Europace Advance Access originally published online on January 16, 2007
Europace 2007 9(2):88-93; doi:10.1093/europace/eul174
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SYNCOPE
Age-related role of ambulatory electrocardiographic monitoring in risk stratification of patients with complete congenital atrioventricular block
1,*1
uti11 Velinovi2
ehi11
1 Department of Paediatric Cardiology, Mother and Child Health Institute ‘Dr Vukan 
upi’, Radoja Dakica 6–8 street, Belgrade, Serbia, Serbia and Montenegro;
2 Institute of Cardiovascular Diseases of Clinical Center of Serbia, Belgrade, Serbia
Manuscript submitted 9 March 2006. Accepted after revision 10 November 2006.
* Corresponding author. Tel: +381 11 3108 140; fax: +381 112697232. E-mail address: vvladavuk{at}ptt.yu
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Abstract |
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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.
Key Words: Complete congenital atrioventricular block, Adams–Stokes attacks, Heart failure, WPW, Electrocardiographic holter monitoring, Heart rate
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Introduction |
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Pacemaker implantation is a therapy of choice in patients with complete congenital atrioventricular block (CCAVB). The latest guidelines for implantation of the permanent pacemaker and antiarrhythmic devices were published in 2002.1
However, the question of optimal timing for pacemaker implantation in asymptomatic children with CCAVB has not been definitely answered.2 Both Adams–Stokes (AS) attacks and sudden death tend to occur more frequently in the natural course of the disease. The predictive significance of the heart rate (HR) in development of AS, heart failure (HF), acquired mitral insufficiency, and sudden death has been the subject of research and evaluation.3–8
Our study is aimed at determining significance of HR analysis from 24 h electrocardiographic Holter monitoring as a predictive factor for AS and HF in children with CCAVB. According to the study of Dewey and coworkers, all the patients who developed either syncope or sudden death had a mean daytime HR of < 50 bpm.9 In order to predict better those patients at risk, we tested Dewey's hypothesis and compared the value of mean daytime HR and the maximum HR in predicting symptoms in children with complete congenital heart block.
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Method |
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Over the period 1992–2004, the data on 45 patients with CCAVB, with their age ranging from 1 day to 17 years were retrospectively analysed. Twenty-four hour Holter monitoring was performed using Del Mar Reynolds Medical System, three-channel recorder (Hertford, United Kingdom).
The diagnostic procedure was based on the Yager's criteria: (i) heart block established in a young patient by graphic records, (ii) evidence of the existence of the slow pulse at a fairly early age, (iii) absence of a history of any infection which might have caused the condition after birth: notably diphtheria, rheumatic fever, chorea, and congenital syphilis. The following electrocardiographic criteria were applied: (i) atrial and ventricular depolarization are completely dissociated, (ii) ventricular rate is lower than atrial rate, and (iii) absence of capture beats.
Study group
The patients were allocated into two groups (A and B) based on the presence of AS or HF and six subgroups (A1–A3 and B1–B3) according to age. Group A with AS or HF included 18 patients, and Group B free of AS or HF included 27 patients (Table 1).
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The groups and subgroups were compared with respect to the five parameters obtained by 24 h electrocardiographic Holter monitoring: (i) minimum HR, (ii) maximum HR, (iii) average HR, (iv) daytime HR, and (v) rhythm and conduction disturbance. The total of 246 recordings of 24 h electrocardiographic Holter monitoring, of which 77 were from patients with AS or HF and 169 from patients free of AS or HF, were analysed. Holter monitoring was performed once or twice a year as well as immediately after development of AS or HF.
Echocardiographic and radiographic examinations
Left ventricular volume in patients with symptoms and signs of HF was calculated using the modified Simpson's rule. Ejection fraction was calculated as 100 x (end-diastolic volume–end-systolic volume)/end-diastolic volume.10 Fractional shortening was calculated as (left ventricular end-diastolic dimension–left ventricular end-systolic dimension)/left ventricular end-diastolic dimension. A cardiothoracic ratio >0.60 indicated cardiomegaly in neonates. A cardiothoracic ratio in children ranging from 0.50–0.65 indicated mild, moderate, or severe cardiomegaly.11
Statistical analysis
Data are presented as mean ± SD or as median (range). The significance of differences between groups and subgroups was assessed using Student's t-test. Statistically significant difference was defined as P < 0.05.
