Resynchronization Therapy in Pediatric and Congenital Heart Disease Patients

Biventricular stimulation improves right and left ventricular function after tetralogy of Fallot repair: acute animal and clinical studies

BACKGROUND

Optimal treatment of right ventricular (RV) dysfunction observed in patients after tetralogy of Fallot (TOF) repair is unclear. Studies of biventricular (BiV) stimulation in patients with congenital heart disease have been retrospective or have included patients with heterogeneous disorders.

OBJECTIVE

The purpose of this study was to determine the effects on cardiac function of stimulating at various cardiac sites in an animal model of RV dysfunction and dyssynchrony and in eight symptomatic adults with repaired TOF.

METHODS

Pulmonary stenosis and regurgitation as well as RV scars were induced in 15 piglets to mimic repaired TOF. The hemodynamic effects of various configurations of RV and BiV stimulation were compared with sinus rhythm (SR) 4 months after surgery. In eight adults with repaired TOF, RV and left ventricular (LV) dP/dt(max) were measured invasively during SR, apical RV stimulation, and BiV stimulation.

RESULTS

At 4 months, RV dilation, dysfunction, and dyssynchrony were present in all piglets. RV stimulation caused a decrease in LV function but no change in RV function. In contrast, BiV stimulation significantly improved LV and RV function (P < .05). Echocardiography and epicardial electrical mapping showed activation consistent with right bundle branch block during SR and marked resynchronization during BiV stimulation. In patients with repaired TOF, BiV stimulation increased significantly RV and LV dP/dt(max) (P < .05).

CONCLUSION

In this swine model of RV dysfunction and in adults with repaired TOF, BiV stimulation significantly improved RV and LV function by alleviating electromechanical dyssynchrony.

Health-e-Child project: mechanical dyssynchrony in children with dilated cardiomyopathy

OBJECTIVE

Left ventricular mechanical dyssynchrony has been poorly studied in the pediatric population with dilated cardiomyopathy. We investigated the degree of dyssynchrony in children with dilated cardiomyopathy using tissue Doppler imaging and speckle tracking strain.

METHODS

Twenty-five children with dilated cardiomyopathy were compared with healthy subjects. Left ventricular mechanical dyssynchrony was assessed by speckle tracking strain and tissue Doppler imaging. Both radial and longitudinal dyssynchrony were analyzed. Left ventricular end-diastolic diameter was measured to assess the relation between dyssynchrony and ventricular function and remodeling.

RESULTS

Radial and longitudinal dyssynchrony parameters were significantly higher in the dilated cardiomyopathy group and correlated with Z-score left ventricular end-diastolic diameter. A logarithmic correlation between left ventricular ejection fraction and left ventricular end-diastolic diameter parameters was found.

CONCLUSION

In children with dilated cardiomyopathy, tissue Doppler imaging and speckle tracking strain allowed the detection of dyssynchrony, which correlates with the severity of left ventricular function.

Biventricular pacing in an infant with noncompaction of the ventricular myocardium, congenital AV block, and prolonged QT interval

We describe the case of a newborn with isolated noncompaction of the ventricular myocardium, congenital atrioventricular block, and prolonged QT, who developed a dilated cardiomyopathy after 4 months of right ventricular permanent pacing. The implanted system was upgraded to biventricular pacing. Resynchronization therapy was associated with normalized septal motion and shortening of the interventricular delay and, within 2 months after initiation, resulted in markedly improved left ventricular ejection fraction and reduced ventricular volume.

Cardiac resynchronization therapy in pediatric congenital heart disease: insights from noninvasive electrocardiographic imaging

BACKGROUND

Electrocardiographic imaging (ECGI) is a novel electrophysiologic imaging modality that may help guide patient selection and lead placement for cardiac resynchronization therapy (CRT).

OBJECTIVE

The purpose of this study was to apply noninvasive ECGI to pediatric heart failure patients with congenital heart disease (CHD) undergoing evaluation for CRT.

