Classic-Pattern Dyssynchrony in Adolescents and Adults With a Fontan Circulation

Assessment of hemodynamic disturbances and impaired ventricular filling in asymptomatic fontan patients: A 4D flow CMR study

Background

The Fontan procedure is a surgical intervention designed for patients with single ventricle physiology, wherein the systemic venous return is redirected into the pulmonary circulation, thereby facilitating passive pulmonary blood flow without the assistance of ventricular propulsion. Consequently, long-term follow-up of individuals who have undergone the asymptomatic Fontan procedure is essential.

Objectives

The aims of this investigation were to: 1) examine the impact of flow components and kinetic energy (KE) parameters on hemodynamic disturbances in asymptomatic Fontan patients and control group; 2) Assess left ventricular diastolic dysfunction through the analysis of 4D flow parameters across different Fontan sub-groups; 3) Compare intracardiac flow parameters among Fontan sub-groups based on morphological features of the left ventricle (LV) and right ventricle (RV).

Methods

Twenty-five Fontan patients (mean age: 10 ± 3 years, male/female: 15/10) and fourteen control subjects (mean age: 10 ± 2 years, male/female: 8/6) were recruited retrospectively for the study. The Fontan patients were further categorized into three groups based on their ventricular function: left ventricular (LV), right ventricular (RV), and biventricular (BiV). Each participant underwent cardiovascular magnetic resonance (CMR) imaging, including cine and 4D flow sequences on a 3.0 T scanner. Ventricular flow components and KE were assessed using 4D flow. The study utilized cine images to analyze cardiac function and inter-ventricular mechanical dyssynchrony. Echocardiography evaluated functional ventricular diastolic dysfunction.

Results

Fontan patients had a higher median functional single ventricle (FSV) residual volume compared to controls (28 % vs. 23 %, P = 0.034), with lower median FSV direct flow (32 % vs. 40 %, P = 0.005) and delayed ejection flow (17 % vs. 24 %, P = 0.024). The parameters of FSV normalized to the ventricular end-diastolic volume (KEiEDV) were found to be significantly lower in Fontan patients (all P < 0.05). In both left ventricle (LV) and biventricular (BiV) Fontan subgroups, direct flow was identified as an independent predictor of LV diastolic dysfunction (AUC=0.76, Sensitivity=86 %, Specificity=70 %). Furthermore, residual volume and E-wave KEiEDV were observed to be significantly different between LV and right ventricle (RV) Fontan subgroups.

Conclusions

The altered flow pattern and reduced kinetic energy observed in Fontan patients may indicate hemodynamic disturbances and compromised ventricular filling. Reduced direct flow is associated with LV diastolic dysfunction in LV and BiV Fontan subgroups. Systemic LV exhibited a more efficient intracardiac flow pattern compare with systemic RV in Fontan patients.

Adverse Effect of Bundle Branch Block on Exercise Performance in Patients with Fontan Physiology: From the Pediatric Heart Network Fontan Public Data Set

Patients with Fontan physiology have reduced exercise performance compared to their peers as well as a higher incidence of bundle branch block (BBB). This study aims to investigate the association between BBB and exercise performance in the Fontan population through a retrospective review of the Pediatric Heart Network Fontan study public use dataset. "Low Performers" were defined as ≤ 25th percentile (for Fontan patients) for each exercise parameter at anaerobic threshold (AT) for gender and age and "Normal Performers" were all other patients. A total of 303 patients with Fontan physiology who underwent exercise testing reached AT and had complete data for BBB. BBB occurred more frequently in Low Performers for VO2 [OR (95% CI): 2.6 (1.4, 4.8)] and Work [OR (95% CI): 2.7 (1.4, 5.1)], suggesting that BBB in the Fontan population is associated with reduced exercise performance. This data adds to the existing clinical evidence of the adverse effects of conduction abnormalities on single ventricle cardiac output and adds support for consideration of cardiac resynchronization and multi-site ventricular pacing in this patient population.

