Depolarization-repolarization inhomogeneity after repair of tetralogy of Fallot. The substrate for malignant ventricular tachycardia?

Management of Fallot's Uncorrected Tetralogy in Adulthood: A Narrative Review

The majority of cyanotic congenital cardiac defects are caused by the tetralogy of Fallot. Some symptoms include a biventricular connection of the aortic root, right ventricular hypertrophy, blockage of the right ventricular outflow tract, and a ventricular septal defect. Our understanding of tetralogy of Fallot (TOF) has significantly advanced since it was first described in 1888, and early diagnosis has led to improved surgical management and increased life expectancy. Adults with unrepaired and repaired TOF present with a range of late complications, including heart failure, the need for re-interventions, and late arrhythmias. Right ventricular (RV) failure, often caused by chronic pulmonary regurgitation, is a significant cause of heart failure in patients with TOF. Current treatment options are limited, and mainstay surgical procedures such as pulmonary-valve replacement (PVR), trans-annular repair (TAR), or infundibular widening repair have not shown a significant reduction in preventing right ventricular (RV) failure or death. Here, we explain the mechanisms of RV failure in ToF, chronic pulmonary regurgitation, heart failure, and secondary polycythemia. HF management in untreated adults is discussed. The progression of the disease, as well as complications, are also discussed. The treatment plan and the need to investigate the best management approach for this unsolved problem are included. This review aims to fill the knowledge gaps and supply valuable information regarding mechanisms of RV failure, chronic pulmonary regurgitation, and secondary polycythemia. To summarize, a new combat strategy must be found to battle RVF, and a more profound vision of these mechanisms is required. If it is not corrected, it will be one of the future research lines that will contribute to designing more efficacious treatment techniques for adults with TOF.

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.

Longitudinal ECG changes in tetralogy of Fallot and association with surgical repair

Background

ECG abnormalities have been linked to adverse changes in right ventricular (RV) morphology and poor clinical outcomes in repaired Tetralogy of Fallot (rTOF). Our aim was to describe how ECG changes progress in early and intermediate follow-up and whether types of surgical strategy at the time of primary repair affected these changes.

Methods

We studied patients with rTOF born 2000-2018 operated at our institution. Seven time points in relation to primary repair, follow-up, and pulmonary valve replacement (PVR) were identified. Patients correct with valve sparing repair (VSR), trans-annular patch (TAP) including with a monocusp valve (TAP + M) and with at least 3 ECGs were included. PQ interval, QRS duration, dispersion, and fragmentation, QTc duration and dispersion, JTc as well as presence of a right bundle branch block (RBBB) were analyzed. Medical records were reviewed for demographic and surgical data.

Results

Two hundred nineteen patients with 882 ECGs were analyzed with a median follow-up time of 12.3 years (8.4, 17) with 41 (19%) needing PVR during the study period. QRS duration increased at time of primary repair to discharge from 66 msec (IQR 12) to 129 msec (IQR 27) (p < 0.0001) and at 1- and 6- year follow-up but showed only a modest and temporary decrease after PVR. QTc increased at the time of primary repair as well as prior to PVR. PQ interval showed a small increase at the time of primary repair, was at its highest prior to PVR and decreased with PVR. Type of surgical repair affected mainly QTc and JTc and was consistently longer in the TAP + M group until PVR. In VSR, QTc and JTc were prolonged initially compared to TAP but were similar after 1 year. After PVR, there were no differences in adverse ECG changes between surgical groups.

Conclusions

PQ interval and QRS duration best correspond to the assumed volume load whereas the relationship with QTc and JTc is more complex, suggesting that these represent more complex remodeling of the myocardium. Before PVR, QTc and JTc are longer in the TAP + M group which may be due to a longer surgical incision.

Relationship between Pulmonary Regurgitation and Ventriculo-Arterial Interactions in Patients with Post-Early Repair of Tetralogy of Fallot: Insights from Wave-Intensity Analysis

This study aimed to investigate the effect of pulmonary regurgitation (PR) on left ventricular ventriculo-arterial (VA) coupling in patients with repaired tetralogy of Fallot (ToF). It was hypothesised that increasing PR severity results in a smaller forward compression wave (FCW) peak in the aortic wave intensity, because of right-to-left ventricular interactions. The use of cardiovascular magnetic resonance (CMR)-derived wave-intensity analysis provided a non-invasive comparison between patients with varying PR degrees. A total of n = 201 patients were studied and both hemodynamic and wave-intensity data were compared. Wave-intensity peaks and areas of the forward compression and forward expansion waves were calculated as surrogates of ventricular function. Any extent of PR resulted in a significant reduction in the FCW peak. A correlation was found between aortic distensibility and the FCW peak, suggesting unfavourable (VA) coupling in patients that also present stiffer ascending aortas. Data suggest that VA coupling is affected by increased impedance.

Uneven vectorial projection is the best explanation for QRS dispersion, not the asynchronic ventricular activation

BACKGROUND

It is believed that QRS dispersion (QRSd) is caused by asynchrony of ventricular activation, but there are no studies that prove it.

OBJECTIVES

To determine the mechanism that best explains QRSd in surface electrocardiogram (ECG).

METHODS

Cross-sectional study in 95 consecutive patients (median age: 31.0 years [25-52], female sex: 66.3%) with atrioventricular nodal reentrant tachycardia. All 12 ECG leads were recorded at once, simultaneously with the intracardiac recordings. QRSd was quantified as the difference between maximum (QRSmax) and minimum QRS duration (QRSmin). QRS was measured firstly at a calibration of 20 mm/mV and a sweep speed of 50 mm/s, enhancement 10× (basic measurement [BM]), and after at sweep speed of 150 mm/s, enhancement 80 - 160×. The interventricular dyssynchrony (IVD) was also quantified.