METHODS

ECGI was applied in eight patients with CHD who were either being evaluated for CRT or undergoing CRT. An electrical dyssynchrony (ED) index was computed from the ECGI epicardial activation maps as the standard deviation of activation times at 500 epicardial sites of the systemic ventricle. A normal ED of 20 +/- 4 ms was calculated from a control group of normal pediatric patients.

RESULTS

Four patients had an ECGI assessment for ED but did not undergo CRT implant. Two other patients had ECGI assessment pre-CRT that demonstrated abnormal ED and went on to CRT implant. In both cases, the resynchronization lead was placed at the site of latest electrical activation (as determined by ECGI) in pre-CRT baseline rhythm. A total of four patients (two responders, two nonresponders) were studied with post-CRT in multiple rhythms. Responders had an average ED of 22 ms in optimal CRT conditions. The nonresponder had very elevated ED (37 ms) in all rhythms including optimal CRT settings. ED and ECG QRS duration showed weak correlation (r = 0.58).

CONCLUSIONS

ECGI can be used in pediatric heart failure patients to evaluate ventricular ED and identify suitable candidates for CRT. In addition, ECGI can guide resynchronization lead placement to the area of latest electrical activation. It could also be used in noninvasive follow-ups for assessing synchrony and the electrophysiological substrate over time.

Cardiac resynchronisation therapy in paediatric and congenital heart disease: differential effects in various anatomical and functional substrates

Background:

Cardiac resynchronisation therapy (CRT) is increasingly used in children in a variety of anatomical and pathophysiological conditions, but published data are scarce.

Objective:

To record current practice and results of CRT in paediatric and congenital heart disease.

Design:

Retrospective multicentre European survey.

Setting:

Paediatric cardiology and cardiac surgery centres.

Patients:

One hundred and nine patients aged 0.24–73.8 (median 16.9) years with structural congenital heart disease (n = 87), congenital atrioventricular block (n = 12) and dilated cardiomyopathy (n = 10) with systemic left (n = 69), right (n = 36) or single (n = 4) ventricular dysfunction and ventricular dyssynchrony during sinus rhythm (n = 25) or associated with pacing (n = 84).

Interventions:

CRT for a median period of 7.5 months (concurrent cardiac surgery in 16/109).

Main outcome measures:

Functional improvement and echocardiographic change in systemic ventricular function.

Results:

The z score of the systemic ventricular end-diastolic dimension decreased by median 1.1 (p<0.001). Ejection fraction (EF) or fractional area of change increased by a mean (SD) of 11.5 (14.3)% (p<0.001) and New York Heart Association (NYHA) class improved by median 1.0 grade (p<0.001). Non-response to CRT (18.5%) was multivariably predicted by the presence of primary dilated cardiomyopathy (p = 0.002) and poor NYHA class (p = 0.003). Presence of a systemic left ventricle was the strongest multivariable predictor of improvement in EF/fractional area of change (p<0.001). Results were independent of the number of patients treated in each contributing centre.

Conclusion:

Heart failure associated with ventricular pacing is the largest indication for CRT in paediatric and congenital heart disease. CRT efficacy varies widely with the underlying anatomical and pathophysiological substrate.

Predictors of left ventricular remodelling and failure in right ventricular pacing in the young

Aims

To identify risk factors for left ventricular (LV) dysfunction in right ventricular (RV) pacing in the young.

