Multimodality 3D image fusion with live fluoroscopy reduces radiation dose during catheterization of congenital heart defects

Introduction

Imaging fusion technology is promising as it is radiation and contrast sparing. Herein, we compare conventional biplane angiography to multimodality image fusion with live fluoroscopy using two-dimensional (2D)-three-dimensional (3D) registration (MMIF2D-3D) and assess MMIF2D-3D impact on radiation exposure and contrast volume during cardiac catheterization of patients with congenital heart disease (CHD).

Methods

We matched institutional MMIF2D-3D procedures and controls according to patient characteristics (body mass index, age, and gender) and the seven procedure-type subgroups. Then, we matched the number of tests and controls per subgroup using chronological ordering or propensity score matching. Subsequently, we combined the matched subgroups into larger subgroups of similar procedure type, keeping subgroups with at least 10 test and 10 control cases. Air kerma (AK) and dose area product (DAP) were normalized by body weight (BW), product of body weight and fluoroscopy time (BW × FT), or product of body weight and number of frames (BW × FR), and stratified by acquisition plane and irradiation event type (fluoroscopy or acquisition). Three senior interventionists evaluated the relevance of MMIF2D-3D (5-point Likert scale).

Results

The Overall group consisted of 54 MMIF2D-3D cases. The combined and matched subgroups were pulmonary artery stenting (StentPUL), aorta angioplasty (PlastyAO), pulmonary artery angioplasty (PlastyPUL), or a combination of the latter two (Plasty). The FT of the lateral plane reduced significantly by 69.6% for the Overall MMIF2D-3D population. AKBW and DAPBW decreased, respectively, by 43.9% and 39.3% (Overall group), 49.3% and 54.9% (PlastyAO), and 36.7% and 44.4% for the Plasty subgroup. All the aforementioned reductions were statistically significant except for DAPBW in the Overall and Plasty (sub)groups. The decrease of AKBW and DAPBW in the StentPUL and PlastyPUL subgroups was not statistically significant. The decrease in the median values of the weight-normalized contrast volume (CMCBW) in all five subgroups was not significant. Cardiologists considered MMIF2D-3D very useful with a median score of 4.

Conclusion

In our institution, MMIF2D-3D overall enabled significant AKBW reduction during the catheterization of CHD patients and was mainly driven by reduced FT in the lateral plane. We observed significant AKBW reduction in the Plasty and PlastyAO subgroups and DAPBW reduction in the PlastyAO subgroup. However, the decrease in CMCBW was not significant.

Evaluation of a nurse-led multi-component transition program for adolescents with congenital heart disease

OBJECTIVE

To evaluate the effectiveness of the transition program for adolescents with congenital heart disease (CHD) 'Transition With a Heart' (TWAH) on disease-related knowledge, quality of life (QoL), transition experiences, and gaps in follow-up.

METHODS

A study with pre-posttest and control group (post-test) using consecutive sampling, including adolescents with moderate to severely complex CHD, without intellectual disability, aged≥ 12 y, and parents. After weighting, t-tests were performed. A multivariable regression analysis explored the outcomes' determinants.

RESULTS

In the intervention group, 28 adolescents and 25 parents were included, and 53 adolescents and 18 parents as controls. Adolescents' knowledge significantly increased after completing TWAH (from 59.8% to 75.7%;p < 0.01). Their knowledge was positively correlated with TWAH (β = +13.3;p < 0.01). Adolescents' transition experiences were also positively related to TWAH (general experience: β = +5.5;p < 0.01; transfer satisfaction: β = +0.8; p < 0.01). Adolescents' QoL was mainly determined by CHD complexity and not by TWAH. No one showed gaps in follow-up. TWAH was not associated with parents' transition experiences.

CONCLUSION

Implementing TWAH substantially improved adolescents' disease-related knowledge and transition experiences.

PRACTICE IMPLICATIONS

The results regarding transition experiences need to be confirmed by further research. The TWAH design with the person-tailored educational program, skills training, and the transition coordinator can be used in settings with other chronic diseases.

Long-term follow-up of atrioventricular valve function in Fontan patients: effect of atrioventricular valve surgery

OBJECTIVES

The aim of this study was to evaluate the relationship between atrioventricular valve and ventricular function in Fontan survivors, including the effect of atrioventricular valve surgery.

METHODS

Analysis focused on transplant-free survival and the need for atrioventricular valve surgery in single ventricle patients after Fontan completion. Longitudinal echocardiographic examination of long-term valve and ventricular function was performed.

RESULTS

Fontan completion was performed in 113 patients, having a right univentricular morphology in 33.6%, a left ventricle morphology in 62.8% and ambiguous in 3.6%. Perioperative mortality was 2.7% (n = 3). Within a median follow-up of 16.3 years (interquartile range 10.6-23.6), transplant-free survival was 96.1 ± 1.9% and 90.4 ± 5.8% at 10-25 years. Twenty AV valve procedures were performed in 14 (12.4%) children, respectively, pre-Fontan (n = 10), per-Fontan (n = 8) and post-Fontan (n = 2), resulting in a cumulative incidence of AV valve surgery is 5.7 ± 2.2% and 12.3 ± 3.2% at 1-5 years. Atrio-ventricular valve function deteriorated over time [hazard ratio (HR) 1.112, 95% confidence interval (CI) 1.089-1.138, P < 0.001], without difference for valve morphology (P = 0.736) or ventricular dominance (P = 0.484). AV valve dysfunction was greater in patients requiring AV valve surgery (HR 20.383, 95% CI 6.223-36.762, P < 0.001) but showed a comparable evolution since repair to those without valve surgery (HR 1.070, 95% CI 0.987-1.160, P = 0.099). Progressive time-related ventricular dysfunction was observed (HR 1.141, 95% CI 1.097-1.182, P < 0.001), significantly less in left ventricle-dominance (HR 0.927, 95% CI 0.860-0.999, P = 0.047) but more after AV valve surgery (HR 1.103, 95% CI 1.014-1.167, P = 0.022).

CONCLUSIONS

In a homogeneously treated Fontan population, 25-year transplant-free survival is encouraging. Atrio-ventricular valve surgery was necessary in 12.4%, resulting mostly in a durable valve function. However, a slow time-related decline of atrioventricular valve function as of ventricular function is worrisome, evoking a role for additional heart failure therapy.

