Cardiac Resynchronization Therapy for Treatment of Chronic Subpulmonary Right Ventricular Dysfunction in Congenital Heart Disease

New Guidelines of Pediatric Cardiac Implantable Electronic Devices: What Is Changing in Clinical Practice?

Guidelines are important tools to guide the diagnosis and treatment of patients to improve the decision-making process of health professionals. They are periodically updated according to new evidence. Four new Guidelines in 2021, 2022 and 2023 referred to pediatric pacing and defibrillation. There are some relevant changes in permanent pacing. In patients with atrioventricular block, the heart rate limit in which pacemaker implantation is recommended was decreased to reduce too-early device implantation. However, it was underlined that the heart rate criterion is not absolute, as signs or symptoms of hemodynamically not tolerated bradycardia may even occur at higher rates. In sinus node dysfunction, symptomatic bradycardia is the most relevant recommendation for pacing. Physiological pacing is increasingly used and recommended when the amount of ventricular pacing is presumed to be high. New recommendations suggest that loop recorders may guide the management of inherited arrhythmia syndromes and may be useful for severe but not frequent palpitations. Regarding defibrillator implantation, the main changes are in primary prevention recommendations. In hypertrophic cardiomyopathy, pediatric risk calculators have been included in the Guidelines. In dilated cardiomyopathy, due to the rarity of sudden cardiac death in pediatric age, low ejection fraction criteria were demoted to class II. In long QT syndrome, new criteria included severely prolonged QTc with different limits according to genotype, and some specific mutations. In arrhythmogenic cardiomyopathy, hemodynamically tolerated ventricular tachycardia and arrhythmic syncope were downgraded to class II recommendation. In conclusion, these new Guidelines aim to assess all aspects of cardiac implantable electronic devices and improve treatment strategies.

Long-Term Outcomes of Cardiac Resynchronization Therapy in Patients With Repaired Tetralogy of Fallot: A Multicenter Study

BACKGROUND

A growing number of patients with tetralogy of Fallot develop left ventricular systolic dysfunction and heart failure, in addition to right ventricular dysfunction. Although cardiac resynchronization therapy (CRT) is an established treatment option, the effect of CRT in this population is still not well defined. This study aimed to investigate the early and late efficacy, survival, and safety of CRT in patients with tetralogy of Fallot.

METHODS

Data were analyzed from an observational, retrospective, multicenter cohort, initiated jointly by the Pediatric and Congenital Electrophysiology Society and the International Society of Adult Congenital Heart Disease. Twelve centers contributed baseline and longitudinal data, including vital status, left ventricular ejection fraction (LVEF), QRS duration, and NYHA functional class. Outcomes were analyzed at early (3 months), intermediate (1 year), and late follow-up (≥2 years) after CRT implantation.

RESULTS

A total of 44 patients (40.3±19.2 years) with tetralogy of Fallot and CRT were enrolled. Twenty-nine (65.9%) patients had right ventricular pacing before CRT upgrade. The left ventricular ejection fraction improved from 32% [24%-44%] at baseline to 42% [32%-50%] at early follow-up (P<0.001) and remained improved from baseline thereafter (P≤0.002). The QRS duration decreased from 180 [160-205] ms at baseline to 152 [133-182] ms at early follow-up (P<0.001) and remained decreased at intermediate and late follow-up (P≤0.001). Patients with upgraded CRT had consistent improvement in left ventricular ejection fraction and QRS duration at each time point (P≤0.004). Patients had a significantly improved New York Heart Association functional class after CRT implantation at each time point compared with baseline (P≤0.002). The transplant-free survival rates at 3, 5, and 8 years after CRT implantation were 85%, 79%, and 73%.

CONCLUSIONS

In patients with tetralogy of Fallot treated with CRT consistent improvement in QRS duration, left ventricular ejection fraction, New York Heart Association functional class, and reasonable long-term survival were observed. The findings from this multicenter study support the consideration of CRT in this unique population.