Methods and results

Left ventricular function was evaluated in 82 paediatric patients with either non-surgical (n = 41) or surgical (n= 41) complete atrioventricular block who have been 100% RV paced for a mean period of 7.4 years. Left ventricular shortening fraction (SF) decreased from a median (range) of 39 (24–62)% prior to implantation to 32 (8–49)% at last follow-up (P < 0.05). Prevalence of a combination of LV dilatation (LV end-diastolic diameter >+2z-values) and dysfunction (SF < 0.26) was found to increase from 1.3% prior to pacemaker implantation to 13.4% (11/82 patients) at last follow-up (P = 0.01). Ten of these 11 patients had progressive LV remodelling and 8 of 11 were symptomatic. The only significant risk factor for the development of LV dilatation and dysfunction was the presence of epicardial RV free wall pacing (OR = 14.3, P < 0.001). Other pre-implantation demographic, diagnostic, and haemodynamic factors including block aetiology, pacing variables, and pacing duration did not show independent significance.

Conclusion

Right ventricular pacing leads to pathologic LV remodelling in a significant proportion of paediatric patients. The major independent risk factor is the presence of epicardial RV free wall pacing, which should be avoided whenever possible.

Chronic left ventricular pacing preserves left ventricular function in children

Chronic right ventricular (RV) pacing can induce structural and functional cardiac deterioration. Because animal studies showed a benefit of left ventricular (LV) over RV pacing, this study compared the effects of chronic RV and LV pacing in children. Retrospectively, echocardiographic data were evaluated from 18 healthy children (control subjects) and from children undergoing chronic epicardial RV pacing (7 RVP) or LV pacing (7 LVP). Assessment included LV end-diastolic wall thickness (LVEDWT) and end-systolic wall thickness (LVESWT) as well as LV end-diastolic diameter (LVEDD) and end-systolic diameter (LVESD). The shortening fraction and eccentricity index (LV diameter/2xLV wall thickness) were calculated as measures of LV function and eccentricity, respectively. Duration of QRS and septal posterior wall motion delay (SPWMD) were used as measures of electrical and mechanical dyssynchrony, respectively. A p value less than 0.05 determined significance. As the findings showed, LVEDD, LVESD, LVEDWT, and LVESWT were not significantly different between the groups. The shortening fraction was significantly lower in the RVP (21.7%+/-6.0%) than in the LVP (32.2%+/-5.2%) or control (29.3%+/-4.3%) children. The systolic LV eccentricity index was significantly larger in the RVP (1.8+/-0.2) than in the LVP (1.4+/-0.1) or control (1.4+/-0.2) children. The SPWMD was significantly larger in the RVP (338+/-20 ms) than in the LVP (-16+/-14 ms) or control (-5+/-35 ms) group, whereas QRS duration was similarly longer in the RVP (157+/-10 ms) and LVP (158+/-22 ms) groups compared than in the control group (69+/-7 ms). The authors conclude that LV function in children is preserved by chronic pacing at the LV lateral wall.

Implication of QRS prolongation and its relation to mechanical dyssynchrony in idiopathic dilated cardiomyopathy in childhood

We explored the role of QRS prolongation (>or=120 ms) and its relation to mechanical dyssynchrony and outcomes in childhood idiopathic dilated cardiomyopathy (IDC). A total of 89 patients <or=18 years old diagnosed as having IDC (21 days to 26 years of follow-up) were investigated. In 20 survivors with residual left ventricular (LV) dysfunction, mechanical (interventricular and intra-LV) dyssynchrony was assessed. The SD of time from the beginning of QRS prolongation to peak systolic contraction was measured in 12 LV segments by tissue Doppler imaging. A cut-off value >32.6 ms was used to define intra-LV dyssynchrony. The 1- and 5-year survivals were 70% and 53%, respectively. Requirement of intravenous inotropes at follow-up (hazard ratio 3.10) and initial LV ejection fraction (hazard ratio 0.95) were major prognostic factors. QRS prolongation, primarily left bundle branch block, was identified in 16 patients (18%) and tended to increase the risk of requiring inotropes. Moreover, none of those with QRS prolongation regained normal cardiac function at follow-up. Two patients with QRS prolongation showed marked improvement in cardiac function after cardiac resynchronization therapy. Mechanical dyssynchrony was noted in all patients with QRS prolongation and in 8% (interventricular) or 38% (intra-LV) of those without. In conclusion, QRS prolongation was common in childhood IDC and was possibly associated with persistent LV dysfunction and worse cardiac outcome. Mechanical (inter- and intraventricular) dyssynchrony was highly prevalent in those with QRS prolongation and was still often observed in those without.