Surgical correction of an infundibular pulmonic stenosis and ventricular septal defect in a Shetland Sheepdog

A four-month-old male Shetland Sheepdog presented with exercise intolerance. Physical examination revealed an IV/VI left cranial systolic heart murmur. Echocardiography showed a severe infundibular pulmonic stenosis and a concomitant restrictive ventricular septal defect. As clinical signs of congestive right-sided heart failure worsened and were refractory to medical treatment, surgical correction was advised. Via sternotomy, with cardiopulmonary bypass and cardioplegic cardiac arrest, ventricular septal defect closure and resection of the stenotic infundibular band were performed through right ventriculotomy, followed by patch enlargement. Postoperative recovery was uneventful and echocardiography showed complete resolution of the stenosis and successful closure of the ventricular septal defect. Follow-up echocardiography revealed restenosis after seven weeks and recurrence of right-sided heart failure three months postoperatively. Stenting of the restenosis was attempted via a hybrid procedure with sternotomy and direct transventricular approach. The dog developed fatal ventricular fibrillation during stent deployment. This is the first dog in which surgical right ventricular patch enlargement under cardiopulmonary bypass is reported for the treatment of a primary infundibular pulmonic stenosis.

Pulmonary artery banding as adjunct therapy for ventricular recovery after ALCAPA-repair: a case report

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital coronary anomaly commonly associated with severe but reversible left ventricular (LV) dysfunction. We present an ALCAPA case of persisting left ventricular failure with inability to wean off the ventilator and inotropes after successful coronary reimplantation, in whom pulmonary artery banding enhanced myocardial recovery.

Hypertension after coarctation repair-a systematic review

BACKGROUND

Coarctation of the Aorta (CoA) leads to increased morbidity and mortality later in life despite early surgical or percutaneous treatment. Many long-term complications are related to hypertension (HT) which is a common finding late after coarctation repair.

METHODS

A systematic Review was performed including articles published between February 2012 to December 2020. Systematic searches were conducted on PubMed and the Cochrane Controlled Trials Register to look for studies on HT after aortic CoA-repair. PRISMA guidelines were used.

RESULTS

In this systematic review on HT after CoA Repair the mean prevalence of HT was 47.3% (20-70%). A progressive character was of the HT was found, furthermore if only studies are included with 24 h blood pressure (BP) recording in addition to standard BP measurements, the incidence of HT rose to 57.8%.

DISCUSSION

Most clinical studies look at complications, mortality rate and residual pressure gradient rather than correlating hemodynamic indices with long-term outcome. Although HT is commonly based in measurement of peripheral BP, it has been shown that peripheral BP in CoA patients has a poor correlation with central aortic pressure. Central aortic hemodynamics are significantly altered in patients with repaired CoA, which can now adequately be investigated non-invasively. At the present time there are no studies linking long-term outcome with abnormal central hemodynamics.

Non-invasive assessment of liver abnormalities in pediatric Fontan patients

Liver abnormalities are well known among long-term survivors of Fontan palliation, which remains the definite surgery for complex congenital heart disease and single ventricle physiology. Pediatric data however are scarce. We assessed the prevalence and degree of liver abnormalities in pediatric Fontan patients through non-invasive investigations suitable for longitudinal follow-up. Thirty-five patients with a median age of 11.8 years (5.2-16.6) and median time since Fontan of 6 years (1.17-13.83) were studied. Each child underwent a blood test, liver Doppler ultrasound (US), and transient elastography (TE). Healthy children were used as controls for TE measurement. AST, ALT, γGT, and direct bilirubin were abnormal in respectively 12 (34%), 5 (14%), 24 (69%), and 7 (20%) patients, while platelet count was decreased in 7 (20%). Splenomegaly was present in 7 (20%) patients. Portal vein mean flow velocity was < 15 cm/s in 19 (54%) patients indicative of portal hypertension. Twenty-two patients (63%) showed inferior vena cava collapsibility index values below 17%, indicating venous congestion. Hepatic artery and superior mesenteric artery resistance index were inversely correlated with time post Fontan (p < 0.05). TE values in Fontan patients were significantly higher than controls, with a median of 12.6 versus 4.6 kPa (p < 0.001) and were already increased shortly after Fontan completion. Conclusion: Liver abnormalities are frequently observed in pediatric Fontan patients. The non-invasive investigations used were not able to confirm liver fibrosis or differentiate hepatic congestion from fibrosis. Based on our findings, we propose a prospective screening protocol with serial measurements of laboratory, (Doppler) US, and TE parameters. What is Known: • Hepatic dysfunction is a well-known consequence of the Fontan circulation. • The natural history of Fontan-associated liver disease in the pediatric age group remains unclear. What is New: • Liver abnormalities are frequently observed in pediatric Fontan patients; however, differentiating liver fibrosis and hepatic congestion with non-invasive investigations remains challenging. Sonographic Doppler measurements may improve our insight in both Fontan-associated liver disease development and the functioning of the Fontan circulation. • A prospective screening protocol is proposed to improve our ability to detect Fontan-associated liver disease early on and understand its natural history.

Ethical and practical dilemmas in cardiac transplantation in infants: a literature review

The waiting time in infants for a cardiac transplant remains high, due to the scarcity of donors. Consequently, waiting list morbidity and mortality are higher than those in other age groups. Therefore, the decision to list a small infant for cardiac transplantation is seen as an ethical dilemma by most physicians. This review aims to describe outcomes, limitations, and ethical considerations in infant heart transplantation. We used Medline and Embase as data sources. We searched for publications on infant (< 1 year) heart transplantation, bridge-to-transplant and long-term outcomes, and waiting list characteristics from January 2009 to March 2021. Outcome after cardiac transplant in infants is better than that in older children (1-year survival 88%), and complications are less frequent (25% CAV, 10% PTLD). The bridge-to-transplant period in infants is associated with increased mortality (32%) and decreased transplantation rate (43%). This is mainly due to MCS complications or the limited MCS options (with 51% mortality in infancy). Outcomes are worse for infants with CHD or in need of ECMO-support.Conclusion: Infants listed for cardiac transplantation have a high morbidity and mortality, especially in the period between diagnosis and transplantation. For those who receive cardiac transplant, the outlook is encouraging. Unfortunately, despite growing experience in VAD, mortality in children < 10 kg and children with CHD remains high. After transplantation, patients carry a psychological burden and there is a probability of re-transplantation later in life, with decreased outcomes compared to primary transplantation. These considerations are seen as an important ethical dilemma in many centers, when considering cardiac transplantation in infants (< 1 year). What is Known: • For infants, waitlist mortality remains high. In the pediatric population, MCS reduces the waiting list mortality. What is New: • Outcomes after infant cardiac transplantation are better than other age groups; however, MCS options remain limited, with persistently high waiting list mortality. • Future developments in MCS and alternative options to reduce waiting list mortality such as ABO-incompatible transplantation and pulmonary artery banding are encouraging and will improve ethical decision-making when an infant is in need of a cardiac transplant.

