ECG predictors of ventricular arrhythmias and biventricular size and wall mass in tetralogy of Fallot with pulmonary regurgitation

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.

Desmosomal Junctions and Connexin-43 Remodeling in High-Pacing-Induced Heart Failure Dogs

BACKGROUND

While desmosomal junctions and gap junction remodeling are among the arrhythmogenic substrates, the fate of desmosomal and gap junctions in high-pacing-induced heart failure remains unclear. This aim of this study was to determine the fate of desmosomal junctions in high-pacing-induced heart failure.

METHODS

Dogs were randomly divided into 2 equal groups, a high-pacing-induced heart failure model group (heart failure group, n = 6) and a sham operation group (control group, n = 6). Echocardiography and cardiac electrophysiological examination were performed. Cardiac tissue was analyzed by immunofluorescence and transmission electron microscopy. The expression of desmoplakin and desmoglein-2 proteins was detected by western blot.

RESULTS

A significant decrease in ejection fraction, significant cardiac dilatation, diastolic and systolic dysfunction, and ventricular thinning occurred after 4 weeks in high-pacing-induced dog model of heart failure. Effective refractory period action potential duration at 90% repolarization was prolonged in the heart failure group. Immunofluorescence analysis and transmission electron microscopy demonstrated connexin-43 lateralization accompanies desmoglein-2 and desmoplakin remodeling in the heart failure group. Western blotting showed that the expression of desmoplakin and desmoglein-2 proteins was higher in heart failure than in normal tissue.

CONCLUSION

Desmosome (desmoglein-2 and desmoplakin) redistribution and desmosome (desmoglein-2) overexpression accompanying connexin-43 lateralization were parts of a complex remodeling in high-pacing-induced heart failure.

The Strength of hERG Inhibition by Erythromycin at Different Temperatures Might Be Due to Its Interacting Features with the Channels

Erythromycin is one of the few compounds that remarkably increase ether-a-go-go-related gene (hERG) inhibition from room temperature (RT) to physiological temperature (PT). Understanding how erythromycin inhibits the hERG could help us to decide which compounds are needed for further studies. The whole-cell patch clamp technique was used to investigate the effects of erythromycin on hERG channels at different temperatures. While erythromycin caused a concentration-dependent inhibition of cardiac hERG channels, it also shifted the steady-state activation and steady-state inactivation of the channel to the left and significantly accelerated the onset of inactivation at both temperatures, although temperature itself caused a profound change in the dynamics of hERG channels. Our data also suggest that the binding pattern to S6 of the channels changes at PT. In contrast, cisapride, a well-known hERG blocker whose inhibition is not affected by temperature, does not change its critical binding sites after the temperature is raised to PT. Our data suggest that erythromycin is unique and that the shift in hERG inhibition may not apply to other compounds.

Biventricular strain and strain rate impairment shortly after surgical repair of tetralogy of Fallot in children: A case-control study

Background

Early biventricular dysfunction in repaired tetralogy of Fallot (TOF) children may lead to poor clinical outcomes. We aimed to assess biventricular function in TOF children before and after surgery by speckle tracking echocardiography (STE) and compare them with the controls.

Methods

Twenty repaired TOF children and 20 normal children as controls were assessed by STE. Tricuspid annular plane systolic excursion (TAPSE), left ventricular ejection fraction (LVEF), biventricular strain, and strain rate were compared before and after surgery and between TOF children and controls.

Results

Postoperative LVEF (p = 0.001), strain (p = 0.001), and strain rate (p = 0.001) for left ventricle improved significantly compared to preoperative phase. However, postoperative left ventricular strain (p = 0.05) and strain rate (p = 0.01) in TOF children were significantly impaired compared to controls. Postoperative LVEF was correlated inversely with postoperative strain rate (r = −0.40, p = 0.04). Postoperative TAPSE (p = 0.001), strain (p = 0.001), and strain rate (p = 0.001) for right ventricle significantly worsened when compared with the preoperative phase. Moreover, postoperative TAPSE (p = 0.001), strain (p = 0.001), and strain rate (p = 0.01) were significantly impaired compared to controls. Postoperative right ventricular strain rate was correlated significantly with the weight of children (r = 0.48, p = 0.02), and postoperative left ventricular strain showed significant correlations with aortic clamp time (r = 0.44, p = 0.04) and with ICU stay (r = −0.46, p = 0.04).

Conclusion

Despite normal LVEF, TOF children exhibit impaired left ventricular strain and strain rate after surgery. TAPSE, strain, and strain rate for the right ventricle worsen after surgical repair. STE‐driven strain can be used to detect early ventricular dysfunction and the associated prognostic implications.

Correlation Between Fragmented QRS and Ventricular Function from Cardiac Magnetic Resonance in Patients with Repaired Tetralogy of Fallot

