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The SelectSecure™ catheter delivery system and active fixation 4.1 French diameter Model 3830 pacing lead (Medtronic, Inc, Minneapolis, MN, USA) has the advantage of permitting precise implant at nearly any desired location due to catheter maneuverability. However, as the lead lacks an internal stylet lumen, it is intrinsically floppy and any repositioning after the delivery catheter is removed is nearly impossible, necessitating lead extraction and a repeat of the implant process. At present, there are no commercially available tools to precisely reposition this lead. This report presents a simplified approach to reimplant a dislodged Model 3830 lead using currently available materials to create an effective maneuverable and removable encircling snare.

Background:Transvenous pacemaker leads in children are often placed with redundant lead length to allow for anticipated patient growth. This excess lead may rarely prolapse into the pulmonary artery and potentially interfere with valve function. We sought to determine the response to lead repositioning on pulmonary valve insufficiency. Methods:Retrospective reviews of demographics, lead type, implant duration, and radiography and echocardiography. Results:A total of 11 pediatric patients were identified with lead prolapse through the pulmonary valve, of which nine patients underwent procedures to retract and reposition the lead (age at implant 9 ± 4 years, age at revision 13 ± 4 years). The implant duration prior to revision was 4 ± 3 years. Two leads required radiofrequency extraction sheaths for removal, two pulled back using a snare, while five leads were simply retracted and repositioned. Tricuspid regurgitation was none/trivial (three), mild (four), or moderate (two) and only two improved with repositioning or replacement. Pulmonary regurgitation preoperatively was mild (three), mild-moderate (two), or moderate (four) compared with trivial (three), mild (four), and moderate (two) after revision. Patients with longer-term implanted leads had less improvement in pulmonary insufficiency. Two patients had mild pulmonary stenosis from lead-related obstruction. Conclusions:Prolapse of transvenous pacing leads into the pulmonary artery can occur when excess slack is left for growth. Leads can often be repositioned, but may require extraction and replacement, particularly if chronically implanted and adherent to valve apparatus. Lead revision does not always resolve pulmonary insufficiency, potentially leaving permanent valve damage.

Standard, 5-7-Fr diameter pacing leads (PLs) can adversely affect atrioventricular valve (AVV) and venous (superior vena cava [SVC], innominate [INN]) integrities. Although chronic pacing/sensing performances have been reported on the steroid-eluting, lumenless, 4.1-Fr PL (Model 3830, Medtronic Inc., Minneapolis, MN, USA), comparative valve and venous effects are largely unknown.Patients (n = 134) were divided into two PL groups: Group 1 (n = 65, Model 3830) and Group 2 (n = 69, various 5-7 Fr models) and followed up to 9 years postimplant. Patient demographics, clinical findings, valve function, and venous dimensions were reviewed. Statistical significance was defined as P0.05.Patient implant age (mean 16.4 years vs 17.3 years), presence of congenital heart defect (CHD), and preexisting valve issues were comparable between groups. New or worsening valve insufficiency occurred in 12% of Group 1 patients (mean follow-up 4.3 ± 2.8 years) and 27% of Group 2 patients (mean follow-up 6.2 ± 3.5 years; P0.05). Significant SVC or INN narrowing was found in 11 % of Group 1 and 24% of Group 2 patients (P = 0.0004). All Group 1 patients12 years of age showed normal while 50% of those from Group 2 exhibited stunted SVC or INN growth (P0.05).The lumenless, 4.1-Fr diameter PL offers improved clinical benefits, better AVV integrity, and venous development compared with larger 5-7-Fr diameter PL and should be considered especially in younger patients with/without CHD.

As a pumping organ with an intrinsic electrical system, the heart is unique. For most individuals, it remains efficient for decades. However, as a pump, it can fail. Often the failure is due to inherent or acquired problems with the electrical system. Failure of maintenance of normal sinus rhythm often results in adverse or no heart rhythm, a term referred to as “arrhythmias.” These can result in the heart rate being too fast (“tachy-”) or too slow (“brady-”) and alter blood flow resulting in patient morbidities and mortalities. Arrhythmias can occur anywhere in the heart and may not always be caused by any adverse lifestyle events such as coronary disease. Certain inherited congenital heart defects can cause abnormalities within the developing electrical system that can appear even before birth. Alternatively, the simple process of normal aging can adversely affect the heart’s ability to maintain normal rhythms. Once initiated, arrhythmias can be sustained by the normal anatomical variations of cardiac structures. There are three common arrhythmia etiologies: “automaticity” “reentry,” and “triggered.” Automaticity results from alterations of the basic cellular ion exchange mechanism which is depicted as a distinct electrical pattern, the action potential. Once an electrical impulse is initiated, it typically propagates cell to cell in a relatively uninterrupted fashion. However, if an obstruction (valves, veins) or postinfarction scar tissue occurs, the impulse can circle around the obstruction, creating a reentrant pathway. In rare instances, drugs or disease states can alter cell action potentials, triggering abnormal impulse initiation. This chapter will address all of these issues.

