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Assessing how genes flow across populations is a key component of conservation genetics. Gene flow in a natural population depends on ecological traits and the local environment, whereas for a livestock population, gene flow is driven by human activities. Spatial organization, relationships between farmers and their husbandry practices will define the farmer's network and so determine farmer connectivity. It is thus assumed that farmer connectivity will affect the genetic structure of their livestock. To test this hypothesis, goats reared by four different ethnic groups in a Vietnamese province were genotyped using 16 microsatellites. A Bayesian approach and spatial multivariate analysis (spatial principal component analysis, sPCA) were used to identify subpopulations and spatial organization. Ethnic group frequencies, husbandry practices and altitude were used to create cost maps that were implemented in a least-cost path approach. Genetic diversity in the Vietnamese goat population was low (0.508) compared to other local Asian breeds. Using a Bayesian approach, three clusters were identified. sPCA confirmed these three clusters and also that the genetic structure showed a significant spatial pattern. The least-cost path analysis showed that genetic differentiation was significantly correlated (0.131-0.207) to ethnic frequencies and husbandry practices. In brief, the spatial pattern observed in the goat population was the result of complex gene flow governed by the spatial distribution of ethnic groups, ethnicity and husbandry practices. In this study, we clearly linked the livestock genetic pattern to farmer connectivity and showed the importance of taking into account spatial information in genetic studies.

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INTRODUCTION: In case of an accessory pathway, children are exposed to severe cardiac events including sudden death. Radiofrequency ablation is a standardized procedure, which can be applied to a significant number of children although complications can still potentially occur. In this context, transesophageal evaluation of the accessory pathway evaluation can be discussed. MATERIALS AND METHODS: Among 140 procedures performed in 19 years, 70 were done for accessory pathway evaluation. The preexcitation was overt in 59 children older than 5 years, which form the basis in this study. RESULTS: Anterograde refractory period was determined in 88% cases and was found<220 ms in 12 cases justifying an ablation procedure. Conversely, in case of a long refractory period (>250 ms), the ablation procedure was not performed in 8 asymptomatic cases and was postponed in 11/20 mildly symptomatic children. Transesophageal electrophysiologic study seems legitimate in asymptomatic or mildly symptomatic children. CONCLUSION: This technique is probably less useful in case of an overt preexcitation and recurrent reciprocating tachycardia requiring long-term antiarrythmic treatment. In this case, endocavitary electrophysiological study eventually followed by an ablation procedure seems the best option.

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Prone sleep position is obviously the main risk factor for sudden infant death. Other risk factors, such as vagal overactivity particularly in the familial form, are still discussed. We here report 15 families characterized by the coexistence of vagal overactivity and sudden infant death. At least, 1 child for each family had documented [Holter or occulo-cardiac reflex (OCR)] vagal overactivity. In 5 families 2 children were affected; in 2 families 3 children were affected and in 1 family 4 children were affected. Sudden death occurred in the elderly of the family in 8 cases, in the twin in 3 cases, in the 2nd in 3 cases and in the 5th child in 1 case. Within the 15 families, at least 1 parent had experienced vagally-induced fainting or syncope in 10 cases. Familial pattern of vagal overactivity is underlined. Possible links between vagal overactivity, risk factor for suddden death and sudden death are discussed. We suggest an Holter-ECG and OCR follow-up for sudden infant death siblings with history of familial vagal overactivity (3 examinations during the 1st year of life, at 1, 3 and 9 months).