RESULTS

QRSmax increased from BM (98 ms [91-103]) to 80× (102 ms [99-108]; p = 0.029) and 160× (104 ms [101.5-110]; p = 0.027). QRSmin, almost equaled the duration of QRSmax at 160× (103 ms [100-108]). With BM, QRSd was 26 ms [22-35] and was reduced 26-fold (p < 0.001) by magnifying the QRS at 160× (1 ms [0-3]). IVD was weakly correlated with QRSd (r = 0.234, p = 0.023), but strongly with the total QRS at 160× (r = 0.676, p < 0.001).

CONCLUSION

When QRS complex is narrow, the best explanation for the origin of QRSd on the surface ECG is the unequal projection of the ventricular depolarization vector in the different axis of the leads.

Tetralogy of Fallot: risk stratification is straightforward. Or is it?

PURPOSE OF REVIEW

Tetralogy of Fallot (TOF) carries a long-term risk of arrhythmias and sudden death after surgical repair. Risk stratification is still less accurate than desired.

RECENT FINDINGS

Several factors have been studied as risk predictors for ventricular arrhythmias and sudden death. Clinical parameters include age at surgery, time since repair, types of previous surgeries, and symptoms such as syncope and palpitations. Electrocardiographic parameters that have been studied include QRS interval, ventricular arrhythmias assessed with Holter monitors, signal averaged ECG, QRS fragmentation, QRS vector magnitude, and microvolt T-wave alternans. Exercising testing has been shown to have prognostic significance. Ventricular function assessment with imaging studies including echocardiography and magnetic resonance imaging (MRI) plays a significant role. Invasive hemodynamic and electrophysiologic studies, in addition to assessment for inducible tachycardia, can provide information regarding the electroanatomic substrate of VT.

SUMMARY

Risk stratification for TOF has improved over the last years with several clinical, electrocardiographic, imaging, and invasive electrophysiologic findings showing promise, but there still a lack of uniformity in approach between various investigators and reproducibility of findings is difficult in larger populations. With use of a combination of factors, a more informed decision can be made.

Electrocardiographic Markers of Appropriate Implantable Cardioverter-Defibrillator Therapy in Young People with Congenital Heart Diseases

Implantable cardioverter-defibrillators (ICDs) are increasingly utilized in patients with congenital heart disease (CHD). Prediction of the occurrence of shocks is important if improved patient selection is desired. The electrocardiogram (ECG) has been the first-line tool predicting the risk of sudden death, but data in CHD patients are lacking. We aim to evaluate the predictive value of electrocardiographic markers of appropriate therapy of ICD in young people with CHD. We conducted a prospective, longitudinal study, in twenty-six CHD patients (mean age 24.7 ± 5.3 years) who underwent first ICD implantation. Forty-two age- and diagnosis-matched controls were recruited. Twelve-lead ECG and 24 h Holter analysis were performed during a mean follow-up of 38.9 months. Data included heart rate, heart rate variability, QRS duration (QRSd), QTc interval and its dispersion, Tpeak-Tend (Tp-Te) interval and its dispersion, presence of fragmented QRS (fQRS), T wave alternans, atrial arrhythmias, and non-sustained ventricular tachycardia. Implant indication was primary prevention in ten cases (38.5%) and secondary prevention in 16 (61.5%). Overall, 17 subjects (65.3%) received at least one appropriate and effective ICD discharge. fQRS was present in 64.7% of cases with ICD therapy compared with patients without events or controls (p < 0.0001). Tp-e and Tp-e dispersion were significantly prolonged in patients with recurrences (113.5 and 37.2 ms) versus patients without ICD discharge (89.6 and 24.1 ms) or controls (72.4 and 19.3 ms) (p < 0.0001 and p < 0.0001, respectively). On univariate Cox regression analysis QRSd (hazard ratio: 1.19 per ms, p = 0.003), QTc dispersion (hazard ratio: 1.57 per ms, p = 0.002), fQRS (hazard ratio: 3.58 p < 0.0001), Tp-e (hazard ratio: 2.27 per ms, p < 0.0001), and Tp-e dispersion (hazard ratio: 4.15 per ms, p < 0.0001), emerged as strong predictors of outcome. On multivariate Cox analysis fQRS, Tp-e and Tp-e dispersion remained in the model. The presence of fQRS, and both Tp-e and Tp-e dispersion are useful ECG tools in daily clinical practice to identify CHD patients at risk for appropriate ICD therapy.

Proarrhythmic remodelling of the right ventricle in a porcine model of repaired tetralogy of Fallot

Objective

The growing adult population with surgically corrected tetralogy of Fallot (TOF) is at risk of arrhythmias and sudden cardiac death. We sought to investigate the contribution of right ventricular (RV) structural and electrophysiological remodelling to arrhythmia generation in a preclinical animal model of repaired TOF (rTOF).

Methods and results

Pigs mimicking rTOF underwent cardiac MRI functional characterisation and presented with pulmonary regurgitation, RV hypertrophy, dilatation and dysfunction compared with Sham-operated animals (Sham). Optical mapping of rTOF RV-perfused wedges revealed a significant prolongation of RV activation time with slower conduction velocities and regions of conduction slowing well beyond the surgical scar. A reduced protein expression and lateralisation of Connexin-43 were identified in rTOF RVs. A remodelling of extracellular matrix-related gene expression and an increase in collagen content that correlated with prolonged RV activation time were also found in these animals. RV action potential duration (APD) was prolonged in the epicardial anterior region at early and late repolarisation level, thus contributing to a greater APD heterogeneity and to altered transmural and anteroposterior APD gradients in rTOF RVs. APD remodelling involved changes in Kv4.3 and MiRP1 expression. Spontaneous arrhythmias were more frequent in rTOF wedges and more complex in the anterior than in the posterior RV.

Conclusion

Significant remodelling of RV conduction and repolarisation properties was found in pigs with rTOF. This remodelling generates a proarrhythmic substrate likely to facilitate re-entries and to contribute to sudden cardiac death in patients with rTOF.

