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Tachyarrhythmia-induced cardiomyopathy (TIC) is a rare, yet life-threatening phenomenon in children. TIC has been defined as myocardial dysfunction that is entirely or partially reversible after control of the responsible tachyarrhythmia and is typically caused by an incessant supraventricular tachycardia. In cases of unsuccessful termination of the tachycardia, cardiogenic shock may occur. Several authors favour the use of mechanical circulatory support in such cases. Particularly with regard to these partly severe cases, the authors would like to present the option of transoesophageal overdrive pacing (TOP) as a tool for initial heart rate control and hemodynamic stabilization of patients with TIC refractory to conventional strategies of tachycardia termination. Chart review for patients receiving TOP during the last 5 years in two centres was performed. A case series of successful TOP including technique and outcomes is depicted. Rate control through TOP is a safe and effective option to restore acceptable hemodynamics in infants with refractory supraventricular tachycardia and severe impairment of ventricular function. It presents the possibility of immediate heart rate control and offers time for myocardial recovery and safe implementation of antiarrhythmic drug therapy.

Background: We evaluated the effects of the site of ventricular pacing on left ventricular (LV) synchrony and function in children requiring permanent pacing., Methods and Results: One hundred seventy-eight children (aged <18 years) from 21 centers with atrioventricular block and a structurally normal heart undergoing permanent pacing were studied cross-sectionally. Median age at evaluation was 11.2 (interquartile range, 6.3-15.0) years. Median pacing duration was 5.4 (interquartile range, 3.1-8.8) years. Pacing sites were the free wall of the right ventricular (RV) outflow tract (n=8), lateral RV (n=44), RV apex (n=61), RV septum (n=29), LV apex (n=12), LV midlateral wall (n=17), and LV base (n=7). LV synchrony, pump function, and contraction efficiency were significantly affected by pacing site and were superior in children paced at the LV apex/LV midlateral wall. LV dyssynchrony correlated inversely with LV ejection fraction (R=0.80, P=0.031). Pacing from the RV outflow tract/lateral RV predicted significantly decreased LV function (LV ejection fraction <45%; odds ratio, 10.72; confidence interval, 2.07-55.60; P=0.005), whereas LV apex/LV midlateral wall pacing was associated with preserved LV function (LV ejection fraction ≥55%; odds ratio, 8.26; confidence interval, 1.46-47.62; P=0.018). Presence of maternal autoantibodies, gender, age at implantation, duration of pacing, DDD mode, and QRS duration had no significant impact on LV ejection fraction., Conclusions: The site of ventricular pacing has a major impact on LV mechanical synchrony, efficiency, and pump function in children who require lifelong pacing. Of the sites studied, LV apex/LV midlateral wall pacing has the greatest potential to prevent pacing-induced reduction of cardiac pump function.

Aims: To evaluate the results of permanent epicardial pacing in children., Methods and Results: All consecutive patients from one country (n = 119, period 1977-2009) undergoing permanent epicardial pacemaker implantation at <18 years of age (median 1.8 years, inter-quartile range 0.3-6.4 years) were studied retrospectively. Median patient follow up was 6.4 years (inter-quartile range 2.9-11.1 years); 207 generators, 89 atrial and 153 ventricular pacing leads were implanted. The probability of absence of any pacing system dysfunction was 70.1 and 47.2% at 5 and 10 years after implantation, respectively. Overall probability of continued epicardial pacing was 92.8 and 76.1% at 5 and 10 years, respectively, and increased in the recent implantation era (post-2000, P = 0.04). The use of steroid-eluting leads decreased the risk of exit block with a hazard ratio (HR) of 0.20 [95% confidence interval (CI) 0.09-0.44, P < 0.001)]. The use of bipolar Medtronic 4968 leads reduced the risk of surgical reintervention because of fracture, insulation break, outgrowth or exit block in comparison to the unipolar 4965 lead design (HR 0.12, 95% CI 0.04-0.40, P < 0.001). The AutoCapture™ feature (HR 0.08, 95% CI 0.02-0.36, P < 0.001) and steroid-eluting leads (HR 0.30, 95% CI 0.11-0.84, P = 0.021) decreased the risk of battery depletion., Conclusion: The probability of continued epicardial pacing in children was 76% at 10 years after implantation, increased for implantation in recent years, and allowed transvenous pacing to be deferred to a significantly greater age. The use of bipolar steroid-eluting leads and of a beat-to-beat capture tracking feature significantly increased pacing system longevity and decreased the need for surgical reinterventions.

