Wenckebach atrioventricular block (Mobitz type I) in children and adolescents

Long-Term Follow-Up of Second-Degree Heart Block in Children

Little is known about the outcomes of children with second-degree heart block. We aimed to determine whether children with structurally normal hearts and Mobitz 1, 2:1 block or Mobitz 2 are at increased risk for progressing to complete heart block (CHB) or requiring a pacemaker (PM) at long-term follow-up. We searched our institutional electrophysiology database for children with potentially concerning second-degree block on ambulatory rhythm monitoring between 2009 and 2021, defined as frequent episodes of Mobitz 1 or 2:1 block, episodes of Mobitz 1 or 2:1 block with additional evidence of conduction disease (i.e. first-degree heart block, bundle branch block), or episodes of Mobitz 2. Ambulatory rhythm monitor, ECG, and demographic data were reviewed. The primary composite outcome was CHB on follow-up rhythm monitor or PM placement. 20 patients were in the final analysis. Six (30%) patients either developed CHB but do not have a PM (4 = 20%) or have a PM (2 = 10%). Median follow-up was 5.8 years (IQR 4.4-7.0). Patients with CHB or PM were more likely to have second-degree block at maximum sinus rate (67% vs. 0%, p = 0.003), a below normal average heart rate (67% vs. 14%, p = 0.04), and 2:1 block on initial ECG (50% vs. 0%, p = 0.02). In this study of children with potentially concerning second-degree block, 30% of patients progressed to CHB or required a PM. Second-degree block at maximum sinus rate, a low average heart, and 2:1 block on initial ECG were associated with increased risk of disease progression.

Is Mobitz type I atrioventricular block benign in adults?

OBJECTIVE

To assess the need for pacing in adults with chronic Mobitz type I second degree atrioventricular block (Mobitz I).

DESIGN

Prospective study.

SETTING

District general hospital.

PATIENTS

147 subjects aged > or = 20 years (age cohorts 20-44, 45-64, 65-79, and > or = 80) with chronic Mobitz I without second degree Mobitz II or third degree (higher degree) block on entry, seen from 1968 to 1993 and followed up to 30 June 1997. Sixty four had organic heart disease. The presence of symptomatic bradycardia was defined as highly likely in 47 patients (class 1); probable in 14 (class 2); and absent in 86 (class 3).

INTERVENTIONS

Pacemakers were implanted in 90 patients for the following indications: symptoms in 74 and prophylaxis in 16.

MAIN OUTCOME MEASURES

The main outcome measure was death, with conduction deterioration to higher degree block or symptomatic bradycardia the alternative measure.

RESULTS

Five year survival to death was reduced in unpaced patients relative to that expected for the normal population (overall mean (SD) 53.5 (6.7)% v 68.6%, p < 0.001; class 3, 54.4 (7.3)% v 70.1%, p < 0.001). Paced patients fared better than unpaced (overall (mean (SD) five year survival 76.3 (4.5)% v 53.5 (6.7)%, p = 0.0014; class 3, 87.2 (5.4)% v 54.4 (7.3)%, p = 0.020; and organic heart disease, 68.2 (7.6)% v 44.0 (9.9)%, p < or = 0.0014). There were no deaths in the < 45 cohort. Survival to first outcome (main or alternative) was further reduced to 31.7 (5.0)% in 102 patients unpaced initially and 34.2 (5.7)% in class 3. Only the 20-44 cohort and patients with sinus arrhythmia had > 50% survival.

CONCLUSION

Mobitz I block is not usually benign in patients > or = 45 years of age. Pacemaker implantation should be considered, even in the absence of symptomatic bradycardia or organic heart disease.

