Mechanisms of Right Ventricular Electromechanical Dyssynchrony and Mechanical Inefficiency in Children After Repair of Tetralogy of Fallot

3D models of the cardiac conduction system in healthy neonatal human hearts

Iatrogenic damage to the cardiac conduction system (CCS) remains a significant risk during congenital heart surgery. Current surgical best practice involves using superficial anatomical landmarks to locate and avoid damaging the CCS. Prior work indicates inherent variability in the anatomy of the CCS and supporting tissues. This study introduces high-resolution, 3D models of the CCS in normal pediatric human hearts to evaluate variability in the nodes and surrounding structures. Human pediatric hearts were obtained with an average donor age of 2.7 days. A pipeline was developed to excise, section, stain, and image atrioventricular (AVN) and sinus nodal (SN) tissue regions. A convolutional neural network was trained to enable precise multi-class segmentation of whole-slide images, which were subsequently used to generate high- resolution 3D tissue models. Nodal tissue region models were created. All models (10 AVN, 8 SN) contain tissue composition of neural tissue, vasculature, and nodal tissues at micrometer resolution. We describe novel nodal anatomical variations. We found that the depth of the His bundle in females was on average 304 μm shallower than those of male patients. These models provide surgeons with insight into the heterogeneity of the nodal regions and the intricate relationships between the CCS and surrounding structures.

The mechanics of congenital heart disease: from a morphological trait to the functional echocardiographic evaluation

Advances in pediatric cardiac surgery have resulted in a recent growing epidemic of children and young adults with congenital heart diseases (CHDs). In these patients, congenital defects themselves, surgical operations and remaining lesions may alter cardiac anatomy and impact the mechanical performance of both ventricles. Cardiac function significantly influences outcomes in CHDs, necessitating regular patient follow-up to detect clinical changes and relevant risk factors. Echocardiography remains the primary imaging method for CHDs, but clinicians must understand patients' unique anatomies as different CHDs exhibit distinct anatomical characteristics affecting cardiac mechanics. Additionally, the use of myocardial deformation imaging and 3D echocardiography has gained popularity for enhanced assessment of cardiac function and anatomy. This paper discusses the role of echocardiography in evaluating cardiac mechanics in most significant CHDs, particularly its ability to accommodate and interpret the inherent anatomical substrate in these conditions.

Longitudinal ECG changes in tetralogy of Fallot and association with surgical repair

Background

ECG abnormalities have been linked to adverse changes in right ventricular (RV) morphology and poor clinical outcomes in repaired Tetralogy of Fallot (rTOF). Our aim was to describe how ECG changes progress in early and intermediate follow-up and whether types of surgical strategy at the time of primary repair affected these changes.

Methods

We studied patients with rTOF born 2000-2018 operated at our institution. Seven time points in relation to primary repair, follow-up, and pulmonary valve replacement (PVR) were identified. Patients correct with valve sparing repair (VSR), trans-annular patch (TAP) including with a monocusp valve (TAP + M) and with at least 3 ECGs were included. PQ interval, QRS duration, dispersion, and fragmentation, QTc duration and dispersion, JTc as well as presence of a right bundle branch block (RBBB) were analyzed. Medical records were reviewed for demographic and surgical data.

Results

Two hundred nineteen patients with 882 ECGs were analyzed with a median follow-up time of 12.3 years (8.4, 17) with 41 (19%) needing PVR during the study period. QRS duration increased at time of primary repair to discharge from 66 msec (IQR 12) to 129 msec (IQR 27) (p < 0.0001) and at 1- and 6- year follow-up but showed only a modest and temporary decrease after PVR. QTc increased at the time of primary repair as well as prior to PVR. PQ interval showed a small increase at the time of primary repair, was at its highest prior to PVR and decreased with PVR. Type of surgical repair affected mainly QTc and JTc and was consistently longer in the TAP + M group until PVR. In VSR, QTc and JTc were prolonged initially compared to TAP but were similar after 1 year. After PVR, there were no differences in adverse ECG changes between surgical groups.

Conclusions

PQ interval and QRS duration best correspond to the assumed volume load whereas the relationship with QTc and JTc is more complex, suggesting that these represent more complex remodeling of the myocardium. Before PVR, QTc and JTc are longer in the TAP + M group which may be due to a longer surgical incision.

Adverse remodelling in tetralogy of Fallot: From risk factors to imaging analysis and future perspectives

Although contemporary outcomes of initial surgical repair of tetralogy of Fallot (TOF) are excellent, the survival of adult patients remains significantly lower than that of the normal population due to the high incidence of heart failure, ventricular arrhythmias, and sudden cardiac death. The underlying mechanisms are only partially understood but involve an adverse biventricular response, so-called remodelling, to key stressors such as right ventricular (RV) pressure-and/or volume-overload, myocardial fibrosis, and electro-mechanical dyssynchrony. In this review, we explore risk factors and mechanisms of biventricular remodelling, from histological to electro-mechanical aspects, and the role of imaging in their assessment. We discuss unsolved challenges and future directions to better understand and treat the long-term sequelae of this complex congenital heart disease.

Tetralogy of Fallot Across the Lifespan: A Focus on the Right Ventricle

Tetralogy of Fallot is a cyanotic congenital heart disease, for which various surgical techniques allow patients to survive to adulthood. Currently, the natural history of corrected tetralogy of Fallot is underlined by progressive right ventricular (RV) failure due to pulmonic regurgitation and other residual lesions. The underlying cellular mechanisms that lead to RV failure from chronic volume overload are characterized by microvascular and mitochondrial dysfunction through various regulatory molecules. On a clinical level, these cardiac alterations are commonly manifested as exercise intolerance. The degree of exercise intolerance can be objectified and aid in prognostication through cardiopulmonary exercise testing. The timing for reintervention on residual lesions contributing to RV volume overload remains controversial; however, interval assessment of cardiac function and volumes by echocardiography and magnetic resonance imaging may be helpful. In patients who develop clinically important RV failure, clinicians should aim to maintain a euvolemic state through the use of diuretics while paying particular attention to preload and kidney function. In patients who develop signs of cardiogenic shock from right heart failure, stabilization through the use of inotropes and pressor is indicated. In special circumstances, the use of mechanical support may be appropriate. However, cardiologists should pay particular attention to residual lesions that may impact the efficacy of the selected device.