Deleterious effect of unintentional pacing from the middle cardiac vein in a patient with congenitally corrected transposition of the great arteries and ventricular septal defect. The beneficial effect of cardiac resynchronization therapy after heart surgery

This report presents a case of a 31-year-old male with congenitally corrected transposition of the great arteries, ventricular septal defect (VSD) and complete heart block who was admitted to our institution because of an exacerbation of heart failure after pacemaker implantation. The ECG and chest radiograph revealed that the ventricular lead was placed in the middle cardiac vein. After cardiosurgical procedure (VSD closure and atrioventricular valves replacement), the clinical symptoms of heart failure were still present. They diminished while the patient was on escape rhythm (40-70 bpm). Therefore, the previously implanted leads were removed and the transvenous, biventricular system was implanted, which resulted in a significant clinical improvement.

Pacemaker and defibrillator therapy in pediatrics and congenital heart disease

Pacemakers and defibrillators have a growing use in pediatrics and in patients with congenital heart disease, but they present unique problems and implications for their implantation and follow-up. Congenital and surgically acquired rhythm disturbances are common, but the efficacy of device therapy is not well established in these patient groups. The diversity and complexity of pediatric patients and congenital heart disease make device management a highly individualized art. There are technical issues related to device implantation that have necessitated novel approaches to using leads and device that were not designed with children specifically in mind. The current guidelines and indications for implantable device therapy for children and congenital heart disease are reviewed, as well as some of the specific limitations and problems encountered.

Presence of ventricular dyssynchrony and haemodynamic impact of right ventricular pacing in adults with repaired Tetralogy of Fallot and right bundle branch block

AIMS

Late after surgical repair, adults with Tetralogy of Fallot (TOF) commonly present with right ventricular (RV) dysfunction and right bundle branch block (RBBB). We aimed at (i) investigating whether this prolonged RV conduction induced detrimental electromechanical dyssynchrony in both RV and left ventricle (LV) and (ii) determining the acute haemodynamic effects of pacing at different RV sites.

METHODS AND RESULTS

A total of 42 adults with surgically repaired TOF and RBBB were investigated by echocardiography. Intra-RV dyssynchrony (IRVD) and intra-left ventricular dyssynchrony (ILVD) were compared with measurements performed in 30 healthy matched control subjects. An acute haemodynamic study was subsequently performed in a subgroup of 10 patients with New York Heart Association functional class II or class III and echocardiographic signs of RV dysfunction. Cardiac index was measured by a thermodilution technique during spontaneous rhythm (SR) and during atrio-synchronized RV pacing at four different sites (infundibulum, apex, septal, and lateral walls). Fifty-five per cent of the patients with repaired TOF demonstrated abnormal RV and/or LV dyssynchrony. We observed an increased IRVD (37 +/- 12 vs. 18 +/- 8 ms; P= 0.02) and ILVD (34 +/- 12 vs. 20 +/- 10 ms; P= 0.04) in TOF patients when compared with control subjects. We did not observe any significant acute improvement in the cardiac output during atrio-synchronized ventricular pacing vs. SR. Similarly, RV pacing did not induce any significant reduction in the QRS duration.

CONCLUSION

Some TOF adults with RBBB exhibit biventricular electromechanical dyssynchrony. However, in symptomatic patients with RV dysfunction, atrio-synchronized RV pacing does not induce significant acute haemodynamic improvement.

Left ventricular dysfunction after cardiac resynchronization therapy in congenital heart disease patients with a failing systemic right ventricle

BACKGROUND

Cardiac resynchronization therapy is rapidly emerging as an effective strategy for managing ventricular dysfunction and heart failure associated with congenital heart disease. Indications for therapy, optimal lead placement, and late outcomes are however lacking.