Effects of cardiac growth on electrical dyssynchrony in the single ventricle patient

Single ventricle patients, including those with hypoplastic left heart syndrome (HLHS), typically undergo three palliative heart surgeries culminating in the Fontan procedure. HLHS is associated with high rates of morbidity and mortality, and many patients develop arrhythmias, electrical dyssynchrony, and eventually ventricular failure. However, the correlation between ventricular enlargement and electrical dysfunction in HLHS physiology remains poorly understood. Here we characterize the relationship between growth and electrophysiology in HLHS using computational modeling. We integrate a personalized finite element model, a volumetric growth model, and a personalized electrophysiology model to perform controlled in silico experiments. We show that right ventricle enlargement negatively affects QRS duration and interventricular dyssynchrony. Conversely, left ventricle enlargement can partially compensate for this dyssynchrony. These findings have potential implications on our understanding of the origins of electrical dyssynchrony and, ultimately, the treatment of HLHS patients.

Contemporary Management of the Failing Fontan

Adult patients with congenital heart disease have now surpassed the pediatric population due to advances in surgery and improved survival. One such complex congenital heart disease seen in adult patients is the Fontan circulation. These patients have complex physiology and are at risk for several complications, including thrombosis of the Fontan pathway, pulmonary vascular disease, heart failure, atrial arrhythmias, atrioventricular valve regurgitation, and protein-losing enteropathy. This review discusses the commonly encountered phenotypes of Fontan circulatory failure and their contemporary management.

Guidelines for Performing a Comprehensive Pediatric Transthoracic Echocardiogram: Recommendations From the American Society of Echocardiography

Echocardiography is a fundamental component of pediatric cardiology, and appropriate indications have been established for its use in the setting of suspected, congenital, or acquired heart disease in children. Since the publication of guidelines for pediatric transthoracic echocardiography in 2006 and 2010, advances in knowledge and technology have expanded the scope of practice beyond the use of traditional modalities such as two-dimensional, M-mode, and Doppler echocardiography to evaluate the cardiac segmental structures and their function. Adjunct modalities such as contrast, three-dimensional, and speckle-tracking echocardiography are now used routinely at many pediatric centers. Guidelines and recommendations for the use of traditional and newer adjunct modalities in children are described in detail in this document. In addition, suggested protocols related to standard operations, infection control, sedation, and quality assurance and improvement are included to provide an organizational structure for centers performing pediatric transthoracic echocardiograms.

Indications for Cardiac Resynchronization Therapy in Patients with Congenital Heart Disease

Heart failure in patients with congenital heart disease (CHD) stems from unique causes compared with the elderly. Patients with CHD face structural abnormalities and malformations present from birth, leading to altered cardiac function and potential complications. In contrast, elderly individuals primarily experience heart failure due to age-related changes and underlying cardiovascular conditions. Cardiac resynchronization therapy (CRT) can benefit patients with CHD, although it presents numerous challenges. The complexities of CHD anatomy and limited access to appropriate venous sites for lead placement make CRT implantation demanding.

Novel Therapeutic Strategies in Heart Failure in Adult Congenital Heart Disease: of Medicines and Devices

PURPOSE OF REVIEW

This paper reviews the latest literature on the growing field of heart failure in the adult congenital heart disease population.

RECENT FINDINGS

After highlighting the increasing prevalence and a few of the unique potential causes, including the concept of early senescence, this review begins with novel medical management strategies such as the angiotensin II receptor blocker and neprilysin inhibitors and sodium glucose cotransporter-2 inhibitors. Then, it addresses the latest applications of percutaneous techniques like implantable hemodynamic monitoring, transcatheter pulmonary and aortic valve replacement, and mitral clips. Cardiac resynchronization therapy and novel lymphatic system imaging and intervention are then described. Finally, the use of mechanical support devices, temporary and durable, is discussed as well as heart and combined heart and liver transplantation. There have been recent exciting advances in the strategies used to manage adult congenital heart disease patients with heart failure. As this population continues to grow, it is likely we will see further rapid evolution in this field.