How to assess and treat right ventricular electromechanical dyssynchrony in post-repair tetralogy of Fallot: insights from imaging, invasive studies, and computational modelling

BACKGROUND AND AIMS

Right bundle branch block (RBBB) and resulting right ventricular (RV) electromechanical discoordination are thought to play a role in the disease process of subpulmonary RV dysfunction that frequently occur post-repair tetralogy of Fallot (ToF). We sought to describe this disease entity, the role of pulmonary re-valvulation, and the potential added value of RV cardiac resynchronization therapy (RV-CRT).

METHODS

Two patients with repaired ToF, complete RBBB, pulmonary regurgitation, and significantly decreased RV function underwent echocardiography, cardiac magnetic resonance, and an invasive study to evaluate the potential for RV-CRT as part of the management strategy. The data were used to personalize the CircAdapt model of the human heart and circulation. Resulting Digital Twins were analysed to quantify the relative effects of RV pressure and volume overload and to predict the effect of RV-CRT.

RESULTS

Echocardiography showed components of a classic RV dyssynchrony pattern which could be reversed by RV-CRT during invasive study and resulted in acute improvement in RV systolic function. The Digital Twins confirmed a contribution of electromechanical RV dyssynchrony to RV dysfunction and suggested improvement of RV contraction efficiency after RV-CRT. The one patient who underwent successful permanent RV-CRT as part of the pulmonary re-valvulation procedure carried improvements that were in line with the predictions based on his Digital Twin.

CONCLUSION

An integrative diagnostic approach to RV dysfunction, including the construction of Digital Twins may help to identify candidates for RV-CRT as part of the lifetime management of ToF and similar congenital heart lesions.

Ebstein's anomaly in children and adults: multidisciplinary insights into imaging and therapy

Although survival has significantly improved in the last four decades, the diagnosis of Ebstein's anomaly is still associated with a 20-fold increased risk of mortality, which generally drops after neonatal period and increases subtly thereafter. With increasing age of presentation, appropriate timing of intervention is challenged by a wide spectrum of disease and paucity of data on patient-tailored interventional strategies. The present review sought to shed light on the wide grey zone of post-neonatal Ebstein's manifestations, highlighting current gaps and achievements in knowledge for adequate risk assessment and appropriate therapeutic strategy.A 'wait-and-see' approach has been adopted in many circumstances, though its efficacy is now questioned by the awareness that Ebstein's anomaly is not a benign disease, even when asymptomatic. Moreover, older age at intervention showed a negative impact on post-surgical outcome.In order to tackle the extreme heterogeneity of Ebstein's anomaly, this review displays the multimodality imaging assessment necessary for a proper anatomical classification and the multidisciplinary approach needed for a comprehensive risk stratification and monitoring strategy. Currently available predictors of clinical outcome are summarised for both operated and unoperated patients, with the aim of supporting the decisional process on the choice of appropriate therapy and optimal timing for intervention.

Complex Substrate Leading to PVC-Mediated Systolic Dysfunction in addition to Sustained Monomorphic VT in Repaired Tetralogy of Fallot

Frequent premature ventricular complexes (PVCs) are associated with deleterious effects on left ventricular (LV) function in various clinical scenarios. Repaired tetralogy of Fallot (rTOF) is frequently affected by sustained ventricular arrhythmias dependent on complex post-surgical substrates. However, there is limited data regarding the potential of arrhythmogenic isthmuses to generate frequent PVCs and PVC-mediated LV systolic dysfunction development in rTOF. We present a case of rTOF experiencing relatively infrequent episodes of internal shocks for episodes of sustained monomorphic ventricular tachycardia and a high burden of PVCs associated with left ventricular systolic function deterioration, in which the successful substrate ablation of the anatomical VT isthmuses also led to PVC abolition and consequently to LV systolic function normalization. In such cases, understanding the pathogenic mechanisms that lead to LV dysfunction is only possible by rigorous clinical reasoning, which leads to a tailored specific treatment.