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Results |
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The average age of patients at the time of onset of AS or HF was 4.5 years, while those from the group free of AS and HF were of mean age 8.3 years by the end of the follow-up period (P < 0.03). Distribution of male and female patients was equal. Pacemaker implantation was performed in 18 patients—six neonates (75%), eight patients (39%) aged from 30 days to 8 years, and in four patients >8 years of age (25%). Two patients diagnosed as having dilated cardiomyopathy of unknown aetiology associated with complete atrioventricular block were excluded from the study.
Congenital heart defects were present in 8 children (17.8%), of whom 4 had corrected transposition of the great arteries with intact ventricular septum and who were free of haemodynamically relevant associated heart lesions. Two patients had atrial septal defects and two had mild stenosis of the pulmonary artery. Of the above listed patients with corrected transposition of the great arteries one developed AS at the age of 6, while the others remained free of symptoms until the age of 8 years.
Adams–Stokes attacks and HF were recorded in 10 and 8 patients, respectively(40%). Minimum, average, and maximum HR determined from 24 h electrocardiographic Holter, monitoring immediately after onset of AS or HF are shown in Figure 1.
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Six neonates (75%) with minimum HR ranging from 38 to 52 bpm, of whom two with atrial septal defect and mild pulmonary stenosis, respectively, developed signs and symptoms of HF, while the other two neonates were asymptomatic. The ejection fraction was determined in three of six neonates, while fractional shortening was determined in all the neonates. The mean ejection fraction in neonates with HF was 38% (range 34–41) and mean fractional shortening was 16% (range 14–18). These neonates had cardiomegaly on X-ray. Two symptomless neonates had significantly higher maximum HR in comparison with those with HF, i.e. neonates with maximum HR >92 bpm were free of HF. Two neonates died because of sepsis and HF, with minimum HR of 40 and 49 bpm, respectively. Highly statistically significant differences in maximum HR and daytime HR were found between the neonates with and without HF (Table 2).
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As for the subgroup of children aged between 30 days and 8 years, 6 patients with minimum HR ranging between 36 and 47 bpm had AS, while two had HF. Ejection fraction and fractional shortening of the left ventricle in the first patient with HF were 28 and 15%, respectively, and 30 and 16%, respectively in the second. These children showed radiological severe cardiomegaly. Statistically significant differences in maximum HR and average HR were seen between the subgroups with AS or HF and the symptomless subgroup, as well as in values of the daytime HR between the patients with AS attacks and symptomless patients. (Table 3). In the group of children with AS or HF, maximum HR was below 68 bpm, while maximum HR <68 bpm in the asymptomatic children was found in only 3 of 14 patients.
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As for the patients over 8 years of age, AS was recorded in four cases with minimum HR ranging between 28 and 37 bpm. A statistically significant difference in maximum HR was noted between the patients with AS and those free of AS in the same age group (Table 4).
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The analysis of all 24 h Holter monitoring records indicates that the maximum HR decreases from birth until the age of 17. This trend (logarithmic type) is more emphasized in patients with AS or HF compared with group of patients free of AS and HF [y1 = – 3.31 Ln(x) + 93.68 vs. y2 = – 5.1 Ln(x) + 80.8] (Figure 2).
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Change of rhythm and conduction
The presence of a wide QRS escape rhythm was seen in a 9-year-old patient with HF. One symptomless patient had widened QRS complex of the right bundle branch block type. QTc interval >0.45 s was recorded in two patients of whom one had AS. Episodes of marked ventricular slowing during sleep (pauses in ventricular rate that are at least twice the basic cycle length) were registered in 4 of 10 (40%) patients with AS, i.e. in 8 of the total number of 52 (15%) analysed Holter findings in patients with AS and in 3 of 27 (11%) symptomless patients, i.e. in 7 of 169 (4%) analysed Holter recordings. No statistically significant difference in number of ventricular premature beats was found between those without symptoms and those with AS or HF.