METHODS

We present three patients, one with Mustard procedure and two with congenitally corrected transposition of great arteries, who developed subpulmonic ventricular dysfunction 3-6 months after biventricular pacing +/- implantable cardioverter defibrillator implantation, despite initial favorable result of resynchronization therapy. Possible factors for adverse outcome are relatively high pacing rate, unfavorable alteration of torsional contraction, and increased atrioventricular valve regurgitation due to suboptimal placement of larger diameter defibrillation leads.

RESULTS

Careful evaluation of patients, particularly indications for therapy, need to be rigorous; assessment of hemodynamic response at the time of implant and appropriate programming may improve the effectiveness of cardiac resynchronization therapy (CRT) in this patient population.

CONCLUSION

Our case series emphasizes the need for a registry in the absence of randomized controlled trials, in order to identify patients who benefit most from CRT, and, importantly, recognize subgroups that respond poorly.

Rhythm management in pediatric heart failure

There are several options now available for the management of arrhythmias and ventricular dysfunction in pediatric patients with heart failure. A hybrid approach that combines the expertise of heart failure and electrophysiology specialists may be well suited for the optimal management of these complex patients. Medical and device therapies may be synergistic in decreasing the morbidity and mortality in pediatric heart failure. Pediatric electrophysiology can now potentially offer therapies that can help prevent both arrhythmic and pump failure deaths, as well as improve functional capacity and quality of life. These therapies and the available supporting data relevant to pediatrics will be the focus of this review.

Mechanical right ventricular dyssynchrony in patients after atrial switch operation for transposition of the great arteries

Recent data suggest potential benefits of cardiac resynchronization therapy in the management of right ventricular (RV) dysfunction in congenital heart disease. The aim of this study was to determine the nature, prevalence, and functional implications of mechanical RV dyssynchrony in patients after Senning or Mustard procedures for transposition of the great arteries. Twenty-eight patients (mean age 21.1 +/- 3.5 years) at 19.9 +/- 3.2 years after atrial switch operations and 29 healthy controls were studied. The times from the onset of QRS to peak systolic strain (T epsilon) at the base of and the mid RV free wall, the ventricular septum (VS), and the left ventricular (LV) free wall were determined using tissue Doppler echocardiography. Intraventricular mechanical delay was defined as Delta T epsilon(RV-VS) and interventricular mechanical delay as Delta T epsilon(RV-LV). In patients, the magnitude of RV intra- and interventricular mechanical delay was correlated with cardiac magnetic resonance-derived RV volumes and ejection fractions (n = 26) and treadmill exercise testing parameters (n = 20). Compared with controls, patients had significantly longer Delta T epsilon(RV-VS) (48.1 +/- 50.9 vs 17.0 +/- 16.1 ms, p <0.001) and Delta T epsilon(RV-LV) (63.1 +/- 49.5 vs 19.0 +/- 12.9, p <0.001). Nine patients (32%) exhibited RV dyssynchrony (Delta T epsilon(RV-VS) >49 ms, control mean +/- 2SD), and 16 patients (57%) showed interventricular dyssynchrony (Delta T epsilon(RV-LV) >45 ms). In patients, RV intra- and interventricular mechanical delay was correlated negatively with the RV ejection fraction (both r = -0.42, p = 0.03) and percentage predicted maximum oxygen consumption (r = -0.50, p = 0.03, and r = -0.52, p = 0.02, respectively) and positively with minute ventilation/carbon dioxide production slope (r = 0.49, p = 0.03, and r = 0.56, p = 0.01, respectively). In conclusion, RV dyssynchrony is common in young adults after atrial switch operations and is associated with RV systolic dysfunction and impaired exercise performance.

