Superior vena cava and innominate vein dimensions in growing children : an aid for interventional devices and transvenous leads

Transvenous Lead Extraction in Pediatric Patients - Is It the Same Procedure in Children as in Adults?

BACKGROUND

Cardiac implantable electronic devices (CIED) are very rare in the pediatric population. In children with CIED, transvenous lead extraction (TLE) is often necessary. The course and effects of TLE in children are different than in adults. Thus, this study determined the differences and specific characteristics of TLE in children vs. adults.

METHODS AND RESULTS

A post hoc analysis of TLE data in 63 children (age ≤18 years) and 2,659 adults (age ≥40 years) was performed. The 2 groups were compared with respect to risk factors, procedure complexity, and effectiveness. In children, the predominant pacing mode was a single chamber ventricular system and lead dysfunction was the main indication for lead extraction. The mean implant duration before TLE was longer in children (P=0.03), but the dwell time of the oldest extracted lead did not differ significantly between adults and children. The duration (P=0.006) and mean extraction time per lead (P<0.001) were longer in children, with more technical difficulties during TLE in the pediatric group (P<0.001). Major complications were more common, albeit not significantly, in children. Complete radiographic and procedural success were significantly lower in children (P<0.001).

CONCLUSIONS

TLE in children is frequently more complex, time consuming, and arduous, and procedural success is more often lower. This is related to the formation of strong fibrous tissue surrounding the leads in pediatric patients.

A reappraisal of pediatric thoracic surface anatomy

Accurate knowledge of surface anatomy is essential for physical examination, invasive procedures, and anatomy education. Individual factors such as age make surface landmarks variable so accurate descriptions are needed. The aim of this study is to describe age-related surface landmarks for intrathoracic structures in children. A total of 156 thoracic computed tomography scans of children aged 0-18 years were categorized into six groups, and the associations between major intrathoracic structures and surface landmarks were analyzed. Sternal angle is an accurate surface landmark for the azygos vein-superior vena cava junction in all age groups. However, the aortic arch (except in the 0-1 year group), the bifurcation of the pulmonary trunk and the tracheal bifurcation in those aged 15-18 years were not within this plane. The left brachiocephalic vein was located behind the ipsilateral sternoclavicular joint except in the 1-3 years group, and the right was behind it in children older than 6 years. The apex of heart was at the 5th intercostal space level in the 0-1 and 12-18 years groups; however, it was higher in the other groups. The lower borders of the lungs were at the sixth costal cartilage level in the midclavicular line, eighth intercostal space level in the midaxillary line, and T12 adjacent to the vertebral column in the 15-18 years group; the lower borders were at higher levels in younger children. Defining the variations in surface anatomy by in vivo studies will increase its clinical and pedagogical value.

Case series of late lead dislodgement of Medtronic SelectSecure 3830 pacing leads in growing paediatric patients

Background 

The SelectSecure lumenless 3830 pacing lead is often considered to be the pacing lead of choice for transvenous pacing in children because of its small diameter, lead strength, and reliable long-term sensing and pacing characteristics. One of the potential long-term pitfalls of a sturdy pacing lead is relative retraction with growth in children resulting in late lead dislodgement.

Case summary 

We report two cases of late SelectSecure 3830 lead dislodgement at 11.8 years (Case 1) and 8.8 years (Case 2), respectively, post the initial implantation. Case 1 was diagnosed with congenital complete heart block (CHB) at 9 months old when he presented with unconfirmed diphtheria infection. Case 2 was diagnosed with CHB at 14 weeks of age with positive maternal anti-Ro antibodies. Both patients underwent implantation of a transvenous permanent pacemaker implantation with Medtronic SelectSecure 3830 lead due to symptomatic bradycardia. Apart from a pulse generator change at 8.5 years (Case 1) and 7 years (Case 2), respectively, post-implant due to normal battery depletion, both patients are well in the interim.

Discussion 

As part of the pacemaker follow-up for rapidly growing children, we recommend more frequent surveillance of lead ‘tautness’ by chest radiography especially in children with CHB with no underlying heart rhythm.