The Evolution of Longitudinal Strain Across Various Univentricular Morphologies Prior to Superior Cavopulmonary Anastomosis

BACKGROUND

Infants with single-ventricle physiology have increased morbidity, mortality, and ventricular dysfunction in the pre-superior cavopulmonary anastomosis (pre-SCPA) period. Echocardiography-derived longitudinal strain (LS) is emerging as a reliable marker of single-ventricle performance. We aim to assess evolution of LS during the pre-SCPA period across univentricular morphologies and explore associations of LS with modifiable and nonmodifiable factors.

METHODS

Ninety-four term infants (36 females) with univentricular physiology who were discharged home prior to stage 2 palliation were serially analyzed for LS (single apical view) and other echo measures at initial hospital discharge and the last pre-SCPA encounter. Ventricular myocardium was tracked for strain along the septum and respective lateral wall for single right ventricular (RV) and left ventricular (LV) groups, and along both right and left lateral walls in functionally univentricular hearts with biventricular (BiV) morphology. Clinical data were obtained from the medical record.

RESULTS

Longitudinal strain improved in the total cohort during the pre-SCPA period (16.48% ± 3.31% to 17.57% ± 3.81%, P = .003). Longitudinal strain improved between encounters in the single LV (P = .04) and BiV groups (P = .02). However, LS failed to improve in the RV group (P = .7) with lower LS at both visits compared with the other groups. The RV group, mostly composed of hypoplastic left heart syndrome patients-87% of cases-had a higher incidence of arrhythmias (57%) and unplanned reinterventions (60%), most of which were arch reinterventions. A subanalysis based on arch reintervention showed that LS improves between encounters in the single LV group needing arch reintervention (P = .05) compared with the single RV group needing arch reintervention (P = .89). Lower LS was independently associated with unplanned reinterventions at both encounters (P = .008 and .02).

CONCLUSIONS

Single-ventricle LS evolves differently across ventricular morphologies during the pre-SCPA period and is related to the need for unplanned cardiac reinterventions. Lower LS is noted in the single RV group, who mostly have hypoplastic left heart syndrome.

Diastolic myocardial mechanics and their relation to ventricular filling pressures and postoperative course in functionally single ventricles

Diastolic dysfunction affects clinical outcomes in patients with a functionally single ventricle (FSV). The objective of this work is to study the association of ventricular mechanics and interventricular dependence on diastolic parameters and early post-Fontan outcomes. Sixty-one patients with FSV underwent echocardiography, cardiac catheterization, and magnetic resonance imaging on the same day before or after the Fontan procedure. Echocardiographic diastolic parameters, ventricular mass, and incoordinate wall motion, defined by the number of dyskinetic segments or by the lateral wall delay, were determined and studied for relationships with invasively measured hemodynamics and early postoperative Fontan course. In subjects with a sizable secondary ventricle, incoordinate motion was additionally analyzed at the left- and right-sided ventricular free walls. Resting ventricular end-diastolic pressure (VEDP) was ≤10 mmHg in most subjects. Individual echocardiographic parameters of the diastolic flow and tissue velocities did not correlate with VEDP, other hemodynamics, or post-Fontan clinical course. Incoordinate wall motion in the dominant and in the sizeable secondary ventricle, defined by the lateral wall delay or by the number of dyskinetic segments, was the only echo parameter that correlated, albeit weakly, with VEDP (r = 0.247, P = 0.040), oxygen saturation (r = -0.417, P = 0.001), pulmonary vascular resistance and flow (Qp) (r = -0.303, P = 0.011), Fontan fenestration flow (r = 0.512, P = 0.009), and duration of endotracheal intubation (r = 0.292, P = 0.022). When the nondominant (secondary) ventricle was accounted for in the analysis of incoordinate wall motion, these associations strengthened. The degree of incoordinate ventricular wall motion in diastole was associated with VEDP and postoperative Fontan course in FSV. Analysis of incoordinate wall motion of the dominant and sizeable secondary ventricle may be warranted and should be included in the assessment of the FSV after the Fontan procedure.NEW & NOTEWORTHY Diastolic dysfunction affects outcomes in patients with functionally single ventricles (FSVs) but is difficult to assess. We found that incoordinate wall motion was the only echo parameter that correlated with FSV end-diastolic pressure, oxygen saturation, pulmonary vascular resistance and flow, and duration of endotracheal intubation. Analysis of incoordinate wall motion in the nondominant (secondary) ventricle strengthened these associations. Analyzing incoordinate wall motion should be included in the assessment of the FSV after the Fontan procedure.