Endomyocardial biopsy is the gold standard survey for cardiac graft rejection. Signal-averaged electrocardiography (SAECG) identifies slowly conducting, diseased myocardium. We sought to determine whether SAECG is a sensitive, noninvasive transplant surveillance method in the young.Ninety-four SAECGs recorded prior to biopsy in 20 young transplant (OHT) patients and those from 15 healthy age-matched controls (CTL) were analyzed. In the OHT group, 56 no-rejection (NOREJ) (ISHLT grades 0 or 1 A) and 37 acute rejection (REJ) (ISHLT grades IB, 2, and 3A) SAECGs were compared, SAECGs were filtered at 40-255 Hz. Total QRS duration (QRSd), duration of terminal low amplitude of QRS under 40 microV (LAS), and root mean square amplitude of terminal 40 msec of QRS (RMS40) were compared.SAECGs were significantly different in CTL vs NOREJ but not in NOREJ vs REJ: QRSd, 81.7 +/- 8, 107.2 +/- 18.4, and 112.3 +/- 21.6 msec, respectively; LAS, (18 +/- 5.8, 23.6 +/- 10.7, and 27 +/- 14.8 msec, respectively; and RMS40, (169.3 +/- 100.4, 68 +/- 48.8, and 57.5 +/- 45.6 microV, respectively. Children following OHT exhibited significant differences in the SAECG compared to controls. Differences between the NOREJ and REJ groups were negligible. Therefore, SAECG may not be effective in detecting OHT rejection in the young.

Objectives Our objective was to evaluate the short-term safety and efficacy of cardiac resynchronization therapy (CRT) in children. Background Cardiac resynchronization therapy has been beneficial for adult patients with poor left ventricular function and intraventricular conduction delay. The efficacy of this therapy in the young and in those with congenital heart disease (CHD) has not yet been established. Methods This is a multi-center, retrospective evaluation of CRT in 103 patients from 22 institutions. Results Median age at time of implantation was 12.8 years (3 months to 55.4 years). Median duration of follow-up was four months (22 days to 1 year). The diagnosis was CHD in 73 patients (71%), cardiomyopathy in 16 (16%), and congenital complete atrioventricular block in 14 (13%). The QRS duration before pacing was 166.1 ± 33.3 ms, which decreased after CRT by 37.7 ± 30.7 ms (p Conclusions Cardiac resynchronization therapy appears to offer benefit in pediatric and CHD patients who differ substantially from the adult populations in whom this therapy has been most thoroughly evaluated to date. Further studies looking at the long-term benefit of this therapy in this population are needed.

Eight patients with venous obstruction secondary to Mustard baffle obstruction or previous transvenous pacemaker leads underwent intravascular stent relief of their obstructions followed by the insertion of new leads. Patients were followed from 1.3 to 6.3 years (median 3) by clinical, hemodynamic, angiographic, and intravascular ultrasound methods and pacemaker evaluations. The median stent patency was 84%, with 1 patient developing complete stent occlusion. Pacing energy thresholds and impedances remained unchanged.

A multicenter prospective study was performed to assess the results and risks associated with radiofrequency ablation in children. This report focuses on recurrences following initially successful ablation.Patients recruited for the study were aged 0 to 16 years and had supraventricular tachycardia due to accessory pathways or atrioventricular nodal reentrant tachycardia (AVNRT), excluding patients with more than trivial congenital heart disease. A total of 481 patients were recruited into the prospective cohort and were followed at 2, 6, and 12 months following ablation.There were 517 successfully ablated substrates out of 540 attempted (95.7%). Loss to follow-up for individual substrates was 3.3%, 10.6%, and 21.2% at 2, 6, and 12 months, respectively. Recurrence was observed in 7.0%, 9.2%, and 10.7% of these substrates at 2, 6, and 12 months, respectively (adjusted for loss to follow-up as an independent source of data censoring). Recurrence rate varied by substrate location (24.6% for right septal, 15.8% for right free wall, 9.3% for left free wall, and 4.8% for left septal), as well as for AVNRT versus all others (4.8% vs 12.9%) at 12 months. The recurrence rate was higher for substrates ablated using power control but was not a function of whether isoproterenol was used for postablation testing.Recurrence after initially successful ablation occurs commonly in children. It is least common after AVNRT ablation and most common following ablation of right-sided pathways. These results serve as a benchmark for the time course of recurrence following initially successful ablation of supraventricular tachycardia in children.

Background: Transthoracic echocardiography (TTE) is reliable for detection of thrombi in the left ventricle and right atrium, but not in the left atrial appendage. Therefore, transesophageal echocardiography (TEE) is routinely performed in adults prior to electric cardioversion for atrial flutter/fibrillation (AFF). Whetheryoung survivors of congenital heart disease repair with AFF need routine TEE prior to electric cardioversion is unknown. Hypothesis: Electric cardioversion for AFF is safe in survivors of congenital heart disease repair/palliation if an intracardiac thrombus is not suspected on TTE imaging. Methods: This study reports the outcome of patients in a pediatric tertiary care cardiac unit where electric cardioversion was performed if no intracardiac thrombus was suspected on TTE. We performed a retrospective chart review of all patients treated with electric cardioversion for AFF at Children's Hospital of Michigan during 1997-2002. Results: Of 35 patients who presented with 110 episodes of AFF requiring electric cardioversion during the study duration, 32 (age 3 months-49 years, median age 20.5 years, 104 AFF episodes) had previously undergone palliative surgery or repair of their congenital heart disease. Of these 32 patients, 18 were survivors of a Fontan palliation (for a single-ventricle variant) and the remaining 14 were survivors of other defects and repairs (septal defects, valve replacements, and tetralogy of Fallot). During 81% of the episodes, patients were receiving aspirin, warfarin, or heparin for anticoagulation at presentation. Transthoracic echocardiography was performed in 74 AFF episodes; of these, 10 TTE studies were suspicious for atrial thrombi. Transesophageal echocardiography confirmed the presence of athrombus in 3 of these 10 patients. These patients received warfarin for 2 weeks and then underwent electric cardioversion. No thromboembolic events occurred immediately after or on follow-up in any patient. Conclusions: These findings suggest that TTE may be an effective imaging tool for precardioversion screening in young patients with AFF.