Prevalence of arrhythmias and conduction disturbances in large population-based samples of children

The aim of our study is to provide data on the prevalence of disturbances of rhythm in the general population of children. Accurate estimates of true prevalence of such disturbances of rhythm from large samples are mandatory if we are to interpret properly electrocardiographic abnormalities. We analysed prevalence of disturbances of rhythm in a population of 152,322, comprised of 71,855 elementary school students, 36,692 males and 35,163 females, aged from 5 to 6 years, and 80,467 students of junior high school, 41,842 males and 38,625 females, aged from 12 to 13 years. We analysed the prevalence of premature atrial and ventricular contractions, first, second and third degree atrioventricular block, incomplete and complete right bundle branch block, Wolff-Parkinson-White syndrome, and prolongation of the QT interval. The prevalence of disturbances of rhythm in total rose with age, being found in 1.25% of elementary school students and 2.32% of junior high school students, and was higher in males than females, at 2.00% as opposed to 1.38%, both values being statistically significant at a level of less than 0.0001. Prevalences of all types of rhythmic disturbances were higher in junior high school students than elementary school students (p < 0.0001). Premature atrial and ventricular contractions and prolongation of the QT interval were higher in female than male students, at percentages of 0.089, 0.497, and 0.02 for males, and 0.123, 0.534 and 0.027 in females (p < 0.0001). In contrast, incomplete and complete right bundle branch blocks were higher in males than females, at 0.983% and 0.083% in males versus 0.410% and 0.161% in females (p < 0.0001). Disturbances of rhythm increased with age, and conduction disturbances were higher in male students than female, although premature atrial and ventricular contractions and prolongation of the QT interval were more frequent in female. These data may be useful for future comparative studies of disturbance of rhythm in children.

Low-dose daunorubicin in induction treatment of childhood acute lymphoblastic leukemia: no long-term cardiac damage in a randomized study of the Dutch Childhood Leukemia Study Group

BACKGROUND

To investigate late cardiotoxicity in childhood acute lymphoblastic leukemia (ALL) survivors after induction treatment with or without daunorubicin (DNR; 25 mg/m(2), i.v., weekly, x4, cumulative dose 100 mg/m(2)).

PROCEDURE

Cardiac function was assessed in 90 event-free survivors of childhood ALL, 11.4-17.8 years (median 14.8 years) after treatment according to the DCLSG protocol ALL V. In this protocol patients were randomized to receive (group B) or not to receive (group A) DNR 25 mg/m(2)/week i.v. during the first 4 weeks of induction treatment. Age at diagnosis was 1.2-14.9 years (median 4.5 years). The cardiac evaluation consisted of a history, physical examination, electrocardiogram (ECG), 24 hr ambulatory ECG, and echocardiography.

RESULTS

Electrocardiographic data, arrhythmias, left ventricular dimensions, left ventricular contractility, wall stress, and diastolic function were within normal limits in both groups. No difference could be shown between data from group A (n = 40) and group B (n = 50).

CONCLUSIONS

No late cardiac damage was demonstrated in childhood ALL survivors after induction treatment including a cumulative dose of 100 mg/m(2) DNR, compared to survivors who received the same treatment but without DNR. DNR 100 mg/m(2) given in 4 doses of 25 mg/m(2)/week appears to be a safe dose in induction treatment of ALL.

ECG variants and cardiac arrhythmias in athletes: clinical relevance and prognostic importance

These findings permit the following conclusions on cardiac changes induced by high-performance sports and high levels of training. Sinus bradycardia and AV block can frequently be observed in athletes, but they do not require attention as long as they are asymptomatic or do not produce pauses exceeding 4 seconds. Persistent rather than transient second-degree AV block or Mobitz second- or third-degree AV block is an extremely unusual finding even in athletes and should be considered a sign of organic lesions until proved otherwise. Supraventricular and AV node ectopic beats are not more frequent in athletes than in the general population except for atrial fibrillation. WPW syndrome is of particular importance, since rapid conduction to the ventricle via the accessory AV pathway is possible, especially if there is a tendency toward atrial fibrillation. Likewise caution is required in athletes with hypertrophic cardiomyopathy. Here hemodynamic deterioration must be anticipated with the occurrence of supraventricular tachycardia. Simple ventricular arrhythmias occur among athletes with the same frequency as in the general population, but they usually disappear with exercise. The occurrence of complex ventricular forms of arrhythmia should always prompt cardiologic examination in search of underlying cardiac disease, particularly hypertrophic or dilated cardiomyopathy. The presence of ventricular arrhythmias without evidence of underlying heart disease does not indicate a special or increased risk of sudden cardiac death. A higher incidence of right and/or left ventricular hypertrophy, exercise-reversible ST elevation, and exercise-reversible changes in T waves (T negativity, sharp and/or excessive T waves) can be considered physiologic changes in the ECGs of athletes. These changes correlate closely with the type of sports activity and degree of training and are reversible when the activity is stopped. Horizontal ST segment depression are by contrast very rare in athletes and should always be clarified by cardiologic examination. Exercise-induced sudden cardiac death in athletes is unusual without preexisting heart disease. The cause of sudden cardiac death among athletes less than 40 years of age can be predominantely ascribed to congenital heart diseases (such as hypertrophic cardiomyopathy or coronary anomalies). In athletes more than 40 years of age and with increasing age, coronary heart disease is the most frequent autopsy finding. A corresponding risk stratification should take these partial dangers into account.

