Prolonged repolarization in atrial septal defect: An example of mechanoelectrical feedback due to right ventricular volume overload

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.

Mid-Term Electrical Remodeling after Percutaneous Atrial Septal Defect Closure with GCO Device in a Pediatric Population

BACKGROUND AND AIM

The GORE® CARDIOFORM (GCO) septal occluder is an atrial septal defect/patent foramen ovale closure device with theoretical advantages over other commercialized devices thanks to its softness and anatomical compliance. Our aim was to evaluate the short- and medium-term electrocardiographic changes after percutaneous ASD closure with GCO in a pediatric population.

METHODS

We enrolled 39 patients with isolated ASD submitted to trans-catheter closure from January 2020 to June 2021. ECG was performed before, at 24 h and 6 months after the procedure. P wave dispersion, QTc and QTc dispersion were calculated. ECG Holter was recorded at 6 months after implantation.

RESULTS

Patients' age and body surface area (BSA) were 8.2 ± 4.2 years and 1.0 ± 0.3 m2 respectively. At the baseline, mean P wave dispersion was 40 ± 15 msec and decreased at 24 h (p < 0.002), without any further change at 6 months. At 24 h, PR conduction and QTc dispersion significantly improved (p = 0.018 and p < 0.02 respectively), while the absolute QTc value considerably improved after 6 months. During mid-term follow-up, QTc dispersion remained stable without a significant change in PR conduction. The baseline cardiac frequency was 88.6 ± 12.6 bpm, followed by a slight reduction at 24 h, with a further amelioration at 6 months after the procedure (87.3 ± 14.2, p = 0.9 and 81.0 ± 12.7, p = 0.009, respectively). After device deployment, two patients developed transient, self-limited junctional rhythm. One of them needed a short course of Flecainide for atrial ectopic tachycardia. No tachy/brady-arrhythmias were recorded at the 6-month follow-up. ASD closure resulted in a marked decrease in right heart volumes and diameters at 6 months after percutaneous closure.

CONCLUSIONS

Percutaneous ASD closure with the GCO device results in significant, sudden improvement of intra-atrial, atrio-ventricular and intraventricular electrical homogeneity. This benefit persists unaltered over a medium-term follow-up. These electrical changes are associated with a documented positive right heart volumetric remodeling at mid-term follow-up.

Downregulated developmental processes in the postnatal right ventricle under the influence of a volume overload

The molecular atlas of postnatal mouse ventricular development has been made available and cardiac regeneration is documented to be a downregulated process. The right ventricle (RV) differs from the left ventricle. How volume overload (VO), a common pathologic state in children with congenital heart disease, affects the downregulated processes of the RV is currently unclear. We created a fistula between the abdominal aorta and inferior vena cava on postnatal day 7 (P7) using a mouse model to induce a prepubertal RV VO. RNAseq analysis of RV (from postnatal day 14 to 21) demonstrated that angiogenesis was the most enriched gene ontology (GO) term in both the sham and VO groups. Regulation of the mitotic cell cycle was the second-most enriched GO term in the VO group but it was not in the list of enriched GO terms in the sham group. In addition, the number of Ki67-positive cardiomyocytes increased approximately 20-fold in the VO group compared to the sham group. The intensity of the vascular endothelial cells also changed dramatically over time in both groups. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the downregulated transcriptome revealed that the peroxisome proliferators-activated receptor (PPAR) signaling pathway was replaced by the cell cycle in the top-20 enriched KEGG terms because of the VO. Angiogenesis was one of the primary downregulated processes in postnatal RV development, and the cell cycle was reactivated under the influence of VO. The mechanism underlying the effects we observed may be associated with the replacement of the PPAR-signaling pathway with the cell-cycle pathway.

Comparison of the early cardiac electromechanical remodeling following transcatheter and surgical secundum atrial septal defect closure in adults

Background

Secundum atrial septal defect (ASD) closure leads to electrical and mechanical remodeling that occurs early after shunt disappearance. The relationship between electromechanical remodeling using electrocardiogram (ECG) and cardiac magnetic resonance (CMR) after percutaneous and surgical closure has not yet been recorded in prospective studies.

Objective

We thought to study right atrium (RA) and right ventricle (RV) changes by CMR 3 months after transcatheter and surgical closure and their comparison with electrical remodeling by ECG.