Percutaneous Pulmonary Valve Implantation Alters Electrophysiologic Substrate

BACKGROUND

Percutaneous pulmonary valve implantation (PPVI) is first-line therapy for some congenital heart disease patients with right ventricular outflow tract dysfunction. The hemodynamics improvements after PPVI are well documented, but little is known about its effects on the electrophysiologic substrate. The objective of this study is to assess the short- and medium-term electrophysiologic substrate changes and elucidate postprocedure arrhythmias.

METHODS AND RESULTS

A retrospective chart review of patients undergoing PPVI from May 2010 to April 2015 was performed. A total of 106 patients underwent PPVI; most commonly these patients had tetralogy of Fallot (n=59, 55%) and pulmonary insufficiency (n=60, 57%). The median follow-up time was 28 months (7-63 months). Pre-PPVI, 25 patients (24%) had documented arrhythmias: nonsustained ventricular tachycardia (NSVT) (n=9, 8%), frequent premature ventricular contractions (PVCs) (n=6, 6%), and atrial fibrillation/flutter (AF/AFL) (n=10, 9%). Post-PPVI, arrhythmias resolved in 4 patients who had NSVT (44%) and 5 patients who had PVCs (83%). New arrhythmias were seen in 16 patients (15%): 7 NSVT, 8 PVCs, and 1 AF/AFL. There was resolution at medium-term follow-up in 6 (86%) patients with new-onset NSVT and 7 (88%) patients with new-onset PVCs. There was no difference in QRS duration pre-PPVI, post-PPVI, and at medium-term follow-up (P=0.6). The median corrected QT lengthened immediately post-PPVI but shortened significantly at midterm follow-up (P<0.01).

CONCLUSIONS

PPVI reduced the prevalence of NSVT. The majority of postimplant arrhythmias resolve by 6 months of follow-up.

Role of right ventricular three-dimensional electroanatomic voltage mapping for arrhythmic risk stratification of patients with corrected tetralogy of Fallot or other congenital heart disease involving the right ventricular outflow tract

BACKGROUND

The post-surgical history of repaired congenital heart disease (rCHD), in particular tetralogy of Fallot (TOF), is often complicated by sudden death. Electrical myocardial abnormalities could be a substrate for malignant ventricular arrhythmias.

METHODS AND RESULTS

146 patients with TOF or other rCHD involving a subpulmonary right ventricle, considered to be at high arrhythmic risk, underwent right ventricular (RV) electroanatomic voltage mapping (EVM). Maps showed endocardial scars (<0.5mV) in all cases, mainly involving the RV outflow tract (n=141, 96.6%). In 28 cases (19.2%), other areas were involved. Total scar extension, expressed as % of total endocardial area, was significantly higher in patients with QRS ≥180ms [4.5% (±2.5) vs 2.8% (±2.4), p=0.014], left and right ventricular systolic dysfunction [4.5% (±3.2) vs 2.8% (±2.3), p=0.016 and 3.5% (±3.0) vs 2.6% (±1.9), p=0.03, respectively], premature ventricular contractions (PVCs) [3.2% (±2.6) vs 2.2% (±1.8), p<0.05], exercise-induced PVCs [3.8% (±2.4) vs 2.6% (±2.2), p=0.01], previous shunt [4.0% (±2.7) vs 2.6% (±2.2), p=0.01] and reintervention [4.2% (±3.2) vs 2.6% (±2.0), p=0.008]. Scar size also showed a positive correlation with duration of post-surgical follow-up (ρ=0.01), age at correction (ρ=0.01) and absolute QRS duration (ρ=0.05).

CONCLUSIONS

Patients with rCHD involving the right ventricle show electrical scars with variable distribution, not necessarily matching with sites of surgical lesions. Scar extension correlates with some of the risk factors for life-threatening arrhythmias in CHD, such as prolonged QRS. Thus EVM could be considered an additional tool in the assessment of risk stratification in this particular population.

Evaluation of Adults With Congenital Heart Disease

The clinical approach to adults with congenital heart diseases (ACHDs) is unique in cardiovascular medicine because these patients encompass a broad range of presentations. Each patient, despite having similar diagnosis, will be anatomically and physiologically unlike others within ACHD population, in relation to the type of repair, age at repair, associated defects, with specific long-term risk factors and complications. Furthermore, as many patients will not complain of symptoms, clinical evaluation and diagnostic testing must also be based on the underlying main diagnostic category, with complete standardized lesion-specific clinical protocols, investigating all known risk factors specific for each congenital heart disease and performed as part of screening for significant long-term complications. The first part of this review will focus on clinical history, physical examination, and the most important diagnostic testing in ACHD population. The second part of the article will focus on some clinical issues we have to face in our daily practice, such as heart failure, cyanosis, and pulmonary hypertension. Furthermore, as survival rates of ACHD population continue to improve and patients with this condition live longer, we will briefly report on a new clinical concern regarding the impact of acquired morbidities like coronary artery disease that appear to be of greater importance in defining outcome in older patients with ACHD.

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

BACKGROUND

Prolonged corrected QT (QTc) intervals are frequently observed in children before atrial septal defect (ASD) closure in our department.

OBJECTIVE

The aim of the study was to assess the effect of long-term right ventricular volume overload on repolarization.

METHODS

QRS, QT, and JT intervals were measured manually in leads II and V5 of a standard 12-lead electrocardiogram in 45 children with an isolated ASD a day before and at least 6 months after ASD closure. QT intervals were corrected for heart rate using the Bazett, Fridericia, Framingham, and Hodges formulas. Each QTc interval calculated using the Bazett formula was compared to sex- and age-matched normal values.

RESULTS

Individual QTc intervals shortened significantly (P < .001) using all correction formulas, whereas the QRS duration did not change. The prevalence of prolonged QTc interval decreased from 22.2% to 2.2% after shunt closure (P = .007).

CONCLUSION

The QTc interval shortens significantly after the closure of a hemodynamically relevant ASD in childhood. This phenomenon is independent of the used QT correction formula and may reflect a mechanoelectrical feedback associated with right ventricular volume overload.