Myocardial strain-curve deformation patterns after Fontan operation

Myocardial deformation analysis by cardiac MRI (CMR) yielding global circumferential and longitudinal strain (GCS and GLS) is an increasingly utilized method to accurately quantify systolic function and predict clinical events in patients with Fontan circulation. The purpose of this study was to use principal component analysis (PCA) to investigate myocardial temporal deformation patterns derived from strain-time curves to learn about latent strain features beyond peak values. We conducted the study with specific attention to dominant single left or right ventricle (SLV and SRV) morphologies. Methods and Results: Patients remote from Fontan operation who underwent follow-up CMR were analyzed for standard volumetric and function hemodynamics including myocardial deformation parameters including GCS and GLS. We applied PCA to investigate in an unbiased fashion the strain-time curve morphology and to calculate patient specific shape scores. All variables were subjected to single variable Cox regression analysis to detect composite clinical outcome including death, heart transplant, protein losing enteropathy and plastic bronchitis. A total of 122 patients, (SLV = 67, SRV = 55) with a mean age of 12.7 years underwent comprehensive CMR analysis. The PCA revealed 3 primary modes of strain-curve variation regardless of single ventricle morphology and type of strain investigated. Principle components (PCs) described changes in (1) strain-time curve amplitude, (2) time-to-peak strain, and (3) post-systolic slope of the strain-time curve. Considering only SLV patients, GCS was only CMR variable predictive of clinical events (HR 1.46, p = 0.020). In the SRV group, significant CMR predictors of clinical events were derived indexed end-diastolic (HR 1.02, p = 0.023) and end-systolic (HR 1.03, p = 0.022) volumes, GCS (HR 1.91, p = 0.003) and its related first component score (HR 1.20, p = 0.005), GLS (HR 1.32, p = 0.029) and its third component score (HR 1.58, p = 0.017). CMR derived global strain measures are sensitive markers of clinical outcomes in patients with Fontan circulation, particularly in patients with the SRV morphology. Myocardial strain-time curve morphology specific to SLV and SRV patients inspired by unbiased PCA technique can further aid with predicting clinical outcomes.

Single ventricular strain measures correlate with peak oxygen consumption in children and adolescents with Fontan circulation

INTRODUCTION

Children with a single ventricle post-Fontan palliation are at increased risk of poor outcomes with peak oxygen consumption acting as a surrogate outcome marker. The purpose of this study is to evaluate the relationship between peak oxygen consumption and echocardiographic measures of ventricular function and deformation, including ventricular global longitudinal strain and dyssynchrony, in children and adolescents following Fontan palliation.

METHODS

Patients (age 8-21 years) with single ventricle post-Fontan palliation were prospectively recruited and participated in an echocardiogram, including views optimised for two-dimensional speckle tracking, and a cardiopulmonary exercise test on a cycle ergometer to maximal volitional fatigue.

RESULTS

Thirty-eight patients (mean age 13.7 ± 2.3 years) post-Fontan palliation had either a single left ventricular (n = 20), single right ventricular (n = 14), or biventricular (n = 4) morphology. Peak oxygen consumption (24.9 ± 5.6 ml/kg/minute) was correlated with global longitudinal strain (r = -0.435, p = 0.007), a strain discoordination time to peak index (r = -0.48, p = 0.003), and the presence of an electro-mechanical dyssynchrony strain pattern (p = 0.008). On multivariate regression modelling, these three variables were associated with peak oxygen consumption independently of age and sex. The single right ventricular group had evidence of possible diastolic dysfunction by E/e' compared to the single left ventricular and biventricular groups (p = 0.001).

CONCLUSIONS

Strain analysis measures are correlated with peak oxygen consumption in this cohort of children, adolescents, and young adults following Fontan palliation, suggesting that ventricular mechanics may influence the efficiency of the Fontan circulation.

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.

