Q-T interval in congenital complete heart block

A Case of Complete Heart Block With Diagnostic Challenge and Therapeutic Dilemma

Permanent pacemaker implantation is a class I indication for all symptomatic patients with complete heart block either congenital or acquired. However, certain portions of patients with congenital complete heart block are asymptomatic. Those patients are often very young, and implanting a permanent pacemaker is not always an easy decision. A therapeutic dilemma arises when a select patient population does not meet certain criteria to gain the maximum benefits out of prophylactic pacemaker therapy. Most asymptomatic patients with congenital complete heart block will eventually become symptomatic and require pacemakers at some point in their life but the definitive answer for the ideal time to initiate pacemaker therapy in such population has not been established. We present a case of asymptomatic congenital complete heart block with junctional escape rhythm, which is capable of incrementing the heart rate with physical activity to result in a challenge in diagnosis as well as the treatment strategy.

QT prolongation and torsades de pointes in a patient with heart block and a pacemaker

Prolongation of the QT interval and development of torsades de pointes are known in patients with complete heart block and profound bradycardia. We report the case of a patient with complete heart block and torsades, with long QT seen during a period of junctional tachycardia at a rate faster than the minimum pacemaker rate.

Congenital complete atrioventricular block associated with QT prolongation: Description of a patient with an unusual outcome

The association of a complete atrioventricular block with long QT syndrome is relatively common and carries a high risk of torsades de pointes (TdP) and sudden death. It is probably due to a downregulation of potassium channel currents (I (Ks) and I (Kr)) that impairs ventricular repolarization, prolongs the QT interval and increases susceptibility to TdP, so it must be considered a channelopathy. This report describes a 6 year-old boy, with a complete atrioventricular block diagnosed at 5 months of age, who at the age of 1 year started having episodes of TdP associated with a prolonged QT interval. He was treated successfully with propranolol and with a pacemaker implant. At age 3 the complete atrioventricular block reversed spontaneously to a first degree atrioventricular block.

Congenital heart block: clinical features and therapeutic approaches

Isolated congenital heart block is strongly associated with anti-Ro antibodies. It occurs in 2% of anti-Ro antibody positive pregnancies with a recurrence rate of 17-19%. Mortality is high in the first year of life (12-41%) and is predominantly due to dilated cardiomyopathy. A prolonged QTc occurs in 15-22% of cases and minor structural defects such as atrial septal defects and patent arterial ducts are well recognized. The 'mechanical' PR interval can now be measured in utero allowing for the detection of first-degree heart block. Both first and second-degree heart block detected in utero respond to therapy with fluorinated steroids. Complete congenital heart block is not reversible. Progression from a normal PR interval to complete heart block can occur within a week. IVIG is under investigation for the prevention of recurrence of congenital heart block, while dexamethasone should not be used for this purpose due to unacceptable toxicity. Data on the use of fluorinated steroids for established complete heart block is conflicting, although their use in cases where there is evidence of hydrops, poor ventricular function or both is not controversial.

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.

Fetal cardiac repolarization abnormalities

Abnormal cardiac repolarization renders the heart susceptible to lethal ventricular tachyarrhythmias, increasing the risk of sudden cardiac death in all ages; however, little is known about the incidence and etiology of T-wave abnormalities in utero. In this study, magnetocardiography was used to better define fetal T-wave characteristics, including the QT interval in the normal fetus, and to characterize T-wave abnormalities in the fetus with arrhythmia. The QT interval and T-wave alternans were assessed from magnetocardiographic recordings obtained at 14 to 39 weeks' gestation from 120 fetuses. Of these fetuses, 78 were from uncomplicated pregnancies and 42 had various forms of fetal arrhythmia (supraventricular tachycardia in 14, congenital atrioventricular block in 17, long QT syndrome with Torsades de pointes in 1, ventricular tachycardia in 2, sinus bradycardia in 4, and bradycardia due to blocked premature atrial contractions in 4). Although the corrected QT interval in normal sinus rhythm was accurately described by Bazett's formula, the corrected QT interval in fetal arrhythmia exhibited a systematic deviation at heart rate extremes. The dependence of the QT interval on the RR interval in arrhythmia was approximately described by QT alpha RR0.8. T-wave alternans was detected in 7 fetuses with arrhythmia, often in association with QT prolongation, suboptimal outcome, or fetal demise. The results of our study have demonstrated that QT-interval abnormalities exist and can be detected in fetal patients. The potential importance of T-wave assessment in the fetus with cardiac arrhythmia was evidenced by the high incidence of marked QT prolongation and T-wave alternans in the fetuses with suboptimal outcomes.

