Infants with apparent life threatening events. Cardiac rhythm and conduction

The role of cardiac dysrhythmias in the pathogenesis of Sudden Infant Death Syndrome (SIDS) is uncertain, but there have been several reports of infants with Apparent Life Threatening Events (ALTE) due to significant dysrhythmias. To further characterize the cardiac rhythm and conduction of these "at-risk for SIDS" infants, we performed 24-hour continuous (Holter) electrocardiograms on 100 full term, healthy infants with ALTE. Sixty-two patients (62%) had one or more dysrhythmias on Holter monitor. Twenty-five patients (25%) had premature ventricular depolarizations (PVD), including five with couplets. Thirty (30%) had QTc greater than 2 SD above the mean, and, of these, 40 percent had PVD's. Fifteen (15%) had premature atrial depolarizations and 39 (39%) had evidence of moderate or marked sinus node irregularity. There was no prexcitation, supraventricular tachycardia, ventricular tachycardia, or atrioventricular block. Two patients with marked sinus node dysfunction were treated with propantheline and did well. All patients were monitored at home, with no deaths or clinically significant dysrhythmias on follow-up (1-32 months (mean = 18]. In summary, when Holter monitoring was performed, a high incidence of dysrhythmia was found in infants with ALTE. Most dysrhythmias were clinically insignificant. The incidence of ventricular dysrhythmias and long QTc are consistent with previously advanced theories of cardiac electrical instability in some of these patients, but no patient with ventricular dysrhythmias required therapy. The incidence of sinus node dysfunction requiring therapy was 2 percent. Although Holter monitoring of infants with ALTE only infrequently determines therapy, it may provide data linking theories of cardiac etiology of SIDS with actual clinical events.     

Cardiac Dysrhythmias in Pediatric Patients Before and 1 Year After Transcatheter Closure of Atrial Septal Defects Using the Amplatzer Septal Occluder

To prospectively assess the incidence of cardiac dysrhythmias before and after closure of atrial septal defects (ASDs) using the Amplatzer septal occluder (ASO), 24-hour Holter electrocardiograms (ECGs) were performed before and 1 year after the procedure in 23 pediatric patients (9 male and 14 female). Patients' ages ranged from 2 to 15 years (mean, 7.1 years). All had an ASD of the secundum type that was completely closed (n = 22) or had a small residual shunt (n = 1). No preexisting dysrhythmia was present in 22 patients; atrioventricular nodal reentrant tachycardia had been diagnosed in 1 patient. During the observation period, no clinical dysrhythmia occurred. Analysis of the Holter ECGs before the intervention showed regular sinus rhythm in 20 patients and sinus rhythm with intermittent atrial rhythm in 3 patients. Atrial premature complexes (APCs) were detected in 1 patient, and a ventricular couplet was present in 1 patient. The Holter ECG 1 year after the intervention showed sinus rhythm in 18 patients and sinus rhythm with intermittent atrial rhythm in 5 patients. APCs were still observed in 1 patient and seen for the first time in 1 patient; 1 patient and rare ventricular premature complexes. In conclusion, cardiac dysrhythmias on Holter ECG in pediatric patients before and 1 year after transcatheter ASD closure with the ASO device are rare and benign. Regular Holter monitoring seems to be useful in detecting late dysrhythmias.     

Dysrhythmias after the modified Fontan procedure

Summary The cardiac rhythm before and after the modified Fontan procedure was reviewed in 24 patients. Transient atrial dysrhythmias were common in the immediate postoperative period. Late postoperative premature atrial contractions were detected by ambulatory monitoring in 20 of 23 patients; eight (34.8%) had supraventricular tachycardia. Late ventricular dysrhythmia was detected in 18 of 23 patients: ten had low-grade ventricular dysrhythmias and eight (34.8%) had multiform premature ventricular contractions. Five of the latter had couplets and one of these five plus another had ventricular tachycardia. Seven patients with supraventricular tachycardia and five patients with ventricular dysrhythmia required antiarrhythmic medication. Asymptomatic bradycardia was detected in five patients (21.7%). One patient had intermittent second-degree atrioventricular block. No specific risk factors predicted dysrhythmias. Thus, cardiac dysrhythmias were common in patients after the modified Fontan procedure, but were well tolerated in most patients. No sudden deaths or syncopal episodes have occurred during a mean follow-up of 5 years. One patient's death was related to severe left ventricular dysfunction. Permanent pacing has not been required in any patient.     