Fragmented QRS is an abnormal sign in an ECG resulting from ventricular dyssynchrony. The presence of fragmented QRS (fQRS) is related to mortality in patients with repaired tetralogy of Fallot (rTOF). This study aimed to analyze the correlations between fQRS and ventricular function parameters from cardiac magnetic resonance (CMR) images. A total of 54 patients with rTOF or repaired DORV, TOF type who had been investigated by CMR at Songklanagarind Hospital from January 2012 to August 2019 were retrospectively reviewed. Most of the patients (47 patients, 87%) were diagnosed with TOF and most of these (57.4%) were treated with a transannular patch (TAP) on the right ventricular outflow tract (RVOT). Forty-four patients (81%) had fQRS. The median time interval between EKG and CMR was 4.2 months (IQR 1.1, 6.9). Patients with fQRS had significantly higher RVEDVi (145.6 [IQR 121.1, 173.1) vs. 115.9 [IQR 96.2, 146.9] mL/m², p = 0.037), higher RVESVi (82.5 [IQR 62.9, 100.8] vs. 58.6 [IQR 46, 77.2] mL/m², p = 0.032) and higher RVEDV/LVEDV ratio [1.6 (IQR 1.4, 1.9) vs. 1.4 (IQR 1.3, 1.5), p = 0.026]. The extent of fQRS was significantly associated with an increase in RVEDVi (r = 0.39, p = 0.004) and RVESVi (r = 0.45, p < 0.001) but a decrease in RVEF (r =  - 0.37, p = 0.006). Fragmented QRS had higher sensitivity and lower specificity than prolonged QRS duration (≥ 160 ms) to predict all of the parameters indicating pulmonary valve replacement (PVR). Patients with rTOF who had fQRS were significantly associated with RV dilatation. The extent of fQRS had only low to moderate correlation with right ventricular parameters (RVEDVi, RVESVi and RVEF). Fragmented QRS could be used for early detection of RV dilatation and the need for PVR in patients with rTOF.

Detection of persistent systolic and diastolic abnormalities in asymptomatic pediatric repaired tetralogy of Fallot patients with preserved ejection fraction: a CMR feature tracking study

OBJECTIVES

A fast cardiovascular magnetic resonance (CMR) feature tracking was applied to assess ventricular systolic and diastolic function. This study sought to detect right ventricular (RV) systolic and diastolic abnormalities in asymptomatic pediatric repaired tetralogy of Fallot (rTOF) patients with preserved RV ejection fraction (EF).

METHODS

One hundred asymptomatic pediatric rTOF patients with preserved RVEF ≥ 45% and 52 control subjects underwent cine CMR examinations. Tricuspid annular plane systolic excursion (TAPSE); peak tricuspid annular systolic (S_m), early diastolic (E_m), and late diastolic (A_m) velocities; and biventricular global radial (GRS), circumferential (GCS), and longitudinal strains (GLS) were analyzed using CMR feature tracking.

RESULTS

TAPSE, S_m, E_m, A_m, and RV GLS were significantly lower in rTOF patients compared with controls (all p < 0.01). The lower limits (mean-2·standard deviations) of TAPSE, S_m, E_m, and A_m among controls were 10.9 mm, 6.3 cm/s, 8.9 cm/s, and 2.4 cm/s, respectively, and 78%, 75%, 75%, and 19% of rTOF patients had corresponding measurements below these thresholds. Among rTOF patients, RV GLS was significantly lower in females than in males (p < 0.05).

CONCLUSIONS

Despite preserved RVEF, there was a high prevalence of RV systolic and diastolic dysfunction among pediatric rTOF patients, which was detected using fast CMR feature tracking.

KEY POINTS

• There was high prevalence of systolic and diastolic dysfunction in asymptomatic pediatric repaired tetralogy of Fallot (rTOF) patients despite preserved right ventricular (RV) ejection fraction (EF). • Significant correlations were observed between right ventricular (RV) measurements (strains, tricuspid annular plane systolic excursion (TAPSE), peak tricuspid annular early diastolic velocity (E_m), peak tricuspid annular late diastolic velocity (A_m)), and left ventricular (LV) strain measurements, which indicates ventricular-ventricular interactions at systolic and diastolic function level. • Right ventricular (RV) global longitudinal strain (GLS) was lower in female repaired tetralogy of Fallot (rTOF) patients than in males, suggesting females with rTOF may be at a higher risk of developing RV systolic dysfunction than males.

Severe pulmonary regurgitation in adolescents with tetralogy of Fallot leads to increased longitudinal strain

Objectives

Postoperative patients with tetralogy of Fallot (TOF) are often compromised by chronic pulmonary regurgitation and chronic right ventricular volume load. We sought to determine whether pulmonary regurgitation (PR) would affect right and left ventricle (RV and LV) strain.

Materials and methods

This cross-sectional analysis included 40 patients who had TOF with surgical repair, with an average follow-up period of 11.8 ± 3.0 years. Altogether, 44 healthy volunteers with similar age and gender distribution were recruited. A cardiovascular magnetic resonance imaging study with feature tracking analysis was performed on all patients and controls.

Results

RV peak longitudinal strain was increased in TOF patients with PR > 30 ml/m² when compared to those with PR < 30 ml/m² (− 22.5% ± 2.7% vs − 19.7% ± 3.5%, p = 0.018) and controls (p = 0.007). PR volume correlated with peak RV longitudinal strain (R = − 0.37, p = 0.030) and peak RV longitudinal strain rate (systolic: R = 0.37, p = 0.03; diastolic: R = 0.39, p = 0.021). The peak RV circumferential strain, from base to apex, increased more than in healthy controls (apex-base difference 7.6% ± 4.2% vs 3.3% ± 2.4%, p < 0.0001).

Conclusions

Pediatric patients with TOF and a severe pulmonary regurgitation show an enhanced longitudinal strain when compared to patients with milder regurgitation or to control subjects. In addition, mean RV circumferential strain of the patients is significantly enhanced compared to healthy individuals.

Additional mechanism for left ventricular dysfunction: chronic pulmonary regurgitation decreases left ventricular preload in patients with tetralogy of Fallot

BACKGROUND

Right ventricular dysfunction in patients with tetralogy of Fallot and significant pulmonary regurgitation may lead to systolic dysfunction of the left ventricle due to altered ventricular interaction. We were interested in determining whether chronic pulmonary regurgitation affects the preload of the left ventricle. In addition, we wanted to study whether severe chronic pulmonary regurgitation would alter the preload of the left ventricle when compared with patients having preserved pulmonary valve annulus.

