Congenital complete atrioventricular block: clinical and electrophysiologic predictors of need for pacemaker insertion

Natural History of Nonsurgical Complete Atrioventricular Block in Children and Predictors of Pacemaker Implantation

BACKGROUND

Data on the natural history of complete atrioventricular block (CAVB) in children are scarce, and criteria for pacemaker (PM) implantation are based on low levels of evidence.

OBJECTIVES

This study aimed to evaluate the natural course and predictors of PM implantation in a nationwide cohort of pediatric patients with nonsurgical CAVB.

METHODS

All children with CAVB in the absence of structural heart disease presenting from 1977 to 2016 were retrospectively identified, yielding 95 subjects with a mean age of 4.05 years at the first presentation with a follow-up median of 0.80 years (IQR: 0.02-6.82 years). PM implantation was performed according to the available guidelines. Serial 24-hour Holter recordings and echocardiograms were reviewed. Predictors of PM implantation performed >1 month after the first presentation were evaluated.

RESULTS

The minimum and mean 24-hour heart rates and maximum RR intervals had a nonlinear correlation with age (P < 0.0001 for all). The left ventricular (LV) size was moderately increased, and the shortening fraction was normal in the majority throughout follow-up. PM implantation was performed in 62 patients (65.3%) reaching guideline criteria. The mean 24-hour heart rate at presentation was a predictor of subsequent PM implantation (HR: 0.938; 95% CI: 0.894-0.983; P = 0.003 per unit increase) regardless of age at presentation. Patients presenting with a mean 24-hour heart rate >58 beats/min (>75th percentile) had a high probability of freedom from PM within the subsequent 5 years (91.7% vs 44.4%; P < 0.001).

CONCLUSIONS

Pediatric patients with CAVB showed an age-dependent decrease in heart rate, moderate LV dilation, and preserved LV function. The probability of subsequent PM implantation could be predicted by the heart rate profile at presentation, defining a low-risk group and allowing for individualized follow-up.

Ventricular Functional Analysis in Congenital Complete Heart Block Using Speckle Tracking: Left Ventricular Epicardial Compared to Right Ventricular Septal Pacing

BACKGROUND

Chronic right ventricular (RV) apical pacing in patients with congenital complete atrioventricular block (CCAVB) is associated with left ventricle (LV) dyssynchrony and dysfunction. Hence, alternative pacing sites are advocated. The aim of this study was to compare LV function using STE in selected patients with LV epicardial pacing (LVEp) vs. RV transvenous pacing (RVSp).

METHODS

This was a single-center, retrospective study in patients with CCAVB who underwent permanent pacemaker implant at age ≤ 18 years. Age- and gender-matched patients with a normal heart anatomy and function served as the control group. LV function was comprehensively assessed by conventional 2D Echocardiography and speckle-tracking echocardiography (STE).

RESULTS

We included 24 patients in the pacemaker group [27.6% male, mean age of 17.1 at last follow-up, follow-up duration of 8.7 years, RVSp (n = 9; 62.5%)] compared to 48 matched healthy controls. Shortening fraction (SF) and ejection fraction (EF) were normal and similar between cases and controls. However, STE detected abnormal LV function in the pacemaker group compared to controls. The former demonstrated lower/abnormal, Peak Longitudinal Strain myocardial (PLS Myo) [- 12.0 ± 3.3 vs. - 18.1 ± 1.9, p < 0.001] and Peak Longitudinal Strain endocardial (PLS endo) [- 16.1 ± 4.1 vs. 1.7 ± 1.7, p < 0.001]. STE parameters of LV function were significantly more abnormal in LVEp vs. RVSp subgroup as demonstrated by lower values for PLS Myo (- 10.1 ± 3.2 vs. - 13.1 ± 2.9, p = 0.03) and PLS Endo (- 13.8 ± 4.4 vs. - 17.5 ± 3.3, p = 0.03).