Repolarization Alternans and Ventricular Arrhythmia in a Repaired Tetralogy of Fallot Animal Model

BACKGROUND

Ventricular arrhythmia is an important cause of late death in patients with repaired tetralogy of Fallot (rTOF). By using an rTOF canine model, we investigated the role of repolarization alternans and its electrophysiological mechanisms.

METHODS AND RESULTS

Six dogs received right ventricular outflow tract (RVOT) transannular patch, pulmonary valve destruction, and right bundle branch ablation to simulate rTOF. After 1 year, we performed high-resolution dual-voltage and calcium optical mapping to record action potentials and calcium transients on the excised right ventricular outflow tract wedges. Another 6 dogs without operation served as control. The rTOF group was more susceptible to action potential duration alternans (APD-ALT) and spatially discordant APD-ALT than control (threshold for APD-ALT: 516±36 vs 343±36 ms; P=0.017; threshold for discordant APD-ALT: 387±30 vs 310±14 ms; P=0.046). We detected 2 episodes of ventricular tachycardia in the rTOF group, but none in the control. Expressions of Kv4.3 and KChIP2 decreased in the rTOF group. Expression of connexin 43 also decreased in the rTOF group with a corresponding decrease of conduction velocity and might contribute to spatially discordant APD-ALT. We also found distinct electrophysiological features of the RVOT, including biphasic relationship between magnitude of APD-ALT and pacing cycle length, uncoupling of APD-ALT, and calcium transients alternans, and shortened APD, but unchanged, APD restitution in rTOF.

CONCLUSIONS

We demonstrated novel electrophysiological properties of the RVOT. In an rTOF model, the RVOT exhibits increased susceptibility to temporal and spatially discordant APD-ALT, which was not totally dependent on calcium transient alternans.

Assessment of Microvolt T Wave Alternans in Children with Repaired Tetralogy of Fallot during 24-Hour Holter Electrocardiography

BACKGROUND

We aimed to examine microvolt T wave alternans (MTWA) in 24-hour Holter electrocardiography (ECG) of children with repaired tetralogy of Fallot (TOF) to assess associations of MTWA with ventricular arrhythmias, ECG parameters, and echocardiographic findings.

METHODS

Holter ECG records and archive files of 56 repaired TOF patients (62.5% male) who were analyzed retrospectively. Subjects' ECG parameters and MTWA values were compared with age-sex-matched control group. T wave changes were analyzed by time-domain-modified moving average method from the three channels of 24-hour Holter ECG.

RESULTS

Mean age was 123.4 ± 48.3 months. Median MTWA value was 55.5 μV in the control group, whereas 95.5 μV in patients group (P < 0.001). A significant weak positive correlation was found between the presence of ventricular extrasystoles and tricuspid regurgitation. There was no correlation between ECG parameters, echocardiographic findings, and MTWA.

CONCLUSIONS

MTWA was increased in children with repaired TOF as reported before. To our knowledge, this is the first study analyzing MTWA with 24-hour Holter ECG in repaired TOF patients.

Heterogeneity of Ventricular Sympathetic Nervous Activity is Associated with Clinically Relevant Ventricular Arrhythmia in Postoperative Patients with Tetralogy of Fallot

This study aimed to clarify whether there is an association between ventricular sympathetic nervous activity (SNA) and clinically relevant ventricular arrhythmia (a run of ≥ 3 consecutive ventricular beats, RVA) in postoperative patients with tetralogy of Fallot (TOF). We performed a retrospective study in a national referral center of pediatric cardiology in Japan. Twenty-four postoperative TOF patients (13 males, median age 17 years) undergoing myocardial (123)I metaiodobenzylguanidine (MIBG) scintigraphy were included. We measured the heart-to-mediastinum ratio (HMR) and washout ratio (WR) from planar MIBG myocardial scintigraphy. Tomographic images and polar maps were generated with 20 segments. The standard deviation of percentage uptake of 20 segments (SD-uptake) as an index of heterogeneous MIBG uptake to the ventricular myocardium was calculated. We compared these MIBG-derived variables with the patients' clinical profiles, including ECG findings and hemodynamics. Eight of 24 patients had RVA (RVA group), and the other 16 did not have RVA (non-RVA group). There were no significant differences in the HMR (1.9 ± 0.5 vs. 2.2 ± 0.4) and WR (50 ± 5 vs. 42 ± 10) between the two groups. SD-uptake was significantly higher in the RVA group than in the non-RVA group (15 ± 3 vs. 12 ± 3, p = 0.03). QT dispersion (ms) was also higher in the RVA group than in the non-RVA group (53 ± 23 vs. 44 ± 18, p = 0.04). Multivariate logistic regression showed that SD-uptake and QT dispersion were independent predictors in the RVA group (p = 0.02, p = 0.03). In addition to greater QT dispersion, heterogeneous SNA is associated with RVA in TOF patients postoperatively.

Haemodynamic consequences of targeted single- and dual-site right ventricular pacing in adults with congenital heart disease undergoing surgical pulmonary valve replacement

AIMS

The purpose of this study was to create an epicardial electroanatomic map of the right ventricle (RV) and then apply post-operative-targeted single- and dual-site RV temporary pacing with measurement of haemodynamic parameters. Cardiac resynchronization therapy is an established treatment for symptomatic left ventricular (LV) dysfunction. In congenital heart disease, RV dysfunction is a common cause of morbidity-little is known regarding the potential benefits of CRT in this setting.