Dysrhythmias following the Mustard and Senning operation for transposition of the great arteries

The prevalence and nature of late dysrhythmias following operative repair of transposition of the great arteries were evaluated in 32 children using pre- and postoperative standard electrocardiograms and postoperative Holter monitoring. The Mustard procedure was performed in 17 patients, the Senning procedure in 15 patients. The mean age at operation was 40 +/- 35 months in the Mustard and 9 +/- 6 months in the Senning group. The mean interval between operation and Holter monitoring 7 +/- 2 years in the Mustard and 1.6 +/- 1 years in the Senning group. All patients had sinus rhythm preoperatively. Following operation, the incidence of sinus rhythm increased from 59% in the Mustard and 87% in the Senning group in the first postoperative week to 76% in the Mustard and 100% in the Senning group at the end of follow-up (mean 4.6 +/- 3.5 years). Holter monitoring revealed dysrhythmias or conduction abnormalities in 12 patients (9 Mustard, 3 Senning). A permanent pacemaker had to be inserted in 2 Mustard patients because of complete atrioventricular block and sinus bradycardia with sinus arrest, respectively. Results indicate a prevalence of late postoperative dysrhythmias of 20% in the Senning and of 59% in the Mustard group (p less than 0.05). However, the significantly longer mean follow-up period of the Mustard group precludes a direct comparison between the 2 types of repair.     

Sinus node dysfunction in children and adolescents: treatment by implantation of a permanent pacemaker in 26 patients

Sinus node dysfunction has been reported rarely in pediatric patients with structurally normal hearts. It has been diagnosed with increasing frequency in children and young adult patients with congenital heart defect, especially in patients who have undergone corrective cardiac surgery related with atrial tissue. Between 1984-1999, 26 patients who were under 22 years of age underwent implantation of a permanent pacemaker for treatment of sinus node dysfunction at our medical center. This subset of patients represents 18.5% of all patients who required permanent pacemakers during this time. The mean age of the 17 male and 9 female patients at initial implantation was 9.2+/-6 years (range, 0.5 to 22 years). Of the 26 patients, 18 (69%) had associated cardiovascular disease and in 11 (34.6%) patients, sinus node dysfunction developed after a cardiac operation. The patients were followed up for a total 1,227 (47+/-45, range 2-176, median 34) pacing months. All symptomatic patients noted a resolution of symptoms after pacing had been performed, and they remained free of symptoms at the latest follow-up examination. Mean acute pacing thresholds and mean latest pacing thresholds for the endocardial atrial and ventricular leads, mean acute impedance and mean latest impedance for the endocardial atrial and ventricular leads and mean acute p wave voltage and the latest p wave voltage did not differ significantly. In this report, we review our experience in children who required implantation of a permanent pacemaker for treatment of sinus node dysfunction during a 15-year period.     

Transesophageal electrophysiologic study in children and young patients

Transesophageal electrophysiologic study (TEEPS) is a semi-invasive method of atrial stimulation and recording. The aim of the study was to report our experience with TEEPS in children and young adults. A total of 153 TEEPS were performed in 147 consecutive patients aged between 26 days to 26 years (mean 9.8 years) with the following indications: evaluation of symptoms that may be signs of any arrhythmias in 89 procedures (Group A), risk assessment of Wolff-Parkinson-White syndrome (WPW) in 17 procedures (Group B), determination of the mechanism of previously detected or ongoing tachycardia on ECG or Holter monitoring in 22 procedures (Group C), assessment of antiarrhythmic therapy effectiveness in 17 procedures (Group D), and follow-up of radiofrequency ablation procedure (RFA) in 8 procedures (Group E). A similar pacing protocol was performed for induction of tachycardia in each patient. Tachycardia was induced in a total of 72 procedures (72/153, 47%): 32/89 (36%) in Group A, 13/17 (76.5%) in Group B, 12/22 (54.5%) in Group C, 12/17 (70.6%) in Group D and 3/8 (37.5%) in Group E. In Group A, the ventriculoatrial (VA) interval of inducible tachycardia was found to be shorter than 70 msec in 16/32 (50%) and longer than 70 msec in 12/32 (37.5%) patients and these patients were diagnosed as having atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT), respectively. In this group, 1 atrial tachycardia, 2 junctional ectopic tachycardia, 1 sinus node reentrant tachycardia and 1 permanent junctional reciprocating tachycardia (PJRT) were also diagnosed. In conclusion, transesophageal atrial stimulation is a valuable tool in the initial evaluation of patients with symptoms possibly related with arrhythmia or in the management of patients who have any arrhythmia.     