CONCLUSION

STE was more sensitive in detecting subtle differences in LV function relative to standard conventional 2D echocardiography (SF and EF) in selected patients with CCAVB and a permanent pacemaker. Furthermore, STE demonstrated that transvenous RV septal pacing was associated with better LV systolic function preservation than LV epicardial pacing for comparable post-implant intervals.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients: Developed in collaboration with and endorsed by the Heart Rhythm Society (HRS), the American College of Cardiology (ACC), the American Heart Association (AHA), and the Association for European Paediatric and Congenital Cardiology (AEPC) Endorsed by the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS)

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consenus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology, (ACC) and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate follow-up in pediatric patients.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients: Executive Summary

Guidelines for the implantation of cardiac implantable electronic devices (CIEDs) have evolved since publication of the initial ACC/AHA pacemaker guidelines in 1984 [1]. CIEDs have evolved to include novel forms of cardiac pacing, the development of implantable cardioverter defibrillators (ICDs) and the introduction of devices for long term monitoring of heart rhythm and other physiologic parameters. In view of the increasing complexity of both devices and patients, practice guidelines, by necessity, have become increasingly specific. In 2018, the ACC/AHA/HRS published Guidelines on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay [2], which were specific recommendations for patients >18 years of age. This age-specific threshold was established in view of the differing indications for CIEDs in young patients as well as size-specific technology factors. Therefore, the following document was developed to update and further delineate indications for the use and management of CIEDs in pediatric patients, defined as ≤21 years of age, with recognition that there is often overlap in the care of patents between 18 and 21 years of age.

This document is an abbreviated expert consensus statement (ECS) intended to focus primarily on the indications for CIEDs in the setting of specific disease/diagnostic categories. This document will also provide guidance regarding the management of lead systems and follow-up evaluation for pediatric patients with CIEDs. The recommendations are presented in an abbreviated modular format, with each section including the complete table of recommendations along with a brief synopsis of supportive text and select references to provide some context for the recommendations. This document is not intended to provide an exhaustive discussion of the basis for each of the recommendations, which are further addressed in the comprehensive PACES-CIED document [3], with further data easily accessible in electronic searches or textbooks.

Congenital heart block: Pace earlier (Childhood) than later (Adulthood)

Congenital complete heart block (CCHB) occurs in 2-5% of pregnancies with positive anti-Ro/SSA and/or anti-La/SSB antibodies, and has a recurrence rate of 12-25% in a subsequent pregnancy. After trans-placental passage, these autoantibodies attack and destroy the atrioventricular (AV) node in susceptible fetuses with the highest-risk period observed between 16 and 28 weeks' gestational age. Many mothers are asymptomatic carriers, while <1/3 have a preexisting diagnosis of a rheumatic disease. The mortality of CCHB is predominant in utero and in the first months of life, reaching 15-30%. The diagnosis of CCHB can be confirmed by fetal echocardiography before birth and by electrocardiography after birth. Whether early in-utero detection and treatment might prevent or reverse this condition remains controversial. In addition to autoantibody-associated CCHB, there is also an isolated (absent structural heart disease) nonimmune early- or late-onset heart block detected later in childhood that may be associated with specific genetic markers or other pathogenic mechanisms. In isolated immune or non-immune CCHB, cardiac pacemakers are implanted in symptomatic patients, however, data on the natural history of CCHB in the adult life indicate that all patients, even if asymptomatic, should receive a pacemaker when first diagnosed. However, important issues have emerged in these patients wherein life-long conventional right ventricular apical pacing may produce left ventricular dysfunction (pacing-induced cardiomyopathy) necessitating a priori alternate site pacing or subsequent upgrading to biventricular pacing. All these issues are herein reviewed and two algorithms are proposed for diagnosis and management of CCHB in the fetus and in the older individual.

Exercise capacity in children with isolated congenital complete atrioventricular block: does pacing make a difference?