Cardiac stimulation from right ventricular apical or free-wall lead positions alters inter- and intraventricular impulse conduction and distorts biventricular contractility. This may contribute to eventual cellular remodeling and the development of histopathological changes which, over time, adversely affect left ventricular systolic and diastolic functions. This concept has especially important implications when pacemaker therapy is initiation in young patients. Recent studies demonstrating physiological benefits of right ventricular septal, outflow, or bundle of His pacing, in deference to the apical implant site, have gained interest to potentially prevent dysfunction and improve paced myocardial contractility. Pacing initiated in children can be expected to have more far-reaching consequences than pacing initiated in the elderly. Unfortunately, there have been limited clinical pediatric studies that evaluate precise site-specific lead locations. This current report presents a review of pacemaker applications in children, both with and without structural congenital heart defects, including the earliest applications in which patient survival was the prime concern, to more recent studies attempting to optimize physiological and histological parameters associated with pacemaker induced contractility. The past decade has seen direct evidence that right ventricular apical pacing in children contributes to adverse histological remodeling and eventual contractile dysfunction. More recent studies demonstrate that selective site pacing can be effectively applied to all children with and without structural congenital defects and shows promise in the prevention of previously documented adverse remodeling and deterioration of systemic ventricular contractility.

The aim of this study was to determine if single chamber rate responsive ventricular pacing (VVIR) predisposes growing children to develop pacemaker syndrome (PS), and if so, what are determining factors and/or clinically useful predictors. PS is a constellation of symptoms that result from the lack of consistent AV sequential filling due to atrial contraction against closed AV valves. PS has not been commonly reported in the young. Data from all patients with pacemakers with congenital complete atrioventricular block (CAVB) with normal anatomy, and those with congenital heart disease (CHD), and surgically acquired CAVB were reviewed. Inclusion criteria were normal ventricular function by cardiac ultrasound and 100% VVIR pacing. Of 89 patients with VVIR pacemaker implants, 33 met these criteria. Of these, 19 developed PS. For statistical analysis, chi-square and independent samples t-test was used with significance defined at P < or = 0.05. No consistent association was found between cardiac anatomy, type of CAVB, or age at implant with development of PS. However, PS did correlate with duration of pacing (P = 0.02). The exercise stress test showed significant differences between 100% VVIR-paced patients with and without PS, in terms of work rate (P = 0.002) and measured oxygen consumption (P = 0.01). This study shows that PS appears to be a time related event in younger children with normal ventricular function who are 100% ventricular paced. Thus, this supports VVIR pacing as an adequate and cost-effective initial therapy for symptomatic bradycardia due to CAVB.

Patient size and congenital heart defects complicate pacemaker therapy in children favoring an initial epicardial approach. Steroid-eluting (SE) epicardial (EPI) leads maintain stable, low pacing thresholds in the short-term when compared to the nonsteroid (NSE) epicardial (EPI) leads. The purpose of this study was to evaluate chronic, 10-year performance of SE leads in growing children compared with NSE EPI leads implanted during the same time interval. From 1990 to 2000, 35 patients (age 1 month to 18 year, median 3 years), 28 with and 7 without congenital heart disease (CHD) received 51 SE leads: 27 ventricular and 24 atrial. NSE leads were implanted in 27 patients (age 1-28 years, median 8 years), 24 with and 3 without CHD: 27 ventricular and 1 atrial. Pacing lead threshold, impedance, and energy were measured at implant and during a 10-year follow-up. Unpaired t-test showed that impedance remained stable for all leads with lower mean values for the SE(376 +/- 55 vs 443 +/- 109 Omega) (P = NS). The mean energy requirement for SE leads at 10 years(1.2 +/- 0.9 microJ)was significantly lower than for NSE(4.4 +/- 5.5 microJ) (P < 0.05). At 2.5-V output, chronic thresholds for SE leads did not significantly differ from implant values for atrial (0.08 vs 0.09 ms) or ventricular (0.08 vs 0.08 ms) sites. There were no differences in SE lead performances among patients with or without CHD. Fracture or dislodgement occurred in two SE (4%) and four NSE (14%) leads. SE outperform NSE EPI leads and show stable, chronic low thresholds over time in all growing children.

The advantages of atrial synchrony over asynchronous ventricular pacing remain unclear in the young, chronically right ventricular (RV) - paced patient. This is in contrast to the older patient with inherent diastolic dysfunction who has been shown to benefit from atrial synchrony with dual chamber (DDD,R/VDD), over single chamber rate response (VVI,R) ventricular pacing. The goal of this study was to noninvasively assess cardiac function in a group of young, RV-paced patients before and after establishment of atrial synchrony. Echocardiographic data were retrospectively analyzed from 10 patients with congenital or acquired complete AV block, who were VVI,R paced for 10.2 ± 2 years (mean age at study 19.2 ± 8.9 years), and were subsequently converted to DDD,R/VDD pacing (mean age at study 20.7 ± 9.5 years). Paired t-test analysis of left ventricular (LV) systolic and diastolic function during VVI,R versus DDD,R/VDD pacing did not result in any short-term difference in LV short axis fractional area of change or FAC (53%± 7.5% vs 56.8%± 8.7%) or mitral maximal velocity (E) normalized to mitral flow velocity time integral (VTI) (5.2/s ± 1.5 vs 4.4/s ± 1.5). A decrease in mitral flow E/A ratio was observed after short term DDD,R/VDD pacing (2.2 ± 0.5 vs 1.9 ± 0.3). Atrial synchronous dual chamber pacing in young patients with complete AV block does not lead to any appreciable early change in global LV function over single-site RV pacing. Therefore, early establishment of atrial synchrony in the young asymptomatic VVI,R-paced patient with normal intrinsic ventricular function may not be warranted. (PACE 2003; 26:1208–1211)

Dilated cardiomyopathy (DCM) due to a primary supraventricular tachycardia not originating from the sinus node is not frequently seen in older children or adolescents. However, it is important to recognize this entity as a reversible cause of DCM to avoid costly and inappropriate treatments for these patients. We describe 7 patients who presented with DCM. Five were misdiagnosed as having "sinus" tachycardia secondary to an idiopathic DCM, and 2 were correctly diagnosed as having DCM secondary to an atrial tachycardia. All underwent electrophysiologic treatment of the tachycardia with remission of the DCM.