Arrhythmia Management in the Fontan Patient

With longer duration of follow-up, as many as 50% of Fontan patients will develop atrial tachycardia, usually in association with significant hemodynamic abnormalities. Arrhythmia management in the Fontan patient is reviewed. The incidence and type of arrhythmia occurrence are examined, including macro-reentrant rhythm which involves the right atrium, reentrant rhythm localized to the pulmonary venous atrium (seen in patients with lateral tunnel procedures), and atrial fibrillation. Risk factors for development of these arrhythmias are considered, and short- and long-term therapeutic options for medical and surgical treatment are discussed. Surgical results are presented for 117 patients undergoing Fontan conversion and arrhythmia surgery (isthmus ablation (9), modified right atrial maze (38) or Cox-maze III (70)). Operative mortality is low (1/117, 0.8%). Seven late deaths occurred, and include two patients who died shortly following cardiac transplantation (2/6, 33%) after Fontan conversion and arrhythmia surgery. Overall arrhythmia recurrence is 12.8% during a mean follow-up of 56 months. Fontan conversion with arrhythmia surgery can be performed with low operative mortality, low risk of recurrent tachycardia, and marked improvement in functional status in most patients. Because the development of tachycardia is usually an electromechanical problem, attention to only the arrhythmia with medications or ablation may allow progression of hemodynamic abnormalities to either a life-threatening outcome or a point at which transplantation is the only potential option. Because cardiac transplantation in Fontan patients is associated with high early mortality, earlier consideration for surgical intervention is warranted.     

Cardiac dysrhythmias after transcatheter closure of ASD with Amplatzer device

Transcatheter closure of atrial septal defect (ASD) has been used as an alternative to open heart surgery. Although transcatheter closure of ASD with the Amplatzer septal occluder is a safe and feasible method in pediatric patients, there is little published data on arrhythmia analysis following transcatheter device closure of secundum ASD. We evaluated cardiac dysrhythmias with 24-hour ambulatory electrocardiographic (ECG) monitoring after transcatheter closure of ASD with Amplatzer device. A total of 85 consecutive patients with ASD underwent transcatheter closure of secundum ASD with Amplatzer device between October 1998 and December 2003. The study involved 65 of these patients assessed by 24-hour ambulatory ECG monitoring. Seven patients were evaluated a second time by 24-hour monitorization. During the procedure, transient complete atrioventricular (AV) block was seen in two patients. One of them returned to normal sinus rhythm in catheterization lab and the other returned to normal sinus rhythm in two hours. Transient junctional rhythm was observed in another patient during the device placement. Twenty-four hour ambulatory ECG monitoring was performed on all patients after a mean four-month period (1-12 months). Holter recordings demonstrated rare supraventricular extrasystole in two patients, rare ventricular premature beats in two patients, and intermittent sinus arrest with sinus pause lasting <1.5 seconds in one patient, for a total of five patients (7.6%). In conclusion, dysrhythmias after transcatheter device closure of secundum ASD with Amplatzer device are rare and benign. We need further long-term follow-up to evaluate late dysrhythmias after the transcatheter device closure of secundum ASD.     