METHODS

The study group comprised 38 patients with tetralogy of Fallot who underwent surgical repair between 1990 and 2003. Transannular patching was required in 21 patients to reconstruct the right ventricular outflow tract. Altogether, 48 age- and gender-matched healthy volunteers were recruited. Cardiac MRI was performed on all study patients to assess the atrial and ventricular volumes and function.

RESULTS

Severe pulmonary regurgitation (>30 ml/m2) was present in 13 patients, of whom 11 had a transannular patch, but only two had a preserved pulmonary valve annulus. The ventricular preload volumes from both atria were significantly reduced in patients with severe pulmonary regurgitation, and left ventricular stroke volumes (44.1±4.7 versus 58.9±10.7 ml/m2; p<0.0001) were smaller compared with that in patients with pulmonary regurgitation <30 ml/m2 or in controls.

CONCLUSIONS

In patients with tetralogy of Fallot, severe pulmonary regurgitation has a significant effect on volume flow through the left atrium. Reduction in left ventricular preload volume may be an additional factor contributing to left ventricular dysfunction.

miR-19b Regulates Ventricular Action Potential Duration in Zebrafish

Sudden cardiac death due to ventricular arrhythmias often caused by action potential duration (APD) prolongation is a common mode of death in heart failure (HF). microRNAs, noncoding RNAs that fine tune gene expression, are frequently dysregulated during HF, suggesting a potential involvement in the electrical remodeling process accompanying HF progression. Here, we identified miR-19b as an important regulator of heart function. Zebrafish lacking miR-19b developed severe bradycardia and reduced cardiac contractility. miR-19b deficient fish displayed increased sensitivity to AV-block, a characteristic feature of long QT syndrome in zebrafish. Patch clamp experiments from whole hearts showed that miR-19b deficient zebrafish exhibit significantly prolonged ventricular APD caused by impaired repolarization. We found that miR-19b directly and indirectly regulates the expression of crucial modulatory subunits of cardiac ion channels, and thereby modulates AP duration and shape. Interestingly, miR-19b knockdown mediated APD prolongation can rescue a genetically induced short QT phenotype. Thus, miR-19b might represent a crucial modifier of the cardiac electrical activity, and our work establishes miR-19b as a potential candidate for human long QT syndrome.

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.

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.

QRS Duration Changes in Patients with Single Ventricle Physiology: Birth to 10 Years

BACKGROUND

QRS prolongation may be a predictor of mortality in certain forms of congenital heart disease. Minimal data exist describing changes in QRS duration in patients with single ventricles (SVs). The goal was to describe changes in QRS duration in patients with SV and to determine if differences existed between single right ventricle (sRV) versus single left ventricle (sLV) patients.

METHODS

Chart review was performed on patients with SV physiology. Patients were divided into sRV and sLV groups. QRS durations were measured monthly for the first 6 months, at 1 year, and then yearly until 10 years. t-tests were used for analysis.

RESULTS

One hundred sixty patients were evaluated (95 sRV, 65 sLV). The greatest change in QRS duration for the entire cohort occurred in the first 6 months of life versus 6 months to 10 years of age (1.81 ms/month vs 0.20 ms/month). sRV QRS durations were significantly longer than sLV QRS durations at 1 year (78.9 ± 12.6 ms vs 73.2 ± 11.9 ms), 2 year (81.7 ± 14.7 ms vs 73.4 ± 12.5 ms), 4 year (84.2 ± 12.1 ms vs 77.9 ± 16.4 ms), 6 year (90.8 ± 12.7 ms vs 83.4 ± 13.4 ms), 7 year (90.8 ± 16.5 ms vs 81.2 ± 16.6 ms), and 8 year (96.7 ± 13.6 ms vs 84.8 ± 13.9 ms) time points.

CONCLUSION

The greatest change in QRS duration in SV patients occurred in the first 6 months of life when these patients' ventricles were volume loaded. Differences in QRS duration between sRV and sLV patients occurred early in life. Further studies are needed to determine if minimizing volume load early in life decreases the rate of change in QRS duration.

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.

Management of arrhythmias in patients with a tetralogy of Fallot

Although arrhythmias are commonly found in patients with all different types of congenital heart disease, perhaps no patient is at higher risk of late development of arrhythmias that may result in sudden death than in the patient following tetralogy of Fallot repair. Despite major improvement in the surgical repair of this disease, a significant percentage of these patients continue to remain at risk for the late development of arrhythmias, and a small percentage will develop life-threatening arrhythmias and sudden death. Which patients remain at highest risk is still not clearly delineated. Diligent arrhythmia surveillance and aggressive treatment strategies are necessary to minimise this risk. This article highlights important strategies to manage arrhythmia development and prevention in this patient population.

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.

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.

QRS duration changes in patients with hypoplastic left heart syndrome undergoing hybrid palliation: prehybrid to post-Fontan

BACKGROUND

QRS prolongation has been shown to be a predictor of mortality in patients with certain forms of congenital heart disease. QRS changes have not been well described in patients with single ventricle physiology, particularly in those undergoing the hybrid procedure.

OBJECTIVE

To describe QRS changes in a cohort of patients with hypoplastic left heart syndrome (HLHS) who underwent hybrid palliation and to evaluate if QRS duration is associated with mortality.

METHODS

Chart review of 54 patients with HLHS who underwent hybrid procedure between 2002 and 2009 was performed. Patients awaiting surgical palliation were excluded. Patients who survived Fontan completion (HLHS-S, n = 30) were compared to non-survivor (HLHS-NS, n = 24). Electrocardiograms were reviewed for maximal QRS duration (ms) at three pre- and postsurgical stages: (1) hybrid procedure, (2) comprehensive stage 2 procedure, and (3) Fontan procedure.