A Reassessment of Copy Number Variations in Congenital Heart Defects: Picturing the Whole Genome

Copy number variations (CNVs) can modulate phenotypes by affecting protein-coding sequences directly or through interference of gene expression. Recent studies in cancer and limb defects pinpointed the relevance of non-coding gene regulatory elements such as long non-coding RNAs (lncRNAs) and topologically associated domain (TAD)-related gene-enhancer interactions. The contribution of such non-coding elements is largely unexplored in congenital heart defects (CHD). We performed a retrospective analysis of CNVs reported in a cohort of 270 CHD patients. We reviewed the diagnostic yield of pathogenic CNVs, and performed a comprehensive reassessment of 138 CNVs of unknown significance (CNV-US), evaluating protein-coding genes, lncRNA genes, and potential interferences with TAD-related gene-enhancer interactions. Fifty-two of the 138 CNV-US may relate to CHD, revealing three candidate CHD regions, 19 candidate CHD genes, 80 lncRNA genes of interest, and six potentially CHD-related TAD interferences. Our study thus indicates a potential relevance of non-coding gene regulatory elements in CNV-related CHD pathogenesis. Shortcomings in our current knowledge on genomic variation call for continuous reporting of CNV-US in international databases, careful patient counseling, and additional functional studies to confirm these preliminary findings.

Paediatric subaortic stenosis: long-term outcome and risk factors for reoperation

 

OBJECTIVES

Surgical repair of subaortic stenosis (SAS) is associated with a substantial reoperation risk. We aimed to identify risk factors for reintervention in relation to discrete and tunnel-type SAS morphology.

METHODS

Single-centre retrospective study of paediatric SAS diagnosed between 1992 and 2017. Multivariable Cox regression analysis was performed to identify reintervention risk factors.

RESULTS

Eighty-five children [median age 2.5 (0.7-6.5) years at diagnosis] with a median follow-up of 10.1 (5.5-16.4) years were included. Surgery was executed in 83% (n = 71). Freedom from reoperation was 88 ± 5% at 5 years and 82 ± 6% at 10 years for discrete SAS, compared to, respectively, 33 ± 16% and 17 ± 14% for tunnel-type SAS (log-rank P < 0.001). Independent risk factors for reintervention were a postoperative gradient >20 mmHg [hazard ratio (HR) 6.56, 95% confidence interval (CI) 1.41-24.1; P = 0.005], tunnel-type SAS (HR 7.46, 95% CI 2.48-22.49; P < 0.001), aortic annulus z-score <-2 (HR 11.07, 95% CI 3.03-40.47; P < 0.001) and age at intervention <2 years (HR 3.24, 95% CI 1.09-9.86; P = 0.035). Addition of septal myectomy at initial intervention was not associated with lesser reintervention. Fourteen children with a lower left ventricular outflow tract (LVOT) gradient (P < 0.001) and older age at diagnosis (P = 0.024) were followed expectatively.

CONCLUSIONS

Children with SAS remain at risk for reintervention, despite initially effective LVOT relief. Regardless of SAS morphology, age <2 years at first intervention, a postoperative gradient >20 mmHg and presence of a hypoplastic aortic annulus are independent risk factors for reintervention. More extensive LVOT surgery might be considered at an earlier stage in these children. SAS presenting in older children with a low LVOT gradient at diagnosis shows little progression, justifying an expectative approach.

Determinants of Physical Fitness in Children with Repaired Congenital Heart Disease

The aim of this study was to determine factors associated with physical fitness (PF) in children who underwent surgery for congenital heart disease (CHD). Sixty-six children (7-14 years) who underwent surgery for ventricular septal defect (n = 19), transposition of great arteries (n = 22), coarctation of aorta (n = 10), and tetralogy of Fallot (n = 15) were included. All children performed PF tests: cardiorespiratory fitness, upper- and lower-limb muscle strength, speed, balance, and flexibility. Cardiac evaluation was done via echocardiography and cardiopulmonary exercise test. Factors related to child's characteristics, child's lifestyle, physical activity motivators/barriers, and parental factors were assessed. Linear regression analyses were conducted. The results showed no significant differences in physical activity (PA) level by CHD type. Boys had better cardiorespiratory fitness (difference = 1.86 ml/kg/min [0.51;3.22]) and were more physically active (difference = 19.40 min/day [8.14;30.66]), while girls had better flexibility (difference = - 3.60 cm [- 7.07;- 0.14]). Physical activity motivators showed an association with four out of six PF components: cardiorespiratory fitness, coefficient = 0.063 [0.01;0.11]; upper-limb muscle strength, coefficient = 0.076 [0.01;0.14]; lower-limb muscle strength, coefficient = 0.598 [0.07;1.13]; and speed, coefficient = 0.03 [0.01;0.05]. Age, sex, and motivators together reached a maximum adjusted R² = 0.707 for upper-limb strength. Adding other possible determinants did not significantly increase the explained variance. Apart from age and sex as non-modifiable determinants, the main target which might improve fitness would be the introduction of an intervention which increases the motivation to be active.

Analysis of the recovery phase after maximal exercise in children with repaired tetralogy of Fallot and the relationship with ventricular function

Background

Few studies demonstrate delayed recovery after exercise in children and adults with heart disease. We assess the recovery patterns of gas exchange parameters and heart rate (HR) in children with repaired Tetralogy of Fallot (rToF) compared to healthy peers and investigate the correlation with ventricular function and QRS duration.

Methods

45 children after rToF and 45 controls performed a maximal incremental cardiopulmonary exercise test. In the subsequent recovery period, patterns of VO₂, VCO₂ and HR were analysed. Half-life time (T_1/2) of the exponential decay and drop per minute (Rec_min) were compared between groups. In the rToF group, correlations were examined between the recovery parameters and QRS-duration and ventricular function, described by fractional shortening (FS) and tricuspid annular plane systolic excursion (TAPSE) measured at baseline prior to exercise.