Antiplatelet Versus Anticoagulation Therapy After Extracardiac Conduit Fontan: A Systematic Review and Meta-Analysis

The benefits of prophylactic anticoagulation or antiplatelet therapy for patients undergoing extracardiac conduit (ECC) Fontan procedure still are a matter of debate. Through a systematic review and meta-analysis, this study aimed to determine the incidence of thromboembolism among patients undergoing ECC Fontan who received anticoagulation or antiplatelet therapy. Until February 2010, MEDLINE studies describing the incidence of thromboembolic events after ECC Fontan were reviewed. Information on type of drugs and clinical outcome was extracted. The 20 studies analyzed involved 1,075 patients: 220 (20.4%) in the antiplatelet group and 855 (79.5%) in the anticoagulation group. The mean follow-up period ranged from 2 to 144 months. The overall thromboembolism rate was 5.2% (95% confidence interval [CI], 3.8–7%; I² = 0%; p_het = 0.32). The effect of different therapeutic strategies on the occurrence of thromboembolic and bleeding events was analyzed. Interestingly, the anticoagulation therapy compared with the antiplatelet therapy was not associated with a significant reduction in the incidence of overall thromboembolic complications (5% vs 4.5%, respectively; I² = 0%; p_het = 0.80). Only two cases of bleeding were observed among patients receiving anticoagulant therapy at the time of the event. For patients undergoing ECC Fontan, the rate of thromboembolic and bleeding events associated with antiplatelet therapy is similar to that associated with anticoagulation therapy.     

Heart Rate Variability in Children With Fontan Circulation: Lateral Tunnel and Extracardiac Conduit

The technique in Fontan surgery has developed from the lateral tunnel (LT) toward the extracardiac conduit (EC) used to reduce long-term complications such as atrial arrhythmia and sinus node dysfunction. Heart rate variability (HRV) examines cardiac nervous activity controlling the sinus node. This study aimed to investigate HRV in a cohort of children with univentricular hearts, focusing on the relation between HRV and surgical procedure. For 112 children with Fontan circulation, HRV was analyzed using power spectral analysis. Spectral power was determined in three regions: very-low-frequency (VLF), low-frequency (LF), and high-frequency (HF) regions. Patients were compared with 66 healthy controls subject. Patients with LT were compared with patients who had EC. The children with Fontan circulation showed a significantly reduced HRV including total power (P < 0.0001), VLF (P < 0.0001), LF (P < 0.0001), and HF (P = 0.001) compared with the control subjects. The LT and EC patients did not differ significantly. Reduced HRV was found in both the LT and EC patients. In terms of HRV reduction, EC was not superior to LT.     

Can Analysis of Heart Rate Variability Predict Arrhythmia in Children with Fontan Circulation?

The aim of this study was to examine whether changes in heart rate variability (HRV) can predict arrhythmias in children who have undergone the Fontan procedure. The study included 15 children with total cavopulmonary connection. All examinations included echocardiography and 24-h ambulatory electrocardiogram with power spectral analysis of HRV and Poincaré plots (plots of each R-R interval as a function of the previous R-R interval). Six patients developed supraventricular tachycardia (four or more consecutive supraventricular beats). One patient was excluded from the study due to the development of bradycardia, necessitating placement of a pacemaker. Compared to the arrhythmia group, the patients without arrhythmias (n = 8) exhibited a significant difference in the standard deviation of instantaneous beat-to-beat R-R interval variability (p = 0.02). Poincaré plots of patients without arrhythmias showed a typical torpedo- or comet-shaped pattern, whereas the arrhythmia group showed a more complex pattern. Although this study examined only a few subjects, needing confirmation by larger studies, it does indicate that patients who develop arrhythmias after receiving the Fontan procedure show a different Poincaré pattern compared to the nonarrhythmic group—even before the arrhythmia can be detected using the conventional Holter procedure. Routine follow-up using the Holter procedure and Poincaré plot analysis could help detect early arrhythmias.     

1028 neonatal electrocardiograms.

Electrocardiograms were recorded from 1028 (99.4%) of 1034 consecutively born babies on the 1st or 2nd day of life. Abnormalities of cardiac rhythm or conduction were found in 49 (4.8%) babies. 17 babies had single or multiple premature beats during the recordings, and 7 babies showed sudden increases in R-R interval possibly due to sinoatrial node dysfunction. One baby had sinus or junctional bradycardia of less than 80 beats/min. One baby had an incessant reciprocating tachycardia and subsequently required digoxin for heart failure. Continuous 24-hour ECG monitoring in 25 babies with abnormalities of the screening ECG, and 25 babies without such abnormalities, failed to show any additional tachyarrhythmias or bradyarrhythmias warranting treatment. In view of the uncertain clinical significance of many neonatal arrhythmias and cardiac conduction disorders, more information concerning their natural history and relationship to sudden unexpected death in infancy is needed before recommending that neonatal ECG screening be generally adopted.     