Electromechanical Dyssynchrony Is Associated With Right Ventricular Remodeling and Dysfunction Independently of Pulmonary Regurgitation Late After Tetralogy of Fallot Repair

BACKGROUND

The aim of this study was to investigate the relationship among right ventricular (RV) dilatation, dysfunction, and electromechanical dyssynchrony (EMD) in patients with repaired tetralogy of Fallot (rTOF).

METHODS

Data from a prospective rTOF registry of subjects with moderate or greater pulmonary regurgitation (PR) and contemporary imaging were analyzed. Electrocardiograms and echocardiograms were analyzed for EMD (prolonged QRS duration [QRSd], echocardiographic septal flash, and mechanical delay) and mechanical dispersion. The relationship among these, RV measurements on cardiac magnetic resonance, exercise capacity, and incident arrhythmia or death was analyzed with adjustment for PR.

RESULTS

In total, 271 patients with rTOF (42% women; median age, 32 years; interquartile range [IQR], 23-34 years) were included. Patients had moderate to severe PR (median PR fraction, 38%; IQR, 30%-47%), moderate to severe RV enlargement (median RV end-diastolic volume index, 161 mL/m2; IQR, 138-186 mL/m2) and mild RV systolic dysfunction (median RV ejection fraction [RVEF], 44%; IQR, 38%-48%). Eleven patients (4%) experienced ventricular arrhythmia or death. Presence of EMD was associated with larger RV size (RV end-diastolic volume index and RV end-systolic volume index, P = .006 and P < .001, respectively) and lower RVEF (P < .001). A sharp inflection in the relation among QRSd, RV size, and RVEF was observed when QRSd exceeded 150 msec (3.1% decrease in RVEF for every 20-msec increase in QRSd between 160 and 200 msec). Similar inflection points were observed for the mechanical delay between the RV basal-lateral and midseptal segments. The mechanical delay was higher in patients with vs without incident atrial arrhythmia (371 vs 276 msec, P = .014).

CONCLUSIONS

In adults with rTOF, EMD is independently associated with larger RV size, lower RVEF, and incident atrial arrhythmias.

Techniques for Cardiac Resynchronization Therapy in Patients with Congenital Heart Disease

Cardiac resynchronization therapy (CRT) for congenital heart disease has shown promising suucess as an adjunct to medical therapy for heart failure. While cardiac conduction defects and need for ventricular pacing are common in congential heart disease, CRT indications, techniques and long term outcomes have not been well establaished. This is a review of the techniques nad short term outcomes of CRT for the following complex congenital heart disease conditions: single ventricle physiology, systemic right ventricle, and the subpulmonic right ventricle.

Advanced Imaging Technologies for Assessing Tetralogy of Fallot: Insights Into Flow Dynamics

Tetralogy of Fallot is the most common cyanotic congenital heart defect requiring surgical repair. Although surgical interventions have significantly reduced mortality, postrepair complications, such as pulmonary valve regurgitation and stenosis, may lead to adverse outcomes, including right ventricular dysfunction and increased risks of morbidity and mortality. This review explores the potential of advanced imaging technologies, including 4-dimensional-flow magnetic resonance imaging and high-frame-rate echocardiography, in providing valuable insights into blood flow dynamics and energy parameters. Quantitative measures, such as energy loss and vorticity, along with qualitative flow analysis, can provide additional insights into adverse haemodynamics at a potentially earlier and more reversible stage. Furthermore, personalized patient-specific information from these imaging modalities aids in guiding treatment decisions and monitoring postoperative interventions effectively. By characterizing flow patterns, these advanced imaging techniques hold great promise in improving the assessment and management of tetralogy of Fallot, providing tailored insights. However, further research and longitudinal studies are required to fully establish their clinical utility and potential impact on patient care.

Right ventricular systolic function and mechanical dyssynchrony in ischemic or non-ischemic dilated cardiomyopathy: A speckle-tracking study

AIM

This study assessed RV dyssynchrony (irrespective to QRS duration) and RV systolic function in non-ischemic dilated cardiomyopathy (NIDCM) versus ischemic dilated cardiomyopathy (IDCM) patients by using different echo-Doppler modalities.

METHODS

Eighty-five cases (48 patients with DCM [whether ischemic or non-ischemic] and 37 age-matched healthy controls) were studied. Conventional echo-Doppler study, tissue Doppler (TDI), and speckle tracking (STE) were carried out to measure LV and RV systolic function. Time-to-peak negative longitudinal strain at the four RV sites were assessed by TDI derived strain and 2D speckle tracking.

RESULTS

Patients with DCM (whether ischemic or non-ischemic) had significantly lower fractional area change, RV tricuspid annular systolic velocity (p < .001 for both), tricuspid annular plane systolic excursion (p = .01), RV-GLS whether TDI or 2D derived (p < .001). Twenty-nine patients (60%) showed right intraventricular delay (RV4SD > 60 ms). The RV-dyssynchrony index was negatively correlated to %FAC (r = -.362, p = .01), RV Sm (r = -.312, p = .04), and 2D-RV GLS (r = -.305, p = .05). Insignificant higher RV-dysynchrony index was detected in NIDCM compared to IDCM group; however, the basal septal segment was significantly delayed in dilated group. More impaired RV systolic function was detected in ischemic group. 2D STE and TDI showed a significant correlation in the assessment of the right-intraventricular delay (p = .001).

CONCLUSION

Right-intraventricular dyssynchrony are detectable in patients with dilated cardiomyopathy (whether ischemic or non-ischemic) with a higher statistically insignificant value in non-ischemic group by using tissue Doppler imaging and 2D speckle tracking. More impairment of the RV systolic function was noticed in the ischemic group. Impaired RV systolic function was associated with right intraventricular delay.