Results

Recovery of VO₂ and VCO₂ was delayed in rToF patients, half-life time values were higher compared to controls (T_1/2VO₂ 52.51 ±11.29 s vs. 44.31 ± 10.47 s; p = 0.001 and T_1/2VCO₂ 68.28 ± 13.84 s vs. 59.41 ± 12.06 s; p = 0.002) and percentage drop from maximal value was slower at each minute of recovery (p<0.05). Correlations were found with FS (T_1/2VO₂: r = -0.517; p<0.001; Rec_1minVO₂: r = -0.636, p<0.001; Rec_1minVCO₂: r = -0.373, p = 0.012) and TAPSE (T_1/2VO₂: r = -0.505; p<0.001; Rec_1minVO₂: r = -0.566, p<0.001; T_1/2VCO₂: r = -0.466; p = 0.001; Rec_1minVCO₂: r = -0.507, p<0.001), not with QRS-duration. No difference was found in HR recovery between patients and controls.

Conclusions

Children after rToF show a delayed gas exchange recovery after exercise. This delay correlates to ventricular function, demonstrating its importance in recovery after physical activity.

Effect of aortic stiffness versus stenosis on ventriculo-arterial interaction in an experimental model of coarctation repair

OBJECTIVES

The aim of this study was to investigate the effect of short- versus long-segment aortic stiffness and stenosis on ventriculo-arterial interaction in a porcine model of coarctation repair.

METHODS

Short-long aortic stiffness was created by transection/suture [coarctation (CoA) suture, n = 6] and stenting (stent, n = 5) of the proximal descending aorta. Short-long aortic stenosis was achieved by wrapping a prosthetic graft around the aorta to 1/3-circumference reduction, over a segment length of 1 cm (CoA suture stenosis, n = 5) and 4.5 cm (stent stenosis, n = 6). After 3 months, aortic pressure-flow haemodynamics, aortic distensibility by intravascular ultrasound and left ventricular performance by pressure-volume loops were compared to a Sham group (n = 5) at baseline and during dobutamine administration.

RESULTS

The aortic impedance increased with 30.3 (12.6%) and 41.3 (20.9%) (P < 0.001) in CoA stenosis and stent stenosis during inotropic response. Impaired haemodynamic aortic compliance was associated with lower aortic distensibility by intravascular ultrasound, specifically in long-segment stenosis. The ventriculo-arterial coupling was disturbed in both groups with stenosis, with blunted contractile response [Sham 140.3 (19.8%), CoA suture 101.3 (14.5%), CoA suture stenosis 75.0 (8.4%), stent 115.5 (12.7%), stent stenosis 55.1 (14.6%), P < 0.001] and increased myocardial stiffness during dobutamine in the long-segment aortic stenosis group [Sham -26.0 (12.9%), CoA suture -27.5 (15.9%), CoA stenosis -9.5 (8.6%), stent -23.4 (4.8%), stent stenosis 19.9 (23.1%), P < 0.001].

CONCLUSIONS

This animal study on the sequelae of coarctation repair demonstrated that aortic stiffness had little effect on aortic pressure-flow characteristics in the absence of stenosis. However, the negative chronic effect of stenosis on aortic haemodynamics-especially a longer segment-leads to the rapid impairment of ventriculo-arterial interaction, which is accentuated by inotropy. Therefore, therapeutical management needs to focus on improving aortic remodelling after coarctation repair, preferably by minimizing residual stenosis, even at the cost of inducing aortic stiffness.

Echocardiography during submaximal isometric exercise in children with repaired coarctation of the aorta compared with controls

Objective

Patients with repaired coarctation (RCoA) remain at higher risk of cardiac dysfunction, initially often only detected during exercise. In this study, haemodynamics of isometric handgrip (HG) and bicycle ergometry (BE) were compared in patients with RCoA and matched controls (MCs).

Methods

Case–control study of 19 children with RCoA (mean age 12.9±2.3 years; mean age of repair 7 months) compared with 20 MC. HG with echocardiography followed by BE was performed in both groups.

Results

During HG (blood pressure) BP increased from 114±11/64±4 mm Hg to 132±14/79±7 mm Hg, without significant differences. During HG as well as BE, HR increased less in patients with RCoA. There were no significant differences in (left ventricle) LV dimensions or LV mass.

The RCoA group had diastolic dysfunction: both at rest and during HG they had significantly higher transmitral E and A velocities and lower tissue Doppler E′ and A′ velocities. E/E′ was higher, reaching statistical significance during HG (p<0001).

Conventional parameters of systolic function (FS and EF) were similar at rest and HG. More sensitive tissue Doppler S′ was significantly lower at rest in CoA subjects (5.1±1.5 cm/s vs 6.5±1±1 cm/s; p<0.01), decreasing further during HG by 5% in the CoA group (NS) while unchanged in controls.

Conclusions

We provide first evidence that HG with echocardiography is feasible, easy and patient-friendly. A decreased systolic (tissue Doppler) and impaired diastolic LV function was measured in the RCoA group, a difference that tended to increase during HG.

Myhre syndrome: A first familial recurrence and broadening of the phenotypic spectrum

Myhre syndrome is a rare multisystem connective tissue disorder, characterized by short stature, facial dysmorphology, variable intellectual disability, skeletal abnormalities, arthropathy, cardiopathy, laryngotracheal anomalies, and stiff skin. So far, all molecularly confirmed cases harbored a de novo heterozygous gain-of-function mutation in SMAD4, encoding the SMAD4 transducer protein required for both transforming growth factor-beta and bone morphogenic proteins signaling. We report on four novel patients (one female proband and her two affected children, and one male proband) with Myhre syndrome harboring the recurrent c.1486C>T (p.Arg496Cys) mutation in SMAD4. The female proband presented with a congenital heart defect, vertebral anomalies, and facial dysmorphic features. She developed severe tracheal stenosis requiring a total laryngectomy. With assisted reproductive treatment, she gave birth to two affected children. The second proband presented with visual impairment following lensectomy in childhood, short stature, brachydactyly, stiff skin, and decreased peripheral sensitivity. Transmission electron microscopy (TEM) of the dermis shows irregular elastin cores with globular deposits and almost absent surrounding microfibrils and suggests age-related increased collagen deposition. We report on the first familial case of Myhre syndrome and illustrate the variable clinical spectrum of the disorder. Despite the primarily fibrotic nature of the disease, TEM analysis mainly indicates elastic fiber anomalies.

Differences in cerebral and muscle oxygenation patterns during exercise in children with univentricular heart after Fontan operation compared to healthy peers

BACKGROUND

We assess whether the lower exercise tolerance in children with univentricular heart (UVH) after Fontan operation is associated with altered peripheral muscular and cerebral tissue oxygenation.