RESULTS

In HLHS-S, there was a significant increase in QRS from birth to Fontan completion (15.6 ± 9.3 ms). QRS duration increased 8.5 ± 8.9 ms between posthybrid to precomprehensive stage 2, and 5.4 ± 9.7 ms between postcomprehensive stage 2 to Fontan. Following Fontan procedure, mean QRS decreased 4.3 ± 8.5 ms. There was no significant mean difference in QRS change between HLHS-S and HLHS-NS following hybrid procedure. Pre- and posthybrid and pre- and postcomprehensive stage 2 QRS durations were not different between HLHS-S and HLHS-NS who underwent a comprehensive stage 2 procedure. There was a significant difference in QRS difference following comprehensive stage 2 in HLHS-S (0.9 ± 7.1 ms) compared to HLHS-NS (-7.1 ± 10.0 ms).

CONCLUSIONS

QRS duration significantly increased from hybrid to Fontan completion in HLHS-S. There was a significant decrease in QRS duration in patients who died following comprehensive stage 2 procedure. Larger studies are needed to assess the significance of these QRS changes.

Systemic right ventricular longitudinal strain is reduced in adults with transposition of the great arteries, relates to subpulmonary ventricular function, and predicts adverse clinical outcome

BACKGROUND

Transposition of the great arteries (TGA) after atrial switch operation and congenitally corrected TGA (ccTGA) are commonly associated with impaired systemic right ventricular (RV) function and impaired prognosis. We aimed to investigate the value of indices of myocardial deformation on speckle-tracking echocardiography for quantifying ventricular function and their potential role in assessing ventricular-ventricular interaction and outcome in patients with a systemic RV.

METHODS AND RESULTS

A total of 129 patients (87 with TGA and atrial switch and 42 with ccTGA, 71 men, age 35 ± 12 years) were investigated, and biventricular myocardial deformation was compared with findings in healthy subjects (n = 38, age 36 ± 10 years). Systemic ventricular longitudinal 2-dimensional (2D) peak systolic strain (RV 2D-LS) was significantly reduced compared with controls (-12.9 ± 3.6 and -15.4 ± 5.1 vs -21.0 ± 5.5 in TGAs, ccTGAs, and controls, P < .0001). Systemic and pulmonary 2D-LS were correlated in patients with TGA (r = 0.46, P < .0001) and ccTGA (r = 0.64, P < .0001), suggesting interventricular interaction, and this was confirmed when ejection fraction on magnetic resonance imaging was assessed (r = 0.53, P < .0001). More importantly, systemic 2D-LS (hazard ratio 1.31, P = .01) was related to adverse clinical outcome (symptomatic progression to New York Heart Association class ≥3, clinically relevant cardiac arrhythmia, or death) in patients with TGA and atrial switch independently of ejection fraction on cardiac magnetic resonance imaging, history of clinically relevant arrhythmia, or functional class.

CONCLUSIONS

Global longitudinal systolic strain is significantly reduced in patients with a systemic RV, is related to subpulmonary ventricular function, and predicts adverse clinical outcome in adults with atrial switch TGA.

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.

Pulmonary valve replacement in chronic pulmonary regurgitation in adults with congenital heart disease: impact of preoperative QRS-duration and NT-proBNP levels on postoperative right ventricular function

BACKGROUND

Chronic severe pulmonary regurgitation (PR) causes progressive right ventricular (RV) dysfunction and heart failure. Parameters defining the optimal time point for surgery of chronic PR are lacking. The present study prospectively evaluated the impact of preoperative clinical parameters, cardiorespiratory function, QRS duration and NT-proBNP levels on post operative RV function and volumes assessed by cardiac magnetic resonance imaging (CMR) in patients with chronic severe PR undergoing pulmonary valve replacement.

METHODS AND RESULTS

CMR was performed pre- and 6 months postoperatively in 27 patients (23.6 ± 2.9 years, 15 women) with severe PR. Postoperatively, RV endsystolic (RVESVI) and enddiastolic volume indices (RVEDVI) decreased significantly (RVESVI pre 78.2 ± 20.4 ml/m² BSA vs. RVESVI post 52.2 ± 16.8 ml/m²BSA, p<0.001; RVEDVI pre 150.7 ± 27.7 ml/m²BSA vs. RVEDVI post 105.7 ± 26.7 ml/m²BSA; p<0,001). With increasing preoperative QRS-duration, postoperative RVEF decreased significantly (r=-0.57; p<0.005). Preoperative QRS-duration smaller than the median (156 ms) predicted an improved RVEF compared to QRS-duration≥ 156 ms (54.9% vs 46.8%, p<0.05). Multivariate analysis identified preoperative QRS duration as an independent predictor of postoperative RVEF (p<0.005). NT-proBNP levels correlated with changes in RVEDI (r=0.58 p<0,005) and RVESVI (r=0.63; p<0,0001). Multivariate analysis identified NT-proBNP levels prior to PVR as an independent predictor of volume changes (p<0.05).

CONCLUSION

Valve replacement in severe pulmonary regurgitation causes significant reduction of RV volumes. Both, preoperative NT-proBNP level elevation and QRS prolongation indicate patients with poorer outcome regarding RV function and volumes.

