Ventricle Hearts

Functional single ventricle represents an intricate congenital cardiac malformation characterized by one dominant pumping chamber alongside an underdeveloped subsidiary ventricle, while isolated true single ventricles remain exceedingly rare. Despite notable refinements in surgical techniques and perioperative management, affected patients continue to face significant mortality risks driven by chronic volume overload, prolonged cyanosis, and elevated pulmonary vascular resistance. Experimental and clinical data confirm that prolonged single chamber volume loading and persistent arterial desaturation progressively impair contractile mechanics, whereas timely intervention to alleviate hemodynamic strain yields superior patient outcomes. Precise functional assessment is consequently essential for optimizing staged reconstructive strategies and continuous clinical monitoring. Although cardiac catheterization supplies critical hemodynamic indices, such as peak rate of isovolumic ventricular pressure rise and ventricular end-diastolic pressure, procedural invasiveness prevents routine serial application. Similarly, cardiac magnetic resonance provides geometry-independent volumetry but requires prolonged examination times, noisy acoustic environments, and frequent pediatric sedation. Non-invasive transthoracic echocardiography has therefore emerged as the definitive modality for routine clinical evaluation.

Traditional assessment of single ventricular function predominantly relies on two-dimensional echocardiography to derive ventricular ejection fraction, an established parameter prized for procedural ease and validated historical correlations with clinical outcomes. However, conventional ejection fraction calculations exhibit significant diagnostic vulnerabilities, most prominently marked load dependency and low diagnostic sensitivity for identifying incipient myocardial injury. Furthermore, ejection fraction serves strictly as a global volumetric index, remaining incapable of resolving localized myocardial dysfunction or tracking regional biomechanical impairments. Of paramount importance in congenital cardiology, conventional two-dimensional ejection fraction algorithms rely on rigid geometric shape assumptions that fail completely when applied to the dysmorphic, non-standard ventricular geometries typical of single ventricle anatomy. Alternative conventional metrics, including fractional area change and tricuspid annular plane systolic excursion, likewise demonstrate poor diagnostic reliability and offer no demonstrable clinical advantage.

To overcome the limitations of geometric modeling, tissue Doppler imaging utilizes ultrasound Doppler shifts to quantitatively evaluate myocardial tissue velocities across the cardiac cycle. When evaluated with tissue Doppler imaging, functional single ventricle patients exhibit stark mechanical discrepancies compared to healthy cohorts, with both single left and single right ventricles showing marked reductions in systolic peak velocity, early diastolic peak velocity, and late diastolic peak velocity along the ventricular free wall. Concurrently, these individuals demonstrate elevated Tei myocardial performance indices, reflecting profound global functional impairment. Because the Tei index evaluates time intervals rather than chamber dimensions, it provides geometry-independent functional measurements that correlate closely with catheterization-derived peak rates of pressure rise. In post-Fontan populations, tissue Doppler imaging readily uncovers subclinical ventricular diastolic dysfunction, identified by attenuated early diastolic mitral annular velocities and depressed early-to-late velocity ratios despite preserved systolic ejection fraction. Nevertheless, tissue Doppler imaging remains constrained by ultrasound beam angle dependency, myocardial tethering from adjacent segments, and inability to isolate systolic from diastolic components.

Addressing the geometric complexities of congenital single ventricle malformations, real-time three-dimensional echocardiography enables complete volume acquisition of cardiac structures without geometric assumptions or fixed orientation constraints. By capturing dynamic full-volume data sets across multiple cardiac cycles, this technology enhances the visualization of spatial relationships frequently distorted by concurrent anomalies like patent ductus arteriosus, atrial septal defects, or transposed great arteries. Comparative clinical investigations demonstrate strong correlations between real-time three-dimensional echocardiographic measurements of ventricular volumes and ejection fraction against cardiac magnetic resonance standards. In pediatric cohorts with hypoplastic left heart syndrome, the three-dimensional technique provides high reproducibility for right ventricular volumetry, permitting dependable serial surveillance. Nonetheless, real-time three-dimensional imaging has distinct technical limitations, notably suboptimal temporal frame rates that impair rapid wall motion tracking. Furthermore, marked eccentric ventricular hypertrophy and chamber overgrowth occurring in pre-Fontan single ventricles can expand chamber dimensions beyond the transducer field of view, preventing complete single-beat volumetric capture and restricting routine clinical feasibility.

Two-dimensional speckle tracking imaging represents a major technological leap, utilizing grayscale acoustic interference patterns to calculate angle-independent global and regional myocardial deformation. Strain and strain rate metrics generated through speckle tracking exhibit robust statistical correlations with invasive catheterization pressures and magnetic resonance markers, demonstrating elevated diagnostic sensitivity compared to conventional ejection fraction for detecting subclinical myocardial dysfunction. Clinical evaluations reveal distinct ventricular phenotypes, whereby single left ventricles systematically exhibit significantly higher longitudinal and circumferential strain and strain rate values than single right ventricles. Moreover, two-dimensional speckle tracking facilitates dynamic serial surveillance across multi-stage surgical palliation, illuminating progressive structural and biomechanical remodeling. Serial studies show that patients with single right ventricles experience gradual declines in both longitudinal and circumferential performance over time, reflecting intrinsic structural vulnerability under systemic demands. Interestingly, between the first and second surgical palliative stages, single right ventricles undergo a compensatory contraction shift, transitioning from predominantly longitudinal shortening to predominantly circumferential deformation as an adaptive response to systemic vascular resistance.