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.

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.

Navigating Arrhythmias in Tetralogy of Fallot Throughout the Lifespan: A Case-based Review

Arrhythmias are a common complication associated with tetralogy of Fallot (ToF), one of the most prevalent forms of congenital heart disease. As illustrated by this case-based review, various forms of arrhythmias can be encountered across the lifespan of patients with ToF, from infancy to older adulthood. These include atrioventricular block, junctional ectopic tachycardia, and atrial and ventricular arrhythmias. Arrhythmias have important implications on the health and quality of life of patients with ToF and require treatment by caregivers with dedicated expertise. The choice of pharmacologic and/or interventional therapies to alleviate symptoms, avoid complications, and mitigate risks depends in part on the type, severity, and frequency of the arrhythmia, as well as on the particularities of individual clinical scenarios. Preventing, monitoring for, and managing arrhythmias are an integral component of the care of patients with ToF throughout their lifespan that is critical to optimizing health outcomes.

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.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

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.

Telemonitoring with Electronic Devices in Patients with a Single Ventricle Anatomy

Background  A growing number of patients with a single ventricle anatomy, who had a Fontan palliation as a child, are now reaching adulthood. Many need an epimyocardial pacemaker system with an optional telemonitoring (TM) unit, which evaluates the collected data and sends it via Internet to the patient's physician. There are no data on the reliability and clinical relevance of these systems in this patient group.

Methods  We analyzed data in 48 consecutive patients (mean age 18 years, standard deviation 9 years) with a Fontan or Fontan-like palliation who received a cardiac implantable electronic device with a TM unit from Biotronik (Home Monitoring) or Medtronic (CareLink) between 2005 and 2020 with regard to the reliability and clinical relevance of the downloaded data.

Results  The observation period was from 4 months to 14 years (mean 7 years, standard deviation 3.9 years). A total of 2.9 event messages (EMs)/patient/month and 1.3 intracardiac electrogram recordings/patient/month were received. Two patients died during follow-up. The combination of regularly arriving statistical data and 313 clinically relevant EMs led to the modification of antiarrhythmic or diuretic medication, hospitalization with cardioversion or ablation, and cortisone therapy to avoid exit block in 21 (44%) patients.

Conclusion  TM is an instrument to receive functional and physiologic parameters of our Fontan patients. It provides the ability to respond early for signs of system failure, or arrhythmia, even if the patient is not experiencing any problems. It is a useful tool to manage this difficult patient population without frequent hospital visits.

Fusion cardiac resynchronization therapy in an left ventricular assist device patient from two devices and crossing leads: a case report

Background

Cardiac implanted electronic devices (CIED) have significantly improved the survival and quality of life in heart failure patients. Although implantable cardioverter-defibrillators (ICD) and cardiac resynchronization therapy (CRT) have a major role in patients with moderate to severe heart failure symptoms, the role of these devices in patients with a left ventricular assist device (LVAD) is not yet well defined. The burden of CIED-related procedures in patients with an LVAD is high. The price of lead malfunctions and pocket complications requires creative approaches to tackle CIED-related issues in this patient population.

Case summary

Here, we describe the clinical course of a 67-year-old ventricular pacing dependent LVAD patient with an ICD indication based on recurrent monomorphic ventricular tachycardias and a CRT indication due to previous deterioration of (right-sided) heart failure in the absence of biventricular pacing. We were confronted with impending right ventricular lead failure and bilateral venous access problems due to chronic subclavian vein occlusion in a patient with a total of five transvenous leads, therapeutic anticoagulation, and pronounced thoracic collaterals. We sought for a creative solution to be able to deliver effective biventricular fusion pacing with the existing leads from two contralateral pulse generators resulting in biventricular fusion pacing. This provided the solution to deliver effective CRT.

Discussion

This case illustrates the complexity of care and CIED-related decision-making in pacing dependent LVAD patients, in particularly those with an ICD and CRT indication.