Congenital heart disease (CHD) patients (pts) often develop early heart failure (HF) with few therapeutic options leading to transplant (HT). Unfortunately, guidelines for cardiac resynchronization therapy (CRT) don't apply and function evaluations by cardiac ultrasound are often inaccurate among

Cardiac resynchronization pacing (CRT) can be an effective mode of therapy in patients (pts) with advanced heart failure (HF). But there are no selection criteria applicable to pts with congenital heart defects (CHD). QRS duration varies with age, dyssynchrony can exist with a narrow QRS, CHD pts

This study evaluates the concept of optimizing ventricular pacing in regard to functional cardiac response. Lead implant based on physiologic variables of contractility at various sites was performed in patients with and without congenital heart disease (CHD). Since right ventricular apical pacing may adversely alter contractility and myocellular function, septal and outflow tract pacing have been advocated. However, there are few studies in the young and essentially none in those with CHD.A total of 113 consecutive patients with and without repaired CHD, aged two to 51 (median 16), some with preexisting epicardial pacemakers, underwent transvenous pacemaker implant using standard sensing/pacing indices plus measurements of pressures, QRS, and contractility responses at each of five predefined potential ventricular implant sites: apex, inflow-, low-, mid-, and infundibular/outflow-septal with each patient serving as his/her own control. Implant was at the site of best contractility with active-fixation, low-threshold steroid-eluting leads.Measured contractility indices varied up to 31% (mean 12%) between sites per patient. Septal regions (mid-, inflow-, and low-) were associated with the most optimal and right ventricular epicardial showed the worst contractility (P0.05) responses. Apex was optimal in some CHD patients. Threshold and sensing were comparable up to 11 years (mean 7) postimplant regardless of septal site.There is no single "sweet spot" for optimal ventricular pacing, and the best implant sites are patient and CHD variable. Current lead designs ensure chronic stability/performance regardless of site. Proactive contractility-guided pacing implant can optimize chronic paced ventricular function.

The pharmacokinetics (PK) of the antiarrhythmic sotalol, which elicits Class III and beta-blocking activity, has not been adequately defined in a pediatric population with tachyarrhythmias. The goal of this single-dose study with administration of sotalol HCl at a dose level of 30 mg/m2 body surface area (BSA) was to define the PK of the drug in the following four age groups: neonates (0-30 days), infants (1 month to 2 years), younger children (> 2 to < 7 years), and older children (7-12 years) with tachyarrhythmias of either supraventricular or ventricular origin. The drug was administered in an extemporaneously compounded syrup formulation prepared from the tablets containing sotalol HCl. For safety, vital signs and adverse events were recorded and the QTc interval and heart rate telemetrically monitored. Scheduled blood samples were taken over a 36-hour time interval following dose administration. The drug concentrations in plasma were measured by a sensitive and specific LC/MS/MS assay. Standard compartment model-independent methods were applied to compute the salient PK parameters of sotalol. Twenty-four clinical sites enrolled 34 patients. Thirty-three had analyzable data. Sotalol was rapidly absorbed, with mean peak concentrations occurring 2 to 3 hours after administration. The elimination of sotalol was characterized by an average half-life of between 7.4 and 9.2 hours in the four age groups. There existed statistically significant linear relationships between apparent total clearance (CL/f) or apparent volume of distribution (V lambda z/f) after oral administration and the covariates BSA, creatinine clearance (CLcr), body weight (BW), or age. The best predictors for CL/f were CLcr and BSA, whereas BW best predicted the V lambda z/f. The total area under the drug concentration-time curve in the smallest children with a BSA < 0.33 m2 was significantly greater than that in the larger children. This finding indicated that the BSA-based dose adjustment used in this study led to a larger exposure in the smallest children, whereas the exposure to the drug was similar in the larger children. The dose of 30 mg/m2 was tolerated well. No serious drug-related adverse events were reported. It can be concluded that the PK of sotalol in the pediatric patients depended only on body size, except for the neonates and smallest infants in whom the disposition of sotalol was determined by both body size and maturation of eliminatory processes.

Recent advances in electrode surface designs have eliminated traditional threshold differences between endo- and epicardial pacing leads. Since the epicardial approach offers the potential of direct left ventricular pacing and the transvenous approach may not be feasible or warranted in all instances, more advanced leads are being designed to optimize epicardial pacing capabilities. This study was conducted to evaluate a bipolar epimyocardial lead. Six immature canines (age 3 months) were instrumented. The lead (Medtronic model 10389) is a single-pass, "in-line" bipolar electrode with low current drain and high impedance, with an intramyocardial steroid-eluting cathode and nonsteroid epicardial anode. Twelve ventricular leads were implanted (two per animal) and the animals followed for 6 months with weekly analysis of pacing and sensing capabilities. Results at explant were compared with implant values and showed no significant differences between sensed R waves or in R wave slew rates in unipolar or bipolar modes. Explant lead impedances remained high in both modes: bipolar, 1658 +/- 331; and unipolar, 1327 +/- 308 omega (P < 0.05). Chronic voltage (V) threshold at 0.5 ms showed no significant change from implant values during the study: unipolar, 0.3 +/- 0.06 versus 1.0 +/- 0.8; and bipolar, 0.4 +/- 0.06 versus 1.6 +/- 1.2. Histologic review showed negligible fibrous reaction at the electrode-tissue interface. This study introduces a high impedance, low threshold, "in-line" bipolar pacing lead design capable of stable chronic pacing with implant facilitated by a single suture technique.