Congenital complete heart block and maternal connective tissue disease

Congenital complete heart block can be isolated or can occur in association with other structural heart diseases. Isolated congenital complete heart block (CCHB) is due to transplacental transfer of autoantibodies from mothers with connective tissue disease. Congenital heart block is usually complete, but incomplete blocks, sinus bradycardia and QTc prolongation are also reported. Anti SS A and Anti SS B antibodies transferred from mothers have inflammatory and arrhythmogenic effects in the fetal conduction system. Cardiac manifestations reported include dilated cardiomyopathy, endocardial fibroelastosis and mitral insufficiency. Low ventricular rate, QT prolongation and arrhythmias on monitoring are high risk features. CCHB has a mortality of 30%, and 60% of infants require pacemaker therapy. Fetal echocardiography is useful in early diagnosis. Prophylactic steroid therapy is controversial. Beta adrenergic agonists were tried in mothers with fetuses having congenital heart block to increase fetal heart rate. Early pacemaker therapy is indicated in patients with symptomatic bradycardia and ventricular dysfunction. The indications for pacing in congenital heart block continue to evolve with advances in techniques and most of these children will ultimately require permanent pacemakers by adulthood.

Ventricular tachycardia secondary to prolongation of the QT interval in a fetus with autoimmune mediated congenital complete heart block

We report a case where fetal echocardiography identified both complete heart block and ventricular tachycardia. The mother tested positive for anti-Ro antibodies. Prenatal detection of this unusual combination of arrhythmias prompted early postnatal evaluation, which revealed prolongation of the QT interval. Autoimmune mediated congenitally complete heart block associated with such prolongation of the QT interval has a poor prognosis. The child was successfully treated with beta blockers and implantation of a pacemaker.

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.

Short- and long-term outcome of children with congenital complete heart block diagnosed in utero or as a newborn

OBJECTIVES

Few data are available in the literature regarding the long-term outcome of newborns with congenital complete heart block (CHB). The aims of this retrospective study were to assess neonatal morbidity and mortality, incidences of dilated cardiomyopathy (DCM), and associated heart defects, and to establish prenatal and postnatal factors that might predict adverse outcome in children with CHB.

DESIGN AND SETTING

The cohort includes 91 infants with CHB diagnosed in 5 tertiary centers in Finland between 1950 and 1998.

PATIENTS

Maternal connective tissue disease was evident in 89% of the patients. At birth, the median gestational age was 37.1 weeks, and the median weight was 2969 g. Of the 91 infants, 60 (66%) were girls and 7 (8%) were twins.

RESULTS

Incidences of perinatal morbidity and mortality were 58% and 7%, respectively. The total mortality of CHB was 16%; 11 of 15 (73%) died during the first 12 months. Cumulative probability of survival at 10 years old was 82%. Pacing as a newborn was indicated in 48 of 90 cases (53%), and 36 received pacemakers at older ages. Cardiac defects not causally related to CHB were found in 38 of 90 patients (42%), of whom 22 were operated on. DCM was found in 21 (23%), of whom 13 died. During the follow-up, among 75 survivors with a median age of 9 years, 54 (72%) are free from symptoms. Poor outcome defined as clinically or pathologically evident congestive DCM was associated with intrauterine hydrops, low fetal and neonatal heart rate, low birth weight, male sex, and neonatal problems attributable to prematurity or neonatal lupus.

CONCLUSIONS

Despite early pacing, CHB carries high mortality during the first 12 months of life. High incidences of DCM and associated heart defects indicate close echocardiographic monitoring of all children with CHB.

Autoimmune-associated congenital heart block: demographics, mortality, morbidity and recurrence rates obtained from a national neonatal lupus registry

OBJECTIVES

The present study describes the demographics, mortality, morbidity and recurrence rates of autoimmune-associated congenital heart block (CHB) using information from the Research Registry for Neonatal Lupus.

BACKGROUND

Isolated CHB detected at or before birth is strongly associated with maternal autoantibodies to 48-kD SSB/La, 52-kD SSA/Ro and 60-kD SSA/Ro ribonucleoproteins and is a permanent manifestation of the neonatal lupus syndromes (NLS). Available data are limited by the rarity of the disease.

RESULTS

The cohort includes 105 mothers whose sera contain anti-SSA/Ro or anti-SSB/La antibodies, or both, and their 113 infants diagnosed with CHB between 1970 and 1997 (56 boys, 57 girls). Of 87 pregnancies in which sufficient medical records were available, bradyarrhythmia confirmed to be CHB was initially detected before 30 weeks of gestation in 71 (82%) (median time 23 weeks). There were no cases in which major congenital cardiac anatomic defects were considered causal for the development of CHB; in 14 there were minor abnormalities. Twenty-two (19%) of the 113 children died, 16 (73%) within 3 months after birth. Cumulative probability of 3-year survival was 79%. Sixty-seven (63%) of 107 live-born children required pacemakers: 35 within 9 days of life, 15 within 1 year, and 17 after 1 year. Forty-nine of the mothers had subsequent pregnancies: 8 (16%) had another infant with CHB and 3 (6%) had a child with an isolated rash consistent with NLS.