Complete congenital atrioventricular block was detected in a 10-year-old patient referred for evaluation of enhanced fatigue and palpitations, while the initial Holter monitoring recorded one episode of tachycardia (up to 127 bpm), which lasted for 12 min. P waves were not clearly visible during tachycardia, being masked in the ST segment and the QRS was not extremely wide, with a delta wave positive in V1 and negative in III and a VF, suggesting conduction by the posterior left accessory pathway. Electrophysiological evaluation was indicated, however, the parents refused the recommendation.
Progression of first-degree atrioventricular block into complete atrioventricular block was observed in two patients aged 4 and 9 years, 9 and 15 months after the initial examination, respectively. A permanent pacemaker was implanted in the younger patient because occasional dizziness, without syncope. Serial ambulatory electrocardiographic Holter monitoring performed in three symptom-free children with CCAVB aged 3, 7, and 10 years showed occasional establishment of normal atrioventricular conduction during a mean follow-up period of 3 ± 1.5 years. In a 7-year-old boy mentioned above, normal atrioventricular conduction was recorded on the last three consecutive Holter monitoring examinations performed over a period of 16 months.
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Discussion |
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Only a few studies have focused on the use of Holter monitoring to provide and determine some indication of the risk of sudden death or syncope in children. One study reported no difference in minimum HR, maximum HR, incidence of pauses >3 s, or amount of ventricular ectopy between symptomatic and asymptomatic patients.12
Syncope, pre-syncope, and HF are relatively frequent in patients with CCAVB.13–14 Eronen reported the incidence of perinatal morbidity and mortality in patients with CCAVB of 58 and 7%, respectively, with total mortality of 16%.15 Popovic and coworkers showed that a permanent pacemaker was implanted, at different periods of life, in three quarters of patients with CCAVB.16 It has been well known that prophylactic pacemaker implantation prevents CCAVB-related symptoms and results in decrease of heart size and normalization of fractional shortening of the left ventricle. However, possible complications, such as dislocation and fracture of electrodes and infection of the pacemaker system cannot be neglected when indications for pacemaker implantation are established.17–19
Neonates
Heart failure was manifest in neonates by fatigue on feeding, tachypnoea, dyspnoea, liver enlargement, cardiomegaly, and decreased left ventricular ejection fraction and fractional shortening. We found that five of six neonates with HF had average maximum HR <74 bpm and average daytime HR <58 bpm. According to the cooperative study carried out by Michaelsson and Engle, a lethal outcome was recorded only in one neonate with HR >55 bpm, while no lethal outcomes were recorded with average daily HR >60 bpm.20 Grolleau and coworkers concluded that development of HF and HR <55 bpm represent indications for implantation of the permanent pacemaker in neonates.21 The primary indications for placement of a pacemaker in the study of Buyon and coworkers were congestive HF and low ventricular rate averaging <60 bpm.22
Children up to 8 years
Adams–Stokes attacks were manifest in this sub-group of patients in the form of syncope (classic form), or in the form of fainting spells, accompanied by pallor or lethargy (less-severe form). Heart failure was manifest in both patients by increasing fatigue, dyspnoea, sleep disturbance, lethargy, or irritability and in one of those patients by dizziness. Physical examination findings revealed in all the patients pallor, cool skin, crepitations, and hepatomegaly. All the patients with AS had daytime HR below 52 bpm. However, we have shown that daytime HR has no predictive significance for onset of HF. On the other hand, all the symptomatic patients, including a child with corrected transposition of the great arteries and intact ventricular septum, had maximum HR below 68 bpm.