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Breath-holding spells are common and usually benign. However, the authors chose to implant a pacemaker in children presenting with severe symptoms. Over the last 15 years, 11 children with severe breath-holding spells were paced. All had reflex spells with loss of consciousness, spontaneously or after minor trauma, and 6 had seizures. All had a normal ECG with marked bradycardic responses to ocular pressure. The 24 hour ECG showed pauses (12-25 s) in 4 patients, sudden bradycardia (< 30/min) in 3 patients, and sinus arrhythmia in the remaining 4 patients. Medical treatment has been unsuccessful. Pacemaker implantation was decided because of the severity and/or the frequency of the episodes in 10 children, and because of intolerable familial anxiety in the other one. Age at implantation ranged from 14 months to 5.5 years (mean: 16.5 +/- 20 months). The device was implanted by an epicardial (7) or from an endocardial (4) approach. All had a ventricular demand device, except for one who was paced from the atrium. The results were spectacular, with disappearance of spells and restoration of normal activities. Holter monitoring showed normal function of the pacemakers. Recurrences were observed in 3 patients, either due to loss of capture (2 cases) or to the need for explantation because of cutaneous erosion. Follow-up ranged from 10 months to 14 years (mean: 7.9 +/- 4.2 years); 2 patients were lost to follow-up; 4 patients totally recovered and only 5 are still vagotonic. Two pacemakers have been changed at 13 and 15 years respectively. The authors conclude that although psycho-social factors play a part in breath-holding spells, pacemaker implantation is very effective in suppressing symptoms in severely affected children.

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Angelman's syndrome is an association of severe mental retardation with absence of language, ataxia, convulsions and hyperactive, joyful behaviour with frequent bouts of laughing. Genetic diagnosis is possible in about 80% of cases. No cardiovascular abnormalities have been described in this syndrome to date. The authors report the cases of three children with Angelman's syndrome who presented with severe malaise due to increased vagal tone. The age of onset of symptoms was between 20 months and 8 years. One of the children had malaises triggered by bouts of laughing. The diagnosis was confirmed in all three cases by the results of Holter 24 hour ECG recording and oculo-cardiac reflex. The treatment chosen was Diphemanil (Prantal) in the two patients under 2 years of age (after failure of a trial of betablockers in one case) and Disopyramide for the oldest child with excellent results in all cases. However, one child died suddenly at the age of 6, two years after stopping diphemanil. Based on these observations, the authors suggest that all malaises in patients with Angelman's syndrome should be investigated by Holter ECG and oculo-cardiac reflex (or tilt test). In view of the potential gravity of the syncopal attacks, long-term medical treatment seems to be justified.

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BACKGROUND: Primary ventricular arrhythmias are rarely seen in children. Some of them have a poor prognosis; they should be diagnosed because adequate treatment can prevent sudden death. POPULATION AND METHODS: Twenty children (11 male, nine female), aged 3 to 16 years (mean: 7.7 +/- 4), with apparently normal hearts and normal QTc intervals were referred for stress or emotion-induced syncope. Primary ventricular arrhythmia, consisting of isolated polymorphic ventricular extrasystoles followed by salvos eventually degenerating into ventricular fibrillation, was reproducibly induced by physical exertion. The syncopal events and "torsades de pointe" disappeared with beta-blocking therapy. A total of four syncopal events and two sudden deaths occurred during a mean follow-up of 8 years, probably due to discontinuation of treatment. DISCUSSION: Fifty-four-cases of stress-induced severe polymorphous ventricular arrhythmia have been reported in the literature. There were four sudden deaths in 37 patients on beta-blocking therapy, and ten sudden deaths in 21 untreated patients. CONCLUSION: Clinically close to the congenital long QT syndrome, this primary ventricular arrhythmia must be looked for in cases of stress or emotion-induced syncope. The diagnosis relies on Holter monitoring and a stress test. Life-long beta blocker therapy is required.