The management of patients with isolated congenital complete atrioventricular block (CCAVB) has changed during the last decades. The current policy is to pace the majority of patients based on a variety of criteria, among which is limited exercise capacity. Data regarding exercise capacity in this population stems from previous publications reporting small case series of unpaced patients. Therefore, we have investigated the exercise capacity of a group of contemporary children with CCAVB. Sixteen children (mean age 11.5 ± 4; seven boys, nine girls) with CCAVB were tested. In 13 patients, a median number of three pacemakers were implanted, whereas in three patients no pacemaker was given. All patients had an echocardiogram and completed a cardiopulmonary cycle exercise test. Exercise parameters were determined and compared with reference values obtained from healthy Dutch peers. The peak oxygen uptake/body mass was reduced to 34.4 ± 9.5 ml kg(-1) min(-1) (79 ± 24% of predicted) and the ventilatory threshold was reduced to 52 ± 17% of peak oxygen uptake (78 ± 21% of predicted), whereas the peak work load/body mass was 2.8 ± 0.6 W/kg (91 ± 24% of predicted), which was similar to controls. Importantly, 25% of the paced patients showed upper rate restriction by the pacemaker. In conclusion, children with CCAVB show a reduced peak oxygen uptake and ventilatory threshold, whereas they show normal peak work rates. This indicates that they generate more energy during exercise from anaerobic energy sources. Paced children with CCAVB do not perform better than unpaced children.

Controversies in the therapy of isolated congenital complete heart block

Controversies in the therapy of congenital complete heart block are reviewed in terms of the timing of pacemaker implantation, the type and complications of pacing and its role in the presence of myocardial dysfunction. Drug treatment may be useful in selected cases in the presence of pleural effusions, ascites and hydrops of the fetus, but have no effect on complete heart block. Administration of fluorinated steroids in anti-Ro antibody-positive mothers with the aim of preventing complete heart block has given controversial results. Because of the variety of the clinical presentations, especially in regard to pacing therapy, it is mandatory to refer patients with congenital complete heart block to specialized centers with adequate resources and experienced personnel.

Bradyarrhythmias in pregnancy: a case report and review of management

We present a case of unpaced pre-existing congenital heart block in pregnancy, diagnosed for the first time in labour. Our patient was asymptomatic and was managed conservatively with temporary pacing equipment on standby. She had a post-partum cardiology follow-up and was paced in the puerperium. We discuss the aetiopathogenesis and the variable presentation patterns of bradyarrhythmia in pregnancy and the multidisciplinary approach to their management. Our recommendations combine the Advanced Life Support algorithm for treatment of bradycardia and the successful management strategies of several documented case reports in the literature.

Age-related role of ambulatory electrocardiographic monitoring in risk stratification of patients with complete congenital atrioventricular block

AIMS

The aim of the paper was to assess the importance of 24 h electrocardiographic Holter monitoring in determining predictive factors for Adams-Stokes (AS) attacks and heart failure (HF) in children and adolescents with complete congenital atrioventricular block (CCAVB).

METHODS AND RESULTS

Forty-five patients were divided into two groups according to the presence of AS attacks and HF and six age-related subgroups. The following parameters of 24 h electrocardiographic Holter monitoring were analysed: (i) minimum heart rate (HR), (ii) maximum HR, (iii) average HR, (iv) daytime HR (v) rhythm and conduction disturbance. Adams-Stokes attacks and HF occurred in 10 and 8 patients, respectively (40%). Five of six neonates with HF had maximum HR < 74 bpm and daytime HR < 58 bpm. Maximum HR below 68 bpm and daytime HR below 52 bpm were recorded in all the children up to 8 years of age with AS attacks and HF and only in 3 of 14 asymptomatic patients. All the patients above 8 years of age with AS attacks had maximum HR below 62 bpm. Of 6 patients with daytime HR < 50 bpm AS attacks were present in two. Episodes of marked ventricular slowing during sleep were registered in 4 of 10 (40%) patients and in 3 of 27 (11%) symptomless patients.

CONCLUSION

Risk factors for development of AS attacks and HF in patients with CCAVB include: (i) maximum HR < 74 bpm in neonates, <68 bpm up to the age of 8 and <62 bpm at ages above 8, (ii) daytime HR <58 bpm in neonates and < 52 bpm till the age of 8, and (iiii) abrupt pauses in ventricular rate that are at least twice the basic cycle length after the neonatal period.