METHODS AND RESULTS

Sixteen adults (age = 32 ± 8 years; 6 M, 10 F) with right bundle branch block (RBBB) and repaired tetralogy of Fallot (n = 8) or corrected congenital pulmonary stenosis (n = 8) undergoing surgical pulmonary valve replacement (PVR) for pulmonary regurgitation underwent epicardial RV mapping and haemodynamic assessment of random pacing configurations including the site of latest RV activation. The pre-operative pulmonary regurgitant fraction was 49 ± 10%; mean LV end-diastolic volume (EDV) 85 ± 19 mL/min/m(2) and RVEDV 183 ± 89 mL/min/m(2) on cardiac magnetic resonance imaging. The mean pre-operative QRS duration is 136 ± 26 ms. The commonest site of latest activation was the RV free wall and DDD pacing here alone or combined with RV apical pacing resulted in significant increases in cardiac output (CO) vs. AAI pacing (P < 0.01 all measures). DDDRV alternative site pacing significantly improved CO by 16% vs. AAI (P = 0.018), and 8.5% vs. DDDRV apical pacing (P = 0.02).

CONCLUSION

Single-site RV pacing targeted to the region of latest activation in patients with RBBB undergoing PVR induces acute improvements in haemodynamics and supports the concept of 'RV CRT'. Targeted pacing in such patients has therapeutic potential both post-operatively and in the long term.

Percutaneous implantation of pulmonary valves

Percutaneous implantation of valves is evolving as the most exciting innovation in transcatheter therapeutics. Valve repairs and replacements form an important indication of re-operations after congenital heart operations. Right ventricular outflow tract surgery is common after repair of conditions such as pulmonary atresia with Tetralogy of Fallot, common arterial trunk and Rastelli operation for transposition of great arteries, ventricular septal defect with pulmonary stenosis. Conduit survival is improving, nevertheless, re-operations are common. Although the re-operations can be performed at low risk, they still involve morbidity and mortality. Percutaneous implantation of valves is emerging as an alternative option for these group of patients. Our experience in percutaneous implantation of pulmonary valves has yielded encouraging results. For incompetence, the results are excellent. Evolving technology is making it applicable in wider clinical situations. Similar technology could also be applied to implantation of valves in the aortic position.

Early changes in myocardial repolarization and coronary perfusion after cardiopulmonary bypass surgery for ASD repair in children

Background

In adults, impaired myocardial repolarization and increased risk of arrhythmia are known consequences of open heart surgery. Little is known, however, about post-operative consequences of cardiopulmonary bypass surgery in children. The aim of this study was to assess ventricular repolarization and coronary perfusion after bypass surgery for atrial septal defect (ASD) repair in children.

Methods

Twelve patients with ASD were assessed one day before and 5–6 days after ASD repair. Myocardial repolarization (corrected QT interval, QTc, QT dispersion, QTd, and PQ interval) was determined on 12-lead electrocardiograms. Coronary flow in proximal left anterior descending artery (peak flow velocity in diastole, PFVd) was assessed by transthoracic Doppler echocardiography.

Results

Ten of the 12 (83%) children had normal myocardial repolarization before and after surgery. After surgery, QTc increased 1-9% in 5 (42%) patients, decreased 2-11% in 5 (42%) patients and did not change in 2 (16%) patients. Post-op QTc positively correlated with bypass time (R=0.686, p=0.014) and changes in PFVd (R=0.741, p=0.006). After surgery, QTd increased 33-67% in 4 (33%) patients, decreased 25-50% in 6 patients (50%) and did not change in 2 (16%) patients. After surgery, PQ interval increased 5-30% in 4 (33%) patients, decreased 4-29% in 6 (50%) patients and did not change in 1 (8%) patient. Post-op PQ positively correlated with bypass time (R=0.636, p=0.027). As previously reported, PFVd significantly increased after surgery (p<0.001).

Conclusions

Changes in QTc, PQ and PFVd are common in young children undergoing surgery for ASD repair. Post-op QTc significantly correlates with bypass time, suggesting prolonged cardiopulmonary bypass may impair ventricular repolarization. Post-op QTc significantly correlates with PFVd changes, suggesting increased coronary flow may also impair ventricular repolarization. The clinical significance and reversibility of these alternations require further investigations.

Right atrial area and right ventricular outflow tract akinetic length predict sustained tachyarrhythmia in repaired tetralogy of Fallot

Aims

Repaired tetralogy of Fallot (rtoF) patients are at risk of atrial or ventricular tachyarrhythmia and sudden cardiac death. Risk stratification for arrhythmia remains difficult.

We investigated whether cardiac anatomy and function predict arrhythmia.

Methods

One-hundred-and-fifty-four adults with rtoF, median age 30.8 (21.9–40.2) years, were studied with a standardised protocol including cardiovascular magnetic resonance (CMR) and prospectively followed up over median 5.6 (4.6–7.0) years for the pre-specified endpoints of new-onset atrial or ventricular tachyarrhythmia (sustained ventricular tachycardia/ventricular fibrillation).

Results

Atrial tachyarrhythmia (n = 11) was predicted by maximal right atrial area indexed to body surface area (RAAi) on four-chamber cine-CMR (Hazard ratio 1.17, 95% Confidence Interval 1.07–1.28 per cm²/m²; p = 0.0005, survival receiver operating curve; ROC analysis, area under curve; AUC 0.74 [0.66–0.81]; cut-off value 16 cm²/m²). Atrial arrhythmia-free survival was reduced in patients with RAAi ≥ 16 cm²/m² (logrank p = 0.0001). Right ventricular (RV) restrictive physiology on echocardiography (n = 38) related to higher RAAi (p = 0.02) and had similar RV dilatation compared with remaining patients.

Ventricular arrhythmia (n = 9) was predicted by CMR RV outflow tract (RVOT) akinetic area length (Hazard ratio 1.05, 95% Confidence Interval 1.01–1.09 per mm; p = 0.003, survival ROC analysis, AUC 0.77 [0.83–0.61]; cut-off value 30 mm) and decreased RV ejection fraction (Hazard ratio 0.93, 95% Confidence Interval 0.87–0.99 per %; p = 0.03). Ventricular arrhythmia-free survival was reduced in patients with RVOT akinetic region length > 30 mm (logrank p = 0.02).

Conclusion

RAAi predicts atrial arrhythmia and RVOT akinetic region length predicts ventricular arrhythmia in late follow-up of rtoF. These are simple, feasible measurements for inclusion in serial surveillance and risk stratification of rtoF patients.