Tetralogy of Fallot

Tetralogy of Fallot is a congenital cardiac malformation that consists of an interventricular communication, also known as a ventricular septal defect, obstruction of the right ventricular outflow tract, override of the ventricular septum by the aortic root, and right ventricular hypertrophy. This combination of lesions occurs in 3 of every 10,000 live births, and accounts for 7-10% of all congenital cardiac malformations. Patients nowadays usually present as neonates, with cyanosis of varying intensity based on the degree of obstruction to flow of blood to the lungs. The aetiology is multifactorial, but reported associations include untreated maternal diabetes, phenylketonuria, and intake of retinoic acid. Associated chromosomal anomalies can include trisomies 21, 18, and 13, but recent experience points to the much more frequent association of microdeletions of chromosome 22. The risk of recurrence in families is 3%. Useful diagnostic tests are the chest radiograph, electrocardiogram, and echocardiogram. The echocardiogram establishes the definitive diagnosis, and usually provides sufficient information for planning of treatment, which is surgical. Approximately half of patients are now diagnosed antenatally. Differential diagnosis includes primary pulmonary causes of cyanosis, along with other cyanotic heart lesions, such as critical pulmonary stenosis and transposed arterial trunks. Neonates who present with ductal-dependent flow to the lungs will receive prostaglandins to maintain ductal patency until surgical intervention is performed. Initial intervention may be palliative, such as surgical creation of a systemic-to-pulmonary arterial shunt, but the trend in centres of excellence is increasingly towards neonatal complete repair. Centres that undertake neonatal palliation will perform the complete repair at the age of 4 to 6 months. Follow-up in patients born 30 years ago shows a rate of survival greater than 85%. Chronic issues that now face such adults include pulmonary regurgitation, recurrence of pulmonary stenosis, and ventricular arrhythmias. As the strategies for surgical and medical management have progressed, the morbidity and mortality of those born with tetralogy of Fallot in the current era is expected to be significantly improved.

Tetralogy of Fallot

Tetralogy of Fallot is a congenital cardiac malformation that consists of an interventricular communication, also known as a ventricular septal defect, obstruction of the right ventricular outflow tract, override of the ventricular septum by the aortic root, and right ventricular hypertrophy. This combination of lesions occurs in 3 of every 10,000 live births, and accounts for 7-10% of all congenital cardiac malformations. Patients nowadays usually present as neonates, with cyanosis of varying intensity based on the degree of obstruction to flow of blood to the lungs. The aetiology is multifactorial, but reported associations include untreated maternal diabetes, phenylketonuria, and intake of retinoic acid. Associated chromosomal anomalies can include trisomies 21, 18, and 13, but recent experience points to the much more frequent association of microdeletions of chromosome 22. The risk of recurrence in families is 3%. Useful diagnostic tests are the chest radiograph, electrocardiogram, and echocardiogram. The echocardiogram establishes the definitive diagnosis, and usually provides sufficient information for planning of treatment, which is surgical. Approximately half of patients are now diagnosed antenatally. Differential diagnosis includes primary pulmonary causes of cyanosis, along with other cyanotic heart lesions, such as critical pulmonary stenosis and transposed arterial trunks. Neonates who present with ductal-dependent flow to the lungs will receive prostaglandins to maintain ductal patency until surgical intervention is performed. Initial intervention may be palliative, such as surgical creation of a systemic-to-pulmonary arterial shunt, but the trend in centres of excellence is increasingly towards neonatal complete repair. Centres that undertake neonatal palliation will perform the complete repair at the age of 4 to 6 months. Follow-up in patients born 30 years ago shows a rate of survival greater than 85%. Chronic issues that now face such adults include pulmonary regurgitation, recurrence of pulmonary stenosis, and ventricular arrhythmias. As the strategies for surgical and medical management have progressed, the morbidity and mortality of those born with tetralogy of Fallot in the current era is expected to be significantly improved.

Changes during exercise of ECG intervals related to increased risk for ventricular arrhythmia in repaired tetralogy of Fallot and their relationship to right ventricular size and function

PURPOSE

Our study aimed to assess pro-arrhythmogenic electrocardiographic changes during maximal physical exercise in patients operated for Tetralogy of Fallot (TOF).

METHODS

TOF patients prospectively underwent: 1) bicycle ergometry, 2) cardiac MRI, and 3) 24-hour Holter. ECG data was analyzed at rest, at 60% of peak exercise and at peak exercise. R-R duration, QRS-, QT- and JT-duration and dispersions were assessed. Changes of ECG parameters during exercise were calculated and correlated to RV volume, RVEF, RV wall-mass, PR-percentage and VO(2max). Exercise ECG data from healthy controls were used as reference.

RESULTS

Thirty-one patients (mean age at repair (SD) 0.8 (0.5) years, age at study 16 (5) years) and 25 controls (age 12 (2) years) were included. With exercise mean QTc and JTc dispersions increased in patients (p<0.001), but not in controls. At peak exercise JTc dispersion was larger in patients (p<0.01). QTc did not change with exercise in patients (p=0.14) and decreased in controls (p<0.05). At all levels of exercise mean QTc, QRS and QRS dispersion were larger in patients (all p<0.001). Significant associations were found for; 1) a larger increase of JTc dispersion with a higher PR-percentage, a larger RV volume, a larger RV wall-mass, 2) a larger QTc increase with a larger RV volume and worse RVEF.

CONCLUSION

During physical exercise inhomogeneity of repolarisation, known to predispose for re-entry ventricular arrhythmia, increases in repaired TOF. Larger inhomogeneity is found with more severe PR.

Pulmonary valve replacement in tetralogy of Fallot improves the repolarization

OBJECTIVE

To assess the effect of pulmonary valve replacement (PVR) on the repolarization of patients with tetralogy of Fallot.

BACKGROUND

Pulmonary valve regurgitation may cause right ventricular failure in adult patients with Fallot's tetralogy. In these patients, prolonged depolarization and disturbed repolarization are associated with ventricular arrhythmias and sudden cardiac death.