[Pediatric cardiac pacing: indications, implant techniques, pacing mode]

Over the last years, pacing leads design and pacemaker (PM) generator size, reliability, and longevity have markedly improved, so that reliable paediatric implant can now be performed at any age with a low complication rate. Main indications include congenital and postoperative atrioventricular block (AVB) and postoperative sick sinus syndrome. Implantation of a PM is mandatory for children who are symptomatic from syncope or congestive heart failure and for those who have advanced block persisting more than 10 days after cardiac surgery. Criteria for pacing have been established in relation with the bradycardia and prophylactic pacing is recommended in children with congenital AVB and a mean heart rate <50 beats/minute. The majority of paediatric cardiologists recommend epicardial pacing in children less than 10 kg and when venous access to the heart is limited by congenital anomalies or prior operation; for older children, transvenous implantation has become the technique of choice. As heart rate is the main determinant of cardiac output at exercise in children with normal heart structures, the VVI-R mode is an alternative to dual chamber transvenous pacing in young patients. Patients with isolated sinus failure are paced in the atrium. Although the majority of patients are doing well, late complications within the paediatric population include venous thrombosis and difficulties in lead extraction. Myocardial dysfunction in children with congenital AVB is increasingly reported, but it is not determined whether it is due to the underlying disease or to right ventricular apical pacing and adverse remodelling.

Chronic Right Ventricular Pacing and Cardiac Performance:. The Pediatric Perspective

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.

[Congenital heart block associated with maternal anti SSA/SSB antibodies :a report of four cases]

Congenital heart block (CHB) associated with maternal anti-SSA/SSB antibodies: a report of four cases. CHB detected in utero is strongly associated with maternal antibodies to SSA (Ro) and SSB (La). Their pathogenic role in the development of CHB has been established in several studies. The mothers of affected infants frequently had autoimmune disease (systemic lupus erythematosus, Sjögren's syndrome) or were entirely asymptomatic. It is very difficult to identify pregnant asymptomatic mothers carrying anti-SSA/SSB antibodies. We report four cases of infants born to asymptomatic mothers with anti-SSA/SSB antibodies, three of them developed isolated congenital cardiac heart block and one with no evidence of CHB. All three CHB are detected during pregnancy between 16 and 24 weeks of gestation. All maternal sera contained antibodies to SSA alone or the both SSA and SSB. Three of four subsequent pregnancies were complicated by heart block. One child affected died in utero. While the two other newborns with CHB required pacemaker insertion during the first 3 months of life. Although the association of anti-SSA/SSB with CHB is widely accepted, the precise mechanism by which these antibodies cause cardiac conduction abnormalities remains to be defined. Antibodies to SSA/SSB have been proposed to be a serologic marker for neonatal lupus syndrome and CHB. Fetal and neonatal diseases are presumed to be due to the transplacental passage of these IgG autoantibodies from the mother into the fetal circulation. Since these antibodies may have a pathogenic role in CHB, screening of infants with isolated CHB or neonatal lupus and their mothers for the presence of anti-SSA and anti-SSB is strongly recommended.

Proposal for a new definition of congenital complete atrioventricular block

The classic old definition of congenital heart block by Yater (1929) is still generally accepted: 'Heart block established in a young patient. There must be some evidence of the existence of the slow pulse at a fairly early age and absence of a history of any infection which might cause the condition after birth: notably diphtheria, rheumatic fever, chorea and congenital syphilis'. However, other definitions are used. We systematically reviewed 1825 cases from 38 separate studies. We conclude that complete AV blocks detected in utero in the absence of structural abnormalities differ from blocks detected later in life with respect to pathogenesis (they are generally associated with maternal anti-Ro/SSA antibodies), poorer childhood prognosis, increased risk of developing late-onset dilated cardiomyopathy, different maternal clinical features and increased risk of recurrence in future pregnancies. For these reasons we propose a new modern definition of congenital complete AV block which might be acceptable to cardiologists, rheumatologists, pediatricians and obstetricians: 'an AV block is defined as congenital if it is diagnosed in utero, at birth or within the neonatal period (0-27 days after birth)'.