Endovascular Neuromodulation: Safety Profile and Future Directions

Endovascular neuromodulation is an emerging technology that represents a synthesis between interventional neurology and neural engineering. The prototypical endovascular neural interface is the Stentrode^TM, a stent-electrode array which can be implanted into the superior sagittal sinus via percutaneous catheter venography, and transmits signals through a transvenous lead to a receiver located subcutaneously in the chest. Whilst the Stentrode^TM has been conceptually validated in ovine models, questions remain about the long term viability and safety of this device in human recipients. Although technical precedence for venous sinus stenting already exists in the setting of idiopathic intracranial hypertension, long term implantation of a lead within the intracranial veins has never been previously achieved. Contrastingly, transvenous leads have been successfully employed for decades in the setting of implantable cardiac pacemakers and defibrillators. In the current absence of human data on the Stentrode^TM, the literature on these structurally comparable devices provides valuable lessons that can be translated to the setting of endovascular neuromodulation. This review will explore this literature in order to understand the potential risks of the Stentrode^TM and define avenues where further research and development are necessary in order to optimize this device for human application.

Improving pacemaker therapy in congenital heart disease: contractility and resynchronization

Designed as effective therapy for patients with symptomatic bradycardia, implantable cardiac pacemakers initially served to improve symptoms and survival. With initial applications to the elderly and those with severe myocardial disease, extended longevity was not a major concern. However, with design technology advances in leads and generators since the 1980s, pacemaker therapy is now readily applicable to all age patients, including children with congenital heart defects. As a result, emphasis and clinical interests have advanced beyond simply quantity to quality of life. Adverse cardiac effects of pacing from right ventricular apical or epicardial sites with resultant left bundle branch QRS configurations have been recognized. As a result, and with the introduction of newer catheter-delivered pacing leads, more recent studies have focused on alternative or select pacing sites such as septal, outflow tract, and para-bundle of His. This is especially important in dealing with pacemaker therapy among younger patients and those with congenital heart disease, with expected decades of artificial cardiac stimulation, in which adverse myocellular changes secondary to pacing itself have been reported. As a correlate to these alternate or select pacing sites, applications of left ventricular pacing, either via the coronary sinus, intraseptal or epicardial, alone or in combination with right ventricular pacing, have gained interest for patients with heart failure. Although cardiac resynchronization pacing has, to date, had limited clinical applications among patients with congenital heart disease, the few published reports do indicate potential benefits as a bridge to cardiac transplant.

Normative MDCT cross-sectional data estimation of superior vena cava and innominate vein in growing children using age as a predictor

This retrospective study aimed to determine the superior vena cava (SVC) and left innominate vein (INV) normative cross-sectional area in children noninvasively using age as a predictor and also to compare the correlation of the area measured with the diameter on multidetector computed tomography (MDCT). Analysis of the SVC-INV cross-sectional area was performed for 73 consecutive patients. The cross-sectional area of the SVC-INV was manually estimated. A regression analysis was performed for the cross-sectional area and age separately, and regression equations were compared. One-way analysis of variance (ANOVA) was performed to evaluate significant differences in the area means according to age groups. Regression analysis showed that age can be a predictor for the area of the SVC (50.6 mm(2) + 1.01 × age), te INV (48.3 mm(2) + 0.93 × age), and the left SVC-INV junction (47.2 mm(2) + 0.92 × age), with respective R(2) values of 93, 88 and 94%. The comparative evaluation of the cross-sectional area and the diameter measurement of SVC showed that the cross-sectional area was more closely associated with the increasing age of the cohort (R(2) of 68 vs. 61%) than the measured diameter. For a cohort of patients without congenital or acquired heart disease, MDCT can be used as a complementary test for a normative cross-sectional normogram area database of SVC-INV using age as a predictor.