QRS Complex Enlargement as a Predictor of Ventricular Arrhythmias in Patients Affected by Surgically Treated Tetralogy of Fallot: A Comprehensive Literature Review and Historical Overview

Tetralogy of Fallot (TOF) is a congenital heart disease frequently treated by surgical repair to relieve symptoms and improve survival. However, despite the performing of an optimal surgical repair, TOF patients are at times characterized by a poor long-term survival rate, likely due to cardiac causes such as ventricular arrhythmias, with subsequent sudden death. In the 80s it was irrefutably demonstrated that QRS prolongation ≥180 msec at basal electrocardiogram is a strong predictor for refining risk stratification for ventricular tachycardia in these patients. The aim of this research was to undertake a review of all studies conducted to assess the impact of QRS duration on the development of life-threatening ventricular arrhythmias in repaired TOF subjects.

Demonstration of value of optimizing ECG triggering for cardiovascular magnetic resonance in patients with congenital heart disease

BACKGROUND

Optimal ECG triggering is of paramount importance for correct blood flow quantification during cardiovascular magnetic resonance (CMR). However, optimal ECG triggering and therefore blood flow quantification is impaired in many patients with congenital heart disease (CHD) due to complex QRS patterns. Therefore, a new ECG-trigger algorithm was developed to address triggering problems due to complex QRS patterns.The aim of this study was to test this new ECG-trigger algorithm in routine patients with CHD and its impact on blood flow quantification.

METHODS

35 consecutive routine patients with CHD undergoing CMR were included in the study. (40% Fallot's Tetralogy, 20% aortic arch pathology, 14% transposition of the great arteries, 26% others; age 26+/-11 yrs).In all patients, blood flow in the ascending aorta was quantified using the old ECG-trigger algorithm and the new ECG-trigger algorithm in random order. Blood flow quantified using the old or new ECG-trigger algorithm was compared by Bland-Altman analysis.Three blinded investigators evaluated the vector clouds and trigger points of both ECG-trigger methods. Evaluation criteria were false positive and false negative triggered QRS complexes (specificity and sensitivity), and accuracy of detection. Accuracy of detection was defined as time scatter of the trigger around the correct trigger point.

RESULTS

Specificity, sensitivity, and accuracy of detection significantly increased using the new ECG-trigger algorithm compared to the old ECG-trigger algorithm.Blood flow quantification using the old or new ECG-trigger algorithm differed more than 5% in 31% of the cases.

CONCLUSIONS

Our results suggest that optimizing ECG triggering during CMR using our new algorithm can avoid errors of >5% in approximately 1/3 of routine patients with congenital heart disease (CHD). We furthermore suggest that incorrect ECG triggering appears to be problematic for blood flow quantification of many patients with CHD undergoing routine CMR.

Melody transcatheter pulmonary valve implantation. Results from the registry of the Italian Society of Pediatric Cardiology

BACKGROUND AND AIMS

Percutaneous implantation of pulmonary valve has been recently introduced in the clinical practice. Our aim was to analyze data of patients treated in Italy by using the Melody Medtronic valve.

METHODS

Prospective, observational, multi-centric survey by means of a web-based database registry of the Italian Society of Pediatric Cardiology (SICP).

RESULTS

Between October 2007 and October 2010, 63 patients were included in the registry (median age: 24 years; range 11-65 years). Forty subjects were in NYHA class I-II while 23 were in NYHA class III-IV. Patients included had a history of a median three previous surgeries (range 1-5) and a median of one previous cardiac catheterization (range 0-4). A cono-truncal disease was present in 39 patients, previous Ross operation in 9, and other diagnosis in 15. Indication to valve implantation was pure stenosis in 21 patients, pure regurgitation in 12, association of stenosis and regurgitation in 30. Implantation was performed in 61 subjects (97%). Pre-stenting was performed in 85% of cases. Median procedure time was 170 minutes (range 85-360). No significant regurgitation was recorded after procedure while the trans-pulmonary gradient reduced significantly. Early major complications occurred in seven subjects (11%). One death occurred in the early post-operative period in a severely ill subject. At a median follow-up of 30 months (range 12-48 months), three patients died due to underlying disease. Major complications occurred in six patients during follow-up (external electric cardioversion: one patient; herpes virus encephalitis: two patients; Melody valve endocarditis needing surgical explant: two patients; major fractures of the stent and need second Melody valve implantation: two patients). Freedom from valve failure at latest follow-up was 81.4% ± 9%.

CONCLUSION

Early results of the SICP registry on transcatheter Melody pulmonary valve implantation show that the procedure is safe and successful. Major concerns are related to the occurrence of stent fracture and bacterial endocarditis. Longer follow-up and larger series are needed.

Fragmented QRS complexes predict right ventricular dysfunction and outflow tract aneurysms in patients with repaired tetralogy of Fallot

BACKGROUND

Fragmented QRS complexes (fQRS) correlate with myocardial scar, and may predict arrhythmias in patients with repaired tetralogy of Fallot (TOF). We investigated the relationship between fQRS in operated TOF patients with right ventricular (RV) dysfunction and RV outflow tract (RVOT) aneurysm.

METHODS

We studied 56 operated TOF patients with moderate/severe pulmonary regurgitation, referred for cardiac magnetic resonance imaging (MRI) over a 4.5 year period. The presence of fQRS (additional notches in the R/S wave in ≥ 2 contiguous leads on the ECG) was correlated with MRI findings.