Right Ventricular Electromechanical Dyssynchrony and Its Relation to Right Ventricular Remodeling, Dysfunction, and Exercise Capacity in Ebstein Anomaly

BACKGROUND

Abnormal atrioventricular and intraventricular electrical conduction and dysfunction of the functional right ventricle (fRV) are common in Ebstein anomaly (EA). However, fRV mechanical dyssynchrony and its relation to fRV function are poorly characterized. We evaluated fRV mechanical dyssynchrony in EA patients in relation to fRV remodeling, dysfunction, and exercise intolerance.

METHODS

We retrospectively analyzed data from nonoperated EA patients and age-matched controls who underwent echocardiography, cardiovascular magnetic resonance imaging, and cardiopulmonary exercise testing to quantify right ventricular (RV) remodeling, dysfunction, and exercise capacity. The relation of these to fRV dyssynchrony was retrospectively investigated. Right ventricular mechanical dyssynchrony was defined by early fRV septal activation (right-sided septal flash), RV lateral wall prestretch/late contraction, postsystolic shortening, and intra-RV delay using two-dimensional strain echocardiography. The SD of time to peak shortening among the fRV segments was calculated as a parameter of mechanical dispersion.

RESULTS

Thirty-five EA patients (10 of whom were <18 years of age) and 35 age-matched controls were studied. Ebstein anomaly patients had worse RV function and increased intra-RV dyssynchrony versus controls. Nineteen of 35 (54%) EA patients had early septal activation with simultaneous stretch and consequent late activation and postsystolic shortening of RV lateral segments. Intra-fRV mechanical delay correlated with fRV end-diastolic volume index (r = 0.43, P < .05) and fRV end-systolic volume index (r = 0.63, P < .001). The fRV ejection fraction was lower in EA with versus without right-sided septal flash (44.9 ± 11.0 vs 54.2 ± 8.2, P = .012). The fRV mechanical dispersion correlated with the percentage of predicted peak VO₂ (r = -0.35, P < .05).

CONCLUSIONS

In EA, fRV mechanical dyssynchrony is associated with fRV remodeling, dysfunction, and impaired exercise capacity. Mechanical dyssynchrony as a therapeutic target in selected EA patients warrants further study.

The prognostic value of right ventricular strain and mechanical dispersion on mortality in patients with normal left ventricle function

AIMS

We aimed to assess if right ventricular (RV) 4-chamber longitudinal strain (RV4CLS), RV free wall longitudinal strain (RVFWLS) and RV mechanical dispersion index (RVMDI) have prognostic independent value in patients with preserved ejection fraction (pEF), without clearly elevated LV filling pressure.

METHODS

Retrospective analysis of Peak RV4CLS, RVFWLS, RVMDI and comprehensive echocardiographic assessment including left ventricle (LV), atrium (LA) strain and RV parameters in patients with pEF (EF ≥ 50%; E/e' < 14). Multivariate Cox regression hazards model were used to determine the independent association between RV strain parameters to all-cause mortality and cardiovascular events.

RESULTS

We analyzed 224 consecutive patients with pEF (age 65.2 ± 19.8, 44% female, Charlson Comorbidity Index median = 3.8), with all-cause mortality of 64 patients and 28 cardiovascular events, during a median follow-up of 8.2 years (interquartile range: 6.8 to 8.4 years). The best strain univariate predictors of mortality were RV4CSL [1.16 (1.07-1.26); p = 0.0001] and RVMDI [1.01 (1.001-1.02); p = 0.02] being superior to LV and LA strain, or other RV functional indices. Moreover, after adjustment for clinical (age, gender, Charlson Comorbidity Index), conventional echocardiographic parameters (LA volume, E/e' average, LVEDD, routine RV functional indices), LV and LA STE, RV4CLS and RVFWLS remained statistically significant associates of all-cause mortality and cardiac events. RV4CLS, or RVFWLS remained statistically significant associated for all-cause mortality, after additional adjustment for RVFAC and RVMDI.

CONCLUSIONS

RV4CSL and RVMDI provide significant prognostic additive value in patients with preserved ejection fraction with excellent reproducibility, incremental to routine clinical, hemodynamic and LV and LA STE parameters.

Right ventricular electromechanical dyssynchrony in adults with repaired Tetralogy of Fallot

Background and purpose

Electromechanical dyssynchrony, manifested by right bundle branch block and regional wall mechanical dysfunction, contributes to inefficient RV function in repaired Tetralogy of Fallot (ToF). This study aims to evaluate the synchronicity of multiple RV walls using two-dimensional multi-plane echocardiography (2D-MPE) in order to augment current understanding of the mechanisms behind RV dyssynchrony.

Methods

Sixty-nine adult ToF patients [aged 33 (23-45) years; 61% male] and twenty-five matched healthy controls underwent deformational analysis of the RV lateral, anterior, inferior and septal walls following 2D-MPE acquisitions. RV synchronicity was assessed by the intra-RV deformation delay between each basal RV wall and mid-septal segment in addition to mechanical dispersion calculated across four, six and eight segments (MD).

Results

All RV wall-septum delays plus MD-4 and MD-6 indices were significantly greater in ToF patients compared to healthy controls (p < 0.001-0.03). In ToF patients, the lateral and anterior RV walls were last to reach peak deformation and anterior wall longitudinal strain was lower (p = 0.001). Post systolic shortening of at least one RV wall segment was identified in 19 (28%) ToF patients. Despite similar ECG characteristics, lateral and anterior wall-septum delays were significantly longer in patients with greater degrees of dyssynchrony (73 [37-108]ms vs. 37 [0-63]ms, p = 0.006; 91 [52-116]ms vs. 41 [1-69]ms, p = 0.013), although RV ejection fraction (RVEF) was not significantly lower. MD-4 and MD-8 indices displayed moderate negative associations with RVEF, strengthened by inclusion of lateral wall longitudinal strain (r = 0.64/0.65; p ≤0.01).

Conclusion

RV dyssynchrony in ToF is characterised by electromechanical delays between the lateral, anterior and septal walls, with anterior wall dysfunction likely associated with surgical repair of the RV outflow tract. Prospectively, 2D-MPE may have an emerging role evaluating RV mechanical response to electrical resynchronisation therapy.