Cardiac arrhythmias in healthy children revealed by 24-hour ambulatory ECG monitoring

Ambulatory electrocardiographic monitoring was performed on 360 healthy children, from newborn infants to junior high school students. They were divided into five groups by age: group A, 63 newborn infants on the first day of life; group B, 50 infants aged 1-11 months; group C, 53 kindergarten pupils aged 4-6 years; group D, 97 primary school pupils aged 9-12 years; and group E, 97 junior high school students aged 13-15 years. The maximal and minimal heart rates were significantly greater in infants than in older children. Sinus arrhythmia was recorded in every child. One boy in group E had an episode of sinus arrest for three seconds without any symptoms. First-degree and Wenckebach type second-degree atrioventricular blocks were not detected in group A and group B, but were most frequent in group E, especially during sleep. Supraventricular premature contractions (SVPCs) were the most common type of arrhythmia detected in this study. More than half of the children had at least one SVPC per 24-h monitoring period, and there were many children with frequent SVPCs in group E. The incidence of ventricular premature contractions (VPCs) in children of groups A and E was rather higher than in the other groups. Ventricular tachycardia was not recorded in any child except one newborn infant who had a couplet of VPCs without symptoms. Each group had different types and incidences of arrhythmias. There was a rising incidence of arrhythmias with advancing age, except in the neonatal period.

The value of electrophysiologic studies in syncope of undetermined origin: report of 150 cases

A prospective study examined the diagnostic yield and therapeutic efficacy of electrophysiologic studies in patients with SUO. We defined SUO as those syncopal or near-syncopal events remaining unexplained after a standardized, noninvasive evaluation that included a history, physical examination, routine laboratory screening, EEG, nuclear brain scan or CAT scan, 12-lead ECG, chest x-ray, orthostatic vital signs, bedside carotid sinus massage, and at least 24 hours of continuous ECG monitoring. The 150 SUO patients included 95 men and 55 women (mean age 62.0 years); 35 had recurrent SUO, 75 (50%) had organic heart disease, and 129 (86%) had abnormal ECGs. There were 162 abnormal electrophysiologic findings that could explain the SUO uncovered in 112 patients, a diagnostic yield of 75%: one finding in 71 patients, two findings in 32, and three findings in nine. These findings were: His-Purkinje disease in 49 patients (30%), inducible ventricular arrhythmias in 36 (22%), AV nodal disease in 20 (12%), sinus node disease in 19 (12%), inducible supraventricular arrhythmias in 18 (11%), carotid sinus hypersensitivity (not elicited by carotid sinus massage prior to electrophysiologic studies) in 15 (9%), and hypervagotonia in five (3%). When electrophysiologic study findings were classified as clearly abnormal or borderline, 54 patients had at least one clearly abnormal finding, a diagnostic yield of 36%. Subgroups of patients presenting with only a single SUO event, no evidence of organic heart disease, or normal baseline ECGs all had substantial diagnostic yields during electrophysiologic studies. Follow-up data in 137 patients (91%) (mean 31 months) showed recurrences in 16 of 34 patients (47%) without and 15 of 103 patients (15%) with electrophysiologic findings despite therapy directed by electrophysiologic testing (p less than 0.0005). This study and a review of the literature indicate that electrophysiologic testing is useful in elucidating the causes of SUO and directing therapy. A significant number of patients benefit from electrophysiologic studies, even when only clearly abnormal findings are considered diagnostic, when only a single syncopal event has occurred, or whether or not organic heart disease or an abnormal ECG is present.

