Role and Applications of Experimental Animal Models of Fontan Circulation.

Over the last four decades, the Fontan operation has been the treatment of choice for children born with complex congenital heart diseases and a single-ventricle physiology. However, therapeutic options remain limited and despite ongoing improvements in initial surgical repair, patients still experience a multiplicity of cardiovascular complications. The causes for cardiovascular failure are multifactorial and include systemic ventricular dysfunction, pulmonary vascular resistance, atrioventricular valve regurgitation, arrhythmia, development of collaterals, protein-losing enteropathy, hepatic dysfunction, and plastic bronchitis, among others. The mechanisms leading to these late complications remain to be fully elucidated. Experimental animal models have been developed as preclinical steps that enable a better understanding of the underlying pathophysiology. They furthermore play a key role in the evaluation of the efficacy and safety of new medical devices prior to their use in human clinical studies. However, these experimental models have several limitations. In this review, we aim to provide an overview of the evolution and progress of the various types of experimental animal models used in the Fontan procedure published to date in the literature. A special focus is placed on experimental studies performed on animal models of the Fontan procedure with or without mechanical circulatory support as well as a description of their impact in the evolution of the Fontan design. We also highlight the contribution of animal models to our understanding of the pathophysiology and assess forthcoming developments that may improve the contribution of animal models for the testing of new therapeutic solutions.

Systematic Electrophysiological Study Prior to Pulmonary Valve Replacement in Tetralogy of Fallot: A Prospective Multicenter Study.

BACKGROUND: Ventricular arrhythmias and sudden death are recognized complications in tetralogy of Fallot. Electrophysiological studies (EPS) before pulmonary valve replacement (PVR), the most common reintervention in tetralogy of Fallot, could potentially inform therapy to improve arrhythmic outcomes. METHODS: A prospective multicenter study was conducted to systematically assess EPS with programmed ventricular stimulation in patients with tetralogy of Fallot referred for PVR from January 2020 to December 2021. A standardized stimulation protocol was used across all centers. RESULTS: A total of 120 patients were enrolled, mean age 39.2±14.5 years, 53.3% males. Sustained ventricular tachycardia was induced in 27 (22.5%) patients. When identifiable, the critical isthmus most commonly implicated (ie, in 90.0%) was between the ventricular septal defect patch and pulmonary annulus. Factors independently associated with inducible ventricular tachycardia were history of atrial arrhythmia (odds ratio, 8.56 [95% CI, 2.43-34.73]) and pulmonary annulus diameter >26 mm (odds ratio, 5.05 [95% CI, 1.47-21.69]). The EPS led to a substantial change in management in 23 (19.2%) cases: 18 (15.0%) had catheter ablation, 3 (2.5%) surgical cryoablation during PVR, and 9 (7.5%) defibrillator implantation. Repeat EPS 5.1 (4.8-6.2) months after PVR was negative in 8 of 9 (88.9%) patients. No patient experienced a sustained ventricular arrhythmia during 13 (6.1-20.1) months of follow-up. CONCLUSIONS: Systematically performing programmed ventricular stimulation in patients with tetralogy of Fallot referred for PVR yields a high rate of inducible ventricular tachycardia and carries the potential to alter management. It remains to be determined whether a standardized treatment approach based on the results of EPS will translate into improved outcomes. REGISTRATION: URL: https://clinicaltrials.gov/ct2/show/NCT04205461; Unique identifier: NCT04205461.

Atrial fibrillation in the presence and absence of heart failure enhances expression of genes involved in cardiomyocyte structure, conduction properties, fibrosis, inflammation, and endothelial dysfunction.

BACKGROUND: Little is known about genome-wide changes in the atrial transcriptome as a cause or consequence of atrial fibrillation (AF), and the effect of its common and clinically relevant comorbidity-heart failure (HF). OBJECTIVE: The purpose of this study was to explore candidate disease processes for AF by investigating gene expression changes in atrial tissue samples from patients with and without AF, stratified by HF. METHODS: RNA sequencing was performed in right and left atrial appendage tissue in 195 patients undergoing open heart surgery from centers participating in the CATCH-ME consortium (no history of AF, n = 91; paroxysmal AF, n = 53; persistent/permanent AF, n = 51). Analyses were stratified into patients with/without HF (n = 75/120) and adjusted for age, sex, atrial side, and a combination of clinical characteristics. RESULTS: We identified 35 genes associated with persistent AF compared to patients without a history of AF, both in the presence or absence of HF (false discovery rate <0.05). These were mostly novel associations, including 13 long noncoding RNAs. Genes were involved in regulation of cardiomyocyte structure, conduction properties, fibrosis, inflammation, and endothelial dysfunction. Gene set enrichment analysis identified mainly inflammatory gene sets to be enriched in AF patients without HF, and gene sets involved in cellular respiration in AF patients with HF. CONCLUSION: Analysis of atrial gene expression profiles identified numerous novel genes associated with persistent AF, in the presence or absence of HF. Interestingly, no consistent transcriptional changes were associated with paroxysmal AF, suggesting that AF-induced changes in gene expression predominate other changes.