Novel Approach to Transvenous Pacemaker Implantation in a Post-Fontan Adolescent

Postoperative bradycardia is not uncommon following the Fontan procedure in patients with a functional single ventricle. The surgical connections created with various Fontan modifications may complicate access to the atria for transvenous implantation of a permanent pacemaker. We describe approaches to overcoming problems with atrial access in an adolescent with complex congenital heart disease who required permanent transvenous atrial pacing for tachycardia-bradycardia after Fontan surgery.     

心外管道全腔肺分流手术的临床应用

目的 探讨心外管道全腔肺分流手术在小儿复杂青紫型先天性心脏病中的应用价值.方法 1998年1月至2008年10月48例患儿接受了心外管道全腔肺分流手术,其中男37例,女11例;年龄3.1～14.5岁,平均(5.6±3.0)岁;体重13～56 kg,平均(21.1±10.3)kg;三尖瓣闭锁23例,单心室20例,右心室双出口(远离大动脉型)2例,室间隔完整的肺动脉闭锁2例,法乐四联症伴完全性房室间隔缺损1例;术前SPO270%～93%,平均(80.2±6.1)%.38例患儿在行心外管道全腔肺分流手术前接受多次手术,包括改良BT分流5例次,肺动脉环缩4例次,双向腔肺分流手术36例次.12例患儿在同一次手术中完成全腔肺分流手术.结果 术后早期死亡3例;乳糜胸7例,气胸2例,胸腔金葡菌感染1例,短暂的交界性心动过速2例,均治愈;术后胸腔引流放置3.5～48 d.随访1个月至12年,晚期死亡2例,其余35例心功能恢复至Ⅰ级,6例心功能Ⅱ级,2例心功能Ⅲ级,随访心电图均为窦性心律.统计分析Ⅰ期Fontan和分期Fontan在术后机械通气时间、监护时间、引流时间,病死率上无统计学差异.结论 心外管道全腔肺分流手术术后心律失常的发生率低,开窗术有助于围术期恢复,Ⅰ期Fontan在部分患儿中是可行的.     

Dual chamber cardiac pacing in children: Single chamber pacing dual chamber sensing cardiac pacemaker or dual chamber pacing and sensing cardiac pacemaker?

BACKGROUND: Dual chamber pacemakers (single chamber pacing dual chamber sensing cardiac pacemaker (VDD) and dual chamber pacing and sensing cardiac pacemaker (DDD)) are being used frequently in children and adolescents. The aim of this study was to verify the safety and performance of the VDD and DDD pacing systems, and to evaluate the differences between two pacing modes with regard to atrial sensing and tracking functions. METHODS: In this study, we evaluated 14 patients with VDD pacing and 15 patients with DDD pacing between 1994 and 2000. In the patient group with VDD pacing, all had congenital or acquired atrioventricular (AV) block. In the patient group with DDD pacing, 11 had congenital or acquired AV block, three had sinus node dysfunction with AV conduction disturbance and one had idiopathic hypertrophic subaortic stenosis. Twenty-eight devices were implanted in the subpectoral area using the transvenous route. After implantation the atrial tracking capabilities of the pacing systems were analyzed by telemetry, Holter monitoring, and treadmill exercise testing. RESULTS: The mean age of patients in the VDD pacing group was younger. The percentage of congenital heart disease was higher in the DDD pacing group. There was no significant difference regarding fluoroscopy time during implantation and follow-up time between the two groups. During implantation, in the VDD pacing group the mean sensed atrial signal was 3.1 +/- 1.3 mV and this decreased to 1.37 +/- 0.68 mV (P < 0.05) during follow-up. This pattern was also observed in DDD group (3 +/- 2 mV vs 1.9 +/- 1.5 mV, P < 0.05). Although the P wave measurement at implantation did not differ between the two groups, it was significantly higher in the DDD pacing group at the last control. Three patients with VDD pacing were reprogrammed to VVI or single chamber pacing and sensing, rate adaptive cardiac pacemaker because of complete loss of AV synchrony. There was no atrial sensing problem in the DDD pacing group. During the follow-up, one patient with VDD pacing developed diaphragmatic stimulation and required lead revision. In one patient with DDD pacing, venous thrombosis occurred in the right subclavian vein and was treated with thrombolytic therapy. During treadmill exercise testing, in one patient with VDD and one patient with DDD pacing temporary failure of atrial sensing occurred. At 24 h Holter monitoring, intermittent loss of atrial sensing was documented in two patients with VDD pacing. CONCLUSIONS: Dual chamber pacing in children with DDD or VDD pacemakers is a suitable method for bradycardia treatment. Atrial sensing problems may occur in VDD pacemakers. Therefore, DDD pacing mode should be preferred whenever suitable for the patient to maintain the AV synchrony.     