The right ventricle in tetralogy of Fallot: adaptation to sequential loading

Right ventricular dysfunction is a major determinant of outcome in patients with complex congenital heart disease, as in tetralogy of Fallot. In these patients, right ventricular dysfunction emerges after initial pressure overload and hypoxemia, which is followed by chronic volume overload due to pulmonary regurgitation after corrective surgery. Myocardial adaptation and the transition to right ventricular failure remain poorly understood. Combining insights from clinical and experimental physiology and myocardial (tissue) data has identified a disease phenotype with important distinctions from other types of heart failure. This phenotype of the right ventricle in tetralogy of Fallot can be described as a syndrome of dysfunctional characteristics affecting both contraction and filling. These characteristics are the end result of several adaptation pathways of the cardiomyocytes, myocardial vasculature and extracellular matrix. As long as the long-term outcome of surgical correction of tetralogy of Fallot remains suboptimal, other treatment strategies need to be explored. Novel insights in failure of adaptation and the role of cardiomyocyte proliferation might provide targets for treatment of the (dysfunctional) right ventricle under stress.

Outcome and right ventricle remodelling after valve replacement for pulmonic stenosis

BACKGROUND

Complications and need for reinterventions are frequent in patients with pulmonary valve stenosis (PVS). Pulmonary regurgitation is common, but no data are available on outcome after pulmonary valve replacement (PVR).

METHODS

We performed a retrospective analysis of 215 patients with PVS who underwent surgical valvotomy or balloon valvuloplasty. Incidence and predictors of reinterventions and complications were identified. Right ventricle (RV) remodelling after PVR was also assessed.

RESULTS

After a median follow-up of 38.6 (30.9-49.4) years, 93% of the patients were asymptomatic. Thirty-nine patients (18%) had at least one PVR. Associated right ventricular outflow tract (RVOT) intervention and the presence of an associated defect were independent predictors of reintervention (OR: 4.1 (95% CI 1.5 to 10.8) and OR: 3.6 (95% CI 1.9 to 6.9), respectively). Cardiovascular death occurred in 2 patients, and 29 patients (14%) had supraventricular arrhythmia. Older age at the time of first intervention and the presence of an associated defect were independent predictors of complications (OR: 1.0 (95% CI 1.0 to 1.1) and OR: 2.1 (95% CI 1.1 to 4.2), respectively). In 16 patients, cardiac magnetic resonance before and after PVR was available. The optimal cut-off values for RV volume normalisation were 193 mL/m² for RV end-diastolic volume indexed(sensitivity 80%, specificity 64%) and 100 mL/m² for RV end-systolic volume indexed(sensitivity 80%, specificity 56%).

CONCLUSIONS

Previous RVOT intervention, presence of an associated defect and older age at the time of first repair were predictors of outcome. More data are needed to guide timing of PVR, and extrapolation of tetralogy of Fallot guidelines to this population is unlikely to be appropriate.

Right ventricular resynchronization in a patient with repaired tetralogy of Fallot and severe ventricular dysfunction

Right ventricular (RV) resynchronization therapy (CRT) with stimulation electrode implantation in the latest activation area guided by a high-density electroanatomic activation map was successfully performed in a patient with repaired tetralogy of Fallot (rToF), severe pulmonary regurgitation (PR), and severe dysfunction and dilatation of the right ventricle. An improvement in his clinical condition and intraventricular synchrony was achieved. There is a mechanical-electrical interaction in the right ventricle of patients with rToF; therefore, RV CRT in selected cases may be beneficial. Electroanatomic activation mapping can help achieve maximum clinical benefit by identifying the optimal stimulation site.

Exploring the cause of conduction delays in patients with repaired Tetralogy of Fallot

AIMS

Cardiac dyssynchrony in patients with repaired Tetralogy of Fallot (rToF) has been attributed to right bundle branch block (RBBB), fibrosis and/or the patches that are inserted during repair surgery. We aimed to investigate the basis of abnormal activation in rToF patients by mapping the electrical activation sequence during sinus rhythm (SR) and right ventricular (RV) pacing.

METHODS AND RESULTS

A total of 17 patients were studied [13 with rToF, 2 with left bundle branch block (LBBB), and 2 without RBBB or LBBB (non-BBB)] during medically indicated cardiac surgery. During SR and RV pacing, measurements were performed using 112-electrode RV endocardial balloons (rToF only) and biventricular epicardial sock arrays (four of the rToF and all non-rToF patients). During SR, functional lines of block occurred in five rToF patients, while RV pacing caused functional blocks in four rToF patients. The line of block persisted during both SR and RV pacing in only 2 out of 13 rToF patients. Compared to SR, RV pacing increased dispersion of septal activation, but not dispersion of endocardial and epicardial activation of the RV free wall. During pacing, RV and left ventricular activation dispersion in rToF patients were comparable to that of the non-rToF patients.

CONCLUSION

The results of the present study indicate that the delayed activation in the right ventricle of rToF patients is predominantly due to block(s) in the Purkinje system and that conduction in RV tissue is fairly normal.

Myocardial Postsystolic Shortening and Early Systolic Lengthening: Current Status and Future Directions

The concept of paradoxical myocardial deformation, commonly referred to as postsystolic shortening and early systolic lengthening, was originally described in the 1970s when assessed by invasive cardiac methods, such as ventriculograms, in patients with ischemia and animal experimental models. Today, novel tissue-based imaging technology has revealed that these phenomena occur far more frequently than first described. This article defines these deformational patterns, summarizes current knowledge about their existence and highlights the clinical potential associated with their understanding.

Asymmetric Regional Work Contributes to Right Ventricular Fibrosis, Inefficiency, and Dysfunction in Pulmonary Hypertension versus Regurgitation

BACKGROUND

Right ventricular (RV) pressure loading from pulmonary hypertension (PH) and volume loading from pulmonary regurgitation (PR) lead to RV dysfunction, a critical determinant of clinical outcomes, but their impact on regional RV mechanics and fibrosis is poorly characterized. The aim of this study was to test the hypothesis that regional myocardial mechanics and efficiency in RV pressure and volume loading are associated with RV fibrosis and dysfunction.