Background: Chronic right ventricular (RV) pacing is associated with deleterious effects on cardiac function., Objective: In an observational multicentre study in children with isolated atrioventricular (AV) block receiving chronic ventricular pacing, the importance of the ventricular pacing site on left ventricular (LV) function was investigated., Methods: Demographics, maternal autoantibody status and echocardiographic measurements on LV end-diastolic and end-systolic dimensions and volumes at age <18 years were retrospectively collected from patients undergoing chronic ventricular pacing (>1 year) for isolated AV block. LV fractional shortening (LVFS) and, if possible LV ejection fraction (LVEF) were calculated. Linear regression analyses were adjusted for patient characteristics., Results: From 27 centres, 297 children were included, in whom pacing was applied at the RV epicardium (RVepi, n = 147), RV endocardium (RVendo, n = 113) or LV epicardium (LVepi, n = 37). LVFS was significantly affected by pacing site (p = 0.001), and not by maternal autoantibody status (p = 0.266). LVFS in LVepi (39 ± 5%) was significantly higher than in RVendo (33 ± 7%, p < 0.001) and RVepi (35 ± 8%, p = 0.001; no significant difference between RV-paced groups, p = 0.275). Subnormal LVFS (LVFS < 28%) was seen in 16/113 (14%) RVendo-paced and 21/147 (14%) RVepi-paced children, while LVFS was normal (LVFS ≥ 28%) in all LVepi-paced children (p = 0.049). These results are supported by the findings for LVEF (n = 122): LVEF was <50% in 17/69 (25%) RVendo- and in 10/35 (29%) RVepi-paced patients, while LVEF was ≥ 50% in 17/18 (94%) LVepi-paced patients., Conclusion: In children with isolated AV block, permanent ventricular pacing site is an important determinant of LV function, with LVFS being significantly higher with LV pacing than with RV pacing.

Aims: To analyse left ventricular (LV) synchrony and function with respect to the epicardial pacing site in the young., Methods and Results: Left ventricular function and synchrony (M-mode, speckle tracking) were evaluated during mid-term follow-up in 32 children with complete non-surgical (n = 15) or surgical (n = 17) atrioventricular block (structural heart disease in 21/32) paced from LV apex (n = 19), right ventricular (RV) apex (n = 7), and RV free wall (n = 6), respectively. Data are in the following order: LV apical, RV apical, and RV free wall pacing. Septal to posterior wall motion delay (SPWMD) = median 0, 69, and 136 ms (P < 0.001), septal to lateral mechanical delay = 54 +/- 29, 73 +/- 24, and 129 +/- 70 ms (P = 0.001), apical to basal mechanical delay = 96 +/- 37, 106 +/- 50, and 79 +/- 18 ms (P NS), and LV ejection fraction (LVEF) = 57 +/- 9, 49 +/- 12, and 33 +/- 10% (P < 0.001), respectively. Left ventricular ejection fraction correlated negatively with SPWMD (R(2) = 0.454, P < 0.001) and septal to lateral mechanical delay (R(2) = 0.320, P < 0.001) but not with apical to basal mechanical delay. Right ventricular free wall pacing (P = 0.014) and SPWMD (P = 0.044) were negative multivariable predictors of LVEF., Conclusion: Compared with other sites, LV apical pacing preserves septal to lateral LV synchrony and systolic function and may be the preferred epicardial pacing site in the young.

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.

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.

This report describes a fetus presenting with second-degree atrioventricular block, sinus bradycardia, and transient ventricular tachycardia with ventriculoatrial dissociation. Long QT syndrome (LQTS) was suspected due to the association of heart rhythm disturbances and very short transmitral early deceleration time. This impaired relaxation of the left ventricle was explained by the extreme prolongation of the refractory period caused by the prolonged relaxation time. The infant was treated successfully with beta-blockers and implantation of a pacemaker. The prognosis is poor when LQTS presents utero or during the first week of life. To date, only a few case reports of a fetus with LQTS have been published.

Cardiac resynchronization therapy (CRT) is an emerging option for treating dyssynchrony-associated heart failure in patients with pediatric or congenital heart disease. CRT has proved beneficial for both the acute manipulation of cardiac output after surgery for congenital heart defects and for the management of chronic systemic ventricular failure. Although there are no prospective and randomized trial data, retrospective series show that CRT is similarly effective for managing dyssynchrony-associated heart failure in this younger population as it is for treating adults with ischemic and idiopathic dilated cardiomyopathy. The heterogeneity of anatomical and functional substrates in which CRT shows efficacy calls for further studies defining the usefulness of CRT in specific subgroups of patients.

Objectives: This study aimed to evaluate the technical feasibility and hemodynamic benefit of cardiac resynchronization therapy (CRT) in patients with systemic right ventricle (RV)., Background: Patients with a systemic RV are at high risk of developing heart failure. Cardiac resynchronization therapy may improve RV function in those with electromechanical dyssynchrony., Methods: Eight patients (age 6.9 to 29.2 years) with a systemic RV and right bundle-branch block (n = 2) or pacing from the left ventricle (LV) (n = 6) with a QRS interval of 161 +/- 21 ms underwent CRT (associated with cardiac surgery aimed at decrease in tricuspid regurgitation in 3 of 8 patients) and were followed-up for a median of 17.4 months., Results: Change from baseline rhythm to CRT was accompanied by a decrease in QRS interval (-28.0%, p = 0.002) and interventricular mechanical delay (-16.7%, p = 0.047) and immediate improvement in the RV filling time (+10.9%, p = 0.002), Tei index (-7.7%, p = 0.008), estimated RV maximum +dP/dt(+45.9%, p = 0.007), aortic velocity-time integral (+7.0%, p = 0.028), and RV ejection fraction by radionuclide ventriculography (+9.6%, p = 0.04). The RV fractional area of change increased from a median of 18.1% before resynchronization to 29.5% at last follow-up (p = 0.008) without a significant change in the end-diastolic area (+4.0%, p = NS)., Conclusions: The CRT yielded improvement in systemic RV function in patients with spontaneous or LV pacing-induced electromechanical dyssynchrony and seems to be a promising adjunct to the treatment and prevention of systemic RV failure.