METHODS

18 children with UVH and 20 healthy subjects performed an incremental ramp exercise test. Changes in the cerebral and muscular pattern of oxygenated (O₂Hb) and deoxygenated hemoglobin (HHb) and local tissue oxygenation (TOI) were analyzed by means of Near Infrared Spectroscopy (NIRS). Correlations between arterial saturation during exercise and tissue oxygenation were evaluated.

RESULTS

In UVH, maximal oxygen consumption (VO₂peak/kg, 28.9 ± 7.9 vs. 46.3 ± 11.9 ml/min/kg, P < 0.001), heart rate (HRpeak, 168 ± 13 vs. 193 ± 12 bpm, P < 0.001) and load (Ppeak, 73 ± 19 vs. 133 ± 68 W, P < 0.001) were lower, VE/VCO₂ slope was higher (34.5 ± 5.9 vs. 27.1 ± 3.9, P < 0.001). A faster and steeper course up to the same level of HHb and absent increase in O₂Hb was seen at cerebral level in UVH; tissue oxygenation index (TOI) demonstrated a steady decrease from the start of exercise. At the muscular level, HHb curve has a similar pattern compared to controls, with an early cessation. O₂Hb has a similar pattern, but with early discontinuation at a higher O₂Hb-level. Muscular TOI has the same course throughout exercise, starting from a lower level. Lower arterial saturation and higher age correlated with lower VO₂peak; higher amplitude of muscular TOI and lower amplitude cerebral TOI correlated with higher VO₂peak.

CONCLUSION

Children after Fontan procedure have different oxygenation mechanisms at muscular and cerebral level. This reflects a different balance between O₂ supply to O₂ demand which might contribute to the reduced exercise tolerance in this patient population.

Local DRLs and automated risk estimation in paediatric interventional cardiology

Introduction

Cardiac catheterization procedures result in high radiation doses and often multiple procedures are necessary for congenital heart disease patients. However, diagnostic reference levels (DRL) remain scarce. Our first goal was finding the optimal DRL parameter and determining appropriate DRLs. The second goal was to calculate organ doses (OD), effective doses (ED) and lifetime attributable risks (LAR) per procedure and to provide conversion factors based on dose area product (DAP).

Materials and methods

DRLs are calculated for each procedure type, as the 75^th percentile of the cumulative value per procedure from the corresponding parameter. All irradiation events in the DICOM Structured Reports were automatically processed and simulated using PCXMC, resulting in OD, ED and LAR. Using a Kruskal Wallis H test and subsequent pairwise comparisons, differences in median values of the DRL parameter between procedure types were assessed.

Results

Linear regression showed a strong correlation and narrow confidence interval between DAP and product of body weight and fluoroscopy time (BWxFT), even when all procedures (diagnostic and interventional) are combined. Only 15% of the pairwise comparisons were statistically significant for DAP normalized to BWxFT (DAP_BWxFT). The latter pairs contained less frequent procedure types with significant outliers. For DAP normalized to BW (DAP_BW), 38% of the pairwise comparisons showed statistically significant differences. Conversion factors from DAP_BW to OD and ED were reported for various weight groups, due to the higher correlation between DAP_BW and both OD and ED than between DAP and both OD and ED.

Conclusions

The P75 of DAP_BWxFT for all procedures combined serves as an appropriate DRL value. This facilitates local DRL determination in smaller paediatric centres, which often have insufficient data to produce appropriate DRLs for different procedure types. Conversion factors are more reliable starting from DAP_BW instead of DAP and should be used according to the appropriate BW group.

Evaluation of cardiopulmonary exercise testing, heart function, and quality of life in children after allogenic hematopoietic stem cell transplantation

BACKGROUND

Physical fitness is an important determinant of quality of life (QOL) after hematopoietic stem cell transplantation. Cardiac function can influence exercise performance. The aim of this study was to assess these factors and their interrelationship.

PROCEDURE

Children underwent cardiopulmonary exercise testing (CPET) at least 1 year after hematopoietic stem cell transplantation (HSCT) and were compared with healthy controls. Systolic and diastolic heart function and left ventricle (LV) wall dimensions were measured. Health-related QOL (HR-QOL) was evaluated using PedsQL questionnaires.

RESULTS

Forty-three patients performed CPET (26 boys, 13.6 ± 3.4 years, weight 45.5 ± 13.3 kg, length 152.9 ± 17.5 cm, body surface area 1.35 ± 0.28). HSCT patients had lower maximal oxygen consumption (VO2peak/kg, 34.7 ± 8.4 vs 46.3 ± 7.1 mL/kg/min, P < 0.001), shorter exercise duration (9.1 ± 2.5 vs 12.9 ± 2.6 min, P < 0.001), and lower maximal load (%Ppeak 70.8 ± 19.7 vs 102.4% ± 15.9%, P < 0.001). Echocardiography demonstrated decreased interventricular septal wall thickness (interventricular septum in diastole [IVSd] Z-value -0.64 ± 0.69, P < 0.001), and more systolic (11% of patients) and diastolic dysfunction (high E/E' Z-value 1.06 ± 1.13, P < 0.001). LV dilatation correlates with VO2max/kg (r = -0.364, P = 0.017). HR-QOL showed lower overall and emotional functioning scores (respectively, P = 0.016 and P = 0.001). Patients after anthracycline therapy have the lowest maximal exercise performance, but have no difference in QOL. Diminished exercise performance is not encountered as a QOL limitation. Total body irradiation influences the domain of psychosocial functioning.

CONCLUSIONS

LV (systolic and diastolic) and right ventricle dysfunctions justify the need for thorough cardiac follow-up in children after HSCT. Lower physical fitness levels and lower HR-QOL emphasize the importance of CPET and fitness programs.

An Alternative Strategy for Bridge-to-Transplant/Recovery in Small Children with Dilated Cardiomyopathy

Dilated cardiomyopathy in children still has a poor prognosis with high rates of mortality and cardiac transplantation (resp. around 20 and 25%). Awaiting transplantation or possible recovery, these pediatric patients are mechanically supported with extracorporeal membrane oxygenation or a paracorporeal ventricular assist device, both resulting in higher survival rates but also entailing considerable risks of infection, thrombosis, or bleeding. A new indication for an old technique, i.e., pulmonary artery banding, presents itself as an interesting alternative to mechanical circulatory support in selected infants and small children with dilated LV cardiomyopathy and preserved RV function. Here we present a brief review of literature and report on two patients in whom PAB has been successfully implemented as either bridge-to-recovery or bridge-to-transplant.