METHODS

Eight PH, six PR, and five sham-control rats were studied. The PH rat model was induced using Sugen5416, a vascular endothelial growth factor receptor 2 inhibitor, combined with chronic hypoxia. PR rats were established by surgical laceration of the pulmonary valve leaflets. Six (n = 4) or 9 (n = 4) weeks after Sugen5416 and hypoxia and 12 weeks after PR surgery, myocardial strain and RV pressure were measured and RV pressure-strain loops generated. We further studied RV regional mechanics in 11 patients with PH. Regional myocardial work was calculated as the pressure-strain loop area (mm Hg ∙ %). Regional myocardial work efficiency was quantified through wasted work (ratio of systolic lengthening to shortening work). The relation of regional myocardial work to RV fibrosis and dysfunction was analyzed.

RESULTS

In rats, PH and PR induced similar RV dilatation, but fractional area change (%) was lower in PH than in PR. RV lateral wall work was asymmetrically higher in PH compared with sham, while septal work was similar to sham. In PR, lateral and septal work were symmetrically higher versus sham. Myocardial wasted work ratio was asymmetrically increased in the PH septum versus sham. Fibrosis in the RV lateral wall, but not septum, was higher in PH than PR. RV fibrosis burden was linearly related to regional work and to measures of RV systolic and diastolic function but not to wasted myocardial work ratio. Patients with PH demonstrated similar asymmetric and inefficient regional myocardial mechanics.

CONCLUSIONS

Asymmetric RV work and increased wasted septal work in experimental PH are associated with RV fibrosis and dysfunction. Future investigation should examine whether assessment of asymmetric regional RV work and efficiency can predict clinical RV failure and influence patient management.

Three-dimensional right ventricular shape and strain in congenital heart disease patients with right ventricular chronic volume loading

AIMS

Right ventricular (RV) function assessment is crucial in congenital heart disease patients, especially in atrial septal defect (ASD) and repaired Tetralogy of Fallot (TOF) patients with pulmonary regurgitation (PR). In this study, we aimed to analyse both 3D RV shape and deformation to better characterize RV function in ASD and TOF-PR.

METHODS AND RESULTS

We prospectively included 110 patients (≥16 years old) into this case-control study: 27 ASD patients, 28 with TOF, and 55 sex- and age-matched healthy controls. Endocardial tracking was performed on 3D transthoracic RV echocardiographic sequences and output RV meshes were post-processed to extract local curvature and deformation. Differences in shape and deformation patterns between subgroups were quantified both globally and locally. Curvature highlights differences in RV shape between controls and patients while ASD and TOF-PR patients are similar. Conversely, strain highlights differences between controls and TOF-PR patients while ASD and controls are similar [global area strain: -31.5 ± 5.8% (controls), -34.1 ± 7.9% (ASD), -24.8 ± 5.7% (TOF-PR), P < 0.001, similar significance for longitudinal and circumferential strains]. The regional and local analysis highlighted differences in particular in the RV free wall and the apical septum.

CONCLUSION

Chronic RV volume loading results in similar RV shape remodelling in both ASD and TOF patients while strain analysis demonstrated that RV strain is only reduced in the TOF group. This suggests a fundamentally different RV remodelling process between both conditions.

Tetralogy of Fallot: cardiac imaging evaluation

Thanks to advances in pediatric cardiology, most infants with tetralogy of Fallot (TOF) now survive into adulthood. This relatively new population of adult patients may face long-term complications, including pulmonary regurgitation (PR), right ventricular (RV) tract obstruction, residual shunts, RV dysfunction, and arrythmias. They will often need to undergo pulmonary valve (PV) replacement and other invasive re-interventions. However, the optimal timing for these procedures is challenging, largely due to the complexity of evaluating RV volume and function. The options for the follow-up of these patients have rapidly evolved from an angiography-based approach to the surge of advanced imaging techniques, mainly echocardiography, cardiac magnetic resonance (CMR), and computer tomography (CT). In this review, we outline the indications, strengths and limitations of these modalities in the adult TOF population.

Persistent left superior vena cava accompanying repaired tetralogy of Fallot: Does it pose a challenge for device implantation?

Persistent left superior vena cava is a thoracic venous return anomaly. Tetralogy of Fallot is one of the most common congenital anomalies seen with persistent left superior vena cava. We are presenting a successful cardiac resynchronisation therapy device implantation in a patient with repaired tetralogy of Fallot and persistent left superior vena cava combination which has not been previously reported in the literature.

Ventricular Myocardial Deformation Imaging of Patients with Repaired Tetralogy of Fallot

In patients with repaired tetralogy of Fallot (TOF), dysfunction of the right and left ventricles remains an important issue. Adverse right ventricular (RV) remodeling has been related to RV dilation secondary to pulmonary regurgitation, electromechanical dyssynchrony, and myocardial fibrosis. Left ventricular (LV) dysfunction is attributed among other factors to altered ventricular-ventricular interaction. Advancements in echocardiography and cardiac magnetic resonance imaging have enabled direct interrogation of myocardial deformation of both ventricles in terms of myocardial strain and strain rate. Emerging evidence suggests that myocardial deformation imaging may provide incremental information for clinical use. In children and adults with repaired TOF, there is a growing body of literature on the use of myocardial deformation imaging in the assessment of ventricular mechanics and its clinical and prognostic values. The present review aims to provide an overview of impairment in RV and LV mechanics, associations between RV and LV deformation, changes in ventricular deformation after pulmonary valve replacement, and associations between measures of RV and LV deformation and outcomes and to highlight the clinical translational potential of myocardial deformation imaging in patients with repaired TOF.