Cardiac catheterisation in infants weighing less than 2500 grams.

OBJECTIVES: The aim of the study was to report the outcome of cardiac catheterisation in low-weight patients. BACKGROUND: Data regarding cardiac catheterisation in infants weighing <2500 g are scarce. METHODS: We reviewed all cardiac catheterisations performed in infants weighing <2500 g between January 2000 and May 2016. An analysis with respect to the type of procedure, the complexity of procedure (procedure type risk), and haemodynamic vulnerability index was finally carried out. We report the occurrence of deaths and complications using the adverse event severity score. RESULTS: A total of 218 procedures were performed on 211 patients. The mean age and weight were, respectively, 15 ± 26 days (range, 0-152) and 2111 ± 338 g (range, 1000-2500). Procedures were interventional and diagnostic, respectively, in 174 (80%) and 44 (20%) patients. Out of 218, 205 (94%) were successful. Eleven complications (5%) occurred - six with an adverse event severity score of 4 and five with an adverse event severity score of 3. Ten patients (91%) showed a favourable outcome, and one died (stent thrombosis few hours after patent ductus arteriosus stenting). No correlation was found between lower weight and occurrence of death (p = 0.68) or complications (p = 0.23). The gravity scores (procedure type risk and haemodynamic vulnerability index) were not predictive of complications. CONCLUSIONS: Cardiac catheterisation in infants weighing <2500 g appears feasible and effective with low risk. The weight should not discourage from performing cardiac catheterisation in this population.

Tetralogy of Fallot and abnormal coronary artery: use of a prosthetic conduit is outdated.

OBJECTIVES: Repair of tetralogy of Fallot (ToF) can be challenging in the presence of an abnormal coronary artery (CA) in 5-12% of cases. The aim of this study was to report our experience with ToF repair without the systematic use of a right ventricle-to-pulmonary artery (RV-PA) conduit. METHODS: We conducted a monocentric retrospective study from 2000 to 2016, including 943 patients with ToF who underwent biventricular repair, of whom 8% (n = 76) presented with an abnormal CA. Mean follow-up time was 50 months (1 month-18 years). RESULTS: The most frequent CA anomaly was the left descending artery arising from the right CA (n = 47, 61.8%). The median age at repair was 7.7 months (1.8 months-16 years). Thirteen patients (17%) required prior palliation, mostly systemic pulmonary shunts for anoxic spells in the neonatal period. Surgical repair allowed us to preserve the annulus in 40 patients (53%) by combining PA trunk plasty, commissurotomy and infundibulotomy under the abnormal CA. If the annulus had to be opened (n = 35, 46%), a transannular patch was inserted after a vertical incision of the PA trunk and extended obliquely on the RV over the anomalous crossing CA (with an infundibulotomy under the abnormal CA). Three patients (4%) required the insertion of an RV-PA conduit (1 valved tube and 2 RV-PA GORE-TEX tubes with annulus conservation). The early mortality rate was 4% (n = 3); none of the deaths was coronary related. Four patients (5%) required reoperation (2 early and 2 late reoperations) for residual pulmonary stenosis, 3 of whom had annulus preservation during the initial repair. The mean RV/left ventricle (LV) pressure ratio and an RV/LV pressure ratio >2/3 were identified as risk factors for right ventricular outflow tract (RVOT) reinterventions (P = 0.0026, P = 0.0085, respectively), RVOT reoperations (P = 0.0002 for both) and reoperation for RVOT residual stenosis (P = 0.0002, P = 0.0014, respectively). Two patients underwent pulmonary valve replacement. Freedom from late reoperation was 100% at 1 year, 97% at 5 years and 84% at 10 and 15 years. CONCLUSIONS: Repair of ToF and abnormal CA can be performed without an RV-PA conduit, with an acceptable low reintervention rate. The high early mortality rate in this series remains a concern. If any doubt remains about the surgical relief of the RVOT obstruction, the RV/LV pressure ratio should always be measured in the operating room.

Pulmonary Atresia With Ventriculocoronary Arterial Connections and a Large Conoventricular Septal Defect.

Ventriculocoronary arterial connections are typically found in patients with pulmonary atresia with an intact ventricular septum. This report describes a case of ventriculocoronary arterial connections in a patient with pulmonary atresia with a ventricular septal defect. Our case supports recent data suggesting a primary coronary artery developmental anomaly in pulmonary atresia. (Level of Difficulty: Advanced.).