Indications for pacemaker implantation in the pediatric population often include sinus or atrioventricular node dysfunction following surgery for congenital heart defects. However, patient size, cardiac defects, and vascular and valvular concerns may limit transvenous lead utilization. Since the epicardial surface of these patients often exhibits variable degrees of fibrosis from scar tissue formation or pericardial adhesions, chronic low output (2.5/1.6 V, 0.3 ms) epicardial pacing from implant is not currently recommended in children due to frequent threshold changes and electrode exit block. As a result, pacing in children is often viewed as a less efficient system than in adults. The addition of steroid combined with newer low threshold electrode designs however stabilizes the electrode-tissue interface and eliminates postimplant changes seen with standard smooth surface electrodes potentially permitting efficient chronic pacemaker application to all patient ages. The stability of chronic low output epicardial pacing with steroid-eluting electrodes was prospectively studied in 22 patients (ages 2 days-18.5 years, median 3.5 years) for up to 6 years. Chronic pulse width thresholds were compared according to implant site and association of prior cardiac surgery. A total of 26 pacing leads were implanted. The acute implant mean pulse width threshold (2.5 V) for all the electrodes studied was 0.10 ms +/- 0.05 ms. Stable low thresholds were maintained for up to 6 years without significant variation from implant. Mean ventricular pulse width thresholds (0.12 ms +/- 0.05 ms) were significantly higher (P < 0.001) than atrial thresholds (0.06 ms +/- 0.03 ms) at implant and throughout the study period. The thresholds in the patients following cardiac surgery were comparable to those without previous cardiac surgery (P = NS). Stable low thresholds may be chronically maintained for up to 6 years for epicardial steroid-eluting electrodes irrespective of pacing site or associated cardiac surgery.

Purpose: Several side effects of intravenous immunoglobulin G (IVIG) therapy are known, but it has never been reported to be associated with cardiac rhythm abnormalities other than sinus tachycardia. Patients and Methods: We describe the development of cardiac dysrhythmias during intravenous immunoglobulin G infusion in two children with thrombocytopenia. One of the patients had a history of supraventricular tachycardia, and the other had evidence suggestive of preexisting long QT syndrome. Conclusion: Cardiac rhythm abnormalities may be exacerbated in individuals with preexisting cardiac problems by IVIG infusion, and such patients should be monitored closely during IVIG administration.

Although recommended as part of a comprehensive pacemaker follow-up protocol, the diagnostic and cost-effectiveness of routine telephone monitoring (TM) in children in the United States is largely unknown. Patient age and size with inherent age-related problems and potential inability to correlate symptoms with pacemaker performance places the pediatric patient in a unique category, different from that of the adult. A total of 96 patients, ages 0.2–32.0 years (mean 12.0 years) were followed for 3 years after pacemaker implant with both routine monthly and anytime emergency TM. A total of 1372 routine transmissions were performed of a recommended 3456 (40% patient compliance). Of these, 99% showed normal rhythm or pacemaker function. The remaining 1% demonstrated asymptomatic pacemaker dysfunction requiring intervention or new-onset dysrhythmias. A total of 75 emergency transmissions were undertaken for patient/parent-perceived problems, only 8% of which showed pacemaker dysfunction or dysrhythmias. The sensitivity of patient/parent capacity to detect pacemaker problems or dysrhythmias based on clinical findings was 29%, with a positive predictive value of 8%. The specificity of routine monthly TM to screen for asymptomatic pacemaker dysfunction or new-onset dysrhythmias was 95%, with a negative predictive value of 99%. TM was effective (p < 0.001) for correlating the presence or absence of pacemaker problems with subjective complaints at any patient age. Financial charges for use of TM were significantly less (p < 0.01) than comparable outpatient visits.

Since the earliest descriptions of the condition, controversy has prevailed as to the existence of as well as appropriate management of attention deficit hyperactivity disorder. Often diagnosed in childhood, symptoms of attention deficit hyperactivity disorder can continue into adolescence and adulthood, requiring lifelong therapy. Effective therapeutic interventions include stimulant medications with all their respective potential side effects, including the cardiovascular system. However, although initial studies raised concerns for an increase in serious adverse cardiovascular effects among children receiving these drugs, more recent and extensive reports have failed to substantiate those findings among young patients.

