Coexistence of tachyarrhythmias in patients with tetralogy of Fallot

Disease severity, arrhythmogenesis, and fibrosis are related to longer action potentials in tetralogy of Fallot

BACKGROUND

Arrhythmias may originate from surgically unaffected right ventricular (RV) regions in patients with tetralogy of Fallot (TOF). We aimed to investigate action potential (AP) remodelling and arrhythmia susceptibility in RV myocardium of patients with repaired and with unrepaired TOF, identify possible correlations with clinical phenotype and myocardial fibrosis, and compare findings with data from patients with atrial septal defect (ASD), a less severe congenital heart disease.

METHODS

Intracellular AP were recorded ex vivo in RV outflow tract samples from 22 TOF and three ASD patients. Arrhythmias were provoked by superfusion with solutions containing reduced potassium and barium chloride, or isoprenaline. Myocardial fibrosis was quantified histologically and associations between clinical phenotype, AP shape, tissue arrhythmia propensity, and fibrosis were examined.

RESULTS

Electrophysiological abnormalities (arrhythmias, AP duration [APD] alternans, impaired APD shortening at increased stimulation frequencies) were generally present in TOF tissue, even from infants, but rare or absent in ASD samples. More severely diseased and acyanotic patients, pronounced tissue susceptibility to arrhythmogenesis, and greater fibrosis extent were associated with longer APD. In contrast, APD was shorter in tissue from patients with pre-operative cyanosis. Increased fibrosis and repaired-TOF status were linked to tissue arrhythmia inducibility.

CONCLUSIONS

Functional and structural tissue remodelling may explain arrhythmic activity in TOF patients, even at a very young age. Surprisingly, clinical acyanosis appears to be associated with more severe arrhythmogenic remodelling. Further research into the clinical drivers of structural and electrical myocardial alterations, and the relation between them, is needed to identify predictive factors for patients at risk.

Rationale and Design of the Multicenter Catheter Ablation of Ventricular Tachycardia Before Transcatheter Pulmonary Valve Replacement in Repaired Tetralogy of Fallot Study

Patients with repaired tetralogy of Fallot are at elevated risk for ventricular arrhythmia and sudden cardiac death. Over the past decade, the pathogenesis and natural history of ventricular tachycardia has become increasingly understood, and catheter ablation has emerged as an effective treatment modality. Concurrently, there has been great progress in the development of a versatile array of transcatheter valves that can be placed in the native right ventricular outflow tract for the treatment of long-standing pulmonary regurgitation. Although such valve platforms may eliminate the need for repeat cardiac operations, they may also impede catheter access to the myocardial substrates responsible for sustained macro-reentrant ventricular tachycardia. This manuscript provides the rationale and design of a recently devised multicenter study that will examine the clinical outcomes of a uniform, preemptive strategy to eliminate ventricular tachycardia substrates before transcatheter pulmonary valve implantation in patients with tetralogy of Fallot.

Quantitative collagen assessment in right ventricular myectomies from patients with tetralogy of Fallot

Aims

Patients with tetralogy of Fallot (TOF) are often affected by right ventricular fibrosis, which has been associated with arrhythmias. This study aimed to assess fibrosis distribution in right ventricular outflow tract (RVOT) myocardium of TOF patients to evaluate the utility of single histology-section analyses, and to explore the possibility of fibrosis quantification in unlabelled tissue by second harmonic generation imaging (SHGI) as an alternative to conventional histology-based assays.

Methods and results

We quantified fibrosis in 11 TOF RVOT samples, using a tailor-made automated image analysis method on Picrosirius red-stained sections. In a subset of samples, histology- and SHGI-based fibrosis quantification approaches were compared. Fibrosis distribution was highly heterogeneous, with significant and comparable variability between and within samples. We found that, on average, 67.8 mm² of 10 µm thick, histologically processed tissue per patient had to be analysed for accurate fibrosis quantification. SHGI provided data faster and on live tissue, additionally enabling quantification of collagen anisotropy.

Conclusion

Given the high intra-individual heterogeneity, fibrosis quantification should not be conducted on single sections of TOF RVOT myectomies. We provide an analysis algorithm for fibrosis quantification in histological images, which enables the required extended volume analyses in these patients.