Early and late outcomes after surgical management of congenital vascular rings

Persistent respiratory or feeding problems in children may be associated with a congenital vascular ring. Surgical management is fairly standardized, but long-term outcomes are not well described. This study aims to investigate clinical presentation, surgical treatment, and risk factors for early mortality and late outcome. Our database revealed 62 surgically treated vascular ring patients between 1993 and 2014. Double aortic arch was the most common diagnosis (53%). Median age at operation was 1 year. Symptoms were mainly respiratory (89%) and feeding problems (32%). Median extubation time and hospital stay were 4 h and 5 days. Mean follow-up was 7.8 ± 5.8 years. Early mortality was 8% and was related to anatomical diagnosis, concomitant anomalies, and a need for preoperative intubation. Freedom from residual symptoms at 1 and 6 months was 63 and 82%, respectively. Freedom from inhalation therapy at the last follow-up was 82% and was influenced by a type of vascular ring and preoperative ventilation. Dysphagia symptoms always disappeared.

CONCLUSION

Surgical relief of tracheoesophageal compression is commonly effective in vascular ring anomalies. Respiratory symptoms necessitating chronic inhalation therapy only persist in a minority of children. Patients with double aortic arch are at increased risk to remain symptomatic, particularly with infectious exacerbations.

The Impact of Oral Intake of Dydrogesterone on Fetal Heart Development During Early Pregnancy

Congenital heart disease is the most frequent form of congenital anomaly in newborn infants and accounts for more than a quarter of all serious congenital afflictions worldwide. A genetic etiology is identified in <20 % of cases of congenital heart defects, and in most cases the etiology remains a mystery. In the context of the health burden caused by congenital heart disease, the contribution of non-inherited risk factors is important especially if it turns out to be caused by a drug which can be avoided during pregnancy. We sought to determine whether maternal dydrogesterone treatment in early pregnancy is associated with congenital heart disease in the infant. We conducted a retrospective case-control study of birth defects and associated risk factors. Data were obtained and compared between 202 children born with congenital heart disease and a control group consisting of 200 children. All children were born in the period of 2010-2013. Dydrogesterone exposure was defined as any reported use during the first trimester of pregnancy. Exclusion criteria included stillbirths, children with chromosomal abnormalities and infants of mothers with chronic medical illnesses, e.g., diabetes. Binary logistic regression analyses were used to analyze the data and attempt to identify a causal relationship between drug exposure and congenital heart disease. Mothers of children born with congenital heart disease received more dydrogesterone during first trimester of pregnancy than mothers of children in the control group [adjusted odds ratio 2.71; (95 % CI 1.54-4.24); P = 0.001]. We identified a positive association between dydrogesterone usage during early pregnancy and congenital heart disease in the offspring. Nevertheless, further studies are needed to confirm these results.

Disease-specific outcome analysis of palliation with the modified Blalock-Taussig shunt

BACKGROUND

Albeit being a simple surgical procedure, adverse outcomes with the modified Blalock-Taussig shunt (MBTS) are commonly reported in generalizing terms, independent of the underlying heart disorder.

METHODS

From August 1995 to December 2013, a total of 150 children underwent an MBTS for tetralogy of Fallot (TOF; n = 44, 29%), pulmonary atresia with ventricular septal defect (PA/VSD; n = 28, 19%), pulmonary atresia with intact ventricular septum (PA/IVS; n = 17, 11%), transposition of the great arteries with ventricular septal defect (TGA/VSD) with pulmonary stenosis (PS; n = 12, 8%), Ebstein malformation (n = 2, 1%), and complex univentricular anomalies (n = 47, 31%). Outcome analysis focused on operative mortality and survival until shunt takedown, adjusted to the underlying disease.

RESULTS

In-hospital mortality was 8.7% (n = 13), and interstage mortality was 5.1% (n = 7), resulting in 86.1% survival to the next surgery. Hospital mortality was 14% in PA/VSD, 13% in univentricular heart, and 18% in PA/IVS, while no mortality was observed in TOF, TGA/VSD/PS, and Ebstein disease. A shunt-related complication was observed in 18% (n = 27) of the children, including acute thrombosis (n = 7, 5%), shunt stenosis (n = 3, 2%), overshunting (n = 7, 5%), and pulmonary artery stenosis (n = 10, 7%). Multivariate analysis of shunt-dependent time survival identified a shunt complication occurring in a univentricular circulation (hazard ratio [HR] 4.10, 95% confidence interval [CI] = 1.05-17.43, P = .01) and increased shunt size-to-weight ratio (HR 2.72, 95% CI = 0.80-9.18, P = .04) as risk factors. Shunt thrombosis was also a negative outcome predictor in PA/VSD, when requiring associated unifocalization (P = .05).

CONCLUSION

This study shows that the outcome of palliation with the MBTS is importantly affected by the occurrence of a shunt-related complication, whose circulatory effect is even more dismal in single ventricle hearts. Since an increased shunt size-to-weight ratio additionally compromises the shunt-dependent survival, it emphasizes that the choice of the shunt with regard to size as well as surgical approach remains critical.

Differential impact of local stiffening and narrowing on hemodynamics in repaired aortic coarctation: an FSI study

Even after successful treatment of aortic coarctation, a high risk of cardiovascular morbidity and mortality remains. Uncertainty exists on the factors contributing to this increased risk among which are the presence of (1) a residual narrowing leading to an additional resistance and (2) a less distensible zone disturbing the buffer function of the aorta. As the many interfering factors and adaptive physiological mechanisms present in vivo prohibit the study of the isolated impact of these individual factors, a numerical fluid-structure interaction model is developed to predict central hemodynamics in coarctation treatment. The overall impact of a stiffening on the hemodynamics is limited, with a small increase in systolic pressure (up to 8 mmHg) proximal to the stiffening which is amplified with increasing stiffening and length. A residual narrowing, on the other hand, affects the hemodynamics significantly. For a short segment (10 mm), the combination of a stiffening and narrowing (coarctation index 0.5) causes an increase in systolic pressure of 58 mmHg, with 31 mmHg due to narrowing and an additional 27 mmHg due to stiffening. For a longer segment (25 mm), an increase in systolic pressure of 50 mmHg is found, of which only 9 mmHg is due to stiffening.

Analysis of the aortic root in patients with tetralogy of Fallot undergoing early repair: form follows function

OBJECTIVE

Aortic root dilatation remains of concern late after repair for tetralogy of Fallot (ToF). We have previously demonstrated that the aortic root size decreases progressively after early correction. To test whether the aortic wall changes are intrinsic or acquired, a histologic study was performed of infants at early repair.