The right ventricular myocardial systolic-to-diastolic duration ratio in children after surgical repair of Tetralogy of Fallot

Right ventricular (RV) function impacts clinical outcomes after surgical repair of Tetralogy of Fallot (rTOF). However, assessment of RV function remains difficult. We investigated the RV myocardial systolic-to-diastolic (S/D) duration ratio derived from strain imaging time intervals to characterize RV myocardial performance, exploring its relation with peak oxygen consumption during exercise (V̇o₂) and cardiac magnetic resonance-derived RV dilation and function in rTOF. We retrospectively analyzed 76 children with rTOF and 42 normal controls. The RV myocardial S/D duration ratio was measured from RV global and regional 2D speckle tracking longitudinal strain. Time from QRS onset to peak systolic strain was defined as the systolic duration. The S/D duration ratio was calculated and corrected for heart rate (HR). Postsystolic shortening (PSS) duration was defined as shortening time after cessation of pulmonary systolic antegrade flow. The RV myocardial S/D duration ratio, corrected or uncorrected for HR, was significantly higher in rTOF vs. controls (1 ± 0.3 vs. 0.8 ± 0.2, P = 0.004) in relation to prolonged PSS. The HR-corrected myocardial S/D duration ratio correlated weakly with RV ejection fraction (EF, r = -0.37, P = 0.001) and V̇o₂ (r = -0.32, P = 0.042). In multiregression analysis, RV EF was independently associated with the myocardial S/D duration ratio. The RV myocardial S/D duration ratio is a parameter of RV myocardial performance and efficiency, incorporating elements of systolic and diastolic performance, mechanical dyssynchrony, and PSS. The S/D duration ratio is associated with exercise capacity and RV dysfunction in rTOF.NEW & NOTEWORTHY This is the first study to assess right ventricular myocardial performance using the systolic-to-diastolic duration ratio derived from 2D strain. Seventy-six children with repaired Tetralogy of Fallot were evaluated. Echocardiographic data were correlated with cardiac magnetic resonance and peak oxygen consumption during exercise. The results show the right ventricular myocardial systolic-to-diastolic duration ratio incorporates systolic and diastolic performance, electromechanical dyssynchrony, and postsystolic shortening and is associated with exercise capacity in repaired Tetralogy of Fallot.

Evolution of ventricular function in children with permanent right ventricular pacing after tetralogy of Fallot repair: A midterm follow-up

OBJECTIVE

We aim to evaluate the midterm effect of chronic apical right ventricular (RV) pacing on right and left ventricular (LV) function using different modalities of echocardiography including conventional echocardiography, tissue Doppler imaging and two-dimension speckle tracking echocardiography.

METHODS

This case-control study enrolled 49 patients divided into two groups: a paced group and a nonpaced group. The paced group included 23 patients that underwent tetralogy of Fallot (TOF) repair and required permanent pacemaker insertion for postoperative complete heart block. The nonpaced group included 26 patients that had TOF repair at the same period.

RESULTS

The median age for the paced and nonpaced groups was 6 and 8 years, respectively (P = .169). The follow-up duration after TOF surgical repair was 4 years for the paced patients and 5 years for nonpaced patients (P = .411). In the nonpaced group, the QRS duration increased and LV global longitudinal strain (GLS) decreased significantly with increasing duration after TOF repair, P value was .006 and .042, respectively. In the paced group, tricuspid annular systolic plane excursion (TAPSE) was significantly correlated with age (r = .578; P = .004) and duration following TOF correction (r = .724; P < .001).

CONCLUSION

Chronic RV apical pacing in children after TOF repair was associated with better clinical status, preservation of RV systolic function, and prevention of progressive QRS prolongation. RV pacing was not associated with progressive deterioration of LV systolic function with increasing the time interval following TOF repair. Therefore, RV pacing can be beneficial in corrected TOF patients presenting with RV failure.

Relative Impact of Right Ventricular Electromechanical Dyssynchrony Versus Pulmonary Regurgitation on Right Ventricular Dysfunction and Exercise Intolerance in Patients After Repair of Tetralogy of Fallot

Background The relative impact of right ventricular ( RV ) electromechanical dyssynchrony versus pulmonary regurgitation ( PR ) on exercise capacity and RV function after tetralogy of Fallot repair is unknown. We aimed to delineate the relative effects of these factors on RV function and exercise capacity. Methods and Results We retrospectively analyzed 81 children with tetralogy of Fallot repair using multivariable regression. Predictor parameters were electrocardiographic QRS duration reflecting electromechanical dyssynchrony and PR severity by cardiac magnetic resonance. The outcome parameters were exercise capacity (percentage predicted peak oxygen consumption) and cardiac magnetic resonance ejection fraction (RV ejection fraction). To understand the relative effects of RV dyssynchrony versus PR on exercise capacity and RV function, virtual patient simulations were performed using a closed-loop cardiovascular system model (CircAdapt), covering a wide spectrum of disease severity. Eighty-one patients with tetralogy of Fallot repair (median [interquartile range { IQR} ] age, 14.48 [11.55-15.91] years) were analyzed. All had prolonged QRS duration (median [IQR], 144 [123-152] ms), at least moderate PR (median [IQR], 40% [29%-48%]), reduced exercise capacity (median [IQR], 79% [68%-92%] predicted peak oxygen consumption), and reduced RV ejection fraction (median [IQR], 48% [44%-52%]). Longer QRS duration, more than PR , was associated with lower oxygen consumption and lower RV ejection fraction. In a multivariable regression analysis, oxygen consumption decreased with both increasing QRS duration and PR severity. CircAdapt modeling showed that RV dyssynchrony exerts a stronger limiting effect on exercise capacity and on RV ejection fraction than does PR , regardless of contractile function. Conclusions In both patient data and computer simulations, RV dyssynchrony, more than PR , appears to be associated with reduced exercise capacity and RV systolic dysfunction in patients after TOF repair.

Quantification of Right Ventricular Electromechanical Dyssynchrony in Relation to Right Ventricular Function and Clinical Outcomes in Children with Repaired Tetralogy of Fallot

BACKGROUND

Electromechanical dyssynchrony occurs ubiquitously following tetralogy of Fallot (TOF) repair, manifesting electrically as a wide QRS duration and mechanically as a right-sided septal/apical flash. Early septal activation and prestretch of the right ventricular (RV) basal lateral wall followed by its postsystolic shortening contributes to inefficient RV mechanics. However, a right-sided septal flash is a dichotomous finding, and the severity of RV dyssynchrony as a continuous spectrum in relationship to RV dysfunction and clinical outcomes in patients with repaired TOF has not been studied. The aim of this study was to quantify the severity of electromechanical dyssynchrony in relation to RV remodeling and clinical outcomes in a pediatric cohort following TOF repair.