METHODS

Thirty Fallot patients (age 32+/-9 years, 19 male) eligible for PVR were studied with cardiac magnetic resonance imaging (CMR) before and 6 months after PVR. Electrocardiograms obtained during initial and follow-up CMR were analyzed and occurrence of ventricular arrhythmias was studied.

RESULTS

Right ventricular end-diastolic volume (RV EDV) decreased from 322+/-87 to 215+/-57 ml after PVR (P<0.0001). The spatial QRS-T angle normalized from 117+/-34 to 100+/-35 degrees , P=0.0004 (normal angle <105 degrees). QT dispersion and T-wave complexity did not change significantly. T-wave amplitude decreased from 376+/-121 to 329+/-100 microV (P=0.01). T-wave area decreased from 43+/-15 to 38+/-13 microV s (P=0.02). Decreases in T-wave amplitude and area were most prominent in the right precordial leads overlying the RV. Three patients had sustained ventricular arrhythmias and one patient died suddenly. These patients had a QRS duration >160 ms. No severe ventricular arrhythmias were found in patients with a RV EDV <220 ml, QRS-T angle <100 degrees , QT dispersion <60 ms or T-wave complexity <0.30.

CONCLUSION

Normal repolarization indices may be associated with the absence of severe ventricular arrhythmias. PVR in Fallot patients with dilated right ventricles has a beneficial effect on electrocardiographic indices of repolarization heterogeneity.

Clinical condition at mid-to-late follow-up after transatrial-transpulmonary repair of tetralogy of Fallot

OBJECTIVES

To assess the clinical condition at mid-to-late follow-up in tetralogy of Fallot corrected by a transatrial-transpulmonary approach at a young age and to identify risk factors associated with right ventricular dilation/dysfunction and with decreased exercise tolerance.

METHODS

Patients with tetralogy of Fallot underwent cardiac magnetic resonance imaging, maximal bicycle ergometry, electrocardiography, Holter monitoring, and spirometry. Multivariate linear regression analyses were used to determine independent predictors for selected clinical parameters.

RESULTS

Fifty-nine patients (mean +/- SD), age at repair 0.9 +/- 0.5 years, interval since repair 14 +/- 5 years, were included. The median pulmonary regurgitant fraction was 32% (0%-57%). Compared with published data on healthy controls, Fallot patients had significantly larger right ventricular end-diastolic and end-systolic volumes and smaller right ventricular and left ventricular ejection fractions. Maximum oxygen consumption was 97% +/- 17% and maximum workload 89% +/- 13% of predicted. Median QRS duration was 110 ms (82-161 ms). No important ventricular arrhythmias were found. Compared with patients without a transannular patch, patients with a patch had more pulmonary regurgitation, a larger right ventricle, worse right ventricular and left ventricular ejection fractions, but comparable exercise capacity. Multivariate regression analysis identified the following independent determinants for larger right ventricular volumes: longer interval since repair, longer QRS duration, and higher pulmonary regurgitation percentage. The following were independent determinants for smaller right ventricular ejection fraction: abnormal right ventricular outflow tract wall motion, longer interval since repair, and longer QRS duration. For smaller maximum oxygen consumption, the independent determinants were smaller right ventricular ejection fraction and longer QRS duration.

CONCLUSIONS

At mid-to-late follow-up, clinical condition in tetralogy of Fallot corrected according to contemporary surgical approaches appears well preserved. However, even these patients show right ventricular dilation and dysfunction associated with impaired functional capacity. Abnormalities relate to right ventricular outflow tract motion abnormalities, longer interval since repair, longer QRS duration, and more severe pulmonary regurgitation.

Pulmonary regurgitation is a powerful factor influencing QRS duration in patients after surgical repair of tetralogy of Fallot

AIMS

QRS prolongation is a negative prognostic factor for the development of ventricular arrhythmia after repair of tetralogy of Fallot (TOF). In this MRI study, we performed a multivariate analysis to determine the influence of volumetric and functional parameters as well as time factors on QRS duration.

METHODS AND RESULTS

Sixty-seven patients after surgical repair of TOF were studied using a 1.5T MRI. Measurement of the ventricles was performed with a multislice-multiphase sequence. Left and right ventricular volumes, ejection fractions (EF) and myocardial masses were determined. Pulmonary regurgitant fraction (PRF) was quantified by velocity encoded flow measurement in the main pulmonary artery. Maximum QRS duration was taken from a 12-channel ECG. Mean maximum QRS duration was 132 ms (+/- 29 ms). Mean PRF was 29.2% (+/- 13.4%). QRS duration correlated significantly with PRF (r = 0.49; p < 0.01; n = 54) and with right ventricular enddiastolic volume index (RVEDVI) (r = 0.29; p < 0.05; n = 67). Multivariate analysis revealed that the combination of PRF, postoperative period, age at surgical repair, and left ventricular (LV) enddiastolic volume are correlated with QRS prolongation.

CONCLUSION

In patients after repair of TOF, pulmonary regurgitation is related to QRS prolongation. Furthermore, even LV size plays a role in the enlargement of the QRS complex.

Indications and timing of pulmonary valve replacement after tetralogy of Fallot repair

Surgical management of tetralogy of Fallot results in anatomic and functional abnormalities in the majority of patients. Although right ventricular volume load due to severe pulmonary regurgitation can be tolerated for years, there is now evidence that the compensatory mechanisms of the right ventricular myocardium ultimately fail and that if the volume load is not eliminated or reduced the dysfunction might be irreversible. In light of that data and with better understanding of risk factors for adverse outcomes late after tetralogy of Fallot repair, many centers are now recommending early pulmonary valve replacement before symptoms of heart failure develop. This article reviews the pathophysiology of chronic right ventricular volume load after tetralogy of Fallot repair and the risks and benefits of pulmonary valve replacement. Finally, recommendations for timing and indications for pulmonary valve replacement are given.