CONCLUSIONS

Data from this large series substantiate that autoantibody-associated CHB is not coincident with major structural abnormalities, is most often identified in the late second trimester, carries a substantial mortality in the neonatal period and frequently requires pacing. The recurrence rate of CHB is at least two- to three-fold higher than the rate for a mother with anti-SSA/Ro-SSB/La antibodies who never had an affected child, supporting close echocardiographic monitoring in all subsequent pregnancies, with heightened surveillance between 18 and 24 weeks of gestation.

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.

Isolated congenital complete atrioventricular block in adult life. A prospective study

BACKGROUND

The prognosis of congenital complete atrioventricular block (CCHB) is usually considered favorable in adults. This belief is based on studies comprising a limited number of patients and with rather short observation times. In the present study, the natural history of the disease was investigated by a prospective follow-up through decades of adult life of patients with a large group having well-defined CCHB without structural heart disease.

METHODS AND RESULTS

The diagnostic criteria of CCHB proposed by Yater were applied. Patients registered as having CCHB in 1964, supplemented by younger patients all without symptoms during their first 15 years of life, were selected. The study was limited to patients with isolated, complete, permanent block. An interview was conducted with all patients and clinical follow-up data obtained. There were finally 102 patients, 61 women and 41 men. In November 1994, the time of observation, after the age of 15 years in survivors, was between 7 and 30 years. The mean age at follow-up or at death was 38 years, median age 37 years, and range 16 to 66 years. Stokes-Adams (SA) attacks occurred in 27 patients, in 8 with a fatal outcome. The first attack was fatal in 6 of these 8 patients. Nineteen survived and a pacemaker (PM) was implanted thereafter. Another 8 patients received a PM because of repeated fainting spells, and 27 others have had a PM implanted for other reasons such as fatigue, effort dyspnea, dizziness, ectopies during exercise tests, mitral regurgitation, and a low ventricular rate (VR). VR decreased with age, with a mean rate at 15 years of 46 beats per minute (bpm), at 16 to 20 years of 43 bpm, at 21 to 30 years of 41 bpm, at 31 to 40 years of 40 bpm, and after 40 years of age of 39 bpm. SA attacks occurred in all 7 patients with prolonged QTc time. Low VR at rest or at work, presence of bundle-branch block pattern, low working capacity, and ectopies at rest and/or during effort were not statistically significant risk factors. SA attacks occurred in 6 patients without any of these signs. Mitral regurgitation developed in 16 patients and 4 died. A PM reduced the risk of death. A change to a lower degree of block occurred in 6 patients.

CONCLUSIONS

Prophylactic PM treatment is recommended even for symptom-free adults with CCHB because of the high incidence of unpredictable SA attacks with considerable mortality from first attacks, a gradually decreasing VR, significant morbidity, and a high incidence of "acquired" mitral insufficiency.

Pseudo 2:1 atrioventricular block and T wave alternans in the long QT syndromes

The extreme prolongation of ventricular action potential duration that occurs in some of the long QT syndromes may result in two forms of alternating activity of the heart: a "pseudo" 2:1 atrioventricular (AV) block and a T wave alternation, both of which are rate dependent. The pseudo 2:1 AV block relates to the extreme prolongation of ventricular refractoriness. The T wave alternation reflects the fact that the rate dependence of action potential duration differs in degree or magnitude in the subendocardial and subepicardial layers of the ventricular wall. Examples of two cases previously reported in the Journal by Weintraub et al. are used to illustrate and discuss these manifestations.

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.

Congenital complete heart block in patients without anatomic cardiac defects

Forty-three patients with congenital complete heart block and an otherwise structurally normal heart were reviewed in an effort to better define the profile of an anatomically homogenous group and to identify factors that may predict the need for pacing. Fourteen patients (32%) developed "symptoms" during follow-up, including two with out-of-hospital cardiac arrest. Heart rate on electrocardiogram or Holter monitor did not clearly distinguish this subgroup. The presence of alternate "risk factors," such as atrial enlargement seen on electrocardiogram, cardiomegaly seen on x-ray film, or prolonged QT interval were independent predictors of symptoms and poor outcome (p less than 0.05). Ventricular ectopy determined on Holter monitoring was also common among the symptomatic group, although this finding was inconsistent. Prophylactic pacing is indicated in select patients with congenital complete heart block and otherwise normal anatomy. Surveillance for rick factors beyond rate criteria alone may refine this selection process.