RESULTS

fQRS was observed in 44 (78.6%) patients. Patients with fQRS had significantly larger RV end diastolic volume index (RVEDVi; 162 ml vs 141 ml, p=0.028) and RV end systolic volume index (RVESVi; 88 ml vs 70 ml, p=0.031). Increasing number of leads with fragmentation was independently associated with increasingly lower RV ejection fraction (adjusted co-efficient -0.97, 95%CI -1.83 to -0.12, p=0.026), greater pulmonary regurgitation fraction (1.65, 0.28 to 3.01, p=0.019), larger RVEDVi (6.78, 2.00 to 11.56, p=0.006) and RVESVi (5.41, 1.66 to 9.15, p=0.005). Anterior fragmentation correlated most significantly with RV dysfunction (p<0.05). fQRS had no significant association with LV dysfunction. Presence of any fQRS (OR 17.5, 95%CI 2.1-147.8, p=0.009) and inferior fQRS (OR 9.0, 95%CI 2.7-30.1, p<0.001) were found to be significant predictors for RVOT aneurysm.

CONCLUSIONS

The presence of fQRS on the ECG is significantly associated with RV dysfunction and RVOT aneurysms in repaired TOF patients. Increasing burden of fragmentation, especially in the anterior leads, is associated with increasing RV dysfunction.

Coexisting mutations/polymorphisms of the long QT syndrome genes in patients with repaired Tetralogy of Fallot are associated with the risks of life-threatening events

Coexisting long QT gene mutations/polymorphisms in Tetralogy of Fallot (TOF) patients may aggravate the repolarization abnormality from cardiac repair. We investigated the impact of these genes on the risk of life-threatening events. Genetic variants of the three common long QT genes were identified from patients with repaired TOF. Life-threatening events were defined as sudden cardiac death and hemodynamic unstable ventricular arrhythmia. Biophysical characterization of the alleles of the genetic variants was performed using a whole-cell voltage clamp with expression in Xenopus oocytes. A total of 84 patients (56.0 % male with 1,215 patients-year follow-up) were enrolled. Six rare variants and six non-synonymous single nucleotide polymorphisms (SNPs) were found in 40 (47.6 %) patients. Life-threatening events occurred in five patients; four received implantable cardioverter defibrillator and one died of sudden cardiac death. Life-threatening events occurred more often in those with genetic variants than those without (5/40 vs. 0/44, P = 0.021); particularly, the hERG or SCN5A gene mutations/polymorphisms (2/5 vs. 3/79, P = 0.027 and 5/27 vs. 0/57, P = 0.003, respectively). Among the five patients with life-threatening events, three had compound variants (hERG p.M645R/SCN5A p.R1193Q, hERG p.K897T/SCN5A p.H558R, and KVLQT1 p.G645S/SCN5A p.P1090L), that also increased the risk of events. Their QTc and JTc were all prolonged. Functional study of the novel variant (hERG gene p.M645R) from patients with life-threatening events revealed a dominant negative effect. In conclusion, in repaired TOF patients, coexisting long QT mutations/polymorphisms might have additive effects on the repolarization abnormality from surgery and thereby increase the risks of life-threatening events.

The role of mechanical-electrical interaction in ventricular arrhythmia: evidence from a novel animal model for repaired tetralogy of Fallot

Pulmonary regurgitation and prolonged QRS duration of right bundle branch (RBB) block are common in repaired tetralogy of Fallot (TOF) and increase the risk of sudden death. We sought to establish an animal model to reflect both abnormalities. Twenty-one canines: group I (n = 7) received a surgical right ventricular outflow tract (RVOT) transannular patch plus pulmonary valve destruction; group II (n = 5) received RBB ablation and sham operation; and group III (n = 9) received combined interventions. Serial electrophysiological data were obtained up to 1 y. Procedure mortality was 27.6%. At 1 y, although severe pulmonary regurgitation was documented in most dogs in groups I (71%) and III (100%), progressive RVOT dilatation was noted in group III. RBB block was present in all dogs in groups II and III. However, the increments of QRS duration, QTc, JTc, and QT dispersion progression between 1 mo and 1 y were all greatest in group III. Ventricular arrhythmia events were frequent in group III (median 3.3/mo) but uncommon in groups I and II (median 1/mo). We have created a novel animal model that adequately reflects both the hemodynamic and electrophysiological characteristics of repaired TOF patients and can be applied to examine the risk of ventricular arrhythmias.

[Arrhythmias in patients with surgically corrected tetralogy of Fallot]

The population of adults with surgically corrected tetralogy of Fallot (TOF) is increasing. Atrial and ventricular arrhythmias are prevalent, and therapeutical approaches including implantable cardioverter-defibrillators and radiofrequency catheter ablation need to be considered carefully for the prevention of hemodynamic deterioration and sudden cardiac death. Complex anatomy, myocardial hypertrophy, and broad channels of slow conduction may in part explain some challenges regarding risk stratification, and identification/modification of the arrhythmogenic substrate in these patients. The aim of this brief review is 2-fold: (1.) To present insights into characteristics of typical TOF related arrhythmias and (2.) to reflect therapeutical concepts targeting tachyarrhythmias in these patients by focusing on catheter ablation.

Pregnancy in women with corrected tetralogy of Fallot: occurrence and predictors of adverse events

BACKGROUND

In women with corrected tetralogy of Fallot (ToF), pregnancy is associated with maternal cardiac, obstetric, and offspring complications. Our aim is to investigate the magnitude and determinants of pregnancy outcome in women with corrected ToF.

METHODS

In this retrospective international multicenter study using 2 congenital heart disease registries, 204 women with corrected ToF were identified. Within this group, 74 women had 157 pregnancies, including 30 miscarriages and 4 terminations of pregnancy. Detailed information on each completed pregnancy (n = 123) was obtained using medical records and supplementary interviews.

RESULTS

Cardiovascular events occurred during 10 (8.1%) pregnancies, mainly (supra)ventricular arrhythmias. Obstetric and offspring events occurred in 73 (58.9%) and 42 (33.9%) pregnancies, respectively, including offspring mortality in 8 (6.4%). The most important predictor was use of cardiac medication before pregnancy (odds ratio for cardiac events 11.7, 95% CI 2.2-62.7; odds ratio for offspring events 8.4, 95% CI 1.4-48.6). In pregnancies with cardiovascular events, significantly more small-for-gestational-age children were born (P value < .01).