Pacing device therapy in infants and children: a review

The number of pediatric pacemakers implanted is still relatively small. Children requiring pacing therapy have characteristics that are distinct from those of adults, including physical size, somatic growth, and cardiac anomalies. Considering these features, long-term follow-up of pediatric pacemaker implantation is necessary. Selection of appropriate generators, pacing modes, pacing sites, and leads is important. Generally, epicardial leads are commonly used in small infants. On the other hand, the use of endocardial leads in children is increasing worldwide because of their benefits over epicardial leads, such as minimal invasiveness, lower pacing threshold, and longer generator longevity. Endocardial leads are not suitable for patients with intracardiac shunts because of the high risk of systemic thrombosis. Venous occlusion is another significant problem with endocardial leads. With the increase in the number of pacing device implantations, the incidence of infection from such devices is also increasing. Complete device removal is sometimes recommended to treat device infection, but experience in the removal of endocardial leads in children is still scarce. This article gives an overview of pacing therapy in the pediatric population, including discussions on new pacing systems, such as remote monitoring systems, magnetic imaging compliant pacemaker systems, and leadless pacing devices.

Quantification of ventricular volume load in the context of a bidirectional cavopulmonary shunt: a theoretical treatise

BACKGROUND

Functional univentricular hearts are currently palliated by a staged procedure of which the bidirectional cavopulmonary shunt is usually the second stage. In addition to this stage, a calibrated amount of additional pulmonary blood flow may be preserved to promote pulmonary artery growth and increase the length of the interval preceding the total cavopulmonary connection. However, additional pulmonary blood flow can be deleterious for ventricular functioning and development as it increases functional ventricular volume load.

METHODS

Using the Fick principle we devised a theoretic framework to estimate the ventricular volume loading caused by additional pulmonary and collateral aortopulmonary flow. To use this framework, blood samples need to be taken intraoperatively from the aorta, pulmonary veins, and inferior caval vein to determine oxygen saturations. The oxygen saturation samples have to be taken sequentially with and without additional pulmonary blood flow.

RESULTS

The objective of this paper is to provide a theoretic framework to estimate the ventricular volume loading caused by collateral aortopulmonary flow and additional pulmonary blood flow in the context of a bidirectional cavopulmonary shunt in the staged palliation of univentricular hemodynamics. The formulas have not yet systematically been applied in vivo.

CONCLUSIONS

The added volume loading of the ventricle caused by additional pulmonary blood flow can theoretically be estimated using the newly devised formulas so as to calibrate ventricular volume loading to a desired level intraoperatively.

Permanent epicardial pacing in children: long-term results and factors modifying outcome

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.

Extravascular lung water measurement using transpulmonary thermodilution in children

OBJECTIVE

Measurement of extravascular lung water (EVLW) may be useful in the treatment of critically ill children and can be performed at the bedside using the transpulmonary thermodilution technique (TPTD). There are currently no data to verify the accuracy of these measurements in (small) children. We compared the results of TPTD measurement with the clinical gold standard transpulmonary double indicator dilution (TPDD) measurement in young children.

DESIGN

Prospective clinical study in children.

SETTING

Catheterization laboratory of a university hospital.

PATIENTS AND METHODS

Twelve children (<2 yrs or <12 kg) under general anesthesia.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Measurements were performed using injections of ice-cold indicator (saline or dye) through a central venous catheter. Mean cardiac index was 3.91 L/min/m, mean intrathoracic blood volume index (ITBVITPDD) was 614.9 mL/m, and mean extravascular lung water index (EVLWITPDD) was 11.7 mL/kg. The correlation coefficient between EVLWITPDD and EVLWITPTD is 0.96 (95% confidence interval: 0.87-0.99; p < 0.0001). Bland-Altman analysis for EVLW measurements showed a mean bias of 2.34 mL/kg (18.13%) and limits of agreement +/-2.97 mL/kg (19.78%). The difference between measurements via the right atrium compared with the femoral vein was 2.8% for cardiac output, 8.2% for global end-diastolic volume, and 0.1% for EVLW.

CONCLUSION

Clinical measurement of EVLW in young children can be performed using the TPTD with the injection catheter inserted in the femoral vein. Further studies are needed to clarify the clinical value of these measurements.