Bradycardia, ventricular pauses, syncope, and sports

16 athletic patients were examined because of syncope, Stokes-Adams attacks, or both. The life-threatening condition required pacemaker implantation in 7 patients. 8 of the 9 other subjects became symptom-free after stopping heavy physical training. 37 top-ranking athletes underwent 24 h Holter monitoring. Pauses longer than 2 s occurred in 19% and resulted from sinus arrest. The longest pause lasted 2.5 s. Second-degree atrioventricular block was noted in 13%.

Ambulatory electrocardiographic monitoring in 100 healthy teenage boys

Ambulatory monitoring of the electrocardiogram in 100 healthy 14 to 16 year old boys showed heart rates ranging from 45 to 200 beats/minute during the day and from 23 to 95 beats/minute during sleep. Sinus arrhythmia was present in all cases and was the only variation noted in 17%. Sudden variations in the PP interval occurred in 41%, but a precise diagnosis of the mechanism was usually impossible; 15% had changes compatible with sinus arrest or temporary complete sinoatrial block, and one boy had a pattern compatible with type II second degree sinoatrial block. Escape rhythms were noted in 26%, first degree atrioventricular block in 12%, and second degree atrioventricular block (Mobitz type I) in 11%. Mobitz type II second degree atrioventricular block was seen on one occasion in one boy. Ventricular extrasystoles seen in 41% were of uniform morphology in 75% and multiform in 25%. Short episodes of ventricular tachycardia were recorded in 3%.

Twenty-four-hour continuous electrocardiography during exercise and free activity in 80 apparently healthy runners

To determine the incidence of arrhythmias and conduction disturbances in trained athletes and the level of physical training at which they occur, 24-hour ambulatory electrocardiographic recordings were obtained in 80 healthy runners during both exercise and free activity. Subjects were grouped according to the number of miles per week (mpw) they had regularly run during the previous 3 months: Group I--0 to less than or equal to 5 mpw (less than or equal to 8 km); Group II--greater than 5 to less than or equal to 15 mpw (greater than 8 to less than or equal to 24 km); Group III--greater than 15 to less than or equal to 30 mpw (greater than 24 to less than or equal to 48 km); and Group IV--greater than 30 mpw (greater than 48 km). Ectopic ventricular complexes occurred in 41 of 80 subjects (50%) and ectopic supraventricular complexes occurred in 33 (41%). There were 2 episodes of paired ventricular ectopic activity and a 5-beat run of ventricular tachycardia with exercise. The study revealed no significant differences in the occurrence of arrhythmias or conduction disturbances in the different groups, although the 2 episodes of paired ventricular ectopic activity and 5-beat run of ventricular tachycardia are of concern.

Multiple electrophysiologic manifestations and clinical implications of vagally mediated AV block

Clinical, surface ECG, and intracardiac findings were analyzed in 20 patients with spontaneous conduction disturbances in whom vagally mediated AV block could be induced by carotid sinus pressure during electrophysiologic evaluation. The latter demonstrated that the surface ECG pattern attributed to bradycardia-dependent (phase 4), and paroxysmal block within the His bundle and bundle branches could reflect vagally mediated, bradycardia-associated (rather than bradycardia-dependent), and paroxysmal AV nodal (AH) block. The decision regarding the use of pacemakers was not based on QRS duration or on patterns (or site) of block but on the underlying clinical settings and the correlation of symptoms with maximal ventricular (R-R) pauses. However, more studies are required to extend our findings, especially to other subgroups of patients (or normal individuals) in whom vagally mediated block occurs.