Hemodynamic and electrocardiographic effects of early pulmonary valve replacement in pediatric patients after transannular complete repair of tetralogy of Fallot

In adults, pulmonary value replacement (PVR) shows improvement in right ventricular (RV) volume and function and reduces QRS duration. In addition, RV volume correlates with QRS duration and QRS change. This has not been shown in pediatric patients. The purpose of this study was to evaluate serial magnetic resonance imaging (MRI) and electrocardiogram measurements before and after early PVR in a pediatric population with repaired Tetralogy of Fallot and whether QRS duration and QRS change correlated with RV volume. A retrospective review of MRIs and electrocardiograms was conducted on 10 patients. Median age at repair was 2.1 +/- 0.7 years, and median age at PVR was 11.5 +/- 2.0 years. There were significant decreases in RV end diastolic volume (EDV)/body surface area (BSA) (p < 0.0004), end systolic volume (ESV)/BSA (p = 0.02), RVEDV/left ventricular (LV) EDV (p < 0.001), RV ejection fraction (p < 0.04), RV stroke volume (SV)/BSA (p < 0.0002), and (RVSV - LVSV)/BSA (p = 0.0007). No significant change in QRS duration occurred (p = 0.08). QRS duration (pre-r = 0.44, p = 0.20; post-r = 0.34, p = 0.33) and QRS change (r = -0.08, p = 0.83) did not correlate with RVEDV. We propose early consideration of PVR in pediatric patients. PVR improves RV volumes and function and may provide beneficial electromechanical effects by slowing the progression of QRS duration.

Cardiovascular magnetic resonance in the follow-up of patients with corrected tetralogy of Fallot: a review

Cardiovascular magnetic resonance (CMR) is becoming an important tool in the clinical management of patients with congenital heart disease. Because of the diverse problems patients may face after initial correction for tetralogy of Fallot and the large amount of CMR techniques that can be applied, creating a patient-orientated imaging protocol is a difficult issue. Although it is still not certain what the impact of some parameters, provided by CMR, should be on clinical decision making, new techniques are being developed and applied. In this report, we review the current clinical issues in patients with tetralogy of Fallot and review the current implication and limitations of CMR in this patient category.

Comparison of real-time three-dimensional echocardiography to magnetic resonance imaging for assessment of left ventricular mass

This is the first study to assess the feasibility and accuracy of real-time 3-dimensional echocardiography (RT-3DE) for the measurements of left ventricular (LV) mass in patients with congenital heart disease (CHD) compared with magnetic resonance imaging (MRI). Twenty patients (60% men) with CHD were evaluated by MRI and RT-3DE on the same day. Their mean age was 29 +/- 8 years (range 19 to 49). RT-3DE was performed with a Philips Sonos 7500 echocardiographic system and LV mass analyses with the assistance of TomTec software. The results for LV mass obtained by manual tracing were compared with Signa 1.5-T MRI data. The acquisition of RT-3DE data sets was feasible in all 20 patients. Nine patients (45%) had good, 5 patients (25%) moderate, and 6 patients (30%) poor image quality of the 3-dimensional data set. The time of 3-dimensional data acquisition was 4 +/- 2 minutes. Off-line image processing and tracing required approximately 11 +/- 3 minutes. A very good correlation was observed between RT-3DE data with sufficient image quality and MRI (r = 0.98, y = 0.96x + 4.1, SEE 9.8 g), with a mean difference of 2.0 +/- 20 g. Interobserver agreement was excellent (r = 0.99, y = 0.97x + 3.81), with a mean difference of -1 +/- 11 g. In conclusion, the assessment of LV mass from RT-3DE data is feasible in patients with CHD. The mass of an abnormally shaped left ventricle can be determined with high accuracy and low interobserver variability in patients with good or moderate echocardiographic image quality.

Changes in QRS duration are associated with maximal exercise capacity in adult patients with repaired tetralogy of Fallot

OBJECTIVE

In adult patients with repaired tetralogy of Fallot (TF) QRS duration at rest seems to be a predictor of maximal exercise. We examined the relationship between QRS duration during exercise and exercise performance.

DESIGN

In 57 consecutive TF patients QRS duration in V1 (ms) was measured at rest, at maximal exercise (Wmax, W), and at peak oxygen consumption (peak VO2, ml/min). Stroke volume (SV) was calculated from cardiac output, obtained by CO2 rebreathing. Spearman rank correlation was used to describe the relationship between QRS duration and exercise performance. Statistical significance was defined as P<0.05.

RESULTS

Seven patients, who didn't pass the anaerobic threshold, and one outlier (Wmax=340 W) were excluded, resulting in a sample of 49 patients (75.5% male; median age=24 years, range 16-43 years). QRS duration at rest (median=160 ms, range 78-194 ms) and at maximal exercise (median=153 ms, range 80-193 ms) did not differ significantly. The median change of QRS duration during exercise was -5 ms (range -31 to +83 ms). This was negatively correlated with Peak VO2 (2081+/-577 ml/min; rho=-0.33, P=0.02) and Wmax (182+/-53 Watt; rho=-0.33, P=0.02). In patients with QRS shortening peak VO2 and the exercise induced increase in SV were significantly higher than in patients with QRS shortening.

CONCLUSIONS

This study indicates that QRS shortening during exercise in TF patients is related with a better exercise performance. Lower increase in stroke volumes may be responsible for this difference. Further research is needed to elaborate these findings.