METHODS

From 24 of 31 infants undergoing ToF repair (mean age, 5.9±4.9 months), ascending aortic biopsies were obtained. After conventional staining, the specimens were given a histologic score (0-3) for medionecrosis, ground substance accumulation, fibrosis, smooth muscle cell disarray, and apoptosis. The aortic root diameters were monitored using echocardiography for ≤2 years postoperatively.

RESULTS

Nearly one half of the specimens showed signs of fibrosis (45%), with increased mucoid accumulation in 15% and elastin fragmentation in 5%. The aortic root was dilated in all infants at operation (mean indexed diameter-annulus, 38.1±5.8; sinus, 47.8±6; sinotubular junction, 38.7±5.4 mm/m2) and had regressed significantly within 2 years (mean indexed diameter-annulus, 27.9±4.7; sinus, 36.4±5.1; sinotubular junction, 30.4±6 mm/m2; P<.0001). The total histology score showed no correlation with indexed diameter regression at 2 years.

CONCLUSIONS

Infants with ToF undergoing repair around 6 months old already had limited features of aortic wall degradation at surgery. Echocardiographic follow-up, however, demonstrated significant reductions in the indexed aortic diameters. We presume that early repair of ToF will prevent a disproportionate aortic diameter increase by halting progression of the limited histologic changes potentially predisposing to late aortic dilatation.

Functional analysis of the anatomical right ventricular components: should assessment of right ventricular function after repair of tetralogy of Fallot be refined?

OBJECTIVE

Follow-up after tetralogy of Fallot (ToF) repair is directed to detect timely right ventricular (RV) dysfunction by following pulmonary regurgitation and global RV size, with little attention for the effective contribution of regional RV dysfunction. This study investigates the contribution of regional RV dysfunction on exercise capacity after ToF repair.

METHODS

Forty-two patients were investigated with cardiac magnetic resonance imaging for regional RV dysfunction in relation to global RV function by functional quantification of the sinus and outflow part of the RV. The impact of regional and global RV dysfunction on clinical status was studied by exercise testing.

RESULTS

Global RV function was lower than sinus function (ejection fraction (EF) 52±12% vs 58±10%, P<0.001), attributable to the adverse influence of right ventricular outflow tract (RVOT) dysfunction (EF 34±17%). Percent predicted peak VO2 correlated better with the RV sinus ejection fraction compared with the global RV ejection fraction (r=0.51, P=0.001 vs r=0.44, P=0.004). Multivariate analysis revealed the EF of RV sinus (β=0.34, 95% CI 0.07-0.61, P=0.013) and the extent of RVOT akinesia (β=-0.28, 95% CI -0.50; -0.06, P=0.015) as significant determinants of exercise capacity. Impaired exercise performance occurred in 43% of the patients, and was independently determined by the type of repair (transventricular vs transatrial: OR 6.0, 95% CI 1.31-17.3, P=0.02) by associating greater sinus and RVOT dysfunction.

CONCLUSION

Functional analysis of the RV components shows that exercise capacity after repair of ToF is better predicted by systolic function of the RV sinus as the extent of RVOT dysfunction commonly leads to underestimation of global RV function. This method of differential quantification of regional RV function might be more appropriate than assessment of global RV function during the long-term follow-up of repaired ToF patients.

Assessment of a right-ventricular infundibulum-sparing approach in transatrial-transpulmonary repair of tetralogy of Fallot

OBJECTIVE

The study aimed to evaluate the outcome of transatrial-transpulmonary repair of tetralogy of Fallot in relation to a right-ventricular outflow tract (RVOT)-sparing surgery.

METHODS

Based on the surgical management of right-ventricular outflow tract obstruction (RVOTO) at repair of tetralogy of Fallot, 140 children were retrospectively divided into three groups: (1) pulmonary valve (PV)-sparing, (2) infundibulum-sparing and (3) extended trans-annular patch (TAP). Clinical and echocardiographic outcome was assessed with regards to three equally divided study time eras between January 1994 and June 2010.

RESULTS

Over a 15-year study period, median age decreased from 11 (2-101) to 5 (1-11) months (p<0.001), whereas type of RVOT repair changed significantly between the first and the last era (group 1: 18-40%, group 2: 25-40% vs group 3: 57-20% (p=0.002)). Mortality was 0%. Complications were mainly related to clinical restrictive RV physiology (27%) and arrhythmia (10%). This cardiac morbidity remained constant over the eras and was associated with younger age (p=0.04), increased postoperative right ventricle/left ventricle (RV/LV) pressure ratio (p=0.01) and type of RVOT repair at the cost of TAP (p=0.03). Median follow-up of 8 years (1-16 years) showed an overall freedom from RVOT re-operation of 84% and 73%, respectively at 5 and 10 years. Most re-operations were for residual/recurrent RVOTO (12%) occurring more frequently in the latter era: 16% versus 7% in era 1 (p=0.08). Late echocardiographic evaluation revealed a strong correlation between severity of pulmonary regurgitation and increased RV/LV size ratio, which was mainly determined by increased TAP length (p<0.001) and duration of follow-up (p=0.06).

CONCLUSION

In a 15-year's experience with transatrial-transpulmonary correction of tetralogy of Fallot, a valve- and infundibulum-sparing approach has been advanced by lowering the age for elective repair. This change has been performed without compromising immediate clinical outcome, despite an increased early re-operation rate for residual obstruction. However, longer follow-up will disclose whether this approach is protective against progressive and late RV dysfunction.

Pulmonary function in children after surgical and percutaneous closure of atrial septal defect

This study aimed to study differences in lung function after surgical and percutaneous atrial septal defect (ASD) closure. Several studies have demonstrated abnormalities of pulmonary function in adults and children with ASD. These abnormalities persist even a few years after correction. This study compared pulmonary function between patients who underwent ASD closure by surgery and those who had closure by device. This is the ideal pediatric population for studying changes in lung function caused by cardiopulmonary bypass or sternotomy. The 46 patients in this study were treated by percutaneous closure (group 1) or surgical closure (group 2) of ASD and then scheduled for pulmonary function testing an average of 5.8 years after ASD closure. The mean values of functional residual capacity, total lung capacity, and residual volume did not differ between the two groups. The surgical group showed a significant decrease in expiratory reserve volume (p < 0.04) and forced vital capacity (p < 0.03). Expiratory flow at 25, 50, and 75% of forced vital capacity did not differ between the two groups but was on the lower limit of normal in both groups. Percutaneous closure of ASD can minimize the side effects of surgical closure on lung function. Longitudinal lung function follow-up assessment after cardiac surgery is warranted to detect and measure restrictive abnormalities in this type of congenital heart disease and others.