Ventricular pacing in children

Ventricular pacing was performed in forty-one children ranging from one day to twenty years of age (median age = 10). Weight of the recipient at implant ranged from 2 kg. to 86 kg. Indications included presyncope, syncope, dyspnea on exertion, congestive heart failure, postoperative infra-Hisian heart block, and inadequate cardiac rate during pharmacotherapy. Four patients died during follow-up, but no deaths were attributable to pacemaker management. In contrast, 66% of the patients required more than one pacemaker related-operative procedure, and 43% of leads implanted failed by 48 hours. Indications for permanent cardiac pacing in this population at this time are symptomatic congenital AV block, symptomatic sinus node disease, and AV block in the postoperative period. Technological developments which might reduce complications seen in this population and electrophysiologic techniques which may better define indications for pacing in children are also reviewed.

Ambulatory electrocardiographic recording in endurance athletes

Data from ambulatory electrocardiographic recording in 35 highly trained endurance athletes and in 35 non-athletic controls of similar ages are given. The minimal, mean hourly, and maximal heart rates were significantly lower in the athletes. Thirteen athletes (37 . 1%) but only two controls (5 . 7%) had sinus pauses exceeding 2 . 0 seconds. First degree atrioventricular block was observed in 13 athletes (37 . 1%) and five controls (14 . 3%), second degree Wenckebach type block in eight athletes (22 . 9%) and two controls (5 . 7%), and second degree block with Mobitz II-like pattern in three athletes (8 . 6%) and no control. All athletes with Mobitz II-type pattern also had first degree and Wenckebach-type second degree atrioventricular block. The behavior of sinus rate on development of atrioventricular block varied, not only interindividually but also intraindividually, from absence of change to an increase or decrease in most subjects in both study groups. A decrease in sinus rate on appearance of atrioventricular block was found constantly in only two athletes and one control. Atrioventricular dissociation with junctional rhythm occurred in seven athletes (20%) and with ventricular rhythm in one athlete. Neither of these phenomena was seen in the group of controls. The athletes had slightly fewer ventricular extrasystoles than controls, and no athlete had ventricular tachycardia, whereas two controls had ventricular tachycardia.

Natural history of chronic second-degree atrioventricular nodal block

This report details our experience with documented chronic second-degree atrioventricular (AV) nodal block (proximal to His [H]) in 56 patients. Forty-six men (82%) and 10 women (18%), ages 18-87 years, were studied. Nineteen of the patients (34%) had no organic heart disease (including seven trained athletes) and 37 (66%) had organic heart disease. ECGs in all patients demonstrated episodes of type I second-degree block; five patients also had periods of 2:1 block. Prospective follow-up patients with no organic heart disease (157-2280 days, mean 1395 +/- 636 days) revealed one patient with clear indication for permanent pacing because of bradyarrhythmic symptoms (permanently placed on day 220 of follow-up). Two patients died nonsuddenly. In patients with organic heart disease (prospective follow-up of 60-2950 days, mean 1347 +/- 825 days), pacemakers were implanted in 10 patients, primarily for treatment of congestive heart failure in eight and syncope in two. Sixteen patients died -- three suddenly, seven with congestive heart failure, two of an acute myocardial infarction and four of causes unrelated to cardiac disease. In summary, chronic second-degree AV nodal block has a relatively benign course in patients without organic heart disease. In patients with organic heart disease, prognosis is poor and related to the severity of underlying heart disease.

24-hour electrocardiographic study of heart rate and rhythm patterns in population of healthy children

Twenty-four hour electrocardiographic recordings were made on 104 randomly selected, healthy 7 to 11-year-old children. Ninety-two were technically adequate and suitable for analysis. The mean highest heart rate measured by direct electrocardiographic analysis over nine beats was 164 +/- 17. The mean lowest heart rates were 49 +/- 6 over three beats', and 56 +/- 6 over nine beats' duration. The maximum duration of heart rates less than 55/minute was 40 minutes. At their lowest heart rates 41 children (45 per cent) had junctional escape rhythms, the maximum duration of which was 25 minutes. Nine children showed PR intervals greater than or equal to 0.20 s and included three with Mobitz type I second degree atrioventricular block. Nineteen (21%) had isolated supraventricular or ventricular premature beats (less than 1/hour). Sixty subjects (65%) had sinus pauses that could not be distinguished on the surface electrocardiogram from those previously described as sinuatrial exit block or sinus arrest. The maximum duration of sinus pause measured over 24 hours on each child was 1.36 +/- 0.23 seconds. Thus apparently healthy children show variations in heart rate and rhythm over 24 hours hitherto considered to be abnormal.