The clinical predictive utility of two-dimensional speckle tracking has established myocardial strain as an essential biomarker for risk stratification in functional single ventricle populations. Longitudinal investigations indicate that global circumferential strain in post-Fontan patients strongly correlates with transplant-free survival, serving as a powerful independent predictor of long-term postoperative prognosis. Similarly, in children afflicted with hypoplastic left heart syndrome, pronounced reductions in global longitudinal strain reliably predict heightened risk of death or heart transplantation. Building upon tracking technology, non-invasive pressure-strain loop analysis integrates peripheral brachial cuff blood pressure measurements with speckle tracking longitudinal strain curves.

Quantified through pressure-strain loops, the myocardial work index provides a highly sensitive diagnostic parameter for early myocardial injury and reliably predicts patient exercise tolerance. Clinical studies reveal that post-Fontan individuals frequently display significantly depressed myocardial work indices despite maintaining completely normal ejection fraction values, underscoring its utility for subclinical surveillance. Furthermore, Fontan patients possessing functional right ventricles demonstrate markedly lower global work efficiency compared to counterparts supported by morphologic left ventricles, highlighting significant chamber-specific energetic disparities. Despite these diagnostic capabilities, pressure-strain loop methodology in single ventricles remains constrained by its exclusive reliance on longitudinal deformation, completely ignoring radial and circumferential mechanics that contribute substantially to systemic chamber output. In parallel, layer-specific strain analysis exploits speckle tracking to differentiate myocardial layers, measuring subendocardial longitudinal fibers and subepicardial circumferential fibers independently. The derived transmural strain gradient, reflecting subendocardial minus subepicardial deformation, correlates negatively with magnetic resonance ejection fraction during exercise, providing a novel metric for assessing functional contractile reserve.

Three-dimensional speckle tracking imaging expands deformation analysis by tracking acoustic speckles across three-dimensional volumetric space, effectively eliminating the through-plane motion loss that inherently limits two-dimensional tracking. This spatial tracking capability enables accurate quantification of complex cardiac twist and torsion, which arise from the opposing helical architecture of subendocardial right-handed spirals and subepicardial left-handed spirals. In post-Fontan children with single left ventricles, three-dimensional tracking reveals significant reductions in apical rotation, basal rotation, and total twist angles compared to healthy controls, reflecting reduced compliance and low preload-induced geometry remodeling. Torsion measurements, derived by normalizing twist angle to ventricular length, offer superior age-independent assessments of systolic function. Additionally, three-dimensional tracking enables principal strain analysis, an engineering technique that measures true maximal deformation independent of predefined anatomical axes. In patients with hypoplastic left heart syndrome, principal strain demonstrates excellent correlation with three-dimensional ejection fraction, quantifying both contraction magnitude and contraction vector angle to eliminate directional ambiguity in strangely deformed single ventricles.

Complementing speckle tracking, velocity vector imaging provides an angle-independent, non-invasive platform that measures myocardial tissue velocities, strain, strain rate, and twist mechanics to detect early subclinical dysfunction. In pediatric patients possessing single right ventricles, velocity vector imaging accurately quantifies longitudinal systolic functional deficits and enables detailed segmental evaluation. Following cavopulmonary anastomosis, children with single right ventricles exhibit significant strain and strain rate reductions across all six analyzed myocardial segments relative to normal controls. However, velocity vector imaging remains partially sensitive to loading conditions, exhibits unknown age-related parameter fluctuations, and suffers potential measurement artifact caused by underdeveloped residual ventricular chambers. Across modern echocardiographic modalities, parameter reproducibility remains a vital clinical benchmark. Published validation data confirm that global longitudinal strain and strain rate derived from two-dimensional tracking, alongside three-dimensional longitudinal strain, circumferential strain, twist, torsion, principal strain, and real-time three-dimensional ejection fraction, consistently demonstrate good to excellent reproducibility across repeated acquisitions.

Integrating artificial intelligence into echocardiographic processing represents an emerging frontier designed to reduce operator dependence and enhance measurement precision in single ventricle evaluations. Deep learning architectures facilitate fully automated detection of complex endocardial borders, with automated fractional area change yielding tighter correlations with cardiac magnetic resonance ejection fraction and superior reproducibility over manual tracings. Similarly, knowledge-based three-dimensional reconstruction cross-references two-dimensional images against extensive lesion-specific template databases, generating reliable right ventricular volumes and functional reconstructions in complex congenital defects. Realizing the full clinical potential of these advanced technologies requires overcoming persistent hurdles, including small single-center cohorts, marked inter-vendor software variability, and the absence of standardized reference values tailored to single ventricle anatomy. Multicenter prospective collaborations, systematic evaluations of load-independent parameters across staged surgical reconstructions, and targeted investigations into the unique physiology of aging single ventricle survivors remain essential research priorities.

Subject of Research: Transthoracic echocardiographic techniques for evaluating ventricular function in functional single ventricle

Article Title: Transthoracic echocardiographic assessment of ventricular function in functional single ventricle: a comprehensive review

Article References: Liao, M., Pan, J., Liao, T., Liu, X., & Wang, L. (2025). Transthoracic echocardiographic assessment of ventricular function in functional single ventricle: a comprehensive review. Cardiovascular Ultrasound, 23(1), Article 9. https://doi.org/10.1186/s12947-025-00345-3

Image Credits: AI Generated

DOI: 10.1186/s12947-025-00345-3

Keywords: functional single ventricle, transthoracic echocardiography, two-dimensional speckle tracking imaging, three-dimensional speckle tracking imaging, real-time three-dimensional echocardiography, tissue doppler imaging, velocity vector imaging, pressure-strain loops, myocardial work index, layer-specific strain, ejection fraction, hypoplastic left heart syndrome, global longitudinal strain, global circumferential strain, principal strain, cardiac twist mechanics, Fontan procedure, congenital heart disease