Results

We prospectively evaluated 30 consecutive adult patients with isolated secundum ASD who were referred for (transcatheter and surgical) ASD closure.

There was significant reduction in all of the electrical parameters within the same group as compared to the baseline values, except P wave dispersion (Pd). (P max was 97.33 ± 16.67 (pre closure) to 76 ± 15.49 (post closure) in the device group and 97.33 ± 12.79 (preclosure) to 73.33 ± 16.32 (post closure) in the surgical group, QRS complex was 104 ± 18.82 (preclosure) to 80 ± 18.51 (post closure) in the device group and 106.67 ± 14.47 (preclosure) to 86.67 ± 17.99 (post closure) in the surgical group. QTc maximum was 478.53 ± 36.79 (preclosure) to 412.53 ± 38.03 (post closure) in the device group and 470.53 ± 65.70 (preclosure) to 405.93 ± 63.08 (post closure) in the surgical group, and QTc dispersion was 70.33 ± 24.04 (preclosure) to 60.26 ± 28.56 (post closure) in the device group and 80.73 ± 30.38 (preclosure) to 60.27 ± 28.57 (post closure) in the surgical group).There was no significant difference between two groups indicating that transcatheter and surgical closure had led to equivalent value of electrical remodeling.

In CMR study, we measured RA maximal volume and right ventricle end diastolic volume (RVEDV), RA maximal volume decreased significantly as compared to the base line values post closure in both groups (P value < 0.001). The reduction in RA max volume was more in the transcatheter closure group; however, this difference was not statistically significant when compared with the surgical arm (P value = 0.5).RVEDV decreased significantly in both groups as compared to the baseline values (P value < 0.001). Transcatheter closure resulted in more significant reduction in the RVEDV than the surgical closure (P value = 0.03).

Conclusion

Our study showed early significant electromechanical reverse remodeling in most of the study parameters from the baseline values after ASD closure. We found no significant differences in all of the electrical and RA mechanical remodeling parameters with significantly better mechanical remodeling of RV in the device group.

Different habitus but similar electrocardiogram: Cardiac repolarization parameters in children - Comparison of elite athletes to obese children

Introduction:

The standard 12-lead electrocardiogram (ECG) remains a widely used tool in the basic cardiac evaluation of children and adolescents. With the emergence of inherited arrhythmia syndromes, the period of cardiac repolarization has been the focus of attention. So far, data on cardiac repolarization and its normal variants in healthy children are scarce. This may cause uncertainties in the differentiation between pathologies and normal variants. As abnormal autonomic regulation seems to be a major influencing factor on cardiac repolarization, this study aimed to evaluate the parameters of cardiac repolarization of children in extremely good physical shape to obese children to improve knowledge about cardiac repolarization in these subgroups of pediatric patients that are vastly affected by the alterations of autonomic regulation.

Methods:

A total of 426 pediatric volunteers (84 lean, healthy controls; 130 obese healthy pediatric volunteers; and 212 elite athletes) were enrolled in the study, and the parameters of cardiac repolarization were determined in 12-lead ECG.

Results:

Most importantly, there were no pathological findings, neither in the healthy controls nor in the obese or athletes. Athletes showed overall shorter corrected QT intervals than children from the other groups. This is also true if a correction of the QT interval is performed using the Hodges formula to avoid bias due to a tendency to lower heart rates in athletes. Athletes showed the shortest Tpeak-to-end ratios between the groups. The comparison of athletes from primarily strength and power sports versus those from endurance sports showed endurance-trained athletes to have significantly longer QT intervals.

Conclusions:

This study suggests that neither obesity nor extensive sports seems to result in pathological cardiac repolarization parameters in healthy children. Therefore, pathology has to be assumed if abnormal repolarization parameters are seen and might not be simply attributed to the child's habitus or an excellent level of fitness.

Electrical remodeling after percutaneous atrial septal defect closure in pediatric and adult patients

BACKGROUND

Several studies have reported changes in electrocardiographic variables after atrial septal defect (ASD) closure. However no temporal electro-and vectorcardiographic changes have been described from acute to long-term follow-up at different ages. We aimed to study electrical remodeling after percutaneous ASD closure in pediatric and adult patients.