Outcomes of adults with repaired tetralogy of Fallot from the national Scottish Cohort

BACKGROUND

The adult population of repaired tetralogy of Fallot is increasing and at risk of pre-mature death and arrhythmia. This study evaluates risk factors for adverse outcome and the effect of pulmonary valve replacement within a national cohort.

METHODS

A retrospective cohort study of 341 adult repaired tetralogy of Fallot (16-72 years) managed through a single national service was undertaken incorporating over 1200 patient-years of follow-up. Demographics, cardiopulmonary exercise testing, cardiac magnetic resonance, reintervention (including pulmonary valve replacement), and clinical events were analysed. The influence of these parameters on a primary outcome (death or arrhythmia) was evaluated.

RESULTS

Compared with an age-/gender-matched population, patients experienced a reduced survival, particularly males over 55 years (standardised mortality ratio : 6.12, 95% CI: 1.64-15.66, p = 0.004). Cox proportional hazards modelling identified increased indexed right ventricle (RV) end-diastolic volume (hazard ratio (HR): 2.86, 95% CI: 1.4-5.85, p = 0.004) and female gender (HR (male): 0.37, 95% CI: 0.14-0.98, p = 0.045) to be predictors significantly associated with the primary outcome. Pulmonary valve replacement undertaken at indexed RV end-diastolic volume = 145 ml/m2 reduced RV volumes and QRS duration but did not improve cardiopulmonary exercise testing nor NYHA class. Pulmonary valve replacement during cohort period was associated with increased risk of primary outcome (HR: 2.82, 95% CI: 1.36-5.86, p = 0.005).

CONCLUSIONS

Although the majority of adult tetralogy of Fallot were asymptomatic in NYHA 1, cardiopulmonary exercise testing revealed important deficits. Tetralogy of Fallot survival was reduced compared to the general population. Female gender and increasing RV end-diastolic volume predicted adverse events. Pulmonary valve replacement reduced RV volumes and QRS duration but did not improve primary outcome.

[The adult with tetralogy of fallot: what the clinical cardiologist needs to know]

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease. After more than seven decades of the first palliative surgery, TOF prognosis has changed dramatically. The prevalence of TOF is approximately 3 per 10 000 births, representing 7 to 10% of congenital heart disease. With a higher survival into adulthood, the clinical cardiologist faces challenges in the management of this population, from severe pulmonary regurgitation to heart failure and ventricular arrhythmias. Its prevalence is approximately 3 per 10 000 live births, representing 7 to 10% of congenital heart disease. This review will describe the most relevant aspects of the care of adult patients with this disease.

Etiology of atrial fibrillation in patients with complex congenital heart disease - for a better treatment strategy

BACKGROUND

The demographics of patients with congenital heart disease (CHD) and atrial fibrillation (AF) differ significantly from the general population. The etiology and treatment strategy for AF in CHD patients have been investigated but are to date inconclusive.

METHODS

To determine the etiology of AF in CHD and to seek a better treatment strategy, we retrospectively evaluated the atrial overload in 42 complex CHD cases with normal atrial arrangements and AF (age 25; range, 9-66 years) and the impact of a reduction in the atrial overload on the atrial rhythm.

RESULTS

Cardiac defect diagnoses varied, with 17% of the patients having a persistent left superior vena cava (PLSVC). In regard to the volume overload, the frequencies of an overload in the right atrium (RA), left atrium (LA), or both, were 50 %, 23%, and 10%, respectively (p = 0.015). Other sustained supraventricular tachycardias were observed in 29 patients (69%) before and after the onset of AF. Among these 29 patients, 26 had intra-atrial reentrant tachycardia. Fifteen patients (36%), 10 of whom had chronic AF, died during the follow-up including 3 with arrhythmias and 10 because of heart failure. Fourteen (33%) patients had no AF at the last follow-up due to medical interventions, 8 of which underwent solely an RA-sided catheter ablation and/or surgical RA overload reduction.

CONCLUSIONS

AF in complex CHD with a normal atrial arrangement correlates with a higher RA-sided overload than an LA-sided and exhibits a high incidence of PLSVCs, high comorbidity of intra-atrial reentrant tachycardias, and high mortality rate. In a substantial number of patients, RA-sided interventions were effective in controlling AF. To effectively manage AF in complex CHD it is essential to understand each individual's hemodynamics and consider hemodynamic interventions.