Impact and Modifiers of Ventricular Pacing in Patients With Single Ventricle Circulation

BACKGROUND

Palliation of the single ventricle (SV) circulation is associated with a burden of lifelong complications. Previous studies have identified that the need for a permanent ventricular pacing system (PPM_v) may be associated with additional adverse long-term outcomes.

OBJECTIVES

The goal of this study was to quantify the attributable risk of PPM_v in patients with SV, and to identify modifiable risk factors.

METHODS

This international study was sponsored by the Pediatric and Congenital Electrophysiology Society. Centers contributed baseline and longitudinal data for functionally SV patients with PPM_v. Enrollment was at implantation. Controls were matched 1:1 to PPM_v subjects by ventricular morphology and sex, identified within center, and enrolled at matched age. Primary outcome was transplantation or death.

RESULTS

In total, 236 PPM_v subjects and 213 matched controls were identified (22 centers, 9 countries). Median age at enrollment was 5.3 years (quartiles: 1.5-13.2 years), follow-up 6.9 years (3.4-11.6 years). Median percent ventricular pacing (Vp) was 90.8% (25th-75th percentile: 4.3%-100%) in the PPM_v cohort. Across 213 matched pairs, multivariable HR for death/transplant associated with PPM_v was 3.8 (95% CI 1.9-7.6; P < 0.001). Within the PPM_v population, higher Vp (HR: 1.009 per %; P = 0.009), higher QRS z-score (HR: 1.19; P = 0.009) and nonapical lead position (HR: 2.17; P = 0.042) were all associated with death/transplantation.

CONCLUSIONS

PPM_v in patients with SV is associated with increased risk of heart transplantation and death, despite controlling for increased associated morbidity of the PPM_v cohort. Increased Vp, higher QRS z-score, and nonapical ventricular lead position are all associated with higher risk of adverse outcome and may be modifiable risk factors.

Cardiac Implantable Electronic Devices in the Fontan Patient

As a result of remarkable progress in operative techniques and cardiology care during childhood, Fontan patients continue to age and require team-based multidisciplinary expertise to manage complications encountered in adulthood. They face particular challenges in terms of altered hemodynamic stressors, cardiac and hepatic failure, and arrhythmias. Arrhythmias in Fontan patients are highly prevalent and associated with underlying anatomy, surgical technique, and postoperative sequelae. Diagnostic tools, treatments, and device strategies for arrhythmias in Fontan patients should be adapted to the specific anatomy, type of surgical repair, and clinical status. Great strides in our understanding of arrhythmia mechanisms, options and techniques to obtain access to relevant cardiac structures, and application of both old and new technologies have contributed to improving cardiac implantable electronic device (CIED) therapies for this unique population. In this state-of-the-art review, we discuss the various arrhythmias encountered in Fontan patients, their diagnosis, and options for treatment and prevention, with a focus on CIEDs. Throughout, access challenges particular to the Fontan circulation are considered. Recently developed technologies, such as the sub-cutaneous implantable cardioverter defibrillator carry the potential to be transformative but require awareness of Fontan-specific issues. Moreover, new leadless pacing technology represents a promising strategy that may soon become applicable to Fontan patients with sinus node dysfunction. CIEDs are essential tools in managing Fontan patients but the complex clinical scenarios that arise in this patient population are among the most challenging for the congenital electrophysiologist.

Complications and management of functional single ventricle patients with Fontan circulation: From surgeon's point of view

Fontan surgery by step-wise completing the isolation of originally mixed pulmonary and systemic circulation provides an operative approach for functional single-ventricle patients not amenable to biventricular repair and allows their survival into adulthood. In the absence of a subpulmonic pumping chamber, however, the unphysiological Fontan circulation consequently results in diminished cardiac output and elevated central venous pressure, in which multiple short-term or long-term complications may develop. Current understanding of the Fontan-associated complications, particularly toward etiology and pathophysiology, is extremely incomplete. What's more, ongoing efforts have been made to manage these complications to weaken the Fontan-associated adverse impact and improve the life quality, but strategies are ill-defined. Herein, this review summarizes recent studies on cardiac and non-cardiac complications associated with Fontan circulation, focusing on significance or severity, etiology, pathophysiology, prevalence, risk factors, surveillance, or diagnosis. From the perspective of surgeons, we also discuss the management of the Fontan circulation based on current evidence, including post-operative administration of antithrombotic agents, ablation, pacemaker implantation, mechanical circulatory support, and final orthotopic heart transplantation, etc., to standardize diagnosis and treatment in the future.