Characteristics and results of epicardial pacing in neonates and infants

The results of epicardial pacing in infants with isolated congenital complete atrioventricular block (CAVB) are reported. Thirty-four patients, aged 1 day to 20 months (22 patients < 1 month), were paced between 1988 and 1998. Thirty had bradycardia < 50 beats/min with symptoms in 12 patients, and 4 patients were paced because of associated ventricular ectopy or prolonged QT interval. In thirty cases, the electrodes were implanted through a left thoracotomy and connected to an abdominal generator; in four, the subxyphoid approach was preferred. Twenty-two children had dual chamber units. There was no operative death, but three patients died later of cardiomyopathy. Seven infants were reoperated for electrode displacement, infection, exit block, and pacemaker sensitivity. Chronic ventricular thresholds ranged from 0.3 to 2 V except in one case (4 V) and proper atrial sensing was lost in two cases. All children are doing well and the generator has lasted at least 5 years in 16 cases. In conclusion, epicardial pacing in infants with CAVB can be done with satisfactory results. There was no mortality in relation with pacing and thresholds have improved with the use of steroid-eluting electrodes. The deep location of the generator prevents cutaneous erosion and allows implantation of large units with a longer life duration.

Comparison of left and right atrial epicardial pacing in patients with congenital heart disease

BACKGROUND

Complex congenital heart disease (CHD) often necessitates the use of epicardial pacing. Adequate right atrial (RA) sensing and pacing thresholds are often difficult to obtain due to suture line scarring and RA dilatation. The purpose of this study was to evaluate the placement of left atrial (LA) epicardial leads in children.

METHODS

Patient demographics, pacing, and sensing data of atrial pacing systems implanted between January 1994 and January 1997 were collected.

RESULTS

Forty-nine pacing systems were implanted: 14 LA epicardial, 19 RA epicardial, and 16 transvenous in the right atrium. Lead impedance, current, and energy were similar in the two epicardial groups throughout the study. Energy thresholds (ET) were lower in the LA than RA at 6 months, and 1 and 2 years (p < 0.05). Analysis of post-Fontan patients performed alone revealed a lower ET in the LA as compared with the RA. Pacing and sensing parameters from transvenous leads are presented for relative comparison.

CONCLUSIONS

Transvenous leads are most efficient but often contraindicated in complex CHD. LA leads offer lower energy thresholds than RA leads with similar sensing parameters.

Esophageal PP intervals for analysis of short-term heart rate variability in patients with atrioventricular block before and after insertion of a temporary ventricular inhibited pacemaker

Heart rate variability (HRV) analysis is a useful method for assessment of the activities of autonomic nervous system. The RR intervals in ECG is measured for this purpose. However, RR intervals are not suitable for HRV analysis in atrioventricular block (AV) block patients with ventricular inhibited (VVI) pacemaker, as the intervals will be fixed by the ventricular pacemaker. Thus we used an esophageal lead to detect PP intervals for analysis of HRV. The aim of this study was to evaluate the short-term HRV by using an esophageal electrode to detect the atrial signal and PP intervals in AV block patients. Fifteen AV block patients before and after temporary VVI pacemaker and 15 subjects with normal AV conduction (control group) were enrolled in this study. The atrial signals from esophageal lead, ECG and intraatrial lead were recorded. The duration was 10 min. We compared correlation coefficient of PP intervals from different leads in AV block patients and the control group. We also compared the PP interval's variability parameters between the control group and AV block patients, before and after insertion of a temporary ventricular inhibited pacemaker. The esophageal PP intervals were excellently correlated with intraatrial AA intervals (r=0.98+/-0.01). The HRV using esophageal PP intervals with time domain demonstrated a significant decrease in patients with AV block (standard deviation of all PP intervals (SDNN) (s)=0.022+/-0.014; percentage difference between adjacent PP intervals that are greater than 50 ms (pNN-50) (%)=0.052+/-0.038; square root of the mean of squares of differences between duration of neighboring PP intervals (r-MSDD) (s)=0.322+/-0.082) but this returned to normal after insertion of a temporary ventricular inhibited pacemaker (SDNN (s)=0.035+/-0.009; pNN-50 (%)=2.540+/-1.682; r-MSDD (s)=0.542+/-0.190). However, the ratio of low frequency/high frequency (LF/HF) still increased (LF/HF=4.120+/-1.802). The result of this short-term HRV analysis suggested that withdrawal of vagal tone or increased sympathetic activity in AV block patients compared with the control group. This appearance was normalized after insertion of a temporary VVI pacemaker. however, abnormal sympathovagal balance still remained.