Young adult patients (pts) with repaired tetralogy of Fallot (TOF) remain at risk for arrhythmias (Ar) and sudden cardiac death (SCD). Based on past studies with earlier pt subsets, Ar/SCD events were associated with right ventricular (RV) systolic pressures60 mm Hg, outflow tract gradients20 mm Hg, and QRS duration180 ms. However, there are limited recent studies to evaluate these risk factors in the current patient generation.Patients with TOF followed over the past 50 years were grouped by presence of any arrhythmias (group 1), absence of arrhythmias (group 2), and presence of SCD or significant ventricular arrhythmias (group 3) and correlated with current pt age, gender, age at repair, repair types, echocardiogram, cardiac magnetic resonance imaging, electrocardiogram/Holter, hemodynamics, and electrophysiology findings.Of 109 pts, 52 were male aged 17-58 years. Of these, 59 (54%) had Ar, two of whom had SCD. These 59 pts were chronologically older at the time of analysis, with repair at an older age and wider QRS duration (78-240, mean 158 ms) when compared with those without Ar. However, there was no correlation with surgical era, surgical repair, gender, RV pressure60 mm Hg, right ventricular outflow tract gradient20 mm Hg, or RV end-diastolic volume on CMRI.Ar/SCD risk continues to correlate with repair age and advancing pt age. QRS duration is longer in these patients but at a shorter interval (mean 158 ms) and less RV pressure (mean 43 mm Hg) than previously reported. In the current TOF patient generation, neither surgical era, type of repair, RV outflow gradient nor RV volume correlate with Ar/SCD. Electrophysiologic testing to verify and identify arrhythmias remains clinically effective.

Supraventricular tachycardia (SVT) in children can be successfully terminated using catheter ablation techniques; however, chronic, true success may be less. Sensed tachycardia (ST) is common following ablation and the differentiation from true arrhythmia recurrences can be challenging.Records of all patients ≤ 18 years who underwent successful ablation for simple forms of SVT and followed-up for at least a year between 2002 and 2012 were reviewed. Patients with congenital heart disease, atrial muscle tachycardia, and associated ventricular tachycardia were excluded. The diagnostic utility of commonly performed tests was assessed.Among the 205 eligible subjects, 202 underwent successful ablation (98.5%), of who five were lost to follow-up before 1 year. The early success rate (6 weeks postablation) and mid-term success rate (1 year postablation) were high (97.5% and 87.4%, respectively) whereas the chronic success (5 years postablation) was only 75%. Although true arrhythmia recurrence was significantly higher in the young (mean 11.5 years vs 13.5 years, P = 0.03) and males (P = 0.02), the presence of diffuse, right-sided fibers was the only independent predictor of true recurrence (odds ratio = 2.7, P = 0.03, 95% confidence interval 1.1, 6.8). Significant ST was reported by 111 patients (56%). The 30-day ambulatory event monitor had the highest sensitivity (71%) when compared to exercise test (19%) and electrocardiogram (24%) in identifying true arrhythmia recurrence.Acute and early success may not guarantee chronic ablation success. Postablation, symptomatic patients can be most effectively evaluated using ambulatory event monitoring; however, true recurrence may still be missed and requires closer monitoring.

Objective To describe the pattern of alterations in creatine phosphokinase (CPK) and creatine phosphokinase-myocardial isoenzyme (CPK-mb) levels and electrocardiogram (ECG) changes in children treated with intravenous infusion of isoproterenol, as determined by elevation of CPK-mb levels/indices and/or ischemic ECG changes. Design Prospective observational study. Setting A pediatric intensive care unit of a university teaching hospital. Subjects Twenty-two critically ill children (age: 3 months—17 years) with severe reactive airway disease who required intravenous isoproterenol. Interventions None. Measurements and Main Results Twenty-two children with severe reactive airway disease [pH 7.25 (7.01-7.54), Paco2 55 (23-113), and Pao2 92 (54-361)] were enrolled in the study. Baseline ECGs prior to intravenous isoproterenol were unremarkable. Baseline CPK-mb levels/indices were found to be abnormally elevated in 5 children prior to intravenous isoproterenol. Four of these children manifested a decrease in CPK...

Cryoablation (Cryo) has augmented radiofrequency (RF) as the ablation energy choice for most supraventricular tachycardias (SVT). Although initial acute results and more recent, but limited, 3-36-month follow-up studies have been reported, more longer follow-up information is required to determine actual efficacy.Data from patients with structurally normal hearts who underwent reentrant forms of SVT ablation at our institution from January 2005 to December 2009 were reviewed. These included demographics, clinical and electrophysiologic findings, and ablative energies used. Following apparent acute success, all patients were then reevaluated for any potential recurrences of SVT or preexcitation up to 5 years later.A total of 155 patients (83 male) were reviewed (mean age 13.4 ± 3.7 years). Ablations were predominantly right-sided (75%). Atrioventricular reciprocating tachycardia was seen in 74% and atrioventricular node reciprocating tachycardia (AVNRT) in 17% of patients. For concerns of atrioventricular node integrity, Cryo ± RF was user-preferred for anteroseptal accessory fiber locations and AVNRT. Acute success rate was 98% and chronic 83.2% over the next 5 years. Among patients with accessory pathways, recurrence was pathway number and location dependent: significantly higher (P0.05) if they were right anterior-anteroseptal, multiple, or with a broad-distribution pattern. There were no significant differences in recurrence rates with use of RF or its combination with Cryo.Radiofrequency ablation and Cryo are both effective therapies for pediatric patients. Although use of Cryo with RF in combination may enhance safety while affording comparable success, risk of recurrence still persists in the current era among patients depending on accessory pathways connection location and characteristics.