Performance of epimyocardial leads in patients with a single ventricle circulation

BACKGROUND

Cardiac pacing can be challenging after a Fontan operation, and limited data exist regarding strategies to plan these epimyocardial systems while minimizing the number of surgical procedures.

METHODS

A retrospective review of all our 47 patients (mean age 18 years, standard deviation 9 years) with a Fontan palliation who received an epimyocardial cardiac implantable electronic device (CIED) between 2002 and 2020 with regard to the stability of the epimyocardial lead parameters and the incidence of system revisions.

RESULTS

Over the last 18 years, 84 implantations or revisions of the epimyocardial CIED in 47 Fontan patients were performed. Mean age at time of the first implantation was 9.4 (range 0.28-29.3) years. Follow-up period ranges from 0.11 to 18.2 (mean 7.7, standard deviation 4.2) years. A total of 123 pacing leads were implanted of which 99 are still active. From 2010 triple lead cardiac resynchronization devices were used in 17 patients to better cope with lead problems. The initial pacing threshold of the leads inactivated during this study period proved significantly higher (mean 1.66 V) than in the "all leads" group (mean 1.27 V, p = .0005) or the group of the still active leads (mean 1.17 V, p = .00004).

CONCLUSIONS

When implanted with a low pacing threshold, the bipolar epimyocardial electrodes show stable and good long-term results in young patients with a Fontan circulation. Resynchronization pacing systems and the prospective implantation of reserve leads may help to reduce the rate of resternotomies and provide a flexible concept to deal with lead failure.

Resynchronizing Right and Left Ventricles With Right Bundle Branch Block in the Congenital Heart Disease Population

OBJECTIVES

This study describes a single center experience with the use of cardiac resynchronization therapy (CRT) in a difficult patient population, including single systemic right ventricles (RVs), subpulmonary RVs, and left ventricles (LVs) with right bundle branch block (RBBB).

BACKGROUND

CRT remains challenging in the congenital heart disease population.

METHODS

Consecutive patients undergoing resynchronization of single RVs, subpulmonary RVs, or LVs in the setting of RBBB were identified between 2016 and 2019. Patients who had CRT performed for complete heart block or had <3 months of follow-up were excluded. Patients underwent pre-procedural advanced imaging by echocardiogram, computed tomography, or cardiac magnetic resonance to assess ventricular function and synchrony; intraoperative mapping was performed to identify optimal lead placement.

RESULTS

All patients undergoing resynchronization presented with at least moderate systolic ventricular dysfunction in the setting of intrinsic atrioventricular nodal conduction and RBBB. Seven patients were identified. Two patients underwent CRT of a single RV, 3 with subpulmonary RVs and 2 with systemic LVs. The median age at CRT was 5 years (range 0.6 to 48 years). The median follow-up was 9 months (range 3 to 18 months). The median baseline QRS duration was 180 ms (range 115 to 260ms). Post-CRT, the QRS duration decreased by a median of 34% (range 19% to 38%). All patients had improvement in their systolic ventricular function.

CONCLUSIONS

Targeted resynchronization in systemic and subpulmonary RVs can be used to improve ventricular function and heart failure in the congenital heart disease population. Similar techniques can be applied to successfully treat patients with LV dysfunction and RBBB and improve their long-term outcomes.

Cardiac resynchronization and implantable defibrillators in adults with congenital heart disease

Cardiac resynchronization therapy (CRT) and implantable cardioverter defibrillators (ICDs) are well-established therapies for adult patients with heart failure that have been shown to improve morbidity and mortality. However, the benefits and indications for use in adults with congenital heart disease (ACHD) are less defined with no significant large prospective studies in this population. There are, however, multiple retrospective studies that demonstrate the efficacy of these devices in the ACHD population. These indicate a role for both CRT and ICDs in select patients with ACHD. The clinician and patient must balance the risks and benefits, summarized in complex evidence that reflects the heterogeneity of the ACHD patient group, and apply them in a patient-specific manner to optimize the utility of CRT and ICDs.