Management of circulatory failure after Fontan surgery

With improvement in survival after Fontan surgery resulting in an increasing number of older survivors, there are more patients with a Fontan circulation experiencing circulatory failure each year. Fontan circulatory failure may have a number of underlying etiologies. Once Fontan failure manifests, prognosis is poor, with patient freedom from death or transplant at 10 years of only about 40%. Medical treatments used include traditional heart failure medications such as renin-angiotensin-aldosterone system blockers and beta-blockers, diuretics for symptomatic management, antiarrhythmics for rhythm control, and phosphodiesterase-5 inhibitors to decrease PVR and improve preload. These oral medical therapies are typically not very effective and have little data demonstrating benefit; if there are no surgical or catheter-based interventions to improve the Fontan circulation, patients with severe symptoms often require inotropic medications or mechanical circulatory support. Mechanical circulatory support benefits patients with ventricular dysfunction but may not be as useful in patients with other forms of Fontan failure. Transplant remains the definitive treatment for circulatory failure after Fontan, but patients with a Fontan circulation face many challenges both before and after transplant. There remains significant room and urgent need for improvement in the management and outcomes of patients with circulatory failure after Fontan surgery.

Failures of the Fontan System in Univentricular Hearts and Mortality Risk in Heart Transplantation: A Systematic Review and Meta-Analysis

The Fontan procedure (FP) is the standard surgical treatment for Univentricular heart diseases. Over time, the Fontan system fails, leading to pathologies such as protein-losing enteropathy (PLE), plastic bronchitis (PB), and heart failure (HF). FP should be considered as a transitional step to the final treatment: heart transplantation (HT). This systematic review and meta-analysis aims to establish the risk of death following HT according to the presence of FP complications. There was a total of 691 transplanted patients in the 18 articles, immediate survival 88% (n = 448), survival from 1 to 5 years of 78% (n = 427) and survival from 5.1 to 10 years of 69% (n = 208), >10 years 61% (n = 109). The relative risk (RR) was 1.12 for PLE (95% confidence interval [CI] = 0.89-1.40, p = 0.34), 1.03 for HF (0.7-1.51, p = 0.88), 0.70 for Arrhythmias (0.39-1.24, p = 0.22), 0.46 for PB (0.08-2.72, p = 0.39), and 5.81 for CKD (1.70-19.88, p = 0.005). In patients with two or more failures, the RR was 1.94 (0.99-3.81, p = 0.05). After FP, the risk of death after HT is associated with CKD and with the presence of two or more failures.

Heart failure with reduced and preserved ejection fraction in adult congenital heart disease

Heart failure with reduced ejection fraction (HFrEF) is common in patients with adult congenital heart disease. Many of the most common congenital defects have a high prevalence of HFrEF, including left-sided obstructive lesions (aortic stenosis, coarctation of the aorta, Shone complex), tetralogy of Fallot, Ebstein anomaly, lesions in which there is a systemic right ventricle, and lesions palliated with a Fontan circulation. However, heart failure with preserved ejection fraction (HFpEF) is also prevalent in all these lesions. Comprehensive evaluation includes physical exam, biomarkers, echocardiography and advanced imaging, exercise stress testing, and, in some cases, invasive hemodynamics. Guideline-directed medical therapy for HFrEF can be applied to left-sided lesions and may be considered on an individual basis for systemic right ventricle and single-ventricle patients. Medical therapy is limited for HFpEF. However, in both HFrEF and HFpEF, ventricular dyssynchrony and arrhythmias play an important role, and medications for rhythm control, ablation, and cardiac resynchronization therapy should be considered. Finally, aggressive management of cardiovascular risk factors and comorbidities, including, but not limited to, hypertension, obesity, diabetes, dyslipidemia, and obstructive sleep apnea, cannot be overemphasized.