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Thirty-five patients aged 6 days to 18 years (average 7.5 +/- 5.2 years) were treated for an average period of 16 months (range 8 days to 50 months) with flecainide acetate at an average dose of 4.8 +/- 1.4 mg/kg (2.9 to 10 mg/kg) or 130 +/- 30.5 mg/m2 administered twice daily. The cardiac arrhythmia was a resistant paroxysmal junctional tachycardia due to a Wolff-Parkinson-White syndrome in 27 cases, intranodal reentry in 6 cases and a chronic reciprocating rhythm in 2 cases. Treatment was successful with complete suppression of the tachycardia in 24 cases. Partial success with a good clinical result was obtained in 4 cases and there were 7 failures, 6 due to inefficacy of the drug, and 1 because of an extracardiac secondary effect. One case of incessant junctional tachycardia was observed in a 9 month old child in whom the preexcitation disappeared. Atrioventricular preexcitation persisted in 20 out of 24 cases. The duration of the non-preexcited QRS complexes increased significantly from 73.6 +/- 13.8 to 82.2 +/- 15.2 ms; n = 14, p less than 0.01. The minimal effective plasma concentration was 347 +/- 147 ng/ml. The plasma concentration/dose ratio of children over 4 years of age was the same as in adults. It was significantly higher in babies and infants suggesting a progressive acquisition of the capacity to metabolise flecainide during the first year of life. In conclusion, flecainide acetate was easy to use with respect to administration and follow-up, and seems to be a drug of choice for the treatment of junctional tachycardia in children.

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On the occasion of a preliminary series of 38 cases, the authors review the esophageal pacing technique and its main indications. On the therapeutic level, the esophageal lead may be successfully used to decrease supraventricular tachycardias due to reentry (typical or atypical flutter, reciprocating nodal tachycardia with or without WPW). As a means of investigation, esophageal pacing is overall useful to diagnose undocumented paroxysmal tachycardia fits (palpitations), to evaluate the refractory stage of an accessory pathway (WPW) or to assess the refractory stage of antiarrhythmia medications. This investigation may also be used to assess the sinusal function, the atrioventricular conduction (Wenckebach point) and the spontaneous rhythm of atrioventricular blocks after pacemaker insertion. Due to the technical improvements achieved, esophageal pacing may be used presently in pediatric units taking care of children with arrhythmias.

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Thirty children aged from 3 months to 20 years were treated with propafenone 250 to 650 mg/m2 divided into 2 to 4 daily doses, for a mean period of 14 months (range: 4 days to 5 years); 8 had chronic atrial tachycardia, 9 had junctional arrhythmia and 13 had ventricular arrhythmia. There were 17 good results (suppression of the arrhythmia), 7 fair results (good clinical effect but partial persistence of the arrhythmia) and 6 failures, either because the drug proved ineffective (3 cases) or on account of side-effects (3 cases). In the treatment of chronic atrial tachycardia propafenone seemed to be more effective than amiodarone in 3 cases and as effective as that drug in 2 cases. In junctional arrhythmia propafenone was certainly effective but unpredictably so (3 good results, 2 fair results, 4 failures). Among ventricular arrhythmias, ventricular tachycardia in bursts was the one which benefited most regularly from treatment with propafenone: the results in 8 patients were better than those obtained with other antiarrhythmic agents (class I drugs, beta-blockers, calcium antagonists); only amiodarone proved superior to propafenone in this type of arrhythmia. Despite a 27% incidence of side-effects, propafenone was generally well tolerated by the children, with no significant gastrointestinal disorders. No depressive effect on the myocardium was noted in 6 children with moderate heart failure well controlled by digitalis and diuretics. However, since overdosage may cause severe disorders of conduction with widened ventriculogram, we recommend regular ECG monitoring during the first 3 days of treatment at least: although there is little slowing down of sinus rate (12%) and little modification of the slow phase under treatment, serious toxicity is possible. Thus, propafenone is a drug that should be handled with caution, but it constitutes a major addition to the range of antiarrhythmic agents which can be used in paediatrics.

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For a period of 20 months, 50 consecutive infants (mean age: 11 months) were given Diphemanil (atropine like synthetic drug) for reflex symptomatic bradycardia of probable vagal origin. Treatment's results were evaluated with the study of oculo-cardiac reflex (OCR) and Holter monitoring performed before and 3 months after the beginning of Diphemanil. If tolerance was generally good, it was not possible to demonstrate the clinical efficacy of the treatment on the whole group. However, assertive success was seen on individual cases. Holter and OCR data improved statistically. The other therapeutical means aiming at warning possible complications of the hypertonic vagal reflex were reviewed: inserting a cardiac pace-maker does not always prevent sudden death; a nodal sinus surgical selective denervation might be justified in certain exceptional cases, because of the severity of the spontaneous evolution or of the resistance to medical treatment.