METHODS

A retrospective analysis was performed in 81 children with RV volume loading after TOF repair, aged 13.6 ± 2.9 years, and compared with 50 matched control subjects.

RESULTS

Patients had higher RV basal-lateral prestretch and postsystolic strain amplitude and duration, RV mechanical dispersion, and basal lateral-septal wall delay compared with control subjects (P < .001 for all). All intra-RV dyssynchrony timing parameters were associated with reduced cardiac magnetic resonance-derived RV ejection fraction and/or echocardiography-derived RV longitudinal strain. Prestretch duration as a percentage of total shortening time and RV basal lateral-to-midseptal delay were independently associated with RV dysfunction. Postsystolic strain amplitude was higher in patients with ventricular arrhythmias compared with arrhythmia-free patients (7.8% [4.2%-13%] vs 2.0% [0%-12.5%], P = .03).

CONCLUSION

RV prestretch duration, postsystolic strain, and RV lateral-septal delay quantify RV electromechanical dyssynchrony severity and reflect the underlying pathophysiology. The prestretch duration percentage and RV basal lateral-to-midseptal delay were independently associated with RV dysfunction, potentially providing a clinical tool to quantify RV electromechanical dyssynchrony.

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.

Right ventricular function in patients with pulmonary regurgitation with versus without tetralogy of Fallot

BACKGROUND

Right ventricular (RV) dilation from pulmonary valve regurgitation (PR) is common after intervention(s) for pulmonary stenosis (PS) or atresia and intact ventricular septum (PA/IVS). It is not well established whether PR and RV dilation have similar effects on RV function and exercise capacity in these patients compared to patients after repair of tetralogy of Fallot (rToF). The aims of this study were to compare exercise tolerance, RV function and myocardial mechanics in non-ToF versus rToF children with significantly increased and comparable RV volumes.

METHODS

Thirty PS or PA/IVS children after intervention(s) with significant PR and RV dilation (non-ToF group) were retrospectively matched for RV end-diastolic volume index (RVEDVi) and age with 30 rToF patients. Clinical characteristics, RV function by echocardiography and CMR, ECG and exercise capacity were compared between groups.

RESULTS

The groups were well matched for RVEDVi and age. Global RV function (RVEF: 48.7 ± 6.4% vs. 48.5 ± 7.2%, P = .81) and exercise capacity (% predicted peak VO₂:82.5 ± 17.7% vs. 75.6 ± 20.4%, P = .27) were similarly reduced between groups. RVEDVi correlated inversely with RVEF in both groups (non-ToF:r = -0.39, P = .04, rToF:r = -0.40, P = .03). QRS duration was wider in rToF patients, and in both groups inversely correlated with RVEF (non-ToF:r = -0.77, P < .001, rToF:r = -0.69, P < .001). In contrast to global function, longitudinal RV strain was lower in rTOF vs non-TOF (-20.1 ± 3.9 vs.-25.7 ± 4.4, P < .001).

CONCLUSIONS

Global RV function and exercise capacity are similarly reduced in non-ToF and rToF patients with severely dilated RV, after matching by RVEDVi, suggesting a comparable impact of RV dilation on RV global function. The significance of reduced RV longitudinal function and worse dyssynchrony in rToF patients require further exploration.

Pulmonary Right Ventricular Resynchronization in Congenital Heart Disease

Background—

Electromechanical discoordination may contribute to long-term pulmonary right ventricular (RV) dysfunction in patients after surgery for congenital heart disease. We sought to evaluate changes in RV function after temporary RV cardiac resynchronization therapy.

Methods and Results—

Twenty-five patients aged median 12.0 years after repair of tetralogy of Fallot and similar lesions were studied echocardiographically (n=23) and by cardiac catheterization (n=5) after primary repair (n=4) or after surgical RV revalvulation for significant pulmonary regurgitation (n=21). Temporary RV cardiac resynchronization therapy was applied in the presence of complete right bundle branch block by atrial-synchronized RV free wall pacing in complete fusion with spontaneous ventricular depolarization using temporary electrodes. The q-RV interval at the RV free wall pacing site (mean 77.2% of baseline QRS duration) confirmed pacing from a late activated RV area. RV cardiac resynchronization therapy carried significant decrease in QRS duration ( P <0.001) along with elimination of the right bundle branch block QRS morphology, increase in RV filling time ( P =0.002), pulmonary artery velocity time integral ( P =0.006), and RV maximum +dP/dt ( P <0.001), and decrease in RV index of myocardial performance ( P =0.006). RV mechanical synchrony improved: septal-to-lateral RV mechanical delay decreased ( P <0.001) and signs of RV dyssynchrony pattern were significantly abolished. RV systolic stretch fraction reflecting the ratio of myocardial stretching and contraction during systole diminished ( P =0.001).

Conclusions—

In patients with congenital heart disease and right bundle branch block, RV cardiac resynchronization therapy carried multiple positive effects on RV mechanics, synchrony, and contraction efficiency.

QRS Width as a Predictor of Right Ventricular Remodeling After Percutaneous Pulmonary Valve Implantation

Recent data showed a right ventricular dyssynchrony in patients with tetralogy of Fallot (TOF). Percutaneous pulmonary valve implantation (PPVI) has become an important procedure to treat a pulmonary stenosis and/or regurgitation of the right ventricular outflow tract in these patients. Despite providing good results, there is still a considerable number of nonresponders to PPVI. The authors speculated that electrical dysfunction of the right ventricle plays an underestimated role in the outcome of patients after PPVI. This study aimed to investigate the influence of right ventricular electrical dysfunction, i.e., right bundle branch block (RBBB) on the RV remodeling after PPVI. The study included consecutive patients after correction of TOF with or without RBBB, who had received a PPVI previously at the Heart Center of the University of Leipzig, Germany during the period from 2012 to 2015. 24 patients were included. Patients without RBBB, i.e., with narrow QRS complexes pre-intervention, had significantly better RV function and had smaller right ventricular volumes. Patients with pre-interventionally QRS width below 150 ms showed a post-interventional remodeling of the right ventricle with the decreasing RV volumes (p = 0.001). The parameters of LV function and volume as well as RV ejection fraction remained unaffected by RBBB. The presented data indicate that the QRS width seems to be a valuable parameter in the prediction of right ventricular remodeling after PPVI, as it represents both electrical and mechanical functions of the right ventricle and may serve as an additional parameter for optimal timing of a PPVI.