Effects of pulmonary valve replacement on QRS duration and right ventricular cavity size late after repair of right ventricular outflow tract obstruction

This study evaluated the effects of pulmonary valve replacement (PVR) on QRS duration and right ventricular (RV) cavity size in patients who had severe pulmonary regurgitation late after previous repair of RV outflow tract obstruction. A significant decrease in maximal QRS duration and RV end-diastolic volume was found after PVR. The change in QRS duration was most significant in patients with a baseline QRS > or =155 ms (176 +/- 15 to 160 +/- 18 ms, p <0.001). RV end-diastolic volume was significantly correlated with maximal QRS duration before (r = 0.93, p <0.0001) as well as after (r = 0.82, p <0.001) PVR. In patients with pulmonary regurgitation late after repair of RV outflow tract obstruction, PVR reduces maximal QRS duration with a concomitant decrease in RV volumes.

Implantable defibrillators: from the adult cardiac to the grown up congenital heart disease patient

The automatic implantable defibrillators (AID) are increasingly used for both secondary and primary prevention of sudden cardiac death (SCD) in high risk adult cardiac patients with sustained ventricular arrhythmias (SVA) and/or significant ventricular dysfunction. The corresponding experience with AIDs in pediatric and young adult population is limited suggesting at least the same benefit as in the adult population. With the growing number of adults with previous corrective surgery of complex congenital heart disease (CHD), a need to address the risk stratification process for SCD among these patients is becoming increasingly important. For the present time, the AIDs have been mostly utilized for the secondary prevention of SCD in those postoperative CHD adult patients with a history of SVA. Currently available data on how to assess the risk for SCD among such patients as well as implications about the potential to prevent SCD with an earlier use of AID in this growing population are presented and discussed.

Timing and type of surgery for severe pulmonary regurgitation after repair of tetralogy of Fallot

Repaired tetralogy of Fallot (rTOF) has an excellent long-term prognosis; however, survival is somewhat less than normal. Of all the residual lesions and sequellae after rTOF, pulmonary regurgitation (PR) is the most important, correlating with right ventricular (RV) size, exercise intolerance and serious ventricular arrhythmias. Pulmonary valve replacement (PVR) has beneficial effects on RV size and function, provided it is performed early, before irreversible RV dysfunction ensues. Moreover, PVR is associated with an improvement in patients' symptoms and exercise tolerance and combined with arrhythmia surgery (cryoablation) it leads to a dramatic decrease in the incidence of fatal ventricular arrhythmias. Associated lesions, especially branch pulmonary artery stenosis, which aggravates PR, and tricuspid regurgitation, which further impacts on RV size and function, need addressing. Large right ventricular outflow (RVOT) akinetic and aneurysmal regions are frequent and further compromise RV function; therefore, resection during PVR should be attempted. Despite excellent mid-term results, homografts and xenografts, usually used for RVOT reconstruction, suffer late dysfunction and failure, committing patients and surgeons to further operations. Therefore, the decision to operate should be based on the balance between progressive RV dilatation, exercise intolerance, symptoms, arrhythmias and the fact that further reoperations will be needed. Research on the ideal valve for RVOT reconstruction is ongoing. Prospective follow-up of patients with rTOF with exercise testing and assessment of RV size and function, preferably with magnetic resonance, will define better the natural history of the disease and will probably provide firm guidelines for PVR timing especially in asymptomatic patients.

Predicting late sudden death from ventricular arrhythmia in adults following surgical repair of tetralogy of Fallot

Tetralogy of Fallot was the first complex congenital cardiac defect to undergo open repair. The life expectancy and quality of life of those surviving surgery is now good, although late survival is compromised by the occurrence of sudden death. The emergence of successful methods for both the prevention of arrhythmias (including valve replacements and electrophysiological ablation) and the treatment of arrhythmias when they occur (including implantable defibrillators), has meant the identification of those at risk is of even greater importance. This paper reviews the predictive methods currently available to the practising physician caring for these increasingly common patients.

Expanding the indications for pulmonary valve replacement after repair of tetralogy of fallot

BACKGROUND

Insertion of a competent pulmonary valve has been advocated to reduce right ventricular volume overload associated with pulmonary regurgitation (PR) after repair of tetralogy of Fallot. However the indications, proper timing, and long-term benefits of restoring pulmonary valve function remain controversial.

METHODS

Thirty-six patients (aged 15.2 +/- 9.2 years) underwent pulmonary valve implantation (31 homografts, 5 heterografts) 12.2 +/- 6.9 years after tetralogy repair. Additional surgical procedures included pulmonary artery augmentation (n = 14), closure of septal defects (n = 10), and cryoablation and endocardial resection of ventricular tachycardia (n = 2).

RESULTS

All patients have had clinical improvement in their exercise capacity. Preoperative and postoperative bicycle ergometry tests in 6 patients demonstrated significant improvement in the percent of predicted peak workload (68.5% +/- 19.8% to 80.7% +/- 17.4%, p < 0.015). One midterm death occurred in a 38-year-old patient with a history of ventricular tachycardia who died suddenly 2 years after pulmonary valve insertion. Postoperative echocardiographic measurements were available in 34 patients at a mean follow-up of 5 years. There was a 30% reduction in right ventricular end-diastolic diameter indexed to body surface area after surgery (30.1 +/- 10.2 to 18.6 +/- 6.0 mm/m(2), p < 0.0001). Two patients required conduit replacements at 1 and 9 years postoperatively.

CONCLUSIONS

Timely insertion of a competent pulmonary valve in children, adolescents, and young adults with significant PR after tetralogy of Fallot repair results in subjective and objective improvement in exercise capacity and is associated with reduction in right ventricle size.