Impact of delayed ventricular wall area ratio on pathophysiology of mechanical dyssynchrony: implication from single-ventricle physiology and 0D modeling

Electrical disparity can induce inefficient cardiac performance, representing an uncoordinated wall motion at an earlier activated ventricular wall: an early shortening followed by a systolic rebound stretch. Although regional contractility and distensibility modulate this pathological motion, the effect of a morphological factor has not been emphasized. Our strain analysis in 62 patients with single ventricle revealed that those with an activation delay in 60-70% of ventricular wall area suffered from cardiac dysfunction and mechanical discoordination along with prolonged QRS duration. A computational simulation with a two-compartment ventricular model also suggested that the ventricle with an activation delay in 70% of the total volume was most vulnerable to a large activation delay, accompanied by an uncoordinated motion at an earlier activated wall. Taken together, the ratio of the delayed ventricular wall has a significant impact on the pathophysiology due to an activation delay, potentially highlighting an indicator of cardiac dysfunction.

Adults with Congenital Heart Disease and Arrhythmia Management

Arrhythmia management in adult congenital heart disease (ACHD) encompasses a wide range of problems from bradyarrhythmia to tachyarrhythmia, sudden death, and heart failure-related electrical dyssynchrony. Major advances in the understanding of the pathophysiology and treatments of these problems over the past decade have resulted in improved therapeutic strategies and outcomes. This article attempts to define these problems and review contemporary management for the patient with ACHD presenting with cardiac arrhythmia.

Septal Flash-like Motion of the Earlier Activated Ventricular Wall Represents the Pathophysiology of Mechanical Dyssynchrony in Single-Ventricle Anatomy

BACKGROUND

In biventricular physiology, abnormal septal motion is a hallmark of mechanical dyssynchrony in the left bundle branch block. However, in single-ventricle (SV) physiology, morphologic variations in systemic ventricles pose a challenge in evaluating the negative impact of mechanical dyssynchrony. The present study aimed to characterize the pathologic dyssynchronous contraction patterns in patients with SV.

METHODS

In this retrospective study, 70 consecutive postoperative patients with SV anatomy with prolonged QRS duration (25 female patients; median age, 14 years) were enrolled. We divided each SV into two regions and analyzed independent strains using two-dimensional speckle-tracking echocardiography. From an earlier activated ventricular wall, we calculated the strain ratio (R_strains) of two values (%) during the QRS period and the ejection period: (100 + Strain_ejection)/(100 + Strain_QRS). We reviewed the clinical profiles, B-type natriuretic peptide plasma levels, exercise capacity, and morbidity. Six patients who underwent cardiac resynchronization therapy (CRT) were analyzed regarding changes in strain patterns and ventricular volume.

RESULTS

Higher R_strains, indicating a preceding contraction and subsequent dyskinetic dilation of the earlier activated ventricular wall, was associated with increased B-type natriuretic peptide, reduced exercise capacity, and poor outcome. However, delayed contraction of the later activated ventricular wall was not associated with the effects. Decreases in R_strains and ventricular volume reductions were observed in all patients after CRT.

CONCLUSIONS

A specific strain pattern in an earlier activated ventricular wall indicates mechanical dyssynchrony in patients with SV. This pattern is very similar to the septal flash in adult patients with left bundle branch block. This strategy might be a promising approach for selecting appropriate candidates for CRT in patients with SV.

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.

Impact of Right Ventricular Geometry and Left Ventricular Hypertrophy on Right Ventricular Mechanics and Clinical Outcomes in Hypoplastic Left Heart Syndrome

BACKGROUND

Right ventricular (RV) function is a major determinant of survival in hypoplastic left heart syndrome (HLHS). However, the relation of RV geometry to myocardial mechanics and their relation to transplant-free survival are incompletely characterized.

METHODS

We retrospectively studied 48 HLHS patients from the Hospital for Sick Children, Toronto, (median age, 2.2; interquartile range, 3.62 years) at different surgical stages. Patients were grouped by the presence (n = 23) or absence (n = 25) of RV "apical bulging" defined as a sigmoid-shaped septum with the RV leftward apical segment contiguous with the left ventricular (LV) lateral wall. Regional and global RV strain were measured using speckle-tracking echocardiography, and regional strains were analyzed for patterns and peak values. These were compared between HLHS anatomical subtypes and between patients with versus without apical bulging. We further investigated the association between RV geometry and dysfunction with the outcomes of heart failure, death, or transplant.