Postsystolic Shortening Is Associated with Altered Right Ventricular Function in Children after Tetralogy of Fallot Surgical Repair

The aim of the study was to determine whether segmental interactions, as expressed by postsystolic shortening (PSS), affects RV mechanics and are connected with impaired systolic and diastolic function in rTOF children. Patients and Methods: 55 rTOF adolescent (study group), and 34 healthy volunteers (control group) were examined using classical Doppler flow (Doppler), Tissue Doppler Imaging (TDI) and Speckle Tracking Echocardiography (STE). PSS was found to occur when time to peak (TTP) was longer than pulmonary valve closure time (PVCT). TTP and strain were derived from RV lateral segments—basal (BL), medial (ML) and apical (AL) in STE. PVCT was measured from the beginning of QRS complex in the ECG to the termination of Doppler flow at the pulmonary valve. TDI was obtained at the lateral tricuspid annulus site and the systolic (S′), early (E′) and late diastolic (A’) peak velocities were measured along with isovolumic contraction (IVCT), and relaxation (IVRT) time. PW was used to measure early tricuspid inflow velocity (E) for calculating the E/E’ ratio. The TDI data in patients with PSS presence (TTP>PVCT) and those in whom it did not occur (TTP≤PVCT) were compared. Results: PSS in BL, ML and AL were observed respectively in: 27(51,9%), 9 (18%), and 8 (16,7%) patients. Mean values of TTP in BL, ML, and AL were respectively: 420.6±55.5ms, 389.8±50.0ms and 366.7±59.0ms. PVCT mean value was 396.6±33.5ms. In the study group, the mean E’ in TTP>PVCT was significantly lower (4.8±1.8 cm/s) compared to mean E’ in TTP≤PVCT (8.4±2.6 cm/s), p<0.01. The average E/E’ was significantly higher in TTP>PCVT than in TTP≤PVCT, respectively 21.6±7.3 vs 12.2±5.1, p<0.05. IVRT was significantly prolonged in TTP>PVCT compared to IVRT in TTP≤PVCT, respectively 95.9±38.7 vs 77.0±35.1, p<0.05. Furthermore, in TTP>PVCT, significantly higher strain in BL (-28.8±8.7%) was observed when compared to that parameter in TTP≤PVCT (-35.3±13.1%), p <0.05. Conclusions: Tissue Doppler Echocardiography and Speckle Tracking Echocardiography are useful techniques for detecting regional systolic and diastolic dysfunction in children after Tetralogy of Fallot surgical repair. Postsystolic shortening in the basal lateral segment is commonly seen in children after the Tetralogy of Fallot surgical repair, and is associated with altered right ventricular systolic and diastolic function.

Repolarization Alternans and Ventricular Arrhythmia in a Repaired Tetralogy of Fallot Animal Model

BACKGROUND

Ventricular arrhythmia is an important cause of late death in patients with repaired tetralogy of Fallot (rTOF). By using an rTOF canine model, we investigated the role of repolarization alternans and its electrophysiological mechanisms.

METHODS AND RESULTS

Six dogs received right ventricular outflow tract (RVOT) transannular patch, pulmonary valve destruction, and right bundle branch ablation to simulate rTOF. After 1 year, we performed high-resolution dual-voltage and calcium optical mapping to record action potentials and calcium transients on the excised right ventricular outflow tract wedges. Another 6 dogs without operation served as control. The rTOF group was more susceptible to action potential duration alternans (APD-ALT) and spatially discordant APD-ALT than control (threshold for APD-ALT: 516±36 vs 343±36 ms; P=0.017; threshold for discordant APD-ALT: 387±30 vs 310±14 ms; P=0.046). We detected 2 episodes of ventricular tachycardia in the rTOF group, but none in the control. Expressions of Kv4.3 and KChIP2 decreased in the rTOF group. Expression of connexin 43 also decreased in the rTOF group with a corresponding decrease of conduction velocity and might contribute to spatially discordant APD-ALT. We also found distinct electrophysiological features of the RVOT, including biphasic relationship between magnitude of APD-ALT and pacing cycle length, uncoupling of APD-ALT, and calcium transients alternans, and shortened APD, but unchanged, APD restitution in rTOF.

CONCLUSIONS

We demonstrated novel electrophysiological properties of the RVOT. In an rTOF model, the RVOT exhibits increased susceptibility to temporal and spatially discordant APD-ALT, which was not totally dependent on calcium transient alternans.

Spatio-Temporal Tensor Decomposition of a Polyaffine Motion Model for a Better Analysis of Pathological Left Ventricular Dynamics

Given that heart disease can cause abnormal motion dynamics over the cardiac cycle, understanding and quantifying cardiac motion can provide insight for clinicians to aid with diagnosis, therapy planning, and determining prognosis. The goal of this paper is to extract population-specific motion patterns from 3D displacements in order to identify the mean motion in a population, and to describe pathology-specific motion patterns in terms of the spatial and temporal components. Since there are common motion patterns observed in patients with the same condition, extracting these can lead towards a better understanding of the disease. Quantifying cardiac motion at a population level is not a simple task since images can vary widely in terms of image quality, size, resolution, and pose. To overcome this, we analyze the parameters obtained from a cardiac-specific Polyaffine motion-tracking algorithm, which are aligned both spatially and temporally to a common reference space. Once all parameters are aligned, different subjects can be compared and analyzed in the space of Polyaffine transformations by projecting the transformations to a reduced order subspace in which dominant motion patterns in each population can be extracted. Using tensor decomposition, the spatial and temporal aspects can be decoupled in order to study the components individually. The proposed method was validated on healthy volunteers and Tetralogy of Fallot patients according to known spatial and temporal behavior for each population. A key advantage of this method is the ability to regenerate motion sequences from the models, which can be visualized in terms of the full motion.