Mesothelioma of the atrioventricular node and congenital complete heart block

Congenital complete heart block (CCHB) has heterogeneous etiologies. It may occur as an isolated entity with no associated congenital cardiac malformations and is difficult to diagnose even with modern technology. Mesothelioma of the atrioventricular (AV) node is a benign tumor that causes CCHB. The occurrence of this tumor is rare, and a definitive diagnosis of the entity is made only at autopsy. The conduction disturbance caused by the mesothelioma is potentially treatable and should be considered in the differential diagnosis of CCHB. We present a case report of a 38-year-old female with CCHB caused by such a tumor. Clinical diagnosis and treatment of CCHB are reviewed.

Pacemakers in children: an update

This report reviews recent pacemaker technological advances as they apply to infants, children, and adolescents. Indications for pacemaker implantation in children have evolved since the 1984 Joint Task Force Guidelines. Recent data show that pacemaker implantation should be strongly considered in patients who have (1) asymptomatic congenital complete AV block with a mean heart rate less than 50 beats/min or other evidence of junctional instability; (2) congenital AV block with long QT interval; or (3) congenital long QT syndrome with bradyarrhythmias, or when conventional beta-blocker therapy is unsuccessful. Permanent pacemaker implantation is not necessarily an effective prophylactic measure against sudden death in patients following their operation who are receiving drug therapy for atrial tachyarrhythmias, and so is not absolutely indicated. New developments in lead technology have made transvenous lead systems more feasible for pediatric use. Because epicardial leads are required for small infants and for cosmetic reasons in some older children, design improvements are needed to enhance epicardial lead performance. Rate-responsive pacing is an acceptable alternative to dual-chamber pacing for augmenting exercise tolerance, and for children with sinus node dysfunction it is the preferred pacing mode. Pacemakers with automatic antitachycardia capabilities and with noninvasive electrophysiology features are valuable in children with atrial tachyarrhythmias. New data suggest that chronic atrial pacing also may be effective in controlling atrial tachyarrhythmias. New developments in pacemaker systems for the young parallel those for the older population, but differences between adult and pediatric patients demand ongoing increased participation by pediatric cardiologists.

Stokes-Adams attacks in congenital complete heart block

Stokes-Adams attacks are a well-known complication of congenital complete heart block. Although they are generally felt to be precipitated by either bradycardia or tachycardia, this is poorly documented. A case is presented in which a 23 month old with congenital complete heart block and an intermittently prolonged QT interval had a Stokes-Adams attack during a spontaneous episode of ventricular tachycardia. The combination of congenital complete heart block and a prolonged QT interval carries a significant risk of ventricular tachycardia.

Use of ambulatory electrocardiographic monitoring to identify high-risk patients with congenital complete heart block

To define the long-term natural history of congenital complete heart block, we followed 27 patients prospectively by means of frequent ambulatory electrocardiographic (ECG) recordings for a mean (+/- SD) of 8 +/- 3 years. During that time, 8 of the 13 patients with a mean daytime heart rate below 50 bpm (Group A) had cardiac complications such as sudden death, syncope, presyncope, or excessive fatigue. Six of the eight patients had additional ECG findings that suggested an instability of the junctional escape mechanism. These findings included nocturnal junctional exit block (three patients), little or no change in the junctional rate with physical activity (three patients), and associated tachyarrhythmias (three patients). None of the 14 patients with a mean daytime heart rate of 50 bpm or more (Group B) had an adverse clinical outcome, and 5 of the 13 patients in Group A also remained well. Among the five patients in stable condition in Group A, three had no evidence of an unstable junctional mechanism. We conclude that patients with a mean daytime junctional rate below 50 bpm and other evidence of an unstable junctional escape mechanism should probably undergo prophylactic pacemaker implantation. Since junctional exit block and tachyarrhythmias sometimes appear first during follow-up, the method of risk stratification employed in this study depends on serial ambulatory ECG recordings.

Supraventricular arrhythmias in children

Sudden death may occur in children with supraventricular arrhythmias. Sick sinus syndrome, particularly if associated with tachycardia, may result in sudden death in children who have had open heart surgery and rarely in children with a normal heart. Children with supraventricular tachycardia rarely die. Only those with junctional automatic tachycardia or Wolff-Parkinson-White syndrome have died. Patients with a short anterograde refractory period may be at risk of sudden death. Surgical division of the accessory connection can prevent sudden death. Digitalis may accelerate atrioventricular (AV) conduction in patients with Wolff-Parkinson-White syndrome and, thus, should be used only after testing in the electrophysiology laboratory. Sudden death due to complete AV block should be preventable using pacemakers. Neonates with a ventricular rate less than 55 beats/min or children with a rate less than 45 beats/min should receive pacemaker therapy because of the statistical probability of death or syncope. Ventricular ectopic beats, particularly if frequent or multiform, may be an indication for pacemaker insertion. Patients with surgical complete AV block that persists for more than 7 to 10 days should receive physiologic pacemakers for the prevention of sudden death and hemodynamic benefit.