Contemporary management of pediatric heart failure

The spectrum of causes of pediatric heart failure is broad and differs significantly from that seen in most adult patients. Left-to-right shunts and outflow obstruction lesions are responsible for a large number of pediatric cases of heart failure. Most of these are now treated successfully with surgery or catheter intervention. Medical therapy is the mainstay of care for myocardial disorders with diuretics, angiotensin-converting enzyme inhibitors, beta-blockade and cardiac glycosides. There are few prospective trials of these agents in a pediatric population, but extrapolated data support their use in children. In addition to medical therapy, interventions such as automatic implantable cardioverter defibrillators and resynchronization therapy have become increasingly common in pediatric heart disease, as well as in adult patients with congenital heart disease.

Evaluation of right ventricular contraction by myocardial strain in children using a two-dimensional tissue tracking method

Two-dimensional tissue tracking makes it possible to detect myocardial strain in any direction. Consequently, this method is applicable for evaluation of myocardial dyssynchrony. This study enrolled 22 healthy volunteers (11 boys and 11 girls) ages 1.6 to 10.8 years (mean, 6.8 years). Echocardiography (subxiphoid right anterior oblique view) of the right ventricle was examined. Three tracking points were put on the right ventricle, and time-strain curves of the inflow tract (strain at the inlet) and the outflow tract (strain at the outlet) as well as time-strain curve of the pulmonary annulus diameter were made. The strain at the inlet was larger than the strain at the outlet (0.31 vs 0.15; p = 0.0003). The time to peak negative strain at the inlet was longer than at the outlet (0.48 vs 0.42 s; p = 0.001). The diameter of the pulmonary annulus shortened in systole, and the time to peak negative strain of the pulmonary annulus was longer than that of the outlet (0.48 vs 0.42; p = 0.001). There was no significant difference in the times between the pulmonary annulus and the inlet (0.48 vs 0.48; p = 0.78). Two-dimensional tissue tracking allows assessment for quantification of myocardial performance and timing of the right ventricle.

Left Ventricular Dysfunction is Associated with Intraventricular Dyssynchrony by 3-Dimensional Echocardiography in Children

INTRODUCTION

We used 3-dimensional (3D) echocardiography to identify and quantify left ventricular (LV) dyssynchrony in children with LV dysfunction compared with control subjects.

METHODS

The 3D echocardiography LV full volumes were acquired in 18 children, 9 with LV dysfunction and 9 control subjects. The LV was subdivided into 16 segments (apex excluded). Time from end diastole to the minimal systolic volume for each segment was expressed as a percent of the R-R interval. The SD of these times provided a 16-segment dyssynchrony index (16-SDI). The second index (12-SDI) was similarly calculated using 6 basal and 6 mid segments. The third index consisted of 6 basal segments (6-SDI).

RESULTS

The dysfunction group exhibited significantly increased 16-SDI (P = .008) and 12-SDI (P = .01). The 16-SDI was negatively correlated with 3D ejection fraction and 2-dimensional fractional shortening.

CONCLUSIONS

Children with LV dysfunction demonstrate increased intraventricular LV dyssynchrony by 3D echocardiography, in a pattern that is negatively correlated with LV systolic function.

What is new in pediatric cardiac imaging?

Cardiac imaging has had significant influence on the science and practice of pediatric cardiology. Especially the development and improvements made in non-invasive imaging techniques, like echocardiography and cardiac magnetic resonance imaging (MRI), have been extremely important. Technical advancements in the field of medical imaging are quickly being made. This review will focus on some of the important evolutions in pediatric cardiac imaging. Techniques such as intracardiac echocardiography, 3D echocardiography, and tissue Doppler imaging are relatively new echocardiographic techniques, which further optimize the anatomical and functional aspects of congenital heart disease. Also, the current standing of cardiac MRI and cardiac computerized tomography will be discussed. Finally, the recent European efforts to organize training and accreditation in pediatric echocardiography are highlighted.