Outcome of isolated congenital complete heart block diagnosed in utero

OBJECTIVE

To establish identifiable prenatal factors in fetal heart block which might predict death in utero, the need for intervention, or the probability of pacemaker requirement.

SETTING

Tertiary referral unit for fetal echocardiography.

SUBJECTS

36 fetuses with congenital complete heart block and structurally normal hearts identified between 1980 and 1993.

METHODS

Maternal anti-Ro antibody status was documented. Prenatal variables examined included absolute heart (ventricular) rate, change in rate, and development of hydrops fetalis. Postnatally, heart rate, need for pacing, and the indications for pacing were detailed.

RESULTS

Of the total of 36 patients, there are 24 survivors; 11 are paced. Of those fetuses which died, two were electively aborted for severe hydrops, seven died in utero, two were immediate postnatal deaths, and one was an unrelated infant death. The trend was for the heart rate to decrease during fetal life and postnatally. Fetuses with deteriorating cardiac function did not always show the lowest heart rates. Bradycardia of less than 55 beats/min in early pregnancy or rapid decrease in heart rate prenatally were poor prognostic signs. Hydrops was also associated with bad outcome, 10 out of the 12 hydropic fetuses dying (83%). Of 10 fetuses presenting with a heart rate above 60/min, nine survived of whom three required pacing. Of seven presenting with heart rates of 50/min or less, only three survived and two of these required pacing. Of the two fetuses with negative maternal anti-Ro antibody status one died in utero and one required heart transplantation after pacemaker insertion.

CONCLUSIONS

Isolated complete heart block identified in fetal life does not always have a good prognosis. An individual heart rate does not accurately predict the outcome in utero or the need for postnatal pacing. Regular, careful monitoring during pregnancy is required in order to optimise care and timing of any interventions.

Complete heart block in nonfamilial hyperekplexia

An infant with nonfamilial hyperekplexia had multiple episodes of tonic spasms that mimicked tonic seizures. They were accompanied by complete heart block and apnea. These episodes did not correlate with electroencephalographic epileptiform changes and were partially responsive to clonazepam, valproic acid, and cardiac pacemaker. Sudden death in hyperekplexia may be related to complete heart block and apnea during seizurelike episodes.

Successful outcome of pregnancy after treatment of maternal anti-Ro (SSA) antibodies with immunosuppressive therapy and plasmapheresis

In this short communication we describe a patient with anti-SSA and anti-SSB antibodies whose first child died of congenital complete heart block (CCHB). During her second pregnancy she was treated with prednisolone, azathioprine, and plasmapheresis, and levels of anti-SSA and anti-SSB antibodies fell significantly. The pregnancy evolved uneventfully and resulted in the birth of an unaffected male infant. This is the fourth reported case of a successful outcome of pregnancy after treatment with immunosuppressive drugs in a woman with a significant risk of recurrence of CCHB.

Ambulatory arrhythmia screening in symptomatic children and young adults: comparative effectiveness of Holter and telephone event recordings