Implantable cardiac devices in adult patients with repaired tetralogy of Fallot

OBJECTIVES

Implantable cardiac devices are common in patients with tetralogy of Fallot (ToF) (18.3-21.3%) according to previous reports from large centres. We conducted this study to investigate the prevalence and incidence of cardiac devices in a less selected population of patients with ToF and assess factors other than arrhythmia associated with having a device. Design: 530 adult (≥18 years) patients with repaired ToF were identified in the national registry of congenital heart disease (SWEDCON) and matched with data from the Swedish pacemaker registry. Patients with implantable cardiac devices were compared with patients without devices. Results: Seventy-five patients (14.2%) had a device; 51 (9.6%) had a pacemaker and 24 (4.5%) had an implantable cardioverter defibrillator. The incidence in adult age (≥18 years) was 5.9/1000 patient years. Estimated device free survival was 97.5% at twenty, 87.2% at forty and 63.5% at sixty years of age. Compared with previous studies, the prevalence of devices was lower, especially for ICD. In multivariate logistic regression, cardiovascular medication (odds ratio [OR] 3.5, 95% confidence interval [CI] 1.8-6.8), impaired left ventricular function, (OR 2.6, 95%CI 1.3-5.0) and age (OR 1.02, 95%CI 1.002-1.05) were associated with having a device. Conclusion: The prevalence of devices in our population, representing a multicenter register cohort, was lower than previously reported, especially regarding ICD. This can be due to differences in treatment traditions with regard to ICD in this population, but it may also be that previous studies have reported selected patients with more severe disease.

Timing of Repair in Tetralogy of Fallot: Effects on Outcomes and Myocardial Health

Early complete repair of tetralogy of Fallot (ToF) prior to 1 year of age has been demonstrated to be safe and has survival benefits over late repair. The age at repair of ToF affects long-term outcomes. This may largely be related to preserved, or comparatively better, myocardial health. Most studies advocate for an age of repair between 3 and 6 months and certainly below the age of 1 year. Patients with severe right ventricular outflow tract obstruction represent an exception to this rule and may require neonatal repair or surgical and catheter-based palliation before surgery. Older age at repair beyond the first birthday leads to unfavorable right ventricular remodeling with increased right ventricular stiffness and hypertrophy and is associated with increased long-term ventricular tachycardia and all-cause mortality. In this article, we review the short- and long-term benefits of early repair, with a focus on long-term morbidity. In conclusion, we emphasize the importance of myocardial health and the relationship to early repair and advocate for the use of magnetic resonance imaging in adult patients with repaired ToF to detect myocardial fibrosis.

Tetralogy of Fallot in the Current Era

Only few studies have reported long-term outcome of the transatrial-transpulmonary approach in the current era of management of tetralogy of Fallot (ToF). We investigated 15-year outcome of correction via a transatrial-transpulmonary approach in a large cohort of successive patients operated in the 21st century. All infant ToF patients undergoing transatrial-transpulmonary ToF correction between 2000 and 2015 were included (N = 177, 106 male, median follow-up 7.1 (interquartile range 3.0-10.9) years. Data regarding postoperative complications, reinterventions, development of atrial and ventricular arrhythmia, cardiac function, and survival were evaluated. Prior shunting was performed in 10 patients (6%). The transatrial-transpulmonary approach resulted in valve-sparing surgery in 57 patients (32%). Postoperative surgical complications included junctional ectopic tachycardia (N = 12, 7%), pericardial (N = 10, 6%) or pleural effusion (N = 7, 3%), chylothorax (N = 7, 4%), bleeding requiring reoperation (N = 4, 3%), and superficial wound infection (N = 1). Fifty-one patients underwent 68 reinterventions, mainly due to pulmonary restenosis (PS) (N = 57). ToF correction at age <2 months and double outlet or double-chambered right ventricle variants of the ToF spectrum were independent predictors for reintervention. Patients undergoing valve-sparing ToF correction had a significant longer PR-free survival than those with a transannular patch (8.5 [95% confidence interval 6.8-10.3] years vs 1.1 [95% confidence interval 0.8-1.5] years; P < 0.001). Overall mortality was 2.8%; mortality rates were higher in premature/dysmature newborns (0.7% vs 9.5%; P < 0.001). Although the 15-year outcome of the transatrial-transpulmonary approach in terms of postoperative complications and mortality rates is excellent, the high incidence of moderate and severe PR is worrisome. Valve-sparing surgery was associated with a substantially lower incidence of PR, yet was surgically not possible in the majority of patients.