Impact of Transesophageal Electrophysiologic Study to Elucidate the Mechanism of Arrhythmia on Children With Supraventricular Tachycardia and No Preexcitation

An electrophysiologic study (EPS) of children and teenagers with paroxysmal supraventricular tachycardia (SVT) and normal electrocardiography (ECG) in sinus rhythm was evaluated. Generally, EPS is performed only before paroxysmal SVT ablation in these patients. In this study, 140 patients (mean age, 15 ± 3 years) with normal ECG in sinus rhythm were studied for SVT by a transesophageal route in baseline state and after isoproterenol. Idiopathic left or right ventricular tachycardia was diagnosed in four patients (3 %). Anterograde conduction over an atrioventricular (AV) left lateral (n = 10) or septal (n = 9) accessory pathway (AP) was noted in 19 patients (13.5 %) at atrial pacing. Orthodromic AV reentrant tachycardia (AVRT) was induced in these children. Five of the patients had a high rate conducted over AP (>240 bpm in baseline state or >290 bpm after isoproterenol). Two of the patients (a 10-year-old girl with well-tolerated SVT and a 17-year-old with syncope-related SVT) had the criteria for a malignant form with the induction of atrial fibrillation conducted over AP at a rate exceeding 290 bpm in baseline state. Of the 140 patients, 74 (53 %) had typical AV node reentrant tachycardia (AVNRT), nine had atypical AVNRT (6 %), 1 had atrial tachycardia (0.7 %), and 33 (23.5 %) had AVRT related to a concealed AP with only retrograde conduction. Electrophysiologic study is recommended for children with paroxysmal SVT and normal ECG in sinus rhythm. The data are helpful for guiding the treatment. Ventricular tachycardia or atrial tachycardia can be misdiagnosed. Masked preexcitation syndrome with anterograde conduction through AP was present in 13.5 % of the patients, and 1.4 % had a malignant preexcitation syndrome.     

Status of survivors after atrial redirection for transposition of the great arteries: a complete long-term follow-up

All 32 survivors with transposition of the great arteries, born in 1964-83 and operated on at our institution using atrial redirection, were evaluated by cardiac catheterization, echocardiography and Holter monitoring. There were 17 Mustard patients, age 17.1 years (±3.5, 12.0-22.0) and 15 Senning patients, age 9.4 years (±1.6, 7.2-12.1). All but one had simple transposition. Six had caval obstruction, one had pulmonary venous obstruction, three had large atrial shunts, four had considerable pulmonary hypertension, seven had mild ventricular outflow tract obstruction, four had significant tricuspid regurgitation, 11 had systemic ventricle dysfunction (one severe), 14 had sinus node dysfunction (three symptomatic) and two had atrioventricular block (one with pacemaker). Eight Mustard patients (47%) and one Senning patient (7%) had symptomatic cardiac sequelae, and only one patient (Senning) was free from sequelae, illustrating that these patient groups will need continuing medical attention.     

Sick sinus syndrome. Symptomatic cases in children.