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Sinus node dysfunction after intra-atrial repair of transposition of the great arteries by a Mustard or Senning procedure is well known. We undertook this study to evaluate the frequency, the nature, the severity and evolution of these dysrhythmias by performing Holter monitoring in 123 children followed up over 5 years; 302 Holter recordings were reviewed. The patients were divided into 3 groups of increasing severity: I = no sinus node dysfunction, II = moderate sinus node dysfunction, III = severe sinus node dysfunction with bradycardia of less than 30/min and/or pauses of over 2000 ms. The association of atrial hyperexcitability was classified in 3 subgroups: A = no extrasystoles, B = at least 4 extrasystoles per 24 hours, C = atrial tachycardia (focal tachycardia or flutter) after the first six postoperative months. There were only 15% of normal recordings (IA) and the majority of children (58%) were classified in the intermediary groups (IB, IIA and IIB). Sinus node dysfunction tended to become more severe with time in nearly 30% of the 69 cases followed up sequentially. The bradycardia tended to become more severe and associated with episodes of atrial tachycardia: the frequency of type B and C increased to 30% in Group I, to 68% in Group II and to 91% in Group III. The attacks were severe, especially in patients with a mediocre postoperative haemodynamic result. This explains the global mortality of 3%, the morbidity of 15% and the pacemaker implantation rate of 12%.(ABSTRACT TRUNCATED AT 250 WORDS)

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Incessant reciprocating tachycardia (IRT) was diagnosed in 10 children aged 0-11 years (mean 2.5 years), followed-up for an average of 11 years (range 4-22 years). 8 children were treated for an average period of 2.8 years (range 0.5-6 years) with the association of amiodarone and digitoxine. All children were treated initially or secondarily with verapamil and/or betablockers with digitoxine for an average of 4.6 years (range 1-9 years). The true frequency of IRT, its tolerance and the age at diagnosis did not indicate the probable required length of treatment with amiodarone, but only the initial response to this drug. Finally, 5 patients were cured and in sinus rhythm, and the other 5 were well controlled, having only occasional bursts of tachycardia. When we compared one group of 5 cases with clinical signs of cardiac failure and radiological cardiomegaly (CTR greater than 0.60) with a second group of 5 cases in which the arrhythmia was better tolerated, surprisingly, the frequency of intreated IRT was not t he factor which influenced its tolerance (198/min vs 194/min). On the other hand, the following differences were observed between the two groups: a younger age at diagnosis in the first group (5 months vs 4.6 years) responsible for the longer follow-up period (14.5 vs 7 years), earlier treatment period with amiodarone (3.6 years compared to 5.5 years) and a longer treatment period with this drug (3.5 vs 2 years). It was only at about the age of 7 that this treatment could be withdrawn or changed with half the children completely cured, and the other half only controlled.(ABSTRACT TRUNCATED AT 250 WORDS)

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Our use of amiodarone in 200 patients during an 8-year period confirms our previous experience which indicated that the drug was close to being the ideal antiarrhythmic agent in children's arrhythmias. Its absence of cardiac toxicity, its powerful antiarrhythmic properties, its depressive effect on the AV nodal conduction, combined with its beta-inhibitory effect makes it effective and harmless in practically all forms of atrial, junctional and ventricular arrhythmias, whatever the reentrant or automatic mechanism of the arrhythmia. The metabolism is much faster in children than in adults, making the drug active in a few hours, with a lesser prolonged duration of action. Though there is practically no limitation for its use on a short- or mean-term basis, the long-term use must be limited to truly refractory arrhythmias, a situation which is rarely encountered. In such cases, combining amiodarone with conventional therapy allows a decrease in the maintenance dosage and a lower incidence of extracardiac side effects.

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