Epicardial pacing typically is associated with decreased pacing and sensing capabilities compared with the endocardial approach. Since endocardial pacing is neither appropriate nor possible in all instances, this study was conducted to evaluate a new concept in a chronic epimyocardial lead design in six 3-month-old growing dogs. The new bifurcated lead (Medtronic model 10401) is a low current drain, high impedance, steroid-eluting, bipolar design. The implant is facilitated by a suture attached with an atraumatic needle. Twelve ventricular leads were implanted (2 per animal) and followed for 6 months with weekly analysis of pacing and sensing capabilities. Results at explant were compared with implant values. There were no significant differences between implant and explant in sensed R waves, or in the slew rate of the R wave in unipolar or bipolar modes. Lead impedances at explant remained high in both modes: bipolar, 1550 +/- 223; unipolar, 1234 +/- 262 omega (P < 0.05). Chronic voltage (v) threshold at 0.5 msec showed no significant change from implant values during the study: unipolar, 0.4 +/- 0.2 vs 0.7 +/- 0.3; bipolar, 0.5 +/- 0.4 vs 1 +/- 0.5. Histologic evaluations of the electrode tissue interface demonstrated negligible fibrotic capsule formation. This study introduces a new, easily implanted, high impedance, low threshold, bipolar epimyocardial pacing lead design with excellent chronic pacing and sensing characteristics.

Intraatrial Mustard baffle repair of dextro-transposition of the great arteries (d-TGA) is vulnerable to complications, typically obstruction and leaks. Because patients often require pacemakers or intracardiac electrophysiology studies (EPS)/ablation for arrhythmias, narrowed or obstructed baffles restrict cardiac access hindering intracardiac procedures. Current guidelines recommend clinical as well as comprehensive transthoracic echocardiographic/Doppler (TTE) studies to identify baffle problems. This study reviews the effectiveness of these guidelines in detection of baffle issues pre-EPS catheterization and need for ancillary vascular interventions.Data from all patients with repaired d-TGA referred for hemodynamic catheterization or EPS between 1995 and 2009 at our institution were reviewed, including symptoms and TTE findings. Obstruction was defined as either a disturbed color Doppler flow or mean velocity1 m/s above the mitral valve or directly measured pressure gradient4 mm Hg or more than 50% baffle diameter narrowing by venography.Of 59 patients (34 pacemaker, 9 ablation, 16 routine hemodynamic) ages 8-39 years (mean 22.8), only three (5%) had symptoms of obstruction. However, baffle complications were found in 33 patients (56%), some with more than one problem: superior vena cava (SVC) obstruction in 32, inferior VC in two and leak in four. Baffle stenting was required in 24 patients and leak closure in two. Precatheterization TTE was available in 51 patients and showed 34% sensitivity, 61% specificity, 63% negative predictive value, and only 37% positive predictive value in recognizing baffle complications when compared with the actual catheterization findings.This study reports that baffle complications in patients with d-TGA following Mustard operation are more common than previously reported. However, comprehensive TTE and clinical symptoms are not effective enough to recognize these complications. Suspicion of and better noninvasive imaging prior to catheterization is required.

Beginning with the first successful surgical closure of a patent ductus arteriosus in 1938, to open heart repair of septal defects in 1955 and into the current era, children born with potentially fatal congenital heart defects are now surviving and attaining adulthood in numbers not previously envisioned. The concept of “long term” survival, originally meaning 10 years postrepair, has been superseded by survival beyond 20 and even 40 years. At the current time, population estimates indicate that there are now nearly 3 million adults with congenital heart disease (ACHD) in the United States, Canada, and Europe; and that number is growing. Since a “repaired” congenital heart does not imply “normal,” most of these patients will experience some complications, requiring lifelong medical care (Fig. 1). Prominent among these complications are arrhythmias that contribute to impaired quality of life, morbidity, and mortality. And although expert consensus guidelines dealing with various aspects of arrhythmia identification and patient management have been published since the 1980s, dealing primarily with ischemic heart disease, none fully apply to this growing ACHD population. At the recent 35th Scientific Sessions of the Heart Rhythm Society, the Pediatric and Congenital Electrophysiology Society (PACES) presented the first-ever expert consensus arrhythmia management guidelines that focus specifically on the ACHD patient, taking into consideration specific cardiac anatomies, surgical repairs, and their sequelae, including heart failure.1 The 22member, multidisciplinary and international writing committee included representatives from, and the publication was endorsed by, the American College of Cardiology, American Heart Association, Heart Rhythm Society, European Heart Rhythm Association, Canadian Heart Rhythm

Ventricular activation sequences and cardiac performance are influenced by pacing sites. Stimulation of or close to the specialized atrioventricular (AV) conduction system optimizes paced ventricular function compared to alternative epi- or endocardial muscle conduction sites. This study reports a new endocardial electrode implant approach to approximate septal His-Purkinje ventricular pacing. Five 6-month-old beagles were used. A custom, platinum-iridium, exposed helical screw electrode (Medtronic, Inc.), 4.5-mm long, with a 17.8-mm2 surface area, was designed with a polyurethane covered 4 filar MP35N nickle conductor lead. An 8 French sheath (USCI, Inc.) was modified as introducer to permit simultaneous implant intracardiac pressure and electrogram recordings. Following a thoracotomy, the introducer was inserted through the right atrial appendage and advanced to record optimal His-bundle electrogram while maintaining atrial pressure along the septal tricuspid valve annulus. After electrode implant, ECG demonstrated narrow paced QRS morphology. Mean implant values showed sensed R wave 6.3 mV, slew rate 0.65 V/sec, pacing impedance 319 ohms, and threshold 0.9 V/3.3 mA at 0.5-msec output. Necropsy showed implant above the tricuspid annulus with electrode extension into and contained within the proximal ventricular septum. This study demonstrates that an endocardial septal approach to His-Purkinje ventricular pacing to optimize paced ventricular function is feasible with a new electrode design and precise septal implant technique. Alternative introducer designs may permit transvenous application of this approach.