CONCLUSIONS

Cardiovascular, obstetric, and offspring events occur frequently during pregnancies in women with ToF. Maternal use of cardiovascular medication is associated with pregnancy outcome, and maternal cardiovascular events during pregnancy are highly associated with offspring events.

Electrical remodeling following percutaneous pulmonary valve implantation

Sudden cardiac death in congenital heart disease is related to increased right ventricular end-diastolic volume (RVEDV), abnormalities of QRS duration, and QRS, JT, and QT dispersions. Surgical pulmonary valve replacement and percutaneous pulmonary valve implantation (PPVI) decrease RVEDV, but the effects of PPVI on surface electrocardiographic parameters are unknown. PPVI represents a pure model of RV mechanical and electrophysiologic changes after replacement. This prospective study sought to determine the effects of PPVI on surface electrocardiographic parameters: Ninety-nine PPVI procedures in patients with congenital heart disease (23.1 ± 10 years of age) were studied before, after, and 1 year after PPVI with serial electrocardiograms and echocardiogram/magnetic resonance images. Forty-three percent had pulmonary stenosis, 27% pulmonary regurgitation (PR), and 29% mixed lesions. In those with predominantly PR (n = 26), QRS duration decreased significantly (135 ± 27 to 128 ± 29 ms, p = 0.007). However, in the total cohort no significant change in QRS duration at 1 year was observed (137 ± 29 to 134 ± 29 ms). Corrected QT interval and QRS, QT, and JT dispersions significantly decreased at 1 year (p ≤0.001). RVEDV correlated with preprocedure QRS duration (r = 0.34, p <0.002) but there was no correlation after PPVI. In conclusion, this is the first study reporting electrical remodeling after isolated PPVI and it confirms that decreases in QRS duration occur after PPVI in PR, as reported for equivalent surgical cohorts. Further, increased homogeneity of repolarization in combination with improved conduction may decrease arrhythmic events in congenital cardiac patients with pulmonary valvular disease.

Unnatural history of the right ventricle in patients with congenitally malformed hearts

The long-term outcome of patients with congenitally malformed hearts involving abnormal right ventricular morphology and haemodynamics is variable. In most instances, the patients are at risk for right ventricular failure, in part due to morphological differences between the right and left ventricles and their response to chronic volume and pressure overload. In patients after repair of tetralogy of Fallot, and after balloon valvotomy for valvar pulmonary stenosis, pulmonary regurgitation is the most significant risk factor for right ventricular dysfunction. In patients with a dominant right ventricle after Fontan palliation, and in those with systemic right ventricles in association with surgically or congenitally corrected transposition, the right ventricle is not morphologically capable of dealing with chronic exposure to the high afterload of the systemic circulation. In patients with Ebstein's malformation of the tricuspid valve, the degree of atrialisation of the right ventricle determines how well the right ventricle will function as the pump for the pulmonary vascular bed.

Practical stepwise approach to rhythm disturbances in congenital heart diseases

Patients with congenital heart diseases (CHD) are confronted with early- and late-onset complications, such as conduction disorders, arrhythmias, myocardial dysfunction, altered coronary flow, and ischemia, throughout their lifetime despite successful hemodynamic and/or anatomical correction. Rhythm disturbance is a well-known and increasingly frequent cause of morbidity and mortality in patients with CHD. Predisposing factors to rhythm disturbances include underlying cardiac defects, hemodynamic changes as part of the natural history, surgical repair and related scarring, and residual hemodynamic abnormalities. Acquired factors such as aging, hypertension, diabetes, obesity, and others may also contribute to arrhythmogenesis in CHD. The first step in evaluating arrhythmias in CHD is to understand the complex anatomy and to find predisposing factors and hemodynamic abnormalities. A practical stepwise approach can lead to diagnosis and prompt appropriate interventions. Electrophysiological assessment and management should be done with integrated care of the underlying heart defects and hemodynamic abnormalities. Catheter ablation and arrhythmia surgery have been increasingly applied, showing increasing success rates with technological advancement despite complicated arrhythmia circuits in complex anatomy and the difficulty of access. Correction of residual hemodynamic abnormalities may be critical in the treatment of arrhythmia in patients with CHD.

Right ventricular failure secondary to chronic overload in congenital heart disease: an experimental model for therapeutic innovation

OBJECTIVE

Mortality and morbidity related to right ventricular failure remain a problem for the long-term outcome of congenital heart diseases. Therapeutic innovation requires establishing an animal model reproducing right ventricular dysfunction secondary to chronic pressure-volume overload.

METHODS

Right ventricular tract enlargement by transvalvular patch and pulmonary artery banding were created in 2-month-old piglets (n = 6) to mimic repaired tetralogy of Fallot. Age-matched piglets were used as controls (n = 5). Right ventricular function was evaluated at baseline and 3 and 4 months of follow-up by hemodynamic parameters and electrocardiography. Right ventricular tissue remodeling was characterized using cellular electrophysiologic and histologic analyses.

RESULTS

Four months after surgery, right ventricular peak pressure increased to 75% of systemic pressure and pulmonary regurgitation significantly progressed, end-systolic and end-diastolic volumes significantly increased, and efficient ejection fraction significantly decreased compared with controls. At 3 months, the slope of the end-systolic pressure-volume relationship was significantly elevated compared with baseline and controls; a significant rightward shift of the slope, returning to the baseline value, was observed at 4 months, whereas stroke work progressed at each step and was significantly higher than in controls. Four months after surgery, QRS duration was significantly prolonged as action potential duration. Significant fibrosis and myocyte hypertrophy without myolysis and inflammation were observed in the operated group at 4 months.

CONCLUSION

Various aspects of early right ventricular remodeling were analyzed in this model. This model reproduced evolving right ventricular alterations secondary to chronic volumetric and barometric overload, as observed in repaired tetralogy of Fallot with usual sequelae, and can be used for therapeutic innovation.