METHODS

ECGs of 69 children and 75 adults (median age 6 [IQR 4-11] years and 45 [IQR 33-54] years, respectively) were retrospectively selected before percutaneous ASD closure and at acute (1-7 days), intermediate (4-14 weeks) and late (6-18 months) follow-up. Apart from electrocardiographic variables, spatial QRS-T angle and ventricular gradient (VG) were derived from mathematically-synthesized vectorcardiograms.

RESULTS

In both pediatric and adult patients, the heart rate decreased immediately post-closure, which persisted to late follow-up. The P-wave amplitude also decreased acutely post-closure, but remained unchanged at later follow-up. The PQ duration shortened immediately in children and at intermediate follow-up in adults. The QRS duration and QTc interval decreased at intermediate-term follow-up in both children and adults. In both groups the spatial QRS-T angle decreased at late follow-up. The VG magnitude increased at intermediate follow-up in children and at late follow-up in adults, after an initial decrease in children.

CONCLUSION

In both pediatric and adult ASD patients, electrocardiographic changes mainly occurred directly after ASD closure except for shortening of QRS duration and QTc interval, which occurred at later follow-up. Adults also showed late changes in PQ duration. At 6-to-18 month post-closure, the spatial QRS-T angle decreased, reflecting increased electrocardiographic concordance. The initial acute decrease in VG in children, which was followed by a significant increase, may be the effect of action potential duration dynamics directly after percutaneous ASD closure.

Immediate and short term effects of percutaneous atrial septal defect device closure on cardiac electrical remodeling in children

Background

The beneficial effects of atrial septal defect (ASD) device closure on electrical cardiac remodeling are well established. The timing at which these effects starts to take place has yet to be determined.

Objectives

To determine the immediate and short term effects of ASD device closure on cardiac electric remodeling in children.

Methods

30 pediatric patients were subjected to 12 lead Electrocardiogram immediately before ASD device closure, 24 h post procedure, 1 and 6 months after. The maximum and minimum P wave and QT durations in any of the 12 leads were recorded and P wave and QT dispersions were calculated and compared using paired T test.

Results

The immediate 24 h follow up electrocardiogram showed significant decrease in P maximum (140.2 ± 6 versus 130.67 ± 5.4 ms), P dispersion (49.73 ± 9.01 versus 41.43 ± 7.65 ms), PR interval (188.7 ± 6.06 ms versus 182.73 ± 5.8 ms), QRS duration (134.4 ± 4.97 ms versus 127.87 ± 4.44), QT maximum (619.07 ± 15.73 ms versus 613.43 ± 11.87), and QT dispersion (67.6 ± 5.31 versus 62.6 ± 4.68 ms) (P = 0.001). After 1 month all the parameters measured showed further significant decrease with P dispersion reaching 32.13 ± 6 (P = 0.001) and QT dispersion reaching 55.0 ± 4.76 (P = 0.001). These effects were maintained 6 months post device closure.

Conclusion

Percutaneous ASD device closure can reverse electrical changes in atrial and ventricular myocardium as early as the first 24 h post device closure.

Evaluation of Prolonged QT Interval: Structural Heart Disease Mimicking Long QT Syndrome

BACKGROUND

In about 20-25% of patients with congenital long QT syndrome (LQTS) a causative pathogenic mutation is not found. The aim of this study was to explore the prevalence of alternative cardiac diagnoses among patients exhibiting prolongation of QT interval with negative genetic testing for LQTS genes.

METHODS

We conducted a retrospective analysis of 239 consecutive patients who were evaluated in the inherited arrhythmia clinic at the Toronto General Hospital between July 2013 and December 2015 for possible LQTS. A detailed review of the patients' charts, electrocardiograms, and imaging was carried out.

RESULTS

The analysis included 56 gene-negative patients and 61 gene-positive patients. Of the gene-negative group, 25% had structural heart disease compared to only 1.6% of gene-positive patients (P < 0.001). Structural heart disease was more likely if only one abnormal QTc parameter was found in the course of the evaluation (35.2% vs 9.1%, P = 0.01). The most common structural cardiac pathology was bileaflet mitral valve prolapse (8.9%). No gene-positive patient had episodes of nonsustained ventricular tachycardia, compared to seven of the gene-negative patients (0% vs 12.5%, P = 0.005).

CONCLUSIONS

Structural pathology was detected in a quarter of gene-negative patients evaluated for possible LQTS. Hence, cardiac imaging and Holter monitoring should be strongly encouraged to rule out structural heart disease in this population.