In 20 children needing treatment for symptomatic sick sinus syndrome, the average age at presentation was 7.1 years and ranged from 9 months to 18 years. Symptoms were never precise but, in retrospect, 5 children had syncope, 7 had a rapid heart action, 6 had dyspnoea or tachypnoea, 2 had nonspecific chest pains, 2 had pale spells, and 1 had a sudden hemiplegia. Symptoms followed cardiac surgery in 15 cases and were related to unoperated congenital heart disease in 2 and to myocarditis in 2. The aetiology was unknown in 1 case. The type of cardiac surgery resulting in the development of the sick sinus syndrome was predominantly related to atrial suturing. Both tachy- and bradydysrhythmias were found, including wandering atrial pacemaker (9 cases), junctional rhythm (19 cases), supraventricular tachycardia (9 cases), atrial flutter (11 cases), and atrial fibrillation (2 cases). Both atrial (8 cases) and ventricular (7 cases) premature beats were seen. All patients were given trials of drug therapy but difficulties were encountered. Cardioversion was used for tachyarrhythmias in 11 cases without serious problems. Six children had permanent cardiac pacemakers inserted with good results. Recognition of the sick sinus syndrome in childhood is important and treatment must be regulated by the severity of symptoms.     

Arrhythmias after pediatric lung transplantation

Atrial arrhythmias have been reported after congenital heart surgery involving extensive atrial suture lines. Experimental studies involving bilateral lung transplantation (Tx) suggest that the left atrial suture lines predispose to atrial flutter. The overall incidence and type of arrhythmias after pediatric lung Tx have not previously been described and therefore the purpose of this study was to prospectively screen and describe arrhythmias in a subset of our lung transplant population. Over a 1-yr study period, all recipients of bilateral lung Tx were admitted to a full-disclosure telemetry unit. Single-lead electrocardiograms were recorded continuously and reviewed daily via a beat-by-beat analysis. A total of 314 patient days (range 9-93, median 43 days) were recorded from seven patients. The incidence of arrhythmias observed per total patient days included junctional escape rhythm (4.8%), non-sustained ventricular tachycardia (4.1%), accelerated junctional (2.5%), sinus bradycardia (2.2%), non-sustained supraventricular tachycardia (1.3%), ectopic atrial tachycardia (1.0%), sustained ventricular tachycardia (0.3%), junctional ectopic tachycardia (0.3%), and second degree heart block (0.3%). No patient had sustained supraventricular tachycardia, atrial flutter, atrial fibrillation, or complete heart block. Arrhythmias were treated in two patients. During the follow-up period, one patient received amiodarone for ventricular tachycardia (which was also noted and treated prior to transplant). We conclude that among pediatric lung transplant recipients admitted for their transplant surgery, arrhythmia is uncommon and rarely requires therapy.     

Adenosine: An Effective and Safe Antiarrhythmic Drug in Pediatrics

Adenosine is an effective, safe drug for the diagnosis and treatment of paroxysmal tachycardias in adult and pediatric patients. A starting dose of 0.05–0.10 mg/kg as a rapid bolus injection is recommended for infants and children. An electrophysiologic effect can be expected within 20 seconds after injection. Dosage may be increased up to 0.3 mg/kg in steps of 0.05–0.10 mg/kg or until conversion to sinus rhythm is reached. Due to its basic electrophysiologic properties of slowing conduction in the atrioventricular (AV) node, which may result in transient AV block, adenosine is almost always effective in terminating supraventricular tachycardias in which the AV node forms a critical part of the reentrant circuit (i.e., AV nodal reentrant tachycardia and AV reciprocating tachycardia). Based on its properties, adenosine is also advocated as a useful diagnostic tool for unmasking primary atrial tachycardias by inducing transient high grade AV block. Advantages over other antiarrhythmic agents include the agent's short half-life (<2 seconds) and minimal or no negative influence on blood pressure. Because of its short half-life, however, early recurrence of the tachycardia is observed in up to one-third of patients treated. Based on rare but serious unwanted side effects, patients with known or suspected irritable airways and sinus node dysfunction and those who have undergone orthotopic cardiac transplantation should probably not be given adenosine. Adenosine may be recommended as the drug of choice for treatment of paroxysmal tachycardia in young patients. Primary success rates range between 85% and 100% of all the tachycardia episodes treated. Termination of the tachydysrhythmia, however, does not always mean that the underlying dysrhythmia was of supraventricular origin with the AV node as a critical part of the tachycardia mechanism. Rare but possible life-threatening side effects (prolonged sinus arrest and complete AV block, atrial fibrillation, acceleration of ventricular tachycardia, apnea) necessitate proper monitoring of the patients.