RESULTS

RV global (-7.3% ± 2.8% vs -11.2% ± 4.4%; P = .001), basal septal (-3.8% ± 3.2% vs -11.4% ± 5.8%; P = .0001) and apicolateral (-5.1% ± 3.5% vs -8.0% ± 5.8%, P = .001) longitudinal strain were lower in patients with versus without apical bulging, respectively. Apical bulging was equally prevalent in all HLHS anatomical variants. Twenty of 22 (91%) patients with apical bulging displayed hypertrophy of the LV apical and lateral segments. Death or transplantation were approximately equal in both groups but related to reduced RV global strain in patients with (seven of seven) and not in those without apical bulging (two of eight; P = .022).

CONCLUSIONS

These results suggest that the finding of apical bulging is related to the presence of a hypertrophied hypoplastic LV, with a negative impact on regional and global RV function. Therefore, analysis of RV and LV geometry and mechanics may aid in the assessment and prognostication of this high-risk population.

Right Ventricular Mechanical Dyssynchrony in Hypoplastic Left Heart Syndrome: Correlation with Systolic Function and QRS Duration

The single right ventricle (RV) in hypoplastic left heart syndrome (HLHS) often develops systolic dysfunction with time and this affects prognosis. Mechanical dyssynchrony has been reported in HLHS but has not consistently correlated with systolic function or electrical dyssynchrony. The aims of this study were to assess the relationship between RV mechanical dyssynchrony, RV systolic function, and QRS duration on surface electrocardiography. We hypothesized that surface QRS duration would not be an adequate indicator of mechanical dyssynchrony compared with dyssynchrony parameters. Retrospective analysis of echocardiograms of patients with HLHS divided into preserved vs reduced RV function. We measured two RV function parameters: (1) fractional area change (FAC) and (2) global longitudinal strain (RVGLS). We measured two dyssynchrony parameters: (1) the standard deviation of the time to peak strain for 9 segments (tPS-9) and (2) time difference between the earliest and latest time to peak strain (RV dyssynchrony index or RVDI) both corrected for R-R interval. We also measured the QRS duration from surface EKG. Mechanical dyssynchrony parameters were compared to both RV systolic function and to QRS duration. 41 patients with HLHS were identified: 21 had preserved function and 20 had reduced function defined by a FAC < 35%. The reduced function group had a significantly lower mean FAC and RVGLS. RVDI was higher in the dysfunction group and had a modest correlation with FAC (r = 0.48) and RVGLS (r = 0.57). tPS-9 was longer in the dysfunction group and had a modest correlation with FAC (r = 0.45) and RVGLS (r = 0.57). QRS duration was longer in the dysfunction group and had a modest correlation with FAC (r = 0.56) and RVGLS (r = 0.56). The weakest correlations were between QRS duration and tPS-9 (r = 0.32) and QRS duration and RVDI (r = 0.10). RV dysfunction measured by FAC was associated with mechanical dyssynchrony measured by increased RVDI and tPS-9. QRS duration was longer in the group with dysfunction but did not correlate with directly measured mechanical dyssynchrony. This may have potential implications for cardiac resynchronization therapy in univentricular patients as assessed by mechanical dyssynchrony parameters rather than QRS duration alone.

Successful biventricular cardiac resynchronization therapy in a failing Fontan patient: Implications of ventriculo-ventricular interdependency in single ventricle physiology

We describe a Fontan patient with severe heart failure who was successfully treated with biventricular cardiac resynchronization therapy (CRT). Our case shows that strain imaging might play a crucial role in guiding placement of pacing leads and in characterizing the electromechanical substrate associated with a favorable CRT response. Furthermore, we demonstrate for the first time that ventriculo-ventricular interdependency seems an important mechanical concept, which can be utilized to augment cardiac performance in failing Fontan patients with a functional hypoplastic ventricle.