The physiological efficacy of single chamber, rate responsive ventricular pacing (VVIR) is unknown for symptomatic patients following the Fontan procedure for univentricular hearts. A total of six postoperative children, ages 6-21 years (mean 13), with symptomatic bradycardia requiring pacing therapy, underwent comparative treadmill exercise testing in randomized fixed rate (VVI) and VVIR pacing modes. In all instances, implanted activity pulse generators (Medtronic Model 8403) were programmed to identical age-appropriate low paced rates during VVI and VVIR modes with the upper rate response at 150 ppm. All studies were performed at least 2 weeks apart. Physiological values of heart rate, blood pressure, work rate (watts), oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) were monitored continuously during each test using a 1 minute incremental treadmill protocol. Ventilatory anaerobic threshold (VAT) was calculated from VO2, VCO2, and minute ventilation. The results demonstrated that although there was a significant increase in paced heart rate per minute throughout exercise (P less than 0.01) with VVIR pacing, maximum watts, VO2, and VAT remained unchanged. These findings indicate that in spite of an improved chronotropic response to exercise, children with univentricular hearts following the Fontan procedure continue to demonstrate altered hemodynamics which negate potential benefits of VVIR pacing.

Background: Atrioventricular reciprocating tachycardia (AVRT) is common in patients (pts) with WolffParkinson-White (WPW) syndrome but atrial flutter/fibrillation (AF) with rapid ventricular response (RVR) is rare. Although AF occurs in 18% of adult WPW pts, its incidence in children is unknown. We sought to determine risk factors for AVRT spontaneously degenerating to AF during electrophysiologic studies (EPS) in children with WPW. Methods: This was a retrospective study of children with WPW referred for accessory pathway (AP) ablation without clinical AF. Standard electrophysiologic protocols were performed to induce AVRT. To determine if AF degeneration was associated with patient characteristics, 2-sample t-tests, Chi-square, and Fisher’s exact were used. Results: There were 53 (31 males) WPW pts studied. During EPS, AVRT degenerated to AF in 27/53 (51%). RVR was seen in 18/27 (67%) patients. The ventricular cycle length (CL) during AF was shorter with RVR (211 + 24 ms) than without (313 + 65 ms) (P = 0.01). AF occurred more commonly among patients with right anterior AP (P = 0.05). Patient gender, age, height, weight, body surface area, persistence of preexcitation on exercise testing, baseline CL, AVRT conduction, and AP number were not significant AF determinants. The AVRT CL was significantly shorter in patients with (265.2 + 41.5 ms) versus those without (308 + 59 ms) AF (P = 0.01). Preliminary data suggest that AP location may be related to patient ethnicity. Conclusion: AF with RVR occurred following AVRT induction during EPS in 34% of our WPW patients, typically associated with right-sided AP locations. Time intervals for RVR to degenerate into ventricular fibrillation and lead to SCD are yet to be determined. (PACE 2008; 31:1307‐1312)

As intuitive as it might appear, it must be remembered that children are not little adults and congenital heart defects do not equate to normal cardiac anatomy. In addition, repaired congenital heart defects in adults (ACHD) might also not equate to normal anatomy. In each of these clinical situations, pacemaker device therapy may dramatically differ from most of the published information available in the field of internal medicine cardiology. Since there are now more patients with structural congenital heart defects over than under the age of 21 years, all present and future generations of pacemaker implanters need to recognize the plethora of anatomical and structural nuances potentially associated with the implantation of device therapy in this continually expanding patient population. Fortunately, advances in pacemaker and lead technology over the past 20 years, which now permit precise implantation at selective endocardial sites other than the right ventricular apex or atrial appendage and improved epicardial leads, have greatly facilitated optimization of pacing therapy. Whereas past interests have focused on lead performance issues such as dislodgement, fractures, and exit block, improvements in lead design technologies now permit more interest in maintaining or improving paced myocardial function by optimizing lead placement at alternate or more select sites. This article reviews recent applications and future directions of these pacing technologies and emphasizes differences among patients with congenital heart defects.

We reviewed our experience over a 10-year period to determine whether children with Down’s syndrome and complete atrioventricular canal develop pulmonary vascular obstructive disease earlier than children with normal chromosomes and this defect. Comparisons were made between Down’s syndrome and normal chromosome children regarding (1) pulmonary blood flow and pulmonary vascular resistance at initial catheterization, (2) operability as related to elevation in pulmonary vascular resistance, and (3) age at diagnosis of fixed pulmonary vascular obstructive disease. The 45 patients with Down’s syndrome catheterized under 1 year of age had a lower mean pulmonary blood flow (3.2 versus 5.7; p = 0.0001) and higher mean pulmonary vascular resistance (8.3 versus 4.6 Wood units · m2; p = 0.0003) than their 34 normal chromosome counterparts. When all ages were included, 38 of 81 (47 %) of the children with Down’s syndrome and 32 of 40 (80 %) of the normal children were considered operable. Non-Down’s syndrome patients who had operations had a higher pulmonary blood flow (5.8 versus 3.3; p = 0.004) and lower pulmonary vascular resistance (3.6 versus 6.0 Wood units · m2; p = 0.005) than Down’s syndrome patients. Of the 34 patients who did not have operations because of pulmonary vascular obstructive disease, 31 had Down’s syndrome. In 10 of 81 children with Down’s syndrome, fixed pulmonary vascular obstructive disease was diagnosed before the age of 1 year, while this was found in none of 40 normal children. Our data demonstrate that Down’s syndrome patients with complete atrioventricular canal have a greater degree of elevation of pulmonary vascular resistance in the first year of life and more rapid progression to fixed pulmonary vascular obstructive disease than children with normal chromosomes.