The etiology of dilated cardiomyopathy associated with congenital complete AV block has not yet been clarified. Two infants with AV block of autoimmune and surgical etiology, respectively, had received a dual-chamber right ventricular-based pacemaker and developed dilated cardiomyopathy with severe septal to left ventricular free-wall dyssynchrony 3.4 (0.9) years later. After 4 weeks of biventricular pacing and spontaneous junctional narrow QRS rhythm, respectively, both children showed significant improvement in left ventricular function along with reverse remodeling. Thus, electromechanical dyssynchrony associated with conventional right-ventricular-based DDD pacing may play a significant role in the development of dilated cardiomyopathy in the young.

Junctional ectopic tachycardia (JET) is a life-threatening arrhythmia frequently seen after surgical correction of congenital heart defects. This study evaluates the use of a modified, commercially available temporary dual chamber pacemaker used to reestablish AV synchrony by R wave synchronized atrial pacing, a technique not routinely applied because of a lack of appropriate equipment. Ten consecutive children with postoperative JET (median maximum heart rate 185, range 130-240 beats/min) age 0.3-45 (median 5.2) months were studied. R wave synchronized atrial pacing was performed using the VAT mode with inverse connection of the pacing wires (effectively AVT mode), short postventricular atrial refractory period (100 ms), and long AV (effectively VA) delay. AV delay was adjusted to achieve maximum increase in arterial pressure by optimal AV resynchronization. Pacing was successfully applied in all patients for a median period of 29 (range 10-96) hours until tachycardia cessation and led to an immediate increase in systolic, mean, and pulse pressure by 8.9 +/- 3.2 (P < 0.001), 8.1 +/- 4.0 (P < 0.001), and 11.9 +/- 7.8% (P < 0.005), respectively. Two patients developed pacemaker-mediated tachycardia, which could be easily stopped by AV (effectively VA) delay prolongation. Atrial flutter was induced in one patient by asynchronous atrial pacing during the VAT (effectively AVT) mode and managed by overdrive pacing. In conclusion, R wave synchronized atrial pacing could be easily performed using a modified, commercially available temporary dual chamber pacemaker. Significant hemodynamic benefit was achieved due to optimal AV resynchronization at intrinsic heart rate and spontaneous ventricular activation sequence. R wave synchronized atrial pacing should be included in the standard management protocol of postoperative JET.

The acute hemodynamic effect of atrioventricular (AV) and inter/intraventricular (IV) resynchronization accomplished by temporary pacing using multiple epicardial pacing wires was evaluated in 20 children (aged 3.4 months to 14.0 years) after surgery for congenital heart defects fulfilling the following criteria: (1) presence of AV and/or IV conduction delay, and (2) need for inotropic support. AV resynchronization (n = 13) was achieved by AV delay optimization during atrial synchronous right ventricular outflow tract pacing. IV resynchronization (n = 14) was accomplished by atrial synchronous pacing from the right ventricular lateral wall in 7 patients with right bundle branch block and normal AV conduction and by atrial synchronous multisite ventricular pacing in another 7 patients with previously performed AV resynchronization. Compared with baseline values, AV resynchronization resulted in an increase in arterial systolic, mean, and pulse pressures by 7.2 +/- 8.3% (p <0.01), 8.6 +/- 8.1% (p <0.005), and 6.9 +/- 13.5% (p = NS), respectively. IV resynchronization used either alone or added to previously performed AV resynchronization led to a pressure increase of 7.0 +/- 4.7%, 5.9 +/- 4.7%, and 9.4 +/- 7.8%, respectively (p <0.001 for all). The combined effect of AV and IV resynchronization resulted in a systolic, mean, and pulse pressure increase of 10.2 +/- 5.0% (range 4.0 to 19.1), 8.6 +/- 5.4% (range 0.8 to 14.8), and 15.2 +/- 8.5% (range 6.1 to 33.3), respectively (p <0.001 for all). The increase in systolic arterial pressure after IV resynchronization was positively correlated with the initial QRS duration (r = 0.62, p <0.05) and extent of QRS shortening (r = 0.66, p <0.05). In conclusion, resynchronization pacing led to a significant increase in arterial blood pressure and was a useful adjunct to the treatment of acute postoperative heart failure in patients with AV and/or IV conduction delay.