The fate of the aortic root after early repair of tetralogy of Fallot

OBJECTIVE

Late aortic root dilatation is a growing concern in patients operated on for tetralogy of Fallot (ToF). This longitudinal follow-up study sought to evaluate the changes in the aortic root dimensions in relation to body growth, assuming that early repair of tetralogy of Fallot might prevent late aortic dilatation.

METHODS

A retrospective analysis of the aortic root dimensions was performed in 88 patients repaired early for tetralogy of Fallot by echocardiographic measurement of aortic annulus, sinus of Valsalva and sinotubular junction, adjusted for body surface area and expressed as z-scores. Mean age at repair was 9.7 + or - 7.4 months. Median age was 7.3 months (range 45 days-29 months).

RESULTS

At the time of repair, all root dimensions were enlarged: z-score of the annulus 3.32 + or - 1.66; sinus 3.54 + or - 1.49; sinotubular junction 2.74 + or - 1.19. Within a mean follow-up of 6.9 + or - 4.4 years, the mean z-scores of both annulus and sinotubular junction significantly decreased to normal size at 7 years postoperatively: z-score of annulus 0.95 + or - 0.7 (p=0.006), z-score of sinotubular junction 0.99 + or - 1.47 (p=0.006). The z-score of the aortic sinuses appeared to regress slower to 2.78 + or - 1.26 (p=0.262). The indexed sinus diameter however regressed significantly from a mean of 51.4 + or - 13.4 mmm(-2) at correction to 28.9 + or - 7.2 mmm(-2) (p=0.0001) at latest follow-up. Evolution of aortic root size after repair was independent of aortic arch side, sex, age at repair or previous shunt palliation.

CONCLUSIONS

The initially dilated aortic root in tetralogy of Fallot normalises in size at the level of the annulus and sinotubular junction within 7 years after early repair. This process seems delayed at the level of the aortic sinuses, although the indexed root diameter shows significant regression over time. These results suggest that early repair of ToF abrogates the enlargement of the aortic root, validating one aspect of the need for tetralogy correction at a young age.

Three-dimensional rotational angiography of a patient with pulmonary atresia intact septum and coronary fistulas

Three-dimensional rotational angiography (3D-RA) was used to image the coronary arteries of a 2(1/2)-year-old boy with pulmonary atresia intact septum and coronary fistulas. As seen in the accompanying video clips and stills, this imaging method is advantageous in depicting the coronary anatomy. Furthermore, less contrast is used for patients undergoing diagnostic coronary angiography with 3D-RA compared with biplane angiography.

Catecholaminergic polymorphic ventricular tachycardia in a child: a case report

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare arrythmogenic disease characterized by exercise--or stress--induced ventricular tachyarrythmias, syncope, or sudden death, usually in the pediatric age group. Familial occurrence has been noted in about 30% of cases. Inheritance may be autosomal dominant or recessive, usually with high penetrance. The causative genes have been mapped to chromosome 1. Mutations of the cardiac ryanodine receptor gene (RyR2) have been identified in autosomal dominant pedigrees, while calsequestrin gene (CASQ2) mutations are seen in recessive cases.

CONCLUSION

Due to its potential lethal outcome, exclusion or confirmation of catecholaminergic polymorphic ventricular tachycardia in children with physical and emotional syncope is mandatory. We report a case of catecholaminergic polymorphic ventricular tachycardia in a three-year-old child only diagnosed by genetic mapping.

Transcatheter closure of secundum atrial defect in small children

OBJECTIVE

To assess safety and efficacy of transcatheter atrial septal defect (ASD) closure in small children.

BACKGROUND

Percutaneous closure of ASD is a well accepted alternative to surgery. Reported experience in small children remains, however, scarce.

METHODS

Fifty-two children underwent percutaneous ASD closure at a weight < or =15 kg, in four Belgian tertiary referral paediatric cardiology centers. Indication for treatment, device implantation rate, procedural details, complication rate, residual shunt on echocardiography, and impact of procedure on symptoms were retrospectively analyzed.

RESULTS

Mean age at procedure was 36 months (7-60), mean weight 13 kg (4.7-15). Associated cardiac lesions were seen in 21% of the patients and noncardiac in 32.7%. Most patients (69.2%) were symptomatic. Mean ASD size was 12 mm (range 5-20 mm). A device could be inserted in 49 patients (94%). No major complications occurred. Minor complications occurred in 8 patients (15.4%) including device embolization in 2, successfully treated with transcatheter retrieval and second device insertion. Mean follow-up reached 27 months (0.03-61.2). Residual shunt was absent, trivial, or small in 93% (n = 42) at latest follow-up. Clinical improvement was noted in 91.7% of the symptomatic patients. Minor complications were more frequent in the presence of large ASDs (>15 mm) but not in smaller babies (<10 kg).

CONCLUSION

Patients < or =15 kg requiring ASD closure form a special population with high incidence of associated anomalies and medical conditions. For this particular set of patients, percutaneous closure is a valid alternative. Asymptomatic or mildly symptomatic children should be treated at a later age.

Gap junctional communication among motor and other neurons shapes patterns of neural activity and synaptic connectivity during development

We are studying the functional roles of neuronal gap junctional coupling during development, using motor neurons and their synapses with muscle fibers as a model system. At neuromuscular synapses, several studies have shown that the relative pattern of activity among motor inputs competing for innervation of the same target muscle fiber determines how patterns of innervation are sculpted during the first weeks after birth. We asked whether gap junctional coupling among motor neurons modulates the relative timing of motor neuron activity in awake, behaving neonatal mice. We found that the activity of motor neurons innervating the same muscle is temporally correlated perinatally, during the same period that gap junction-mediated electrical and dye coupling are present. In vivo blockade of gap junctions abolished temporal correlations in motor neuron activity, without changing overall motor behavior, motor neuron activity patterns or firing frequency. Together with preliminary studies in mice lacking gap junction protein Cx40, our data suggest that developmentally regulated gap junctional coupling among motor and other neurons affects the activity in nascent neural circuits and thus in turn affects synaptic connectivity. Dynamic monitoring of dye coupling can be used to explore this possibility in normal mice and in mice lacking gap junction proteins during embryonic and neonatal development.