According to the findings of others, CCAVB in an infant with a ventricular rate <50–55 bpm or with congenital heart disease and a ventricular rate <70 bpm represents a risk factor for onset of AS and sudden death.20,23 It is well known that the patients with corrected transposition are permanently exposed to the risk of development of complete atrioventricular block during life.24
Children over 8 years
The symptoms of CCAVB were manifest in children aged between 12 and 15 years. In the group aged over 8 years, statistically the greatest significant difference was found in maximum HR. All the AS patients had maximum HR below 62 bpm. There was no significant difference in values of daytime HR between the patients with AS and symptomless patients. Five of 6 patients with daytime HR <50 bpm, only one had AS. Michaelsson and coworkers considered that implantation of pacemaker in all patients above 15 years of age is recommended for prevention of AS and sudden death.25 Our results show that there is a decrease in maximum HR on 24 h Holter monitoring over time in children with CCAVB, as well as a more prominent decrease in maximum HR from birth to the age of 17 years in patients with AS or HF in comparison with those free of AS or HF. Based on the findings of other authors, HR decrease is also shown in adults with CCAVB, which is not observed in healthy adults.3 Michaelsson reported in his study that average HR at the age of 15 was 46 bpm, being 43 bpm between the ages of 16 and 20, and 41 bpm between the ages of 21 and 30, etc.
Change of rhythm and conduction
Based on our findings, the episodes of marked ventricular slowing during sleep tend to occur significantly more frequently in patients with AS. Ambulatory ECG monitoring with abrupt pauses in ventricular rate that are two or three times the basic cycle length, or associated with symptoms due to chronotropic incompetence have been noted in patients with adverse outcome and they have predictive significance for AS.9 In our study, Wolff-Parkinson-White (WPW) syndrome was found in one patient with CCAVB and there was one episode of tachyarrhythmia. The association between CCAVB and the WPW syndrome is highly infrequent. Although the accessory pathway may be the reason for establishment of good atrioventricular conduction in these patients during exercise, the possibility of onset of antidromic tachycardia or association with dilated cardiomyopathy cannot be excluded.26,27
QTc longer than 45 ms was registered in 4% of patients with CCAVB. The reports of other authors demonstrated the incidence of the prolonged QTc in patients with CCAVB ranged between 7 and 22% as well as that it was one of the risk factors for onset of AS and sudden death.28,29
Heart failure was found in one of two patients in our group with wide QRS escape rhythm. Although it has not be definitely proven that wide QRS escape rhythm, as well as complex ventricular ectopy per se are the predictors of sudden death, they have an important place in risk stratification for onset of severe CCAVB complication.3,11 In Texas Children's Hospital pauses longer than 3 s, while awake or longer than 5 s while sleeping, wide QRS escape rhythm, prolonged QTc, complex ventricular ectopy (couplets or greater), and ventricular ectopy on exercise represent indications for permanent pacemaker implantation.30
Establishment of normal atrioventricular conduction was registered in 3 of 45 patients. Normalization of the atrioventricular conduction may occur several years after establishment of the diagnosis of CCAVB or pacemaker implantation.31 The predictive significance of 24 h ECG monitoring analysis for establishment of intrinsic conduction in these patients has not been determined.
Limitation of the study
We have included in the study two patients with progression of first-degree atrioventricular block into complete atrioventricular block and three children with occasionally normal atrioventricular conduction, thus only partially meeting the criteria for congenital complete atrioventricular block. The small number of patients with HF after the neonatal period and asymptomatic neonates, as well as their relatively short time of follow-up represent a limitation in the wide applicability of our experience.
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Conclusions |
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Adams–Stokes attacks and HF may develop at any age in children with CCAVB. Heart failure is predominantly the problem of the younger age group, as are AS attacks in the older age group. Maximum HR <74 bpm in neonates, <68 bpm up to the age of 8, and <62 bpm at above the age of 8 years represent risk factors for onset of AS attacks and HF in patients with CCAVB. A value of daytime HR <58 bpm in neonates and <52 bpm up to the age of 8 has great predictive significance for onset of HF and AS attacks, respectively. Our results did not fully confirm the hypothesis proposed by Dewey and coworkers on significance of daytime HR in prediction of AS attacks in patients with CCAVB. We have shown that maximum HR is a better predictor of symptoms than daytime HR. Abrupt pauses in ventricular rate that are at least twice the basic cycle length have predictive significance for onset of severe CCAVB complications. Analysis of 24 h electrocardiographic Holter monitoring performed in each patient once or twice a year may considerably contribute to risk stratification for AS attacks and HF in children with CCAVB and decision-making for preventive pacemaker implantation.
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References |
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