Effective initial identification of potential cardiac arrhythmias in symptomatic children is difficult due to the infrequency, brief duration, and vague nature of subjective complaints in the young. Although both telephone event and Holter monitoring are used for this purpose, no comparative studies of the initial screening efficacy of either have been performed. A total of 202 consecutive symptomatic children (age 11 days to 26 years, mean 10.2 years) were evaluated for potential cardiac arrhythmias with either 24-h Holter (97 patients) or telephone event (105 patients) recorders and grouped according to the presence or absence of congenital heart defects, normal or abnormal resting electrocardiogram (ECG), and presence or absence of cardiac surgery. The results showed 30% of all recordings (61% event; 14% Holter) failed to substantiate any arrhythmias in spite of subjective symptoms. Event recordings showed a better correlation of sensed symptoms with arrhythmias (32%) compared to Holters (5%) (p < 0.01) with 73% of Holter recordings performed during both asymptomatic and arrhythmia-free 24-h periods. Holter monitoring was more effective in detecting nonsensed and asymptomatic events (8% versus 0.5%, (p < 0.01), among high-risk children. This study demonstrates that although both monitoring devices are applicable to children, each has inherent limitations and usefulness. These must be considered in choosing either device to permit their most optimal and cost-effective application.

Perinatal outcome of fetal complete atrioventricular block: a multicenter experience

The clinical course and outcome of 55 fetuses with complete atrioventricular (AV) block detected prenatally were studied to identify factors that affect the natural history of this lesion. In 29 fetuses (53%) complete AV block was associated with complex structural heart defects, usually left atrial isomerism (n = 17) or discordant AV connection (n = 7). The other 26 fetuses had normal cardiac anatomy; in 19 cases the mother had connective tissue disease or tested positive for antinuclear antibodies. Six fetuses showed progression from sinus rhythm or second degree block to complete AV block. Of the 55 pregnancies, 5 were terminated and 24 fetuses or neonates died; at the end of the neonatal period 26 fetuses were still alive. Fetal or neonatal death correlated significantly with the presence of structural heart defects (4 of 29 surviving, p less than 0.001), hydrops (0 of 22 surviving, p less than 0.001), an atrial rate less than or equal to 120 beats/min (1 of 12 surviving, p less than 0.005) or a ventricular rate less than or equal to 55 beats/min (3 of 21 surviving, p less than 0.001). Mean atrial and ventricular rates were higher in surviving than in nonsurviving fetuses (142 +/- 8 vs. 127 +/- 21 beats/min, p less than 0.002; 64 +/- 8 vs. 52 +/- 8 beats/min, p less than 0.001, respectively). A slow atrial rate, however, was frequently associated with left atrial isomerism.(ABSTRACT TRUNCATED AT 250 WORDS)

Detecting arrhythmia by exercise electrocardiography in pediatric patients: assessment of sensitivity and influence on clinical management

We studied 49 patients with suspected arrhythmias (group 1) and 92 patients with previously documented arrhythmias (group 2) who underwent exercise electrocardiography (EECG) at our institution between 1979 and 1987. Among group 1 patients, all of whom had sinus rhythm before exercise, 10 (20%) had abnormal findings on EECG, and treatment was modified in 4 of these 10 (8% of group 1). Further testing (24-hour ambulatory or transtelephonic electrocardiographic monitoring or electrophysiologic study) of the 39 patients with normal EECG findings revealed 8 additional patients with arrhythmias. In group 1, the sensitivity of EECG was 56%, and its negative predictive value was 79%. Group 2 consisted of 38 patients with atrial arrhythmias, 31 with ventricular arrhythmias, and 23 with atrioventricular conduction abnormalities before EECG. Of these 92 patients, 68 (74%) had abnormal EECG findings. All but 1 of the 24 patients with normal findings underwent further testing, and rhythm abnormalities were induced in 16. Patients with atrial arrhythmias were more likely to have normal EECG results (42%) than were those with ventricular arrhythmias (23%) or an atrioventricular conduction abnormality (4%). Of the 35 patients who had been referred for suppression of an arrhythmia, 25 (71%) had abnormal rhythm suppressed during exercise. Clinical management was modified in 27% of group 2 patients on the basis of EECG findings.

Congenital complete atrioventricular block

The various etiologies, pathologic findings, clinical concerns, and features of congenital complete atrioventricular block are presented and discussed. In addition, prenatal and antenatal diagnostic techniques are explained and analyzed. Lastly, treatment and the issues involved in deciding proper treatment are discussed in such a way that the general pediatrician can help the family to understand and handle the problem.