Sinuatrial disease in young people

A survey at three cardiac centres disclosed nine patients under the age of 25 years with sinus node dysfunction in the absence of other forms of heart disease. All were male and seven were above the 90th centile for height. Ambulatory monitoring was performed on all the first-degree relatives of six of the patients and three families showed conducting system disturbances in the form of sinuatrial disorders or delayed atrioventricular conduction. A genetic factor may be involved in the aetiology of sinuatrial disease in young people.

Wenckebach second-degree A-V block in top-ranking athletes: an old problem revisited

The occurrence of Wenckebach second-degree (Mobitz I) A-V block in apparently normal persons still provides a puzzle for the cardiologist, as the benign nature of this event has been recently questioned. This problem becomes more intriguing when Wenckebach A-V block is encountered in asymptomatic top-ranking athletes, because of medico-legal implications. We report 10 cases of highly-trained athletes, including three with mitral valve prolapse (MVP) features, with a spontaneous or induced Wenckebach second-degree A-V block. Previous ECGs of six subjects, dating from a maximum of 6 years to a minimum of 18 months, were available. Deterioration of A-V conduction has never been documented and all six cases have remained asymptomatic for the whole follow-up period. Athletes have been submitted to a protocol study consisting of ECG recording at rest, during, and after vagal and sympathetic reflex maneuvers, drug administration (isoproterenol and atropine), submaximal and maximal exercise. Nine subjects have been considered to have "normal" responses of the A-V node to provocative tests, since conduction disturbances were improved or normalized by reflex sympathetic stimulations and were completely normalized by autonomic drug administration and exercise. One athlete showed "abnormal" responses to tests. In order to give a conclusive prognostic and medico-legal assessment, we advised him to submit to an invasive electrophysiological investigation. Wenckebach second-degree A-V block in athletes may be a more common finding than so far described, especially when a systematic search is made. In our opinion, this event can still be considered a vagally-induced benign feature of athlete's heart, provided that an immediate improvement of A-V conduction is obtained in response to reflex sympathetic maneuvers, and that a complete normalization after sympathomimetic and vagolytic drug administration and physical exercise is observed. The clinical histories of our athletes and the observed complete disappearance of conduction disturbances after detraining, strongly support this opinion. Wenckebach second-degree A-V block in asymptomatic athletes with MVP features probably does not affect the prognosis if similar favorable responses to the aforesaid tests are observed.

Clinical and electrophysiologic findings in patients with paroxysmal slowing of the sinus rate and apparent Mobitz type II atrioventricular block

Over five years, 13 patients with episodic apparent type II atrioventricular (AV) block associated with sinus slowing were seen. This phenomenon occurred only transiently during an acute illness in eight patients (group I) but recurred chronically in five (groupII). For the group as a whole, the mean spontaneous cycle length was 42% longer during the period of AV block compared with periods of 1:1 AV conduction (800 +/- 116 msec to 1138 +/- 489 msec) (P less than 0.05). Electrophysiologic studies in four group I patients showed no abnormalities, whereas abnormalities in AV nodal conduction and refractoriness or provocation of intranodal Mobitz type II AV block (during carotid massage) were observed in three patients in group II and were totally abolished by atropine. In group I patients, apparent type II AV block was self-limited. In the chronic group, recurrent symptoms required insertion of permanent pacemakers in two patients. Simultaneous type II block and sinus slowing appeared to be related to the effects of increased vagal tone on both nodal structures. Intracardiac pacing is not indicated for patients with transient episodes associated with an acute illness, but may